# Torque is irrelevant or relevant?



## major (Apr 4, 2008)

I was engaged in discussion with a member on another thread and the OP politely suggested we take it elsewhere. If interested that can be found here: http://www.diyelectriccar.com/forums/showthread.php/new-build-new-builder-ninja-250-36771.html 

The other member claims


> when talking about motors of any kind torque is totally irrelevant


I realize this quote is out of context, but I have pointed the way to the origin.

I am of the opinion that motor torque is of great relevance when it comes to vehicle performance. Anyway, being an opened minded type of guy, I'd like to get some other opinions without totally hijacking hppyfngy's thread.

Regards,

major


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## paker (Jun 20, 2008)

Torque is very relevant. Take a 9" motor and a 13" motor. Putting the same amount of current to both which would move more weight in the same time period? The 13" motor.


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## CroDriver (Jan 8, 2009)

Power is torque X RPM. 

Formula1 engines have about 300-400 Nm torque. My BMW X6 has double that torque but guess who's faster 

However, torque is important in real life when you cruse around at low RPM. More torque means less shifting (if we talk about ICEs)


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## MalcolmB (Jun 10, 2008)

Since I started looking at EVs and series motors in particular I've come to think of power as the rate of torque delivery (in other words torque is the key parameter).

When I wanted to work out if the motor I'd found was suitable for a fixed ratio conversion I first estimated the torque at my maximum current and then worked out if that torque would be sufficient to pull away on a 1 in 3 gradient.

I'm not sure how I could do a similar calculation using power alone, since power is zero at zero rpm, isn't it?


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## Qer (May 7, 2008)

MalcolmB said:


> I'm not sure how I could do a similar calculation using power alone, since power is zero at zero rpm, isn't it?


Power = RPM * Torque, so yes indeed.

As I see it, and since my background is mainly from electricity, I tend to see it as torque is related to current and rpm is related to voltage. Both torque and rpm are potentially very powerful, but rpm without load or torque without movement won't make anyone happy, current without voltage or voltage without current are equally pointless. Of course.

At that perfect time zero when you slam the throttle there's no movement and thus no rpm and thus there can't be any power released and no actual work is done. There's nothing but torque and that torque will force the car to move by simply overcome friction and in THAT very instant, when the car starts to move, there's rpm and therefore you get power! If you don't have the torque you can never overcome the friction and if there's no rpm there's no movement.

Now, power = rpm * torque, if we apply that to the wheel the ONLY thing that regulate the final power at a certain speed of the car is torque! Nothing else. The rpm is directly related to the speed of the vehicle (decided by the size of the wheels) and there's nothing you can do to change that (except by changing speed or tires, of course) so if you want to alter the power that propel the car you alter torque. That's how all cars work.

CroDriver mentioned that Formula 1 cars have engines that only have half the torque of his BMW. That might be true, but that's missing the fact that a Formula 1 car is very aerodynamic and can rev to up to 18000 rpm, thus it doesn't need as much power as the BMW to gain speed and there's a lot of potential power in the high top rpm. However, those 18000 rpm can't be applied to the tires directly so they have to be geared down, trading rpm for, yep, torque and therefore better acceleration.

So my personal view is that torque is the main key here. For an EV acceleration is all about how much motor current you can keep up (which is why the Zilla 2K is still unbeaten on the drag racing track as far as I know), the motor current turns to torque which then is transformed to acceleration. The gear ratio has to be optimized for maximum continumous torque without hitting the limits (max rpm, max motor voltage etc), a motor with less torque but higher rpm can be geared down to trade all those rpms to torque, but torque is, in the end, what accelerates cars.


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## Batterypoweredtoad (Feb 5, 2008)

I think this is an interesting discussion. Heres my take: If you have unlimited flexibility in design of your vehicle, then power is the only thing you need to know. For example, 50hp is 50hp whether it comes from a motor that spins 50,0000 rpm or whether it spins 500 rpm. The problem is that you cant make a 50,000 rpm (or really a 500rpm) motor work because you cant gear your car appropriately. So I say torque is key, but what rpm range the motor can carry that torque through is more important.


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## CroDriver (Jan 8, 2009)

I would rather have more RPM than torque. This would make a single speed setup much easier. I think that such a setup is almost impossible with DC motors (except for very short runs -> drag racers) because the motor would run at very low RPM most of the time and would probably overheat (and the efficiency would probably suck). I think that a single speed transmission is especially hard to achieve with a sports car that has to be geared for high speeds. 

I bet that the Tesla Roadster has less torque than a good DC conversion 




Qer said:


> CroDriver mentioned that Formula 1 cars have engines that only have half the torque of his BMW. That might be true, but that's missing the fact that a Formula 1 car is very aerodynamic and can rev to up to 18000 rpm


Yeah, I forgot to mention the 18.000RPM (limited by regulations, a few years ago the red line was at 22.000RPM)

They trade torque for RPM with a short piston rod


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## Bowser330 (Jun 15, 2008)

Batterypoweredtoad said:


> ...So I say torque is key, but what rpm range the motor can carry that torque through is more important.


+1

Torque without considering speed(rpm) is irrelevant...


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## samborambo (Aug 27, 2008)

Batterypoweredtoad said:


> I think this is an interesting discussion. Heres my take: If you have unlimited flexibility in design of your vehicle, then power is the only thing you need to know. For example, 50hp is 50hp whether it comes from a motor that spins 50,0000 rpm or whether it spins 500 rpm. The problem is that you cant make a 50,000 rpm (or really a 500rpm) motor work because you cant gear your car appropriately. So I say torque is key, but what rpm range the motor can carry that torque through is more important.


-1

You're irrelevant.

You might as well say that Amps are irrelevant too.


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## Qer (May 7, 2008)

CroDriver said:


> I think that such a setup is almost impossible with DC motors (except for very short runs -> drag racers) because the motor would run at very low RPM most of the time and would probably overheat (and the efficiency would probably suck).


Yep, that's a limitation. But is that because of the RPM or the construction?


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## CroDriver (Jan 8, 2009)

Qer said:


> Yep, that's a limitation. But is that because of the RPM or the construction?


I'm just thinking hypothetical. If I could trade 30% torque for 30% more RPM I would do it

The power would theoretically be the same, wouldn't it?


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## major (Apr 4, 2008)

samborambo said:


> You might as well say that Amps are irrelevant too.


Please stay civil here.

Obviously you need both to do work. But you can have the across variable without the thru variable. Like you can have force without motion, torque without RPM, voltage without current, pressure without flow, etc. But unless you reside in the frictionless universe, you cannot have the converse. Just plain old systems talk.

The context of the discussion was vehicle performance, including launch. Which includes zero speed. Which I think makes torque of prime relevance. When I confronted Drew with this, he said


> Actually, the initial time period of takeoff is mostly governed by a sort of a squirm


Glad to see some opinions come in 

major


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## Qer (May 7, 2008)

CroDriver said:


> I'm just thinking hypothetical. If I could trade 30% torque for 30% more RPM I would do it
> 
> The power would theoretically be the same, wouldn't it?


Yep. And there's a few advantages with rpm instead of torque, transaxles etc can be smaller. But then, balance is more critical instead so, well, it doesn't really matter. Or it does matter, but, well, hmm... 

Apples and oranges, I guess. However, the torque I mainly talked about was the torque at the tire, that one won't change.


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## paker (Jun 20, 2008)

CroDriver said:


> I'm just thinking hypothetical. If I could trade 30% torque for 30% more RPM I would do it
> 
> The power would theoretically be the same, wouldn't it?


How do you think Wayland's Datsun get's off the line faster than any other car he races? It ain't RPM that does it.


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## Bowser330 (Jun 15, 2008)

major said:


> Please stay civil here.
> 
> Obviously you need both to do work. But you can have the across variable without the thru variable. Like you can have force without motion, torque without RPM, voltage without current, pressure without flow, etc. But unless you reside in the frictionless universe, you cannot have the converse. Just plain old systems talk.
> 
> ...


So "launch" does include zero speed but to make the launch relevant to the launching vehicle's performance dont you need speed involved? Thus launch is dependent upon speed to make it relevant, right?


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## Bowser330 (Jun 15, 2008)

paker said:


> How do you think Wayland's Datsun get's off the line faster than any other car he races? It ain't RPM that does it.


Performance at launch is not the only form of performance...


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## PhantomPholly (Aug 20, 2008)

If you had a perfect CVT, only HP would be relevant. The CVT would keep the motor right at it's optimum rpm while using all of the available power. However, there is no such thing as a perfect CVT today...

Electric motors often out-perform ICE motors of similar hp because of the range of rpms over which they will deliver full hp. ICE motors peak at a very narrow rpm range, usually right at or near max rpm with a sharp falloff. Electric motors typically increase hp linearly (and quickly) until they produce max hp, then produce that same hp all the way up to max rated rpm. Usually they can produce 100% rated hp over 50% or more of their rpm range.

That's probably the same thing someone else said and I just didn't understand their explanation...


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## paker (Jun 20, 2008)

Bowser330 said:


> Performance at launch is not the only form of performance...


Isn't the thread about torque being relevant?


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## major (Apr 4, 2008)

paker said:


> > Originally Posted by *Bowser330*
> > _Performance at launch is not the only form of performance..._
> 
> 
> Isn't the thread about torque being relevant?


Yes, it is, but isn't torque relevant at all speeds? Just that in a drag race, gettin' goin' faster sooner is a big benefit for ET.

Regards,

major


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## paker (Jun 20, 2008)

This is about the best answer I've seen about torque.

*Torque is what accelerates the vehicle and horse power keeps it there. Just about any car can travel at 100 kph or 60 mph but how fast it can get there depends on how much torque the engine produces.*


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## Drew (Jul 26, 2009)

PhantomPholly said:


> If you had a perfect CVT, only HP would be relevant. The CVT would keep the motor right at it's optimum rpm while using all of the available power. However, there is no such thing as a perfect CVT today...
> 
> Electric motors often out-perform ICE motors of similar hp because of the range of rpms over which they will deliver full hp. ICE motors peak at a very narrow rpm range, usually right at or near max rpm with a sharp falloff. Electric motors typically increase hp linearly (and quickly) until they produce max hp, then produce that same hp all the way up to max rated rpm. Usually they can produce 100% rated hp over 50% or more of their rpm range.
> 
> That's probably the same thing someone else said and I just didn't understand their explanation...


This is mostly what I was getting at when I was talking about torque being irrelivant in the other thread. My point was that torque, in context of any motor is actually only used to indicate power at a certain PRM, the example I gave in the other thread was ;



Drew said:


> Thats right, tractive effort is a force, not a torque, the force at the wheel for a given speed is related to tyre diameter, differential ratio, gearbox ratio as well as any transfer cases involved.
> 
> Take the previous example, if you use a CAT diesel engine with 280kW and approx 1500Nm at 1800RPM vs a small helicopter turbine with 280kW and approx 52Nm of torque at 52000RPM. Assuming that both of these engines are geared to produce maximum power at 50km/h then what would the tractive effort be in each case? Simple answer, the same.
> 
> More complex version is that if you assume that you're talking about a medium to large truck with a 295/80R22.5 and a rolling diameter of approximately 1.050m and rolling circumference of 3.3m making for a wheel RPM of 252.5RPM, so your total system ratio for the CAT diesel will be around 7.14:1 and the turbine will have a total system ratio of 206:1 but the wheel torque is the same for both, the torque might diverge at the differentials based on different ratios, or there might be portal hubs, or they might even be using the same driveline, but the turbine has a planetary reduction gearbox of 28.8:1 before it goes into the transmission... the point is that torque is totally irrelivant unless you're designing components in a driveline, but its certainly not relevant when talking about engine power outputs or vehicle performance.


I should also mention that the maths I used to demonstrate the calculation of tractive effort without use of torque was simply P=F/V where power is the engines mechanical power in Watts, F is the tractive effort in Newtons and V is the vehicles current velocity.

You can use that formula to calculate maximum available tractive effort if you know or can estimate the maximum theoretical Mu of the tyres and the mass over the drive wheel(s) when taking into account weight transfer. The result is something like this;










Which is a set of calculations based on using the Azure Dynamics AC24L as a drive motor in a motorbike that I've been designing up for a while. This is working with an estimated rider+bike combination of 150kg and a Mu of 1.1 from memory and I've simply taken the power curve of the AC24LS and mapped it directly against the theoretical power limit to determine an ideal performance set. My calcs indicated (using only the data that I've posted up) that I'd get something like a 4.5 sec 0-100 and a top speed of 145-150km/h, but I didn't go ahead with this plan because I'm pretty sure that I'd have problems with grades at 110km/h (top highway speed in Australia).

The reason the above was feasible was because of the fact that the motor has a significant run on after reaching peak power (major complained when I called it a constant power region ) but my point in the other thread, which still stands is that if I was using a DC motor then I'd still want to reach peak power (assuming the same peak value) at the same road speed of 60km/h which means I'd have different gearing but the same wheel torque and therefore the same tractive effort, but if I didn't have the available overrun then I'd have to either re-gear the motor diminishing the bikes performance or alternately install a gearbox.


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## Bowser330 (Jun 15, 2008)

Setup#1
*300ftlbs* 0-2000rpm
200fltbs 2000-4000rpm
100ftlbs 4000-6000rpm

Setup#2
*200ftlbs* 0-6000rpm

Which setup would you pick and why...

_Note: Horsepower Formula:_
_TQ * RPM / 5252 = HP_


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## major (Apr 4, 2008)

Bowser330 said:


> Setup#1
> *300ftlbs* 0-2000rpm
> 200fltbs 2000-4000rpm
> 100ftlbs 4000-6000rpm
> ...


Well, first off, you're comparing a peak of 228 hp to a peak of 152.

Why don't we ask ZX-E to run the 1/4 mile with these two set-ups on equal vehicles and see which one wins? Ref: http://www.diyelectriccar.com/forums/showthread.php/new-ev-calculator-36920.html?p=142547#post142547 Maybe adjust mass or gear ratio so exit speed on the winner is just below 6000 RPM.

Interesting 

major


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## CroDriver (Jan 8, 2009)

paker said:


> This is about the best answer I've seen about torque.
> 
> *Torque is what accelerates the vehicle and horse power keeps it there. Just about any car can travel at 100 kph or 60 mph but how fast it can get there depends on how much torque the engine produces.*


I have a better one

*"Understeer"* is when you hit the fence with the front of the car. 
*"Oversteer"* is when you hit the fence with the rear of the car. 
*"Horsepower"*is how fast you hit the fence. 
*"Torque"* is how far you take the fence with you.


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## ZX-E (Aug 31, 2009)

In Reply to Major and Drew. I simulated two cars with the same shape and weight as Tesla Roadsters and chose the gear ratios based on when the cars hit 6000 RPM at the end of the quarter mile. 

The car with the step function:
gear ratio 5.2
0-60 in 7.95 seconds
quarter mile in 16.5 @ 84.44 mph










The car with the constant 200 ft-lbs:
gear ratio 4.45
0-60 in 9.95 seconds
quarter mile in 17.3 seconds @ 100.4 mph











So you trade good acceleration for a high top speed. Not a big surprise.





Even if you have enough power to move your vehicle.Torque is relevant because it determines how you need to gear it. Also higher RPMs means more losses right?


-Rich


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## Batterypoweredtoad (Feb 5, 2008)

ZX-E, can you do the same calcs, but add a 2 speed trans with about a 1.7 first and a 1 to 1 second please? I'm curious how much it changes things. 
Thanks!


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## tomofreno (Mar 3, 2009)

The forces acting on a vehicle to impede its forward motion apply a torque to the wheels. The vehicle moves at constant speed when the torque applied to the wheels from the motor through the drive train is equal to this torque. Call this the required torque. Acceleration from a given vehicle speed is proportional to the difference in this required wheel torque and available wheel torque, where available wheel torque is determined by the drive train and the max torque the motor/controller can deliver at that vehicle speed. This will be determined by the max current the controller can supply at lower motor rpm, and by the pack voltage and back emf at higher motor rpm.

Power is the product of motor torque and shaft angular velocity. Torque is the more fundamental parameter, just as force is the more fundamental parameter in rectilinear motion, where power is the product of force and velocity. Power matters because it describes how much torque can be delivered at a given rpm. A motor/controller that has high torque at low motor rpm but drops off rapidly at higher rpm, will have good acceleration at lower vehicle speeds, but poor at higher speeds. This of course will be affected by gear ratios which determine the mechanical advantage of the motor. I've calculated and graphed required and available wheel torques as a function of vehicle speed for a number of motor/controller combinations, and also plotted available power versus vehicle speed in a spreadsheet referred to as "ev calculator" at electricnevada.org. 

Tom


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## ZX-E (Aug 31, 2009)

Why would you want such a low gear ratio Batterypoweredtoad? It would take 30 seconds to reach 60 mph with the 1.7 to 1 gear ratio.

Make sure that's what you want because it'll take a while to set it up for more than one speed. Post it over here. 
http://www.diyelectriccar.com/forums/showthread.php/new-ev-calculator-36920.html?p=142567#post142567

-Rich


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## neanderthal (Jul 24, 2008)

Well put tomofreno I studied physics in college. So its nice to see someone put it in terms like that. great stuff.

Anyhow, I think its best to put this stuff in terms of goals. I think we have fleshed out what torque and horsepower are. But what are your goals for your car?

If you want a drag car, especially one with direct drive, thats one thing. If you are into calculus, then you can see a graph showing this example. If you start off with mega acceleration, and it peeders off toward then end, you will still have finished the quarter mile faster than a car that starts off slower, but finishes with stronger acceleration. If you graph high initial acceleration vs time, you get more area under the curve in the first situation than in the second. 

Sorry. In different terms, If you start fast you re already covering more ground faster and finishing faster and end up than someone who starts slower and finishes stronger. Even if they have the same overall power. So you win the quarter mile. Its about the curve.

However, most of us have street cars, so what matters is the torque capability in the rpm range we use it in.

It seems like some of us are talking about all out performance in a drag race, and others about driveablilty.


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## ZX-E (Aug 31, 2009)

Would you agree that driveability has a lot to do with 0-60 acceleration? A faster 0-60 time at least for single speed drives would also mean that you are in the effective torque band at cruising speeds.


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## Qer (May 7, 2008)

Drew said:


> which still stands


No, which still means you're comparing apples with oranges.

The only thing that's interesting is what kind of performance you get out, wether it's AC or DC is just one parameter out of many and I'd say it's not even the most important. How much power and torque you get out in the end doesn't mainly depend on AC versus DC, it depends much more on how much power you can squeeze out of your poor batteries, how much current (and thus torque) your controller can handle and, finally, how much abuse your motor can take. THAT will decide your performance.

The only thing that AC versus DC can hint about is top RPM.


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## Bowser330 (Jun 15, 2008)

ZX-E said:


> Would you agree that driveability has a lot to do with 0-60 acceleration? A faster 0-60 time at least for single speed drives would also mean that you are in the effective torque band at cruising speeds.


depends if you mean highway cruising speeds or local low-speed cruising speeds...you are in a pretty poor torque band with Setup#1 at highway cruising speeds...Setup#1 has pretty poor highway acceleration, from 60-86 especially...(86 being 6000rpm)

If you were to gear both setups the same, at 5.2:1, then it would be pretty close in the 1/4 mile to 86mph, and at highway acceleration (60-86) Setup#2 takes the cake...

in retrospect it might have looked as if I was comparing AC (constant 200ftlbs) to DC (high to low step down), truth is I wasn't going there at all...

I was simply trying to show a point about an effectiveness of wide torque band that is possibly available to DC motors as well with this new Warp_11_HV Motor (9000rpm)....

So really I should have written it like this...

Setup#1
300ftlbs 0-2000rpm
200ftlbs 2000-4000rpm
100ftlbs 4000-6000rpm

Setup#2
300ftlbs 0-2000rpm
200ftlbs 2000-6000rpm

Setup#2 wins by holding enough amps for 200ftlbs until 6000rpm compared to 4000rpm in Setup#1.

Therefore i see torque being only as relevant as its application across a range of speeds....the higher the torque at higher the speeds the higher the relevance...


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## ZX-E (Aug 31, 2009)

Yea I should have clarified. I meant better highway acceleration at 60 mph cruising speeds and comparing two vehicles that have the same motors but different gear ratios . *phew*


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## Drew (Jul 26, 2009)

tomofreno said:


> The forces acting on a vehicle to impede its forward motion apply a torque to the wheels. The vehicle moves at constant speed when the torque applied to the wheels from the motor through the drive train is equal to this torque. Call this the required torque. Acceleration from a given vehicle speed is proportional to the difference in this required wheel torque and available wheel torque, where available wheel torque is determined by the drive train and the max torque the motor/controller can deliver at that vehicle speed. This will be determined by the max current the controller can supply at lower motor rpm, and by the pack voltage and back emf at higher motor rpm.
> 
> Power is the product of motor torque and shaft angular velocity. Torque is the more fundamental parameter, just as force is the more fundamental parameter in rectilinear motion, where power is the product of force and velocity. Power matters because it describes how much torque can be delivered at a given rpm. A motor/controller that has high torque at low motor rpm but drops off rapidly at higher rpm, will have good acceleration at lower vehicle speeds, but poor at higher speeds. This of course will be affected by gear ratios which determine the mechanical advantage of the motor. I've calculated and graphed required and available wheel torques as a function of vehicle speed for a number of motor/controller combinations, and also plotted available power versus vehicle speed in a spreadsheet referred to as "ev calculator" at electricnevada.org.
> 
> Tom


Tom,

Torque is actually a fairly meaningless derivative when looking at the output of a motor of any kind, if you want to move then you want tractive effort, which is only governed by motor power at a given speed. The only way that torque is relevant is when considering power generated at RPM which is what it is an indicator of. If you're calculating loads on structural components then I'd definitely advocate working out driveline torques at all points and sizing drive parts commensurately, but if you're after calculating performance or evaluating the effectiveness of a motor then torque is absolutely meaningless.

A good example is a geared down whippersnipper vs a 1000cc motorbike engine. The geared down whippersnipper can achieve whatever torque you like, just add gears but it still only puts out maybe 1-3kW at the end of the day, whereas a 1000cc motorbike engine might only put out a little over 100Nm of torque, but the 130-140kW of power is what gets you moving down the road.



Qer said:


> No, which still means you're comparing apples with oranges.
> 
> The only thing that's interesting is what kind of performance you get out, wether it's AC or DC is just one parameter out of many and I'd say it's not even the most important. How much power and torque you get out in the end doesn't mainly depend on AC versus DC, it depends much more on how much power you can squeeze out of your poor batteries, how much current (and thus torque) your controller can handle and, finally, how much abuse your motor can take. THAT will decide your performance.
> 
> The only thing that AC versus DC can hint about is top RPM.


Qer,

I just don't understand what you're getting at, what I meant and what I stated was that, generically speaking, a DC motor has a much more rapid power falloff after peak when compared to an AC motor, which means that the AC motor will be able to produce a much better result from direct driving than a DC motor will. I'm not necessarily talking about drag racers or anything like that, I'm simply referring to your average every day vehicle, in which achieving a higher power earlier will give you better performance and maintaining that power may enable you to eliminate your gearbox.

As I stated, an AC motor appears to be more amenable to direct driving than a DC due to this continued power.

If you don't agree then can you please explain why?


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## major (Apr 4, 2008)

ZX-E said:


> In Reply to Major and Drew. I simulated two cars with the same shape and weight as Tesla Roadsters and chose the gear ratios based on when the cars hit 6000 RPM at the end of the quarter mile.
> 
> The car with the constant 200 ft-lbs:
> gear ratio 4.45
> ...


The above is *Setup#2*.

First off. Thanks Rich. Excellent job on this analysis.

This is *Setup#1*



> The car with the step function:
> gear ratio 5.2
> 0-60 in 7.95 seconds
> quarter mile in 16.5 @ 84.44 mph


Setup#1 has a peak of 152 HP. Setup#2 has a peak of 228 HP. Both at 6000 RPM*. Yet #1 wins the 1/4 mile race. Why? Because torque is relevant 

This was a great exercise in my opinion. Thanks to Bowser for posting up that example.

Regards,

major

*Set-up#1 has the peak of 152 HP at 4000 RPM. Both had a 6000 RPM max speed.


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## major (Apr 4, 2008)

Drew said:


> which is only governed by motor power at a given speed.


Drew,

"Motor power at a given speed" is the definition of torque.

Regards,

major


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## Batterypoweredtoad (Feb 5, 2008)

ZX-E said:


> Why would you want such a low gear ratio Batterypoweredtoad? It would take 30 seconds to reach 60 mph with the 1.7 to 1 gear ratio.
> 
> Make sure that's what you want because it'll take a while to set it up for more than one speed. Post it over here.
> http://www.diyelectriccar.com/forums/showthread.php/new-ev-calculator-36920.html?p=142567#post142567
> ...


ZX-E, I was asking if you could set up the same exact car you used in each of your calculations (same final drive, weight, etc...) but add in a 2 speed transmission. I used the powerglide gear ratios because I am considering using one when I get around to a conversion. Sorry if it wasnt clear that I was adding a transmission to the mix instead of using a 1.7 differential gear.


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## Qer (May 7, 2008)

Drew said:


> I just don't understand what you're getting at, what I meant and what I stated was that, generically speaking, a DC motor has a much more rapid power falloff after peak when compared to an AC motor[...]


A DC motor doesn't have peak power, simple as that. A DC motor will peak when the back EMF starts to get close to pack voltage, if your pack voltage is high enough and your controller isn't a cheap shoe box the only limit will be when the rotor starts to fling itself to pieces due to centrifugal force or the whole motor blows up due to too much power.

So generally speaking, you're simply *WRONG*! A weak controller or too low pack voltage will limit an AC-motor as well, naturally.



Drew said:


> As I stated, an AC motor appears to be more amenable to direct driving than a DC due to this continued power.


And it appears you're still wrong. In a typical commuting situation if you have a strong enough motor and controller (regardless of type) what will limit your power output is the BATTERIES, not the type of motor. When you hit maximum battery current you'll get "continued power" no matter of motor type, and you will continue to get "continued power" as long as there's enough voltage because you can only get as much power out of the motor as the batteries can provide. Unless, of course, if you have a shoe box controller that's undersized for the task, but then that's the problem, not the motor or the kind of technology.

I have logs of this, thousands of lines of data that says the same thing; when duty cycle hits a certain level the controller starts to limit the motor current to not blow up the batteries and since battery current suddenly goes flat it means the battery sag gets more or less flat as well and, presto, the power curve goes flat. With a DC-motor. This happens to the White Zombie as well, as soon as the Zilla starts to spank Amps and rpm starts to rise, the Zilla starts to cut down to limit battery amps (otherwise the batteries blow up) and you get the same result in the end, flat power curve.

With good enough batteries, for example A123-cells, and enough voltage to provide more voltage than back EMF plus internal losses in the motor can ever reach, you don't get a flat power curve anymore, you get a power curve that will keep rising with rpm until the motor blows up. There is no peak in DC-motors! That peak is caused by external factors. With a Soliton1 that WILL be the batteries, trust me on that.



Drew said:


> If you don't agree then can you please explain why?


I have. Several times. And I haven't been alone trying to. If you still don't get it, please consider another career path than engineering.


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## Drew (Jul 26, 2009)

major said:


> The above is *Setup#2*.
> 
> First off. Thanks Rich. Excellent job on this analysis.
> 
> ...


I think you might have missed the point of what I was getting at, maybe consider it against an engine with a similar power distribution but twice the rev limit and I think you'd find that you'd need higher gearing and get exactly the same result, because you're not interested in torque, you're interested in power.


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## Drew (Jul 26, 2009)

Qer said:


> A DC motor doesn't have peak power, simple as that. A DC motor will peak when the back EMF starts to get close to pack voltage, if your pack voltage is high enough and your controller isn't a cheap shoe box the only limit will be when the rotor starts to fling itself to pieces due to centrifugal force or the whole motor blows up due to too much power.
> 
> So generally speaking, you're simply *WRONG*! A weak controller or too low pack voltage will limit an AC-motor as well, naturally.
> 
> ...


I'm going to use some pictures now because words don't seem to be working;










This is a graph I just knocked up using a Kostov 11" running at 192V according to manufacturers specs. This is a direct comparison to the AC24LS as per last graph except this time I've added on the Kostov to illustrate what words did not apparently convey, which is that the overrun on the AC24LS allows it to give a good top speed and good acceleration. The Kostov on the other hand, dispite being more powerful would have a similar 0-100 due to the rapid decline of of the power after the peak, and if geared to match the top speed of the AC24LS then it wouldn't have a hope in a drag race.

This is of course based on the assumption that I'm reading the chart on the Kostov website properly, but I think I am.


Major,

This also goes to illustrate my point about power being important, rather than torque, the kostov produces HEAPS more torque than the AC24LS (and more power) but the distribution of power means that without a gearbox the AC24LS will smoke the kostov according to my calcs.


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## major (Apr 4, 2008)

Drew said:


> I think you might have missed the point of what I was getting at, maybe consider it against an engine with a similar power distribution but twice the rev limit and I think you'd find that you'd need higher gearing and get exactly the same result, because you're not interested in torque, you're interested in power.


Drew,

Motor, engine, it does not matter. Bowser didn't specify what the power plant was. Just the torque/speed profile, which with simple arithmetic gives you the power distribution. So if you take one or the other of the two examples, double the RPM and keep the power the same, you will half the torque. Then if you double the gear ratio, the results are identical. So what?

You're right; I miss your point entirely.

If torque is irrelevant as you claim, why does the lower power example outperform the higher power? It's the torque.

Regards,

major


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## Qer (May 7, 2008)

Drew said:


> I'm going to use some pictures now because words don't seem to be working


Quite right, words don't seem to be working. You're still not getting it.

What you see in that graph is the Kostov plotted for a certain voltage! Since back emf is proportional to the rpm you need higher pack voltage to overwin the increasing back EMF and thus moving the peak to a higher rpm.

It's not even rocket science, really.


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## Drew (Jul 26, 2009)

major said:


> Double the RPM and keep the power the same, you will half the torque. Then if you double the gear ratio, the results are identical.


This is what I'm getting at, the motor torque is completely irrelevant, the only thing that is important is the distribution of power, obviously a motor with more torque at low RPM relative to its higher RPM behaviour will produce somethign more like constant power, but while we were talking about torque there we weren't using absolute terms, we were comparing it to its self, so its a dimensionless ratio, not a torque. My basic point is and was that the numbers for torque are irrelevant. People obsess over it, but the only important thing is the amount of power which the engine produces at a set RPM. You might argue that this is still a torque, but because its tied to an RPM its actually power.


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## major (Apr 4, 2008)

Drew said:


> This is what I'm getting at, the motor torque is completely irrelevant, the only thing that is important is the distribution of power, obviously a motor with more torque at low RPM relative to its higher RPM behaviour will produce somethign more like constant power, but while we were talking about torque there we weren't using absolute terms, we were comparing it to its self, so its a dimensionless ratio, not a torque. My basic point is and was that the numbers for torque are irrelevant. People obsess over it, but the only important thing is the amount of power which the engine produces at a set RPM. You might argue that this is still a torque, but because its tied to an RPM its actually power.


Drew,

Using your logic, you could say RPM is irrelevant. Just use the torque/power profile. See that? So because power is the product of angular velocity and torque, if you know any 2 of 3 parameters, you are using the third, whether you're willing to admit it not.

But where your calculations fall apart is at and near zero RPM. And as I have said, you can have torque without speed. But there is no power at zero speed, so your logic falls apart and you have to resort to such statements as:


> Actually, the initial time period of takeoff is mostly governed by a sort of a squirm


As for your Kostov example, looks fishy to me. The curve I found shows power up to 71 kW, 500A at 192V. And your power vs speed curve does not address the launch. So I do not understand how you can draw any valid conclusions from it. Oh yeah, squirm.

Well, got to go. Check back later.

major


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## ZX-E (Aug 31, 2009)

Batterypoweredtoad just tell me exactly what you want to compare. I'll need to know what RPM you want the transmission to shift at etc over here: 
http://www.diyelectriccar.com/forums/showthread.php/new-ev-calculator-36920.html?p=142753#post142753


Qer is definitely right when he said torque is the mechanical equivalent of current. You can do simulations where dampers replace resistors and springs replace capacitors. Torque and current are just two variables multiplied by angular velocity and voltage respectively to form power; and both variables are equally important.


Drew, I think I can see what you're trying to say. If you're comparing the power of different motors you would not _need_ to compare the torque output. That absolutely doesn't mean that torque is "completely irrelevant". When you say absolutes like that you have to watch out. Be more specific please!


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## tomofreno (Mar 3, 2009)

> Torque is actually a fairly meaningless derivative when looking at the output of a motor of any kind, if you want to move then you want tractive effort, which is only governed by motor power at a given speed.


 Do you mean vehicle speed? Vehicle speed is determined by the angular velocity and diameter of the wheels, and the angular velocity of the motor and overall gear ratio. The motor power at a given speed is determined by the product of the motor torque and motor shaft angular velocity at that speed. Sure you can gear down and get as much wheel torque as you want - but not at the vehicle speed you may want. When you gear down, the motor runs at higher rpm for a given vehicle speed, where it has less torque, so power at that speed may decrease. It depends on how fast motor torque falls off with motor rpm, the torque-speed curve. I agree that what matters as far as moving the car at a given vehicle speed is power, or work/unit time, at the wheels, but I calculate that through the parameters above. How do you start with peak motor power and calculate at what vehicle speed that peak motor power is reached without knowing the torque-speed curve? 

Tom


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## tomofreno (Mar 3, 2009)

> A DC motor doesn't have peak power, simple as that.


 That's true. And a DC motor doesn't move a vehicle, a motor, controller, and battery pack do. Either of the last two can limit the torque and power of a DC or AC motor at higher vehicle speeds as you well know, and in fact DO limit them in most conversions.

Tom


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## tomofreno (Mar 3, 2009)

> you get a power curve that will keep rising with rpm until the motor blows up.


 That determines its peak power.  I agree with you Qer, but your bias toward DC is a bit distracting. AC, DC doesn't matter in this regard. You can increase power output of either until it blows up by increasing pack voltage and controller max current - and the timing in the DC motor. But all existing ev conversions have peak power because they are limited by the controller or the pack voltage. So inquiring minds what to know what that peak is, and at what vehicle speeds it occurs for given gear ratios.

Tom


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## tomofreno (Mar 3, 2009)

> The Kostov on the other hand, dispite being more powerful would have a similar 0-100 due to the rapid decline of of the power after the peak


 More powerful at what vehicle speed? That's the point. Power is the product of torque and angular velocity. The Kostov is only more powerful at lower rpm where, with the given overall gear ratio, gives lower vehicle speed. At higher rpm it is less powerful than the AC24LS because of the falloff of torque with motor rpm is greater for it than the AC24LS. Now you could lower the overall gear ratio to run both motors at an rpm where the Kostov has more torque, and thus more power than the AC24LS, but you loose mechanical advantage. The resultant WHEEL torque will then depend on how fast torque falls off with rpm for the two motors. So peak MOTOR power means nothing in itself. You need the torque-speed curve for the two motors, or equivalently a power-speed curve (speed as in motor rpm in this case). But of course you can't generate the power-speed curve without knowing torque as a function of motor rpm - the torque-speed curve.

Tom


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## Qer (May 7, 2008)

tomofreno said:


> That determines its peak power.  I agree with you Qer, but your bias toward DC is a bit distracting.


If I sound biased it's because I'm trying to prove Drew wrong when he seem to have been drinking too much AC cool aid. I'm fully aware that brushless motors has many advantages, but the main advantages in my book isn't "flat power curve" or some other nonsense but rather things like water cooling, sealed enclosure etc. On the other hand, brushed DC-motors has one advantage that means they're still much preferred by many when it comes to DIY, simplicity. Which one you prefer, well, that very much depends on the circumstances I'd say but for the average communting EV the batteries will, as you've pointed out, probably be the bottleneck for quite some years.

To me motor and controller are a power unit. What actual technology that's used doesn't really matter, what's interesting is what performance do you get in the tire end. You can't determine that by "AC" or "DC" and that's what I've been (banging my head while) trying to explain (that) to Drew!


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## Bowser330 (Jun 15, 2008)

What we need is some real world testing examples.

Same general aero, same weight, same battery chemistry...

Setup#1: Max Voltage + Max Amperage into an AC24 motor and inverter

Setup#2: Max Voltage + Max Amperage into a 9" DC motor and Soliton-1


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## Qer (May 7, 2008)

Bowser330 said:


> Setup#1: Max Voltage + Max Amperage into an AC24 motor and inverter
> 
> Setup#2: Max Voltage + Max Amperage into a 9" DC motor and Soliton-1


That would, however, compare AC24 and WarP/Soliton, not AC versus DC. Even though I'm convinced a WarP 9" with a serious LiFePO4-pack would beat the AC24 (either that or the WarP would blow up due to the absurd level of abuse  ) it still doesn't prove DC superior, only that the Soliton is able to dish out more than 63 hp peak.

On the other hand, we've already proved it can. There's even a video of it on YouTube.


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## CroDriver (Jan 8, 2009)

Bowser330 said:


> What we need is some real world testing examples.
> 
> Same general aero, same weight, same battery chemistry...
> 
> ...


I will have the AC55 soon here and a Zilla powered DC setup so I can make a AC vs. DC race 

I should limit the Zilla current to leave a chance for the AC


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## Qer (May 7, 2008)

CroDriver said:


> I should limit the Zilla current to leave a chance for the AC


No cheating!


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## Drew (Jul 26, 2009)

Qer said:


> Quite right, words don't seem to be working. You're still not getting it.
> 
> What you see in that graph is the Kostov plotted for a certain voltage! Since back emf is proportional to the rpm you need higher pack voltage to overwin the increasing back EMF and thus moving the peak to a higher rpm.
> 
> It's not even rocket science, really.


So you're arguing that to overcome the issue with not having a (sorry major) constant power phase you can overdrive the motor pushing the peak power further toward the redline of the motor and have even less overrun?



major said:


> Drew,
> 
> Using your logic, you could say RPM is irrelevant. Just use the torque/power profile. See that? So because power is the product of angular velocity and torque, if you know any 2 of 3 parameters, you are using the third, whether you're willing to admit it not.
> 
> ...


Well, you can check the Kostov data yourself if you like, it was sourced from http://kostov-motors.com/files/productattachments/da0012f5e806b95241ea09d19be9abe3_11-192V.pdf which I believe is the manufacturer website.

During launch, as with all times that a wheel is driven a tyre will actually be operating at a different speed to the road, its this speed difference which allows you to generate traction, as, for tyres, there is no such thing as static friction. What this means is at times like launch there is a required amount of wheelspin to move the car, its not normally detectable by the driver, but the wheel will start to move before the car does, even on a very normal takeoff. I'm not talking about big smokey burnouts either, but in the case of a normal hard acceleration on a clean dry bitumen surface the wheel will be moving up to 30% faster than the vehicle relative to the road surface, this is in a sort of an instantaneous picture.

On launch, as you pointed out, because you can't evaluate slip either, because the vehicle isn't moving, its a sort of divide by zero problem, but needless to say the wheels are moving, enabling the transfer of power, but the vehicle isn't. Needless to say you end up with something which can't be defined as wheelspin but certainly isn't a static tyre.

The same issue exists with ICE cars because a car has as set minimum idle speed and the clutch can only transfer torque, not power, so its pretty hard to describe based on power the ability of the vehicle to take off, its also not really possible to describe takeoff in any sense, but its easier to see with ICE because to take off quickly you just drop the clutch and if you get it right the wheels spin just the right amount and you're off.

Either way, I think I've found a way of explaining what I was getting at;

A vehicles tractive effort and mass are the only two things which govern acceleration, tractive effort is most simply defined as force applied to the road by the rear wheels. The relationship between power and tractive effort is simple, the supplied power divided by the vehicle velocity is equal to the tractive effort at the rear wheel (not accounting for losses). Now if you play the same game following torques through the system then you end up finding out that the tractive effort is related to the wheel torque, but only if you have already know the wheel diameter, which is pretty useless if you're working on an existing vehicle. Even if you're working on an existing vehicle the next problem you have is that there is no set ratio between the motor and the wheel unless you're using an existing gearbox and differential, in which case then you're stuck with what you've got so theres not much point doing the calcs.

So basically, wheel torque means nothing because of wheel diameter, gearbox torque means nothing because of diff and wheel info and motor torque means nothing because of all of the other ratios. Bottom line is that the only thing thats important is power.

Oh, also, with reference to power being the product of torque and RPM, you're right, you could neglect RPM, but then it makes it impossible to determine drive ratios etc, so it makes the whole exercise meaningless 



tomofreno said:


> More powerful at what vehicle speed? That's the point. Power is the product of torque and angular velocity. The Kostov is only more powerful at lower rpm where, with the given overall gear ratio, gives lower vehicle speed. At higher rpm it is less powerful than the AC24LS because of the falloff of torque with motor rpm is greater for it than the AC24LS. Now you could lower the overall gear ratio to run both motors at an rpm where the Kostov has more torque, and thus more power than the AC24LS, but you loose mechanical advantage. The resultant WHEEL torque will then depend on how fast torque falls off with rpm for the two motors. So peak MOTOR power means nothing in itself. You need the torque-speed curve for the two motors, or equivalently a power-speed curve (speed as in motor rpm in this case). But of course you can't generate the power-speed curve without knowing torque as a function of motor rpm - the torque-speed curve.
> 
> Tom


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## Qer (May 7, 2008)

Drew said:


> So you're arguing that to overcome the issue with not having a (sorry major) constant power phase you can overdrive the motor pushing the peak power further toward the redline of the motor and have even less overrun?


No, I'm mainly saying you're still wrong and don't understand how a motor works.

Let's restart this.
*
Warning! Bad analogy below! Try not to read too much into it but a feeble attempt to set some things straight.*

In many aspects thinking of a motor as an electrical engine is wrong, an engine takes fuel and air as input, the throttle regulates the amount of fuel and air that's required and thus regulates the power that comes out of the engine. A motor doesn't regulate anything, a motor takes the electrical energy you provide it with and turns it into mechanical energy.

You could actually say that the real "engine" in an EV isn't the motor, it's the controller! The controller takes the "fuel" (battery energy), regulates and converts it to energy of fitting voltage and current that's needed to propel the car as the driver prefers. This means that the motor isn't the engine, it's the gear box and as any gear box it can only convert energy, not regulate energy. If the controller feeds, for example, 40 kW electrical energy into the motor you will get 40 kW mechanical energy (minus losses, of course) out of the motor, if the engine feeds 40 kW mechanical energy into a gear box the gear box will give you 40 kW (minus losses again) mechanical energy out. It's simply just energy conversion and thus the motor doesn't have peak power, the only thing the motor can do is convert the energy or break while trying. Just like a gear box.

This analogy is of course flawed (like most analogies), but if you prefer it you can look at the controller as the injection and ignition electronics, the "stuff" that controls how much the engine will work, and the motor is the mechanical parts that transform the fuel to mechanical movement. That works too and as in the case above it still means that the motor has no option but to try to perform what is demanded from it. And just like an engine can blow the top, break a transaxle or whatever if you push it too hard a motor can zorch or fling itself to pieces if you push that too hard.

It's no different from that the same mechanical engine can get very different performance curves depending on the fuel- and ignition system (or turbo or not etc), an electrical motor will behave very differently depending on what controller and battery you use with it.


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## Abel (Sep 16, 2009)

i have to go with everyones opinion. I dont know any one here or there experances. The truth is EVERY spec counts. Here are some setup info that have help me with my gas,disel,and now electric cars/trucks. this is to biuld a well rounded set up. more iteams apply but this is for basic set up.

Low HP - High Torque - Light car -------- A wide ratio trany, mid range final gear. 

Low HP - High Torque - heavy car--------Close ratio trany, low-mid rang final final gear

High HP - Low Torque - Light car --------a wide ratio trany, low final gears

High HP - Low Torque - heavy car -------Close ratio trany, super low final gear.

Low HP - Low Torque - Light car---------close ratio trany, low or mid-low final gear.

Low HP-Low Torque - heavy car---------- GET A BETTER MOTOR

High HP-High Torque - Light car-----------wide ratio trany,high to mid final gear

High HP-High Torque - Heavy car---------wide ratio trany, mid final gear

This is for a well rounded car. Drag racing you all ways use close ratio tranys and track cars mid to wide ratios. I have work with meny comeros, stengray vetts, and mustanges.


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## tomofreno (Mar 3, 2009)

> On launch, as you pointed out, because you can't evaluate slip either, because the vehicle isn't moving, its a sort of divide by zero problem, but needless to say the wheels are moving


 As the tires rotate they move along the surface they are in contact with unless they slip against that surface (burning rubber). As they move, they pull the rest of the vehicle with them unless they slip against the wheel or shear. I can see that there may be some slight rotation of the tires without vehicle movement due to shear in the tires, but other than this, it seems the vehicle must move when the torque applied to the wheels is greater than the torque required to move the vehicle (ignoring the minute play in the axle bearings). Work (energy) is the product of force and distance, or in rotational kinematics, the product of torque and angular displacement. The wheels must turn for work to be done on them, and that work/time is power. If you apply a torque to the wheels infinitesimally less than that required to rotate them, then no mechanical work is done. Energy from the batteries is dissipated in resistive losses in the motor, controller, cables, and batteries, and friction losses in the drive train and tire shear. This energy/time is the power. The power output will increase if the torque is increased enough to make the tires rotate. It will increase by the work/time done to rotate the wheels.

Tom


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## Drew (Jul 26, 2009)

Qer said:


> No, I'm mainly saying you're still wrong and don't understand how a motor works.
> 
> Let's restart this.
> *
> ...


This seems to be an AC vs DC thing that you're getting at Qer, and all I was saying is that an AC motor appears to be a better motor for single gearing, it doesn't mean that its not a great motor or can't produce power it just means that from what I've seen you get a good run at something approaching constant power which is pretty much what an idealised car motor should be.

Here is my understanding of how a DC motor works; A current limit is set by the manufacturer which limits the total torque produced, leading to a linearly increasing power curve, at some point the motor reaches a voltage where something(back EMF?) limits the amount of current which can go in, at this point the power drops off rapidly and at some point near there a mechanical limit is reached whereby the motor will fling its self apart if speed is exceeded, correct?

I, quite frankly, don't understand how an AC motor works, but from what I've seen it effectively reproduces the initial curve on a DC motor and then seems to reach a limitation which I guess is related to temperature or something else which simply means that it can't deal with any more power, at which point it slowly generates less and less power until it reaches the (higher due to different rotor construction) RPM limit at which it must be shut down or it flings its self to pieces.

PM AC motor seem to be something of a middle ground.

I don't know why, I'm only commenting on how the characteristics are beneficial.

I also have worked out that if I were to use an AC150 motor from ACPropulsion I would still have to have a gearbox because there isn't enough power spread to maintain an acceptable top speed whilst producing good acceleration at the bottom end, whereas I've located a PMDC motor which weighs 55kg including controller and produces something in the ballpark of 210kW and a good spread of power which actually will give me a good top speed and accel. I'm not biased toward one solution, I'm simply looking at it as an exercise in powerplant selection in mechanical design.



tomofreno said:


> As the tires rotate they move along the surface they are in contact with unless they slip against that surface (burning rubber). As they move, they pull the rest of the vehicle with them unless they slip against the wheel or shear. I can see that there may be some slight rotation of the tires without vehicle movement due to shear in the tires, but other than this, it seems the vehicle must move when the torque applied to the wheels is greater than the torque required to move the vehicle (ignoring the minute play in the axle bearings). Work (energy) is the product of force and distance, or in rotational kinematics, the product of torque and angular displacement. The wheels must turn for work to be done on them, and that work/time is power. If you apply a torque to the wheels infinitesimally less than that required to rotate them, then no mechanical work is done. Energy from the batteries is dissipated in resistive losses in the motor, controller, cables, and batteries, and friction losses in the drive train and tire shear. This energy/time is the power. The power output will increase if the torque is increased enough to make the tires rotate. It will increase by the work/time done to rotate the wheels.
> 
> Tom


Tom,

I'd suggest you read Race Car Vehicle Dynamics, which gives an excellent account of vehicle tyre bahavior among other things.

I'd guess that at a hard launch (not smoking them up, just quick) a vehicles tyres are turning at maybe 20-30km/h while the vehicle is stationary, the vehicle obviously rapidly moves to this speed, but you'll find that something like 30% faster tyre speed than road speed is considered a good target for optimum acceleration and from memory the SAE defines that over 50% slip as wheel spin.

The same thing goes for cornering, a wheel usually points somewhere up to 6 or so degrees further into a cornering direction than the vehicle ends up. The end to end ratio of the slip angles is what gives you an understeering, oversteering or neutral car.


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## Qer (May 7, 2008)

Drew said:


> This seems to be an AC vs DC thing that you're getting at Qer,


As Tesseract would've put it, don't be so obtuse.

I've said several times that you have to compare systems, not technologies. You can't generalize AC versus DC since there's too many variables involved.



Drew said:


> A current limit is set by the manufacturer


Which manufacturer? The motor manufacturer?


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## major (Apr 4, 2008)

Bowser330 said:


> Setup#1
> *300ftlbs* 0-2000rpm
> 200fltbs 2000-4000rpm
> 100ftlbs 4000-6000rpm
> ...


Hi There,

View attachment 4468











This is a chart I made for Bowser's examples. Sorry for the quality. Click on it and it gets better. Had to resort to taking a photo and loading it. Frustrating not being able to load an xls chart into the message. Probably simple, but I am unable to figure it out.

Anyway, it is HP vs RPM, Setup#1 is blue and Setup#2 is red. 

Bowser asked which you would pick and why. He didn't specify for what application. I elected to use the 1/4 mile race. It seems pretty popular. Just from his specs it was hard for me to pick. Obviously #2 has 50% more power than #1. But #1 has 50% greater torque up to 1/3rd top speed. So I asked Rich to simulate it. Sorry Bowser. It would have been interesting to see how the vote would have gone.

I was actually surprised when #1 won by about a second. Especially after I had drawn this chart. Rich had adjusted the gear ratios of each to hit 6000 RPM at the finish line. Meaning #2 finishes with twice the HP of #1. So how does #1 win? Pretty obvious that it is due to torque, 50% more up to 1/3rd speed.

Referring back to my crappy chart, this is the format which Drew (and etischer before him) likes to use. They seem to think that the greater area below the curve indicates the "better" setup. Even without counting squares, it is obvious that #2 has the most area by far. Why then does #1 win the race? Perhaps it is the slope of the curve which is important. #1 has the greater initial slope. What is the slope? Rise over run. Or HP over RPM. Let's see, power divided by angular velocity? Isn't that torque?

Also obvious is that #2 has greater power and therefore will have a higher speed. Also it has a greater slope in the top 1/3rd of the range, so will accelerate faster at the higher speeds.

And while we're on the area under the curve. I'm a big fan of units and what they represent. So when you talk area under a power vs angular velocity curve, it is watts times rad/sec. So watts per second. Or take it thru the rolling radius and get watt meters per second. What is a watt? Power is the rate of work. Work is Newton meters. Then power is Newton meters per second. So the area is Newton meters squared/seconds squared. I'm sorry; I just can't grasp the physical quantity this represents.  

Forgive my poor graphics. Hope I got my point across.

major


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## major (Apr 4, 2008)

Trying again.


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## major (Apr 4, 2008)

Drew said:


> Well, you can check the Kostov data yourself if you like, it was sourced from http://kostov-motors.com/files/productattachments/da0012f5e806b95241ea09d19be9abe3_11-192V.pdf which I believe is the manufacturer website.


Yeah, same curve I found. Looks like 71 kW.

major


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## PhantomPholly (Aug 20, 2008)

Bowser330 said:


> Setup#1
> *300ftlbs* 0-2000rpm
> 200fltbs 2000-4000rpm
> 100ftlbs 4000-6000rpm
> ...


The only undiscussed variables are
a) the weight of each motor
b) the transmission to be used

Are those even relevant? Weight could be, and so could the tranmission.

#1 is a bit of a trick, because from 4000-6000rpm it creates less power than from 2000-4000rpm. In any case it never develops as much power (max hp @ 200*4000/5252 = 152) as motor #2 (200*6000/5252 = 228).

Given a scenario where both motors weigh the same, the only way #1 could win would be a transmission which prevents exceeding 2000rpm.

Given a "perfect CVT," motor # 1 would optimally spin at 4000rpm and motor #2 would spin at 6000rpm (leaving motor #1 in the dust).


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## major (Apr 4, 2008)

Drew said:


> During launch, as with all times that a wheel is driven a tyre will actually be operating at a different speed to the road, its this speed difference which allows you to generate traction,


That's a new one on me. How does this work for vehicles like locomotives, tracked vehicles and elevators? 

I'm not a drag racer, but have watched a few. From what I can tell, the guys that go quicker are not the guys spinning wheels. Most times, if they break traction, they just let up and give up the run.

Regards,

major


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## major (Apr 4, 2008)

PhantomPholly said:


> The only undiscussed variables are
> a) the weight of each motor
> b) the transmission to be used
> 
> ...


Phantom,

Both were direct drive (single ratio) with the ratios as indicated by ZX-E in post #25. #1 was 5.2:1 and #2 was 4.45:1. Vehicles were equal mass. All other things equal. From my understanding, each was at 6000 RPM at the 1/4 mile marker.

Regards,

major


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## Tesseract (Sep 27, 2008)

major said:


> Yeah, same curve I found. Looks like 71 kW.
> 
> major


yeah, well, I crammed 1200A at 145V (actual at the motor) through a Kostov 9"/144V for about 0.5 seconds. That counts as peak power, no?

(That's 174kW for the math impaired...)


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## Sunking (Aug 10, 2009)

As the ole saying goes:

Torque wins races, HP sales cars on the showroom floor.


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## major (Apr 4, 2008)

Tesseract said:


> yeah, well, I crammed 1200A at 145V (actual at the motor) through a Kostov 9"/144V for about 0.5 seconds. That counts as peak power, no?


Hi Tesseract,

It counts, but for what? How many races are won in 0.5 seconds? Maybe it was the all time peak ever for that motor 

Do you think torque is relevant?

Glad to see you pop in on my second thread.

major


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## Tesseract (Sep 27, 2008)

major said:


> ... How many races are won in 0.5 seconds? Maybe it was the all time peak ever for that motor


Yep - power is only relevant when considered with time.

Sadly, we'll never know if that was the all time peak for the Kostov 9", since it was blown up not too long after by subjecting it to ~100kW for ~10 seconds and we are not inclined to buy another. The Kostov 11" (192V) motor we also have might be fun to barbecue, but zorching motors is an expensive hobby so we are trying to behave ourselves for the time being.




major said:


> Do you think torque is relevant?


I think torque is very relevant to overall performance, whether one is drag racing the 1/4 mile or simply accelerating from a stoplight. Indeed, the amount of torque available at 0 rpm is the _only_ relevant factor in determining how quickly you can accelerate from a stop. Unless the top speed of said motor is, say, 100 rpm, in which case you better have a multi-speed transmission like those found in semi tractor-trailers to accommodate so narrow a power band.

Of course, once wind resistance starts to play a role in determining how much power is required then even having a semi's transmission won't allow you to go faster than the max output from your motor can sustain.

BTW, Drew, one of the reasons the calculus was invented was to solve such seemingly contradictory problems in physics like this one.


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## tomofreno (Mar 3, 2009)

Hi Drew,



> a vehicles tyres are turning at maybe 20-30km/h while the vehicle is stationary


 Yes, that is the tire shear I mentioned: 


> As they move, they pull the rest of the vehicle with them unless they slip against the wheel or shear.


 Although I admit it is a greater magnitude than I suspected. 

Tom


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## tomofreno (Mar 3, 2009)

> Here is my understanding of how a DC motor works; A current limit is set by the manufacturer which limits the total torque produced, leading to a linearly increasing power curve, at some point the motor reaches a voltage where something(back EMF?) limits the amount of current which can go in, at this point the power drops off rapidly and at some point near there a mechanical limit is reached whereby the motor will fling its self apart if speed is exceeded, correct?
> 
> I, quite frankly, don't understand how an AC motor works, but from what I've seen it effectively reproduces the initial curve on a DC motor and then seems to reach a limitation which I guess is related to temperature or something else which simply means that it can't deal with any more power, at which point it slowly generates less and less power until it reaches the (higher due to different rotor construction) RPM limit at which it must be shut down or it flings its self to pieces.


 Both AC and DC motor/controller combinations commonly used in electric vehicles have quite similar shaped torque-rpm and power-rpm curves. The DC motor/controller torque at lower rpm is generally limited by maximum current the controller can deliver, so the maximum available torque is constant at lower rpm and power increases linearly with rpm, until back emf (electromotive force, which is voltage - see Faraday's law) of the rotor on the field starts decreasing the input voltage and current through the field, and torque and hence power, decrease, in general agreement with what you said. The AC motors I am familiar with, AC24, AC24LS, AC31, AC50, all have similar curves to this, in that torque is constant at lower rpm then falls off at higher rpm. So again, power increases linearly with rpm where torque is constant, then decreases. The AC24 and AC24LS power versus rpm curves from Azure Dynamics display this behavior. Eric says that power remains constant above base speed (rpm at which torque starts to decrease) for AC motors, but I see no evidence of this in the above mentioned graphs.

If you compare an Advanced Energy 8" series DC motor/Curtis 1221C 74xx controller with the AC50/Curtis 1238-7501 controller for example, a vehicle with the AC50/1238 controller will get to 60 mph quicker than it will with the DC motor/controller. If you compare the same two motors, but use a Curtis 1231C-77xx controller (2 minute current = 500A), the DC motor/controller will do better. And of course if you use a Soliton controller with 1000A the vehicle with DC motor/Soliton will leave the same vehicle with AC50/1238 controller in the dust.

The rpm at which a fall off in torque occurs for either AC and DC motors is of course affected by maximum voltage the controller can apply, which is limited by the battery pack voltage, as has also been said here, by Qer I think. This gives more voltage to overcome the back emf.

If your figure of merit for performance is time from zero to sixty mph, then I agree the motor/controller with the highest integrated power output over this range of vehicle speed and associated motor rpm will win, since that combination will do the most work/unit time. Equivalently, the motor/controller combination with the highest integrated torque over that motor rpm range will win, since the product of torque and motor shaft angular velocity is work/unit time. Power is just the product of some constants, rpm, and torque, so either can be used.

Tom


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## tomofreno (Mar 3, 2009)

Drew,

In your post #40 you are comparing a Wye connected AC24LS with 312V pack with the Kostov at 71V. The low pack voltage severely limits the performance of the Kostov, since torque falls off at relatively low motor rpm due to back emf.

Tom


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## DavidDymaxion (Dec 1, 2008)

Just a math nitpick here. Generally, in real life, the vehicle with the fatter torque curve or power curve accelerates better. Mathematically, it turns out it depends on the shape of the torque curve as well as the area under the curve. Quick gedanken proof: Suppose you make 0 torque (or zero power) from 0 to 100 rpm, and have infinite torque from 100 rpm to redline. You'll sit there forever trying to hit 60 mph, because the car never starts moving, despite a very fat torque curve. A car with a modest 100 ft*lbs of torque will easily beat it. It turns out, for a given area under the torque curve, the fastest accelerating shape for the torque curve is flat (talking v vs. t).

Torque isn't too bad to prove, as you are linear in t and v (ignoring air resistance). When you talk power vs. rpm, then it gets trickier as now v scales with sqrt(t) for a given power.

Throw in air resistance, Peukert's losses, and decreasing battery power, and now things get really tricky! It's a problem I've been meaning to solve. I want to go as fast as I can (highest top speed) given a fixed amount of battery energy. Should I draw constant current? Should I gradually ramp up the current? Should the current step up for each gear? It'll be a fun problem to work out.


tomofreno said:


> ... If your figure of merit for performance is time from zero to sixty mph, then I agree the motor/controller with the highest integrated power output over this range of vehicle speed and associated motor rpm will win, since that combination will do the most work/unit time. Equivalently, the motor/controller combination with the highest integrated torque over that motor rpm range will win, since the product of torque and motor shaft angular velocity is work/unit time. Power is just the product of some constants, rpm, and torque, so either can be used.
> 
> Tom


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## Bowser330 (Jun 15, 2008)

major said:


> Phantom,
> 
> Both were direct drive (single ratio) with the ratios as indicated by ZX-E in post #25. #1 was 5.2:1 and #2 was 4.45:1. Vehicles were equal mass. All other things equal. From my understanding, each was at 6000 RPM at the 1/4 mile marker.
> 
> ...


I attached a zipped excel file which I was using to see the Torque HP MPH Gear Ratio and "Multiplied Torque"

You can see clearly how the 4.45 ratio makes setup#2 weak..

I then changed both to have 5.2:1 and you can see the multiplied torque improves, and the overall average multiplied torque is almost the same for both setups. Then again, since setup#1 gets more torque at the start, ahh well..I dont know if this helps anyone...but there it is...


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## Drew (Jul 26, 2009)

Qer said:


> As Tesseract would've put it, don't be so obtuse.
> 
> I've said several times that you have to compare systems, not technologies. You can't generalize AC versus DC since there's too many variables involved.
> 
> ...


Yup, the motor manufacturer, if I were looking to compare motors used outside of their design parameters then it wouldn't make much sense using the OEM graph for the AC24LS either 



major said:


> Hi There,
> 
> View attachment 4468
> 
> ...


Actually, this is a bit of a funny one, because I sort of think of this as proving my point, as, essentially the first motor configuration is a crude representation of constant power, and the main difference between the motors is that one produces constant torque and the other varies slope (dimensionless). BTW the thing that I was getting at in the first place is the point that you appear to be using to justify the torque arguement, the first motor produces power more consistently, which is what does it, which you could argue is related to torque, but certainly not the actual torque value, just the relative values of torque across the curve...

Let me give you a motor number 3 and four to compare then, motor number 3 can be a motor with a much higher rev limit, say double, or 12000RPM, and the same torque as motor 2, motor number 4 can be something much like a low speed diesel, with 15000lbft of torque for a grand total 160RPM. Obviously motor 4 has much more torque, but they both have the same power and the same linearity of torque, neither wins.



major said:


> That's a new one on me. How does this work for vehicles like locomotives, tracked vehicles and elevators?
> 
> I'm not a drag racer, but have watched a few. From what I can tell, the guys that go quicker are not the guys spinning wheels. Most times, if they break traction, they just let up and give up the run.
> 
> ...


Again, I'm not talking about people spinning up the wheels, I'm talking about the tread distorting in such a way as to allow the wheel to rotate faster than the road beneath it, I'm sure you can now see why I referred to it as squirm, as slip immediately makes people imagine great smokey burnouts.

Unfortunately I can't find any graphs for linear slip vs traction data, but i did find a photo which might assist a bit with understanding how the tyres tend to behave under high tangential loads.










The tyre is of course doing the same thing right across the tread engagement area, not just at the sidewall.

Its very similar to slip angle, which I can find the odd diagram of;










Load in both cases is proportional to tread distortion, as per this graph;












Oh, and BTW I might have... er... a little bit converted the 71 of what I assumed was Horsepower into Kilowatts  it does still go to prove my point though, which is that an approximation of constant power is very useful in reducing the need for gearing.


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## major (Apr 4, 2008)

Drew said:


> Again, I'm not talking about people spinning up the wheels, I'm talking about the tread distorting in such a way as to allow the wheel to rotate faster than the road beneath it, I'm sure you can now see why I referred to it as squirm, as slip immediately makes people imagine great smokey burnouts.


Hi Drew,

Yeah, but isn't this just like adding a spring into the system? What you get, you give back. Net energy from it is zero. And if, as I think you imply, squirm is responsible for launching a wheeled vehicle from rest, how do vehicles with steel wheels get started?

Regards,

major


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## Qer (May 7, 2008)

major said:


> And if, as I think you imply, squirm is responsible for launching a wheeled vehicle from rest, how do vehicles with steel wheels get started?


Like this one?










Not much "squirm" there...


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## Tesseract (Sep 27, 2008)

Drew said:


> ... it does still go to prove my point though, which is that an approximation of constant power is very useful in reducing the need for gearing.


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## major (Apr 4, 2008)

Drew said:


> Let me give you a motor number 3 and four to compare then, motor number 3 can be a motor with a much higher rev limit, say double, or 12000RPM, and the same torque as motor 2, motor number 4 can be something much like a low speed diesel, with 15000lbft of torque for a grand total 160RPM. Obviously motor 4 has much more torque, but they both have the same power and the same linearity of torque, neither wins.


Yes, and I never argued differently. My point, way back at the start of this discussion was that you need to look at the shape of the motor's torque curve when selecting a motor to suit you needs, not just the power (either rated or peak). Your example of #3 and #4 have the same shape torque curve, so as you say, neither wins. You just need to gear them differently.

However not all motors have the same shape torque curve. One which produces a higher wheel torque after your gearing at the lower speed range will accelerate faster off the line. So if your metric is the 1/4 mile ET or 0-60 time, that motor would outperform the other even though it is power rated the same.

And thinking back to you tire shear or squirm, isn't that caused by the wheel torque? And isn't wheel torque just the motor torque times the ratio? So how is torque irrelevant? Beats me 

And why not look at deceleration? Don't the brakes on the vehicle apply a force to the rotor or drum at a radius from the axis of rotation producing a torque opposing rotation? Is that torque also irrelevant? Like if the vehicle is at rest on an incline. The brake holds it there due to the force at that radius imparting a torque on the wheel which prevents rotation. You have torque and it is useful, but no motion (RPM) and no power. 

Regards,

major


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## Drew (Jul 26, 2009)

major said:


> Hi Drew,
> 
> Yeah, but isn't this just like adding a spring into the system? What you get, you give back. Net energy from it is zero. And if, as I think you imply, squirm is responsible for launching a wheeled vehicle from rest, how do vehicles with steel wheels get started?
> 
> ...


Nope, thats rolling resistance, its higher when you're driving harder, not a constant.

TBH I've got no idea how steel or other wheels would behave, I've not worked on any cars with steel wheels, trains or the like.



major said:


> Yes, and I never argued differently. My point, way back at the start of this discussion was that you need to look at the shape of the motor's torque curve when selecting a motor to suit you needs, not just the power (either rated or peak). Your example of #3 and #4 have the same shape torque curve, so as you say, neither wins. You just need to gear them differently.
> 
> However not all motors have the same shape torque curve. One which produces a higher wheel torque after your gearing at the lower speed range will accelerate faster off the line. So if your metric is the 1/4 mile ET or 0-60 time, that motor would outperform the other even though it is power rated the same.
> 
> ...


That essentially harks back to what I was saying before, the distribution of power is important, the specific numbers can be compared, whereas torque can only ever be meaningfully compared to its self for a given motor and is completely irrelevant when considered for anything other than gearbox strength, you've just said as much above. You're only interested in how much torque is produced in what areas of the torque curve, which is essentially looking at the power distribution. I'm not trying to be obtuse, but the whole point of what I was saying is that torque is irrelevant right? So taking the torque numbers from two motors and comparing them means absolutely nothing, the only thing that is relevant when comparing two motors is power.

As I've pointed out before, you're not interested in wheel torque either, you're interested in tractive effort which is dependent on another factor as well, wheel diameter, so making wheel torque also irrelevant when establishing performance characteristics for a vehicle.

We're talking about the specific application of torque to vehicle drivetrains right? Brakes are a different kettle of fish, they behave in a torque/power limited fashion, in much the same way as I understand a lithium ion battery charger to work, you can only achieve the lowest of the design torque or design power. Thats a passable approximation of their behaviour anyway


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## major (Apr 4, 2008)

Drew said:


> but the whole point of what I was saying is that torque is irrelevant right?


Drew,

No, I disagree. Could you not do everything and never consider the power? Use only speed and torque? If you know the speed and torque, you know everything, so you never need to use power at all. If you only know the power speed profile, calculations get real cumbersome at very low speed. 

And yes. I realize that wheels come in different diameters. But for the sake of comparison, like Rich's simulation, they were kept equal for the two cases. 

Regards,

major


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## major (Apr 4, 2008)

Drew said:


> We're talking about the specific application of *torque* to vehicle drivetrains right?


Ahh, so torque is relevant 

I think brakes are located in the driveline. And isn't the power plant sometimes used for braking as well? Either engine compression braking or with motors, regenerative braking. It is just the direction of the torque vector, positive for motoring and negative for braking.

Regards,

major


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## Drew (Jul 26, 2009)

major said:


> Drew,
> 
> No, I disagree. Could you not do everything and never consider the power? Use only speed and torque? If you know the speed and torque, you know everything, so you never need to use power at all. If you only know the power speed profile, calculations get real cumbersome at very low speed.
> 
> ...


But again, you're not talking about torque as an external or stand alone value, you're only ever discussing torque relative to other torques in a different speed range on the same motor, so its useless for selecting powertrain etc. Its only useful for details of powertrain design. As I said before, ICE vehicles can't run below a few thousand RPM and so can't produce a start torque, so you just use a clutch, CVT or torque converter to deal with that. You're using torque as an internal unit, rather than as something which you can use as a basis of comparison, which is exactly the point I was making. I guess in theory you could use torque the same way I'm using power and map tractive effort vs torque curve rather than power limit vs power, but it isn't as simple or neat... I guess at the end of the day I like neat and it also strikes me again that using that methodology still means that you're using a characteristic which isn't useful for comparison so you have to do extra work...



major said:


> Ahh, so torque is relevant
> 
> I think brakes are located in the driveline. And isn't the power plant sometimes used for braking as well? Either engine compression braking or with motors, regenerative braking. It is just the direction of the torque vector, positive for motoring and negative for braking.
> 
> ...


I think I've just fallen into the trap of using convenient words as well  Brakes operate on a tractive effort/power limit,,, better?


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## Qer (May 7, 2008)

Drew said:


> As I said before, ICE vehicles can't run below a few thousand RPM and so can't produce a start torque, so you just use a clutch, CVT or torque converter to deal with that.


Which takes power (rpm * torque) in but by allowing slip extracts the rpm from the power which leaves ... torque!


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## major (Apr 4, 2008)

Drew said:


> ...ICE vehicles can't run below a few thousand RPM and so can't produce a start torque,...


Bingo! And electric motors do. Dc motors produce their maximum torque down there. So using the methods common to ICE calculations become cumbersome trying to properly evaluate the high torque launch you get with an electric motor. 

I've been an electric motor head all my life, so it seems. Always used torque for everything. It is intuitive to me. These silly power vs speed curves from the ICE world give me fits. It is just your perspective. But torque is relevant to me 

Regards,

major


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## Drew (Jul 26, 2009)

Qer said:


> Which takes power (rpm * torque) in but by allowing slip extracts the rpm from the power which leaves ... torque!


Actually it transfers a given torque at reduced RPM, making it a power.

Let me put it this way, how much performance do you think you could get out of a motor which produced 400Nm of torque? How much performance do you think you could get out of a motor which produced 100kW of power? Only one of those is a useful measure or means anything in the real world.


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## Drew (Jul 26, 2009)

major said:


> Bingo! And electric motors do. Dc motors produce their maximum torque down there. So using the methods common to ICE calculations become cumbersome trying to properly evaluate the high torque launch you get with an electric motor.
> 
> I've been an electric motor head all my life, so it seems. Always used torque for everything. It is intuitive to me. These silly power vs speed curves from the ICE world give me fits. It is just your perspective. But torque is relevant to me
> 
> ...


I understand that torque can be useful for some calcs, but you can't do anything with it without having a complete set of information on the driveline and motor characteristics, wheres power is effectively a standalone unit... I guess you're right, horses for courses


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## Qer (May 7, 2008)

Drew said:


> Actually it transfers a given torque at reduced RPM, making it a power.


My, you must've skipped more classes than I did, and I was horrible at being present.

http://en.wikipedia.org/wiki/Acceleration
http://en.wikipedia.org/wiki/Torque

This is science! Science is pretty well proven by now and if you look carefully there's not a word about squirm or even power. Acceleration is defined as force divided by mass and thus torque is VERY relevant, period.

Go do your home work.


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## ZX-E (Aug 31, 2009)

Drew said:


> I understand that torque can be useful for some calcs, but you can't do anything with it without having a complete set of information on the driveline and motor characteristics, wheres power is effectively a standalone unit... I guess you're right, horses for courses



How is power useful without a complete set of information about the drivetrain and motor characteristics? If you don't know the gearing and the RPM you're getting your power at, it's just as useful as knowing where the torque peaks without knowing the RPM it occurs at.


If I was using your own logic, I would disagree that power is a standalone unit. In fact I would even say it's "irrelevant". You still need to know the weight of the car, transmission characteristics, drag coefficients and frontal area to calculate how the car will react to the motor's power. Right?






-Rich


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## major (Apr 4, 2008)

Rich,

Do you use power in any of the calculations for your simulation program?

Regards,

major


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## ZX-E (Aug 31, 2009)

Not once. I don't have a variable that is power anywhere in the program, but I do use torque at different RPMs. Which in effect is power, just not multiplied out.



-Rich


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## ZX-E (Aug 31, 2009)

I think what Drew is trying to say is that _peak_ power, can give you an idea of the performance of a vehicle and the force that propels it. While _peak_ torque alone, without a RPM really is useless in that sense. He just hasn't been very specific. 

Saying torque is irrelevant was definitely not a great way to explain it.




-Rich


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## Overlander23 (Jun 15, 2009)

I think I know what Drew is saying... But really it's a pedantic, semantic argument. 

What I think Drew is saying is that Torque BY ITSELF doesn't give you enough information to be useful. Power, or hp, does because it, by definition, incorporates multiple concepts (including torque).

Torque without time, for instance, doesn't tell you anything.

But that's not really how we use the info in the real world. I don't think anyone considers the torque rating of a motor in a vacuum, bereft of context. There's always some reasonable assumption. No one really assumes that a motor with 400nm of torque only provides that figure at a discrete moment in time in a completely useless part of the rev band.


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## ZX-E (Aug 31, 2009)

Overlander23 said:


> Torque without time, for instance, doesn't tell you anything.


You mean RPM, not time right? And even if you didn't know the RPM, torque can still tell you useful data. For example: the force applied to the gears or the drive shaft.


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## Overlander23 (Jun 15, 2009)

ZX-E said:


> You mean RPM, not time right? And even if you didn't know the RPM, torque can still tell you useful data. For example: the force applied to the gears or the drive shaft.


Well, yes... RPM by nature involves time... and you can't have revolutions without time. 

But you're right, I was going to say that a torque figure will give you an idea of whether a component can handle an amount of stress.


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## ZX-E (Aug 31, 2009)

Overlander23 said:


> Well, yes... RPM by nature involves time... and you can't have revolutions without time.


Just admit it. You meant RPM. Saying you can't have a torque without time is ambiguous.


I've been on this thread for way too long


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## Drew (Jul 26, 2009)

ZX-E said:


> How is power useful without a complete set of information about the drivetrain and motor characteristics? If you don't know the gearing and the RPM you're getting your power at, it's just as useful as knowing where the torque peaks without knowing the RPM it occurs at.
> 
> 
> If I was using your own logic, I would disagree that power is a standalone unit. In fact I would even say it's "irrelevant". You still need to know the weight of the car, transmission characteristics, drag coefficients and frontal area to calculate how the car will react to the motor's power. Right?
> ...


Not really, all you need are the power and the mass over the drive axle, vehicle mass, frontal area, Cd, Crr and some CoG information to be able to determine pretty much any aspect of a vehicles performance.

What I'm saying is that as an absolute value torque has nothing to do with a vehicles acceleration unless you know a large amount of information about powertrain etc. If you consider the instantaneous example of a vehicle accelerating, if you know power at the motor, disregarding losses you know the tractive effort, if you know the engine torque and nothing about the transmission you know nothing.



Overlander23 said:


> I think I know what Drew is saying... But really it's a pedantic, semantic argument.
> 
> What I think Drew is saying is that Torque BY ITSELF doesn't give you enough information to be useful. Power, or hp, does because it, by definition, incorporates multiple concepts (including torque).
> 
> ...


Sort of, I'm trying to say that torque is not a good basis of comparison between motors, a lot of people seem to be focusing more and more on torque, especially on ICEs, but I've seen it pop up on the forum a bit as well... either way, what I mean is that torque is only relevant when viewed with references to other values of the same motor. Its not a valid number to compare with any other motors torque.



ZX-E said:


> I think what Drew is trying to say is that _peak_ power, can give you an idea of the performance of a vehicle and the force that propels it. While _peak_ torque alone, without a RPM really is useless in that sense. He just hasn't been very specific.
> 
> Saying torque is irrelevant was definitely not a great way to explain it.
> 
> ...


What I'm saying is that all performance calcs that I can think of are much simpler when calculated based on power rather than torque.

Here are some good examples;

Maximum tractive effort is obviously a force, but the easiest way to translate it is by calculating it as a power.

Maximum tractive effort is governed by the mu of the tyres times the vertical weight on the axle.

If you multiply that by your velocity in m/s then you end up with a power, which you can then match to your power curve, which gives you a maximum power that you can use.

If you then calculate your drag, as 1/2 Rho V ^3 times area times Cd then and add your total vehicle mass times Crr times V then you get your minimum power requirement.

All you need to do then is select a wheel diameter and to slot in peak power and first and final gear ratios fall out.

Obviously the ideal spread of gears after that point puts them pretty evenly between the two as a common fraction and you've pretty much designed your power train...

Maybe you could explain how to do that without using power?

Of course once you've designed your powertrain then it becomes meaningful to view in terms of torque as well, but during initial powertrain design I certainly wouldn't bother with it.


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## Drew (Jul 26, 2009)

ZX-E said:


> You mean RPM, not time right? And even if you didn't know the RPM, torque can still tell you useful data. For example: the force applied to the gears or the drive shaft.


I did mention this in an earlier post, that torque is, of course, important for calculating belt or chain tension, hertzian stress on gears and the like.


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## Overlander23 (Jun 15, 2009)

ZX-E said:


> Just admit it. You meant RPM. Saying you can't have a torque without time is ambiguous.
> 
> 
> I've been on this thread for way too long



Yeah, but that's Drew's point... I believe. You CAN have torque without time because it can give you a bending force value. Torque, by definition, does not involve time, it is a bending moment. 

But without time (rpm) you can't figure out power. So... in a very pedantic way, torque, by itself, is irrelevant except in figure out component strength. Even Drew has admitted this.

For example, imagine you're quoted singular torque figures for two different motors. One is capable of producing 100Nm of torque, the other 500Nm. That's all the information you're given. What does that information tell you about the motors other than one has the ability to overwhelm a drivetrain component that can only handle, say, 200Nm of bending force?

My personal opinion is that, that specific an argument is irrelevant with EV discussions because the only reason to compare torque values with motors is with assumptions that involve time/power. And whenever Torque is referred to, it comes with another piece of information, like Torque at a particular rpm, or current. Either way, the information can be traced back to a point of performance on a graph that gives you an idea of a motor's "personality" beyond a singular moment in time.

But when I wrote "time" I meant time because rpm is derived from torque over time. It's not ambiguous to say that in order of complexity, Torque < Time < Rpm < Horsepower.


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## Qer (May 7, 2008)

Drew said:


> Not really, all you need are the power and the mass over the drive axle, vehicle mass, frontal area, Cd, Crr and some CoG information to be able to determine pretty much any aspect of a vehicles performance.
> 
> What I'm saying is that as an absolute value torque has nothing to do with a vehicles acceleration unless you know a large amount of information about powertrain etc. If you consider the instantaneous example of a vehicle accelerating, if you know power at the motor, disregarding losses you know the tractive effort, if you know the engine torque and nothing about the transmission you know nothing.


Acceleration is force divided by mass, force is torque divided by radius. There's no need to know about power to calculate acceleration, or do you claim that Sir Isaac Newton was wrong and that his second law of motion is flawed?

Drag is defined as:










http://en.wikipedia.org/wiki/Drag_(physics)#Drag_at_high_velocity

As you can see power is not part of that equation as well, thus you don't need power to calculate the effect of drag on your acceleration. So in the end you get something like:

a = (F - Fd) / m

Where F is the resulting force from the torque divided by wheel radius.

Power only comes in as a result of actually GETTING somewhere, ie

P = F * v

Power actually don't affect acceleration directly, however if there's a limit on how much power that's available to you (for example a maximum amount of kW from the battery pack) this will affect the acceleration indirectly since force will start to decrease with increasing RPM.

Or do you claim that science is wrong and you're right?


----------



## major (Apr 4, 2008)

Drew said:


> Not really, all you need are the power and the mass over the drive axle, vehicle mass, frontal area, Cd, Crr and some CoG information to be able to determine pretty much any aspect of a vehicles performance.


Hey Drew,

Then why did the 152hp car win the race against the 228HP car in Rich's simulation? re: post#25

Regards,

major


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## major (Apr 4, 2008)

Drew said:


> What I'm saying is that all performance calcs that I can think of are much simpler when calculated based on power rather than torque.
> <snip>
> Maybe you could explain how to do that without using power?


Drew,

Take a look back at post #25. Rich did not use power in any of the calculations. See post #92. And in post #101 Qer shows you again.

Speed and power are consequences of torque. Torque makes the world go around 

Regards,

major


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## Drew (Jul 26, 2009)

major said:


> Hey Drew,
> 
> Then why did the 152hp car win the race against the 228HP car in Rich's simulation? re: post#25
> 
> ...


Its pretty simple, because the first car produced more power earlier, which is why its quarter mile time was achieved at a top speed of 84mph, which is pretty woeful, the other car was doing about 100mph, but had lost out so much by the end that it wasn't in the race. Basically it proves my earlier point about appropriate gearbox selection and traction calcs.

To prove the point I would simply pick the top power and assume that the tesla people took the opertunity to distribute the weight 50/50 by moving batteries around meaning that of the 1250kg of curb mass 625kg is over the rear axle. I'd also assume that its got some reasonable tyres on it so Mu of 1.1 isn't out of the question and that its CoG is pretty low so there won't be much weight transfer. Based on that I get a maximum tractive effort of 6737N, 220bhp is 165kW in real units so first should have been geared for 165000/6737 or 24.5m/s or 88km/h (55mph in the units of the ancients) and it should achieve around .55g acceleration through the entire range... which its obviously not, through poor gear selection it was getting something more like .25g or less and basically demonstrates poor gearing and gearbox selection, nothing else. And BTW that puts it at a 5 second 0-100 approximately.

The other one is a bit more complex, because you can either go for the widest first gear range and gear for the first power peak, or go for best acceleration and gear for top power (185bhp), which will result in a requirement for throttle control or traction control in the first part of the rev range, but isn't a big deal after that. I'm not going to redo the calcs for that one, but I'm sure you can see that what this example really does is demonstrate why man invented multispeed gearboxes, not that torque is relevant.



Qer said:


> Acceleration is force divided by mass, force is torque divided by radius. There's no need to know about power to calculate acceleration, or do you claim that Sir Isaac Newton was wrong and that his second law of motion is flawed?
> 
> Drag is defined as:
> 
> ...


I've done a quick working out to demonstrate how I'd calculate first gear ratio for a car using power above, I was wondering if you'd be so kind as to similarly demonstrate how you'd use the above formula to calculate top speed without reference to power in a car which doesn't yet have a fixed set of transmission ratios (ie every design example)...


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## Qer (May 7, 2008)

Drew said:


> I've done a quick working out to demonstrate how I'd calculate first gear ratio for a car using power above, I was wondering if you'd be so kind as to similarly demonstrate how you'd use the above formula to calculate top speed without reference to power in a car which doesn't yet have a fixed set of transmission ratios (ie every design example)...


I'd rather see that you answered the question. Do you believe that Sir Isaac Newtons theories are obsolete and that you actually know better?


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## major (Apr 4, 2008)

Drew said:


> Its pretty simple, because the first car produced more power earlier, which is why its quarter mile time was achieved at a top speed of 84mph, which is pretty woeful, the other car was doing about 100mph, but had lost out so much by the end that it wasn't in the race.


Drew,

You avoid the point completely. Show me how you explain it with this: 



> Originally Posted by *Drew*
> _Not really, all you need are the power and the mass over the drive axle, vehicle mass, frontal area, Cd, Crr and some CoG information to be able to determine pretty much any aspect of a vehicles performance._


The mass, drive axle, frontal area, Cdd, crr, CoG are all the same. All you have to work with are 152hp and 228hp. Show me the different 1/4 miles with this information as you claim you can do. Please.

Regards,

major


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## 2cycle (Jul 2, 2009)

Drew has hit the nail on the head with the statement "What I'm saying is that as an absolute value torque has nothing to do with a vehicles acceleration unless you know a large amount of information about powertrain etc. If you consider the instantaneous example of a vehicle accelerating, if you know power at the motor, disregarding losses you know the tractive effort, if you know the engine torque and nothing about the transmission you know nothing." 
To argue the point without putting some real world text to it just makes no sense to me. Give some real world examples of what your trying to prove or disprove and both sides may learn some more. I would bet by his (Drew) statements he actually has set up race cars or at least some sort of race vehicle before. To us that build and race stuff his statements make sense. But I can also see where a non builder/gear head can confuse himself with non motorsport electric motor propaganda. My father happens to be an extremely proficient electric motor authority when it comes to driving a large piece of equipment with 2000 hp motors but if he tried building a race vehicle he would have the same thought process road blocks as most non gear heads. It's not that he doesn't understand the formulas it's just the practical end of racing things get lost because he doesn't set up transmisions and is too use to direct driving everything. 
I've tried explaining this to others, just like the lack of performance in the EV drag world thread, that there is more to just having some torque on take off. The best fit for the EV race cars/bikes would be drag racing and they still are working on making that right. I think it's great what Killa cycle can do but I surely think it's just the beginning. It's impressive but not unbelievable. When the top fuel cars hit 100 mph in under 1 second that starts to get close to the unbelievable point.


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## Tesseract (Sep 27, 2008)

This argument is getting awfully pedantic and it isn't really an argument in the first place.

Motor torque is important.
Motor RPM is important.
Total power is important.

To argue that torque is irrelevant is, well, stupid. Lets consider some hypothetical motors that all have the exact same hp rating:

100,000 rpm at 1Nm
5,000 rpm at 20Nm
100 rpm at 1,000Nm

Now, which of those motors do you think would work best in a practical vehicle? The first one would suffer such horrendous losses in the gear train from the crazy amount of reduction required there'd be no point. The third motor would require such heavy gear teeth the transmission would weigh more than the car.

Somewhere along the way you shifted your argument from "torque is irrelevant" to "having constant hp is best"... I disagree with the latter mainly because constant torque provides a constant rate of acceleration which is more fun, if nothing else.

Perhaps next you will tackle the real enigmas of our time: "how many angels can dance on the head of a pin?" and "does centrifugal force really exist?"


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## major (Apr 4, 2008)

2cycle said:


> Drew has hit the nail on the head with the statement "What I'm saying is that as an absolute value torque has nothing to do with a vehicles acceleration unless you know a large amount of information about powertrain etc.


Yes, 2cycle,

But we are designing the drive trains. Or converting ICE cars to electric motors which have defined drive trains. Go back to post#22 (Bowser's example) and post#25 (Rich's analysis). A simple comparison. Equal vehicles. A slight ratio difference to set exit RPM to 6000. Now show me how Drew's method of performance calculation could have predicted #1 would win.

That has been my whole point from the beginning. Electric motor characteristics are widely different than those of the ICE. If you want a valid picture of electric motor driven vehicle performance, particularly at launch, you must consider motor torque. Period.

And for what it's worth, I've done a fair amount of racing, from the engineering and build side, not driving. But this discussion isn't about racing; it is about electric motor application to cars. The 1/4 mile race was just a metric to use which is common. But all EVs must accelerate from rest to be useful to us. And we want that launch to be reasonably fast to keep up with traffic. This is of particular importance when one considers options in the driveline, like direct drive or multispeed transmissions.

Regards,

major


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## Drew (Jul 26, 2009)

Qer said:


> I'd rather see that you answered the question. Do you believe that Sir Isaac Newtons theories are obsolete and that you actually know better?


I know a fair amount about what I'm talking about and newtonian mechanics is only one aspect of it, I'm sure Mr Rayleigh would agree, and so a large number of other people... so... can you calculate the top speed of any of the example vehicle without transmission or wheel information without using power or not?



major said:


> Drew,
> 
> You avoid the point completely. Show me how you explain it with this:
> 
> ...


I most certainly didn't say that I would only use peak horsepower, you need the complete power curve to make any valid calculation. If I were actually doing the work to produce a set of gearbox ratios and I was looking at how many gears are required or the like then what I'd do is simply carry out the calculation above to determine the first gear ratio, carry out a simple drag analysis based on rule of thumb information to calculate final gear ratio, then put in additional ratios as fractions of the current pair so that the shift points were similar in each gear. Usually that gets you to about the right start point, obviously ratios need to be tailored to suit tracks if your racing etc but as a rule of thumb, for a road car thats it.

After carrying out the above then I'd have a basic power curve and a bunch of ratios, I'd work out speed in gear for each gear then divide the relevant point on the power curve by the given velocity for each ratio, which would give me tractive effort. At this point I can do a simple F=ma calc to work out a step by step element process and I'm off, I have a complete basic analysis of the vehicles performance... I'll even include a diagram that I did to compare a few motorbikes for some friends on another forum to demonstrate... keep in mind that these are existing vehicles though;









This Diagram is a representation of the actual tractive effort that can be produced by each of the bikes in each gear, it is of a Ducati 1098, a Suzuki gsxr1000 and a CBR600, all 08 models. From this point its pretty simple to convert those into instantaneous accelerations for all vehicles and from there you simply sum for velocity and you're done, you have your 0-100, if you integrate again, by summing that you end up with distance, which gives you quarter mile, standing kilometer, whatever.



major said:


> Yes, 2cycle,
> 
> But we are designing the drive trains. Or converting ICE cars to electric motors which have defined drive trains. Go back to post#22 (Bowser's example) and post#25 (Rich's analysis). A simple comparison. Equal vehicles. A slight ratio difference to set exit RPM to 6000. Now show me how Drew's method of performance calculation could have predicted #1 would win.
> 
> ...


See above, the maths doesn't change between ICE and electric, the only thing that changes is power source (or in some cases where its burnt).

As I have pointed out numerous times before, as an absolute value, even in a clutchless takeoff on an electric vehicle absolute torque value isn't relevant, as the ratio changes what it means when it hits the road. Case in point is the graph I posted above, where the GSXR1k and the 1098 have pretty similar torques, but wildly different results for gearing.

PS I couldn't help but laugh when I saw that you referred to a Quarter Mile as a Metric


----------



## major (Apr 4, 2008)

I reviewed this thread and I think this is one of the better posts. So I'm reposting it. 



tomofreno said:


> The forces acting on a vehicle to impede its forward motion apply a torque to the wheels. The vehicle moves at constant speed when the torque applied to the wheels from the motor through the drive train is equal to this torque. Call this the required torque. Acceleration from a given vehicle speed is proportional to the difference in this required wheel torque and available wheel torque, where available wheel torque is determined by the drive train and the max torque the motor/controller can deliver at that vehicle speed. This will be determined by the max current the controller can supply at lower motor rpm, and by the pack voltage and back emf at higher motor rpm.
> 
> Power is the product of motor torque and shaft angular velocity. *Torque is the more fundamental parameter*, just as force is the more fundamental parameter in rectilinear motion, where power is the product of force and velocity. Power matters because it describes how much torque can be delivered at a given rpm. A motor/controller that has high torque at low motor rpm but drops off rapidly at higher rpm, will have good acceleration at lower vehicle speeds, but poor at higher speeds. This of course will be affected by gear ratios which determine the mechanical advantage of the motor. I've calculated and graphed required and available wheel torques as a function of vehicle speed for a number of motor/controller combinations, and also plotted available power versus vehicle speed in a spreadsheet referred to as "ev calculator" at electricnevada.org.
> 
> Tom


When Drew, and now 2cycle, talk power, they qualify it with speed. So they are in fact talking torque. 

Well I have to go try to get some more torque out of a motor to make the vehicle go faster. And yeah, that will increase its power . But I'm at the limit on RPM, so what else can I do. Just got to change the sprocket and get some more torque.

See ya,

major


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## major (Apr 4, 2008)

Drew said:


> I most certainly didn't say that I would only use peak horsepower, you need the complete power curve to make any valid calculation.


Oh, so you do use torque then. 

And I don't understand why you keep saying motor torque is irrelevant because we don't know the GR or RR. Of course we need those, and have those. Always have. Look back at my 2nd post reply to you in hppy's thread. I mention doubling the ratio to accommodate the motor which was twice as fast. 



> PS I couldn't help but laugh when I saw that you referred to a Quarter Mile as a Metric


Excuse me. The 402.336 meter race.


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## Qer (May 7, 2008)

Drew said:


> I know a fair amount about what I'm talking about and newtonian mechanics is only one aspect of it, I'm sure Mr Rayleigh would agree, and so a large number of other people...


Yet you have to resort to ... what was it you called it? Squirm?



Drew said:


> so... can you calculate the top speed of any of the example vehicle without transmission or wheel information without using power or not?


I never claimed I could, not without transmission or wheel information. However, I've already pointed at the relevant parts to calculate acceleration from force and how to calculate force from torque without knowing power. I've also pointed at how to calculate the force from drag and when the force from drag and torque are equal you've reached top speed since acceleration is zero.

When you calculate the theoretical top speed of a vehicle from power without having transmission information, how can you be sure the resulting rpm won't tear the motor/engine to pieces or the torque won't snap the transmission?


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## Drew (Jul 26, 2009)

Qer said:


> Yet you have to resort to ... what was it you called it? Squirm?


I called it slip as well, and people jumped to the conclusion which I was trying to avoid, which was that I was referring to wheelspin... you're welcome to come up with a more complete explanation on that one too if you like



> I never claimed I could, not without transmission or wheel information. However, I've already pointed at the relevant parts to calculate acceleration from force and how to calculate force from torque without knowing power. I've also pointed at how to calculate the force from drag and when the force from drag and torque are equal you've reached top speed since acceleration is zero.
> 
> When you calculate the theoretical top speed of a vehicle from power without having transmission information, how can you be sure the resulting rpm won't tear the motor/engine to pieces or the torque won't snap the transmission?


I was under the impression you were implying that torque and power were interchangable, I need to know nothing about the transmission to predict the top speed of a vehicle and select gearing based on that, same the other way, its the only way you can realistically select ratios for a vehicles gearing is to use the methods I've outlined. Or take a guess... I guess...

As I've pointed out numerous times before, to design gearbox internals and work out stresses you need torque, but not for anything else, just the power curve.


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## Drew (Jul 26, 2009)

major said:


> Oh, so you do use torque then.
> 
> And I don't understand why you keep saying motor torque is irrelevant because we don't know the GR or RR. Of course we need those, and have those. Always have. Look back at my 2nd post reply to you in hppy's thread. I mention doubling the ratio to accommodate the motor which was twice as fast.


But thats what I'm talking about, you can't just pluck a ratio out of the air, you need to select it based on one or another performance criteria, so you need to do calculations rather than guess... as I said regarding the drag race example, some pretty simple calcs demonstrated quite completely that running a single ratio car for the constant torque example gave it under half its potential performance off the line, demonstrating that it actually needed a 2 or more speed gearbox, otherwise its just a waste. This is the sort of thing that I'm talking about as being important to have assessed up front.

I can't see how you're advocating just picking a random number and then, if there are problems later then applying a band aid, switching to trial and error or eventually deciding that its time to do the calcs. 



> Excuse me. The 402.336 meter race.


I didn't mean to criticise, I just found it humorously ironic


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## major (Apr 4, 2008)

Drew said:


> I can't see how you're advocating just picking a random number and then, if there are problems later then applying a band aid, switching to trial and error or eventually deciding that its time to do the calcs.


Drew,

I am not advocating anything of the sort. Let's keep the context here. What do most of these guys do? They get a donor car (or cycle), rip out the ICE and plunk in an electric motor. And how do they choose which motor to use? What I'm trying to do is to help them (and you) select one which has a good chance to meet their goals. 

The proper way to go about it is to calculate (or at least estimate) the load torque curve and evaluate the motor torque curve, and then do a simulation such as Rich did.



> I didn't mean to criticise, I just found it humorously ironic


Yeah, some of my best humor is unintentional.

Regards,

major


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## Primoglass (Sep 30, 2009)

I am looking for or will build a transaxle 5 speed for a mid engine Porsche 906, looking at a pretty tall gear set. 

Has anyone in this forum addressed electronic clutch and shift controllers to make the most efficient use of the torque band from 2000-8000 RPM of 240 NM, and optimize the control for regenerative braking functions?
I am contemplating using a water cooled poly phase AC traction motor.


Im starting the project in a porsche 912 platform to workout the bugs while I start the titainium frame assembly for the carbon fiber replica on the 906 platform. Ultra capacitors will be part of the mix in both cars.


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## major (Apr 4, 2008)

Primoglass said:


> Has anyone in this forum addressed electronic clutch and shift controllers to make the most efficient use of the torque band from 2000-8000 RPM of 240 NM,


Hey,

If you convert that to watts, maybe Drew can help.  Just kidding. Kind of. He does claim his method is good at determining the best gears.

Seriously, welcome to the forum, Primo. You picked a bitch of a thread to get started. I haven't heard of any here doing a tranny like that. I did do an auto downshift with a 2-speed electro hydraulic wet clutch way back when. We'd ramp down motor torque, shift and ramp torque back up in like 200 milliseconds. Driver never had to lift. Same on the up shift, but driver insisted on control there, so it was a push button on the steering wheel. Worked nice. No clutch pedal and a no lift shift.

Ambitious project. Good luck.

major


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## a4111 (Feb 25, 2009)

Drew said:


> As I've pointed out numerous times before, to design gearbox internals and work out stresses you need torque, but not for anything else, just the power curve.


The power curve, power vs velocity, shows the same information as the torque curve, torque vs RPM. There are only 2 independent variables here, and both are important in motor performance. Power is torque*rpm, and rpm gives you velocity through the gear ratios and wheel diameters.

Torque and RPM are more useful (and intuitive) to look at in judging motor performance and designing geartrains because it shows you where the motor is producing torque. You can get the same information from your power vs velocity graph, but you have do some calculations to get there.


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## azdeltawye (Dec 30, 2008)

Drew said:


> ...
> As I have pointed out numerous times before, as an absolute value, even in a clutchless takeoff on an electric vehicle absolute torque value isn't relevant ...


If torque isn't relevant then why do EV drag racers with siamese motor configurations bother switching from series to parallel? If they had to work within the confines of limited pack voltage then it would be easier to just leave the motors wired in parallel. 

When the two motors are wired in series the effective output torque at the shaft is doubled as compared to wiring the motors in parallel. The net power output is the same in either case. 

Torque matters. Just ask anyone who got smoked by the White Zombie...


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## 2cycle (Jul 2, 2009)

azdeltawye said:


> If torque isn't relevant then why do EV drag racers with siamese motor configurations bother switching from series to parallel? If they had to work within the confines of limited pack voltage then it would be easier to just leave the motors wired in parallel.
> 
> When the two motors are wired in series the effective output torque at the shaft is doubled as compared to wiring the motors in parallel. The net power output is the same in either case.
> 
> Torque matters. Just ask anyone who got smoked by the White Zombie...


Tess just gave a great example of why, because just giving the 1000 Nm of torque sounds great, right, just not when you get the rest of the story which is the 100 rpm part. Which is my point from before, by giving the rpm it now gives you some important info for transmission design. 
The part that Tesseract still isn't getting is which power curves to compare. He said all motors making the same hp but have different torque. That's not really the point of this topic. The route of the question should be understood more like this; Take a 2000 rpm motor which makes 500 lb/ft of torque and 190 hp at or really close to 2000 rpm and compete in the same weight vehicle with the optimal transmission for the powerband of each motor and compare with a 200 lb/ft torque @ 6000 rpm and 304 hp @8000 rpm. Now this is more like what is being compared from what I have seen. Basically a slow rpm and torquey DC motor vs a high rpm AC motor. Just looking at these numbers the untrained builder would be tempted to choose the higher torque motor because his EV friends told him torque is all you need to know. While the experienced builder who knows a thing or two about transmissions would choose the higher hp set up because he knows he can manipulate torque output with the tranny but there's no changing hp with a tranny and 114 hp less makes a big difference.


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## ZX-E (Aug 31, 2009)

2cycle said:


> Tess just gave a great example of why, because just giving the 1000 Nm of torque sounds great, right, just not when you get the rest of the story which is the 100 rpm part. Which is my point from before, by giving the rpm it now gives you some important info for transmission design.
> The part that Tesseract still isn't getting is which power curves to compare. He said all motors making the same hp but have different torque. That's not really the point of this topic. The route of the question should be understood more like this; Take a 2000 rpm motor which makes 500 lb/ft of torque and 190 hp at or really close to 2000 rpm and compete in the same weight vehicle with the optimal transmission for the powerband of each motor and compare with a 200 lb/ft torque @ 6000 rpm and 304 hp @8000 rpm. Now this is more like what is being compared from what I have seen. Basically a slow rpm and torquey DC motor vs a high rpm AC motor. Just looking at these numbers the untrained builder would be tempted to choose the higher torque motor because his EV friends told him torque is all you need to know. While the experienced builder who knows a thing or two about transmissions would choose the higher hp set up because he knows he can manipulate torque output with the tranny but there's no changing hp with a tranny and 114 hp less makes a big difference.



Nobody on this thread ever said torque is all that matters. There really is no arguing with you and Drew. Have you guys actually read anybody's replies and tried to understand what they are saying?


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## 2cycle (Jul 2, 2009)

I think the thread genuinely started because of a real question of wether a torque figure by itself without any supporting data is really valuable, and my answer would be no. When you state torque AND hp now your telling me some more useful info like an rpm range which can now be useful in determining transmission details. Of coarse torque is needed for movement, nobody is denying that either. 
Part of me thinks that somebody was just trying to get EV motor heads in a tissy because they knew it would stir the pot by wording it like that. When Drew gets hammered by you guys for trying to explain a different point of view it just shows how close minded some can be. MOST everybody may well be on the same page but this thread was aimed at those with some questions still.


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## Tesseract (Sep 27, 2008)

2cycle said:


> I think the thread genuinely started because of a real question of wether a torque figure by itself without any supporting data is really valuable, and my answer would be no.


Anyone with a clue's answer would be no. Torque without any rotational movement is useless.

The point us "EV motor heads" are trying to make is that electric motors have some very compelling advantages over IC engines because they can deliver tremendous torque starting at 0 rpm. Drew then veered off into an exceptionally pedantic argument that no matter what the torque is, at 0 rpm there is no net hp delivered - which is correct, but totally sidesteps one of the main reasons the calculus was invented.

That is all we have been saying: having a high amount of torque available at 0 rpm is useful and relevant. It means no need to slip the clutch to accelerate from a stop, for one thing, and less need for multiple gear ratios in the transmission.


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## 2cycle (Jul 2, 2009)

I'm following you. Given an already known good rpm range motor it would be of great help to have a better starting torque. Just so I can chew on some real world figures can you give an actual torque v RPM plot that you believe to be desirable or better yet can you/ do you have any info about any known drag race vehicles that have their performance and motor output documented, such as white zombie.


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## major (Apr 4, 2008)

2cycle said:


> Just so I can chew on some real world figures can you give an actual torque v RPM plot that you believe to be desirable or better yet can you/ do you have any info about any known drag race vehicles that have their performance and motor output documented, such as white zombie.


Take a look at http://www.diyelectriccar.com/forum...pinto-16474p3.html?highlight=crazyhorse+pinto post #27, I think. Actual dyno charts of the car. Mike uses two Warp 9 motors. His build is (or was) well documented and you should be able to find out what you want to know. If not, just ask Mike. At one time he also had a number of performance plots from his truck posted using different set-ups for comparison.

White Zombie was also well documented on John's site. plasmaboyracing.com, I think.


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## major (Apr 4, 2008)

2cycle said:


> I think the thread genuinely started because of a real question of wether a torque figure by itself without any supporting data is really valuable,


No, I started this thread to refute the claim by Drew that torque is irrelevant. See post #1. I never said "torque by itself".

Let's keep the story straight.

Thanks,

major


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## ZX-E (Aug 31, 2009)

The Tesla's torque curve is quite desirable because it has over 200 ft-lbs of torque over 6000 rpm and still has 50 ft-lbs at 14000 rpm. Meaning it can use a high gear ratio (8.27:1) and have enough force to reach about 130 mph at 14000 rpm. In fact, Tesla says the torque peaks at 275 ft-lbs! Which isn't actually represented in this graph. I don't use a power vs rpm graph in my simulations because I need to find the torque to determine the force propelling the vehicle at different rpms. Why not just sidestep power vs rpm and use torque vs rpm? torque vs rpm in my opinion, has a more intuitive and useful plot.










Notice how the gasoline engine is even described using a torque curve.

To me, _Peak _power is useful to describe the performance of a vehicle. If you just want one term to describe performance, sure just go ahead and use power. But remember you can do exactly the same thing with torque and rpm.




Here's the original quote from Drew in the original thread:


Drew said:


> the point is that torque is totally irrelivant unless you're designing components in a driveline, but its certainly not relevant when talking about engine power outputs or vehicle performance.


He never said torque is useless without a rpm. He just said it was useless unless you're designing components in a driveline.....



2cycle said:


> I think the thread genuinely started because of a real question of wether a torque figure by itself without any supporting data is really valuable, and my answer would be no.


So that's really not why the thread was started. Atleast I couldn't tell by the way Drew worded his reply.


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## Drew (Jul 26, 2009)

major said:


> I reviewed this thread and I think this is one of the better posts. So I'm reposting it.
> 
> 
> 
> ...


Actually no, I'm not, I'm using RPM as a reference, nothing more, what I was getting at is that if I had a bin of references for a vehicle labelled point 1 to point x then I could produce as much data about the vehicles performance, I just can't produce a gearing chart. The same can't be said for torque.

And by changing a sprocket or whatever you're actually not manipulating power, you're simply manipulating where its produced, which is exactly my point. You can calculate a reference and hit a target using my system, its simple and its effective and allows you to design a transmission system without having trial and error and the associated time and cost impost ruining your day... not only that, what about the physical limitations of the thing? If you chuck something together then decide it doesn't work you've got two choices, try and change ratios or live with it, if there are no useful ratios available for your chosen components then you're stuck and you either have to replace whole subsystems or live with it.



azdeltawye said:


> If torque isn't relevant then why do EV drag racers with siamese motor configurations bother switching from series to parallel? If they had to work within the confines of limited pack voltage then it would be easier to just leave the motors wired in parallel.
> 
> When the two motors are wired in series the effective output torque at the shaft is doubled as compared to wiring the motors in parallel. The net power output is the same in either case.
> 
> Torque matters. Just ask anyone who got smoked by the White Zombie...


The serial to parallel thing is just about producing a more constant level of power AFAIK, it avoids them having to use a gearbox. It would be interesting to see how close they are to the limit of traction with a direct drive transmission though  On a drag strip you'd want logged data though, rather than approximations, so I guess I'm not going to get to see it 




ZX-E said:


> The Tesla's torque curve is quite desirable because it has over 200 ft-lbs of torque over 6000 rpm and still has 50 ft-lbs at 14000 rpm. Meaning it can use a high gear ratio (8.27:1) and have enough force to reach about 130 mph at 14000 rpm. In fact Tesla says the torque peaks at 275 ft-lbs which isn't actually represented in this graph. I don't use a power vs rpm graph in my simulations because I need to find the torque to determine the force propelling the vehicle at different rpms. Why not just sidestep power vs rpm and use torque vs rpm? torque vs rpm in my opinion, has a more intuitive and useful plot.
> 
> 
> 
> ...


They're using a torque curve because 1. You think its important; and 2. It compares more favourably than power.

As I said previously, the reason that I find power more useful is because of its diirect translation to tractive effort, you just divide it by velocity in m/s which gives you force in N... simple really, far more simple than doing the three or four calcs to bring torque at the motor back to torque at the wheel, even when you have decided on a set of drive ratios, and even then you can't carry out simple calculations to determine ideal ratios because you don't know when critical points pop up, like peak power.


----------



## ZX-E (Aug 31, 2009)

Drew said:


> They're using a torque curve because 1. You think its important; and 2. It compares more favourably than power.
> 
> As I said previously, the reason that I find power more useful is because of its diirect translation to tractive effort, you just divide it by velocity in m/s which gives you force in N... simple really, far more simple than doing the three or four calcs to bring torque at the motor back to torque at the wheel, even when you have decided on a set of drive ratios, and even then you can't carry out simple calculations to determine ideal ratios because you don't know when critical points pop up, like peak power.


I can find the peak power using a torque vs rpm graph. And no I don't think torque is more important than power. I really do think they're equally important.


Anyway, Drew, If power is easier to use for _you, _for _your _calculations: where you don't know the gear ratios and wheel size. That's fine. I can see what you're getting at. But you still can find power from motor torque and rpm. I thought Overlander23 put it really well.



Overlander23 said:


> And whenever Torque is referred to, it comes with another piece of information, like Torque at a particular rpm, or current. Either way, the information can be traced back to a point of performance on a graph that gives you an idea of a motor's "personality" beyond a singular moment in time.



Here's the definition of irrelevant:
[adjective] having no bearing on or connection with the subject at issue;

Just because torque needs another piece of information to find power doesn't mean it's irrelevant to vehicle performance. In fact, how can you even say that power is relevant and torque isn't, when one is derived from the other...


Really, I think a lot of this has resulted from poor communication. You do have some really good points. I should have said this earlier because I think a lot of the confusion and arguments are coming from that word choice.

Who knows, I could be wrong


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## Drew (Jul 26, 2009)

ZX-E said:


> Just because torque needs another piece of information to find power doesn't mean it's irrelevant to vehicle performance. In fact, how can you even say that power is relevant and torque isn't, when one is derived from the other...


Thats essentially what I've been getting at, torque is a derivative value, which is meaningless unless its coupled with the information its been derived with respect to in any task except for design application.

I don't know if you've looked through the thread that started this, but essentially what started it was that I proposed an AC motor of a similar power and cost to the DC motor that the guy was looking at using. My argument was that it had a more consistent power output, I was decried because DC motors of a similar size can produce more torque. I pointed out that more torque was completely irrelevant in a system which produced the same power. I also pointed out that AC motors typically have significantly more overrun past peak power which makes them more amenable to direct drive.

In the context of the conversation we were comparing motors, but in the wider context I also believe it to be the case for the reasons I've outlined in this thread.


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## Qer (May 7, 2008)

Drew said:


> My argument was that it had a more consistent power output, I was decried because DC motors of a similar size can produce more torque. I pointed out that more torque was completely irrelevant in a system which produced the same power. I also pointed out that AC motors typically have significantly more overrun past peak power which makes them more amenable to direct drive.


No, you got a lot of protests because your conclusions simply aren't right. You have admitted you actually don't quite understand how an AC motor works and you have proven verbally that your understanding of a DC motor is more or less lacking as well.

Wether a motor is suitable for direct drive or not has very little to do with if it's AC or DC.


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## ZX-E (Aug 31, 2009)

Well I think we can come to an agreement that it is relevant simply because it is a derivative.


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## Drew (Jul 26, 2009)

Qer said:


> No, you got a lot of protests because your conclusions simply aren't right. You have admitted you actually don't quite understand how an AC motor works and you have proven verbally that your understanding of a DC motor is more or less lacking as well.
> 
> Wether a motor is suitable for direct drive or not has very little to do with if it's AC or DC.


Which part? That series wound DC motors don't seem to have much overrun past peak power or that AC motors do?

I wasn't under the impression that I needed that much understanding of the electrical workings of the motor to simply read a dyno graph.



ZX-E said:


> Well I think we can come to an agreement that it is relevant simply because it is a derivative.


Sure, as a derivative value torque is an important part of the process of determining performance of vehicles.


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## Qer (May 7, 2008)

drew said:


> which part? That series wound dc motors don't seem to have much overrun past peak power or that ac motors do?
> 
> I wasn't under the impression that i needed that much understanding of the electrical workings of the motor to simply read a dyno graph.


q.e.d. ...


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## major (Apr 4, 2008)

Drew said:


> And by changing a sprocket or whatever you're actually not manipulating power, you're simply manipulating where its produced,


Yeah, Drew, I know that. And we can change the ratio to suit. For top speed, it is a pretty simple choice, right? Gear to match top speed with peak power.

In this case, all I have to work with is the motor, actually the controller. How can I get more power? More motor torque. That simple. 

Regards,

major


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## Drew (Jul 26, 2009)

major said:


> Yeah, Drew, I know that. And we can change the ratio to suit. For top speed, it is a pretty simple choice, right? Gear to match top speed with peak power.
> 
> In this case, all I have to work with is the motor, actually the controller. How can I get more power? More motor torque. That simple.
> 
> ...


If you're in a situation where you can't put down more than 50% of limit tractive effort then I'd be seriously sceptical about whether is a sensible idea running direct drive at all... I'd be looking for something like at least a 3 speed transmission at a guess. If you're desperate to make up time in a drag race and you're that down on power then I'd say buying a sequential shifter or one of the drag transmissions that are available would be a very sensible investment.

For road use it would be even more important to just buy a gearbox because you're not only compromising performance, you're risking voiding your warranty and blowing up your motor to avoid having to play with a gear stick.


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## PhantomPholly (Aug 20, 2008)

I'm rather amused that this thread has gone on this long.

Acceleration = force / mass. For a wheeled vehicle, this means that accelleration is strictly a factor of how much horsepower is applied to the pavement. This imposes only three limits:

- How much horsepower is the motor generating at any given moment that can be directed to the wheels
- How much power can be applied to the pavement without losing traction
- How much time is spent shifting (zero accelleration) during the time spent accelerating

The available horsepower depends upon your ability to keep the motor turning within the rpm band of it's maximum output. Thus, if the motor outputs a wide range of horsepower over the range of rpms at which it can turn, accelleration will be a factor of how well the transmission can maintain optimum rpm range without interruption of the power for events such as shifting.

Thus, given a "Perfect CVT" the motor with the maximum horsepower beats the motor with the maximum torque every time, provided the maximum horsepower can actually be absorbed by the wheels. A perfect example of this is an airplane with a constant speed prop (pitch varies to "absorb" all available power). Although maximum torque is available at, say, 2400 rpm, maximum hp occurs at 2700 (most Lycosaurus engines). 2700 rpm always beats 2400.

In the real world with transmissions on the drag strip the equation changes. Too many gears and you spend too much time shifting.

However, torque is still not what defines the winner - it is available power across a sufficiently wide rpm band to "keep the power on" rather than shifting (zero accelleration).


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## major (Apr 4, 2008)

Drew said:


> If you're desperate to make up time in a drag race....


Drew,

Everything in life isn't a drag race. This particular application is not. I probably should not have even mentioned it. But if you think you might be able to help us select the best gear, please send me your contact info in a PM. 

major


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## major (Apr 4, 2008)

PhantomPholly said:


> However, torque is still not what defines the winner - it is available power across a sufficiently wide rpm band to "keep the power on" rather than shifting (zero accelleration).


Phantom,

How do explain the example in post #25? No shifting to confuse the issue. An apples to apples comparison of two motors with different torque curves. And the low power guy (setup#1) won the race. Setup#2 clearly had more power across the RPM band. I think torque did define the winner. 

Regards,

major


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## tomofreno (Mar 3, 2009)

Drew, 

Is there a detailed description of your analysis method anywhere? I am interested in seeing what I can learn from it. I haven't found details in this thread - maybe in another one?

Tom


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## tomofreno (Mar 3, 2009)

ZX-E,

Do you describe how you do your calculations somewhere (didn't see it on the thread you started)? Do you fit an equation to the manufacturer's torque-speed curves? This would give torque as a function of motor rpm, but of course the latter is a function of vehicle speed and gear ratio. Would be interesting to see how you approach this.

Tom


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## Drew (Jul 26, 2009)

tomofreno said:


> Drew,
> 
> Is there a detailed description of your analysis method anywhere? I am interested in seeing what I can learn from it. I haven't found details in this thread - maybe in another one?
> 
> Tom


There are details scattered throughout the thread, how much detail of which particular part are you interested in?

The basics are just in dimensional analysis, because power is Nm/sec it means that you can just use a force (N) like tractive effort, and a velocity (m/sec) to work out a power, so you can determine all sorts of interesting information, like idealised maximum performance by simply using the point of peak power to work out how fast the vehicle would accelerate using an idealised CVT and that sort of thing. It might not seem particularly relevant, but the neat thing about it is that it can give you a lot of insight into what you're gaining or losing by having more or less gears in your transmission.


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## tomofreno (Mar 3, 2009)

> by simply using the point of peak power


 What do you mean by the POINT of peak power, ie with respect to what - motor rpm, vehicle velocity...?


> ...it can give you a lot of insight into what you're gaining or losing by having more or less gears in your transmission.


 Would you give an example of this? It would likely give me insight into what you are talking about.

Thanks,
Tom


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## tomofreno (Mar 3, 2009)

Drew,

Is the basic idea to work off a power versus motor rpm curve, and choose gearing to maximize the power to the wheels over the range of motor rpm used?

Tom


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## PhantomPholly (Aug 20, 2008)

major said:


> Phantom,
> 
> How do explain the example in post #25? No shifting to confuse the issue. An apples to apples comparison of two motors with different torque curves. And the low power guy (setup#1) won the race. Setup#2 clearly had more power across the RPM band. I think torque did define the winner.
> 
> ...


The example turns out the way it does BECAUSE there is no shifting. Torque is irrelevant except in terms of total power and gear ratio because changing your total gear ratio can multiply or divide torque. Thus given your straight line torque motor, for some given gear ratio the wheels would hold at low speed but break loose at higher rpms (because of the higher total power being generated).

In the example there is an assumption the wheels never slip. Because you never shift gears, you never actually spend any relevant amount of time at an rpm where hp=maxium. Thus, you need to calculate the instantaneous hp with respect to time (this is "fundamental" calculus, but it's been 30 years since I did this kind of equation and don't recall the details). So, if you broke the duration into smaller and smaller rectangles and calculate the "limit as the size of the rectangle approaches zero" you end up with a formula which will predict your speed at any point in time.










The total net accelleration is the area under the curve described by the sum of instantaneous horsepower over time, also known as the "integral." Total cumulative Energy over time minus cumulative drag (which increases as we accellerate) defines our final speed.

Interestingly, if you changed the gear ratio slightly for one of those one-gear cars you might find the results are different. Having one achieve full rpm earlier than the 1/4 mile finish line may limit top speed but result in an earlier finish due to more rapid accelleration earlier on.

In any event, having some sort of gearing to keep the motors in the 4000-6000rpm range would clearly change the outcome - the winner would be the one with the most horsepower provided that shift time (zero accelleration) was small with respect to total duration.


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## ZX-E (Aug 31, 2009)

tomofreno said:


> What do you mean by the POINT of peak power, ie with respect to what - motor rpm, vehicle velocity...?
> Would you give an example of this? It would likely give me insight into what you are talking about.


 He’s referring to the rpm the motor reaches its peak power. 




tomofreno said:


> ZX-E,
> Do you describe how you do your calculations somewhere (didn't see it on the thread you started)? Do you fit an equation to the manufacturer's torque-speed curves? This would give torque as a function of motor rpm, but of course the latter is a function of vehicle speed and gear ratio. Would be interesting to see how you approach this.
> Tom


That's exactly what I do: use the torque vs. rpm graph and create a polynomial with a n/2 order to fit the plot. Where n is the number of points you input. There are probably better methods to fit an equation to the torque curve, but it has worked really well for me so far. 


Here's the function I use to find the tractive force. 


Torque = polyval(LineFitCoeff,RPM);
DriveForce = Efficiency*Torque/(WheelCircumference/(2*pi*12))*GearRatio;


Everything is tied into rpm and the gear ratio. Sure you can find the top speed using P=Fv when the rolling resistance and air drag are equal to the tractive force. Then find successive points to shift to maintain that peak power. But you would still need to use rpm, torque and gear ratios to find the shift points eventually. Few people would actually find your method practical because for one, most people aren't designing a transmission, they're already using one. And two, even if you were designing a transmission, sure you could use P=Fv to find one gear ratio where you can reach a maximum velocity, but would you actually want to use that as a shift point unless you’re designing a performance vehicle? 

The maximum tractive force at different velocities isn’t very useful to most of us DIYers. You could design around it if you had a perfect transmission like you said yourself, but not much else. I think there has been a lack of communication because all you’re really trying to say is that ideally you would want to design a transmission around peak power, but you haven’t been very clear. 

Drew what's really funny to me is how you say your method is useful because you can ignore the drivetrain. Then you say your method is useful to find the ideal power band to design a drivetrain, where you would _need_ to find the gear ratios anyway. Can you post some of your calculations? I know my method works without power, and I've shown evidence in a working program. I even added an option so the vehicle can shift. It’s pretty easy to find peak power and design the transmission around it using my program. Simply because power and torque completely related to each other and relevant. You only showed us a mess of confusing thread posts where I think few if any people have actually figured out what you’re trying to say. It could be because your arguments have been slowly evolving over time. Here’s evidence:



Drew said:


> you can determine all sorts of interesting information, like idealised maximum performance by simply using the point of peak power to work out how fast the vehicle would accelerate using an idealised CVT and that sort of thing. It might not seem particularly relevant, but the neat thing about it is that it can give you a lot of insight into what you're gaining or losing by having more or less gears in your transmission.


 Now you’re talking about ideal transmissions; and it makes perfect sense why you would only need power to estimate performance. But remember what your original argument was? That torque is irrelevant. Not less important when you have a perfect cvt. When you say torque is completely irrelevant, and power is, you’re saying torque isn’t related to power. Obviously, torque is related to power in every situation we’ve mentioned. So let’s just clear that up.



Drew said:


> This is what I'm getting at, the motor torque is completely irrelevant, the only thing that is important is the distribution of power, obviously a motor with more torque at low RPM relative to its higher RPM behaviour will produce somethign more like constant power, but while we were talking about torque there we weren't using absolute terms, we were comparing it to its self, so its a dimensionless ratio, not a torque. My basic point is and was that the numbers for torque are irrelevant. People obsess over it, but the only important thing is the amount of power which the engine produces at a set RPM. You might argue that this is still a torque, but because its tied to an RPM its actually power.


 


Drew said:


> You might notice that I didn't actually mention torque in there at all, this is because torque is absolutely meaningless.


 Power is the only thing that’s important to _you_ when you're designing a transmission! That’s fine . Most people have a transmission already or want to go direct drive. I think that’s what people are getting caught up on.


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## major (Apr 4, 2008)

PhantomPholly said:


> The example turns out the way it does BECAUSE there is no shifting.


Phantom,

You don't answer my question. You make excuses.

1.) It was an example to compare two motors having different characteristics. Not intended to be an exercise in optimizing ET by adding a shifting gearbox.

2.) A direct drive example was pertinent to the discussion because it all started when I answered this question from Drew: 



Drew said:


> Major,
> ......if I wanted a direct drive solution then I'd have to accept less performance for the same rated output... is this correct?


3.) The quickest electric drag racers all use direct drive, like John, Mike, Bill and Dennis.

I did ask Rich to run the example and set the GR to get an exit speed of 6000 RPM. I thought that would make a fair comparison and be close to optimal. If you can use your calculus and figure better ratios, please do. And supply the simulations, or maybe Rich will be kind enough to run those for us.

Regards,

major


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## Batterypoweredtoad (Feb 5, 2008)

Is enough information out there to run a sim with White Zombie as it sits in all of its direct drive goodness Vs. all the same specs but adding a powerglide. (2/1 first gear, 1/1 second, maybe 10% added driveline loss)?


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## ZX-E (Aug 31, 2009)

Well it is true that you can accelerate faster and reach higher top speeds with a transmission. 

Although, when you're doing 0-60 in seconds like the white zombie. In some cases less than a second, e.g. killacycle, you really don't need one. Shifting would be difficult and really only useable when you've reached high speeds. It also takes up potential battery space and adds weight. Not to mention the transmission would have to be quite large to handle the torque.


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## ZX-E (Aug 31, 2009)

Batterypoweredtoad said:


> Is enough information out there to run a sim with White Zombie as it sits in all of its direct drive goodness Vs. all the same specs but adding a powerglide. (2/1 first gear, 1/1 second, maybe 10% added driveline loss)?



Great idea! Sounds fun. Is this relevant to this thread though? We've gotten far off topic, maybe we should make a new thread or use mine.


I'll run it this week. Help me find the specs


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## Batterypoweredtoad (Feb 5, 2008)

Rich, can you throw a link for your thread up again. The last one was several pages ago so some may have missed it.


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## Batterypoweredtoad (Feb 5, 2008)

A powerglide can be 18" long and handle whatever power you want to throw at for a reasonably priced build. I guess the question in this case is if the Zombie is on the brink of traction the entire run, and if not, can some gearbox torque multiplication make it faster.


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## ZX-E (Aug 31, 2009)

http://www.diyelectriccar.com/forums/showthread.php?t=36920


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## Drew (Jul 26, 2009)

ZX-E said:


> He’s referring to the rpm the motor reaches its peak power.
> 
> 
> 
> ...


Unfortunately quite the opposite, my job roles of recent have moved away from this type of thing and its a bit rusty 

I'll put up a spreadsheet a bit later, unfortunately I generally just hack around in excel and don't bother too much about collecting up sheets.


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## PhantomPholly (Aug 20, 2008)

major said:


> Phantom,
> 
> You don't answer my question. You make excuses.


I cannot answer the questions locked in your mind, and it is impolite to blame others for your own failure to communicate. My response was keeping to the topic of the thread - "whether Torque is relevant or irrelevant." If you are seeking a better formula to optimize the 1/4 mile race for a given motor, you should have said so explicitly.

The example provided showed that the sum of instantaneous power over a given distance at a given gear ratio was greater for one motor than the other, but did nothing to illustrate whether torque was the defining element. It is not, because it tells you nothing absent rpm (and thus power).

A better example to explain why torque by itself is irrelevant would have been to describe two motors, A and B.

A generates 200 ft/lbs of torque between 0 and 6000 rpm
B generates 100 ft/lbs of torque between 0 and 12000 rpm.

Using the "Torque defines performance theroy" you would predict that A would beat B in a drag race - and you would be correct if the gearing were the same. However, if geared 2:1 for B and 1:1 for A the result would be identical (presuming no losses, or equivalent losses, in the respective drive trains). Note that this example uses no shiftable transmission. Thus, torque means nothing absent a value for power.

For predicting performance, the given example might be perfectly modeled by the polynomial function described by another poster with inputs for mass and gear ratio, given that the function is somewhat linear (at least in discrete linear blocks). I don't know that for a fact, but it sounds reasonable. However, for a more complex power curve function you would need to take the derivative and then map it against different gear ratios to find out which would end up the fastest. As I said, 30 years after that college course I don't remember how to do that myself.

One other consideration for those seeking to maximize 1/4 mile speed: 

Provided the gear ratio does not allow the wheels to "break free and spin," you may find that a slightly lower gear ratio which peaks in speed before the end of the 1/4 mile might provide a better time. This is what NASA does with rockets - accelerate like crazy and then coast. This is because distance = rate * time, so the less time you spend moving slow the greater your total distance traveled will be in a given amount of time. Just be sure you have an overspeed limiter!


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## PhantomPholly (Aug 20, 2008)

ZX-E said:


> http://www.diyelectriccar.com/forums/showthread.php?t=36920


Interesting app.

Do you think you could use it to experiment with predicting 1/4 mile times if you gear down just a little and reach peak speed before the finish? It would be interesting to see if that could make a meaningful difference in the final time.


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## DavidDymaxion (Dec 1, 2008)

Don't forget most of the successful direct drive cars use 2 motors, or an AC setup. The 2nd motor is bigger and weighs more than a transmission. For AC, the controller is huge and takes a lot of space; I think the AC Propulsion AC controller weighs 70 pounds, too.

Berube is the only guy I know doing well with just one DC motor direct drive, but he uses huge GE 13 inch motors.


ZX-E said:


> Well it is true that you can accelerate faster and reach higher top speeds with a transmission.
> 
> Although, when you're doing 0-60 in seconds like the white zombie. In some cases less than a second, e.g. killacycle, you really don't need one. Shifting would be difficult and really only useable when you've reached high speeds. It also takes up potential battery space and adds weight. Not to mention the transmission would have to be quite large to handle the torque.


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## major (Apr 4, 2008)

PhantomPholly said:


> I cannot answer the questions locked in your mind, and it is impolite to blame others for your own failure to communicate.


Phantom,

First off, I apologize if I came off as impolite. Was not my intention.

I have tried very hard to communicate clearly and give the context of why I started this thread. See post #1. But very few, if any of us can claim perfect communication skills.

The question is not locked in my head. It is the title of this thread. Is torque relevant? I have never said it is the only relevant parameter. Yet Drew has said it is irrelevant.

I have never argued that gears are unimportant in manipulating torque. And do not understand why so many here dwell on that fact. The gears also change RPM, don't they? So what? What I am concerned with is the power plant. The electric motor. Is the torque characteristic profile with regard to RPM relevant? And the example clearly shows that it is.

Do you see that now?

major


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## PhantomPholly (Aug 20, 2008)

major said:


> Phantom,
> 
> First off, I apologize if I came off as impolite. Was not my intention.


Thanks - as a person who routinely suffers from hoof-in-mouth I am acutely aware that forums are the perfect media for imperfect communication...





> I have tried very hard to communicate clearly and give the context of why I started this thread. See post #1. But very few, if any of us can claim perfect communication skills.
> 
> The question is not locked in my head. It is the title of this thread. Is torque relevant? I have never said it is the only relevant parameter. Yet Drew has said it is irrelevant.


I have had some difficulties understanding it, too. What, for example, is the horsepower of a 300 ft/lb motor at zero rpm? Zero, of course, be cause until it moves torque * rpm = 0. But then how does the car accellerate from zero? Torque IS a Force as applied to the wheel. but (using a silly example) if you gear a a 1/2 amp motor to 1,000,000:1 then that motor might "beat" a 1,000 amp motor geared at 1:1 "off the blocks," because torque is multiplied or divided by gear ratio. Still, I feel confident that the 1,000 amp motor will win in the 1/4 mile.



> I have never argued that gears are unimportant in manipulating torque. And do not understand why so many here dwell on that fact. The gears also change RPM, don't they? So what? What I am concerned with is the power plant. The electric motor. Is the torque characteristic profile with regard to RPM relevant? And the example clearly shows that it is.
> 
> Do you see that now?


We may be saying the same thing differently. I'm saying that the torque number is only important in as much as it, together with rpm, tells you how much total horsepower is being delivered. You are saying that the torque curve gives an indication of power being delivered - which it does. Given two motors with identical rpm limits (0-6000 in the example) comparing the torque at any point on their power curve tells you which one is making more power.

Both arguments are correct - we win!


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## major (Apr 4, 2008)

PhantomPholly said:


> I'm saying that the torque number is only important in as much as it, together with rpm, tells you how much total horsepower is being delivered.


You can figure the power if you want to, but it is not necessay to get the vehicle performance.



major said:


> Rich,
> 
> Do you use power in any of the calculations for your simulation program?





ZX-E said:


> Not once. I don't have a variable that is power anywhere in the program, but I do use torque at different RPMs. Which in effect is power, just not multiplied out.
> -Rich


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## PhantomPholly (Aug 20, 2008)

major said:


> You can figure the power if you want to, but it is not necessay to get the vehicle performance.
> 
> _
> 
> ...


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## ZX-E (Aug 31, 2009)

Well like I said. I didn't actually multiply them together and use power. I refer to a torque at a certain rpm on the torque vs rpm plot and use that to find tractive force. But that's beside the point.

I think it's pretty clear that torque is relevant whenever power is relevant simply because it's a derivative. Sure power is more useful than torque without a rpm. But it doesn't mean that torque isn't useful or irrelevant. I think most of us really are on the same page; although, we've all had some poor communication in the thread. Oh well! I learned a few things and updated my matlab program because of it.


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## major (Apr 4, 2008)

PhantomPholly said:


> So, he is using torque * rpm, which is power. PotAto, potAHto...


Exactly my point all along. So when Drew says "torque is irrelevant", but uses power at speed, it smells fishy.

And when you consider output at zero speed, which the ICE guys don't have to worry about I guess, the calculations get cumbersome. The electric motors used in EVs have maximum torque at zero speed. So enter the calculus.

And as you were saying, that is like taking smaller and smaller increments. So using power and speed to figure output at one millisecond after launch, you're looking at something like picohorsepower/revolution per century. Isn't it a lot easier to just use pound feet?

I guess we have beaten this to death. Thanks to everybody that contributed.

Regards,

major


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## bazou (Sep 11, 2009)

major said:


> The above is *Setup#2*.
> 
> 
> 
> ...



Hi Major,

I politely disagree with your analysis. We have to remember that Setup2 has more HP at *peak*, but that setup 1 has more HP at lower RPM. Please see the attached graph for the HP curve of both motors. 

Having only one gear and forcing the car to finish the race at it's top RPM defintiely must hurt that car. 

I'm curious what the optimal results would be for a setup with multiple gears allowing 'setup2' to reach it's top hp faster... Or maybe just one gear, but that would allow the 'setup2' car to reach 6000 rpm at mid-race and keep a constant speed from there..

*the only result we can generalize here is 'on a very short race with only one gear and with the rule of finishing the race at top rpm , having power in the lower rpm will win over having power in the higher rpm.*


Rich, I'm curious to try some stuff.. would you mind sharing your matlab code?


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## ZX-E (Aug 31, 2009)

bazou said:


> Hi Major,
> 
> I politely disagree with your analysis. We have to remember that Setup2 has more HP at *peak*, but that setup 1 has more HP at lower RPM. Please see the attached graph for the HP curve of both motors.
> 
> ...


His entire point is that you could also say having higher _torque_ at a low rpm tells you exactly the same thing. Torque is relevant. Nobody said you don't want to design around peak power.

I should be able to make a .exe soon. Post on this thread if you want me to run any simulations in the mean time.
http://www.diyelectriccar.com/forums...ad.php?t=36920


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## major (Apr 4, 2008)

Hi bazou,



bazou said:


> Hi Major,
> 
> I politely disagree with your analysis.


Great, join the club. Boring when everyone agrees with me 



> We have to remember that Setup2 has more HP at *peak*, but that setup 1 has more HP at lower RPM.


Yes, I mention that in post #23.



> Please see the attached graph for the HP curve of both motors.


Looks the same as mine in post #61,62. Except a better quality job pasting it in. Please tell me how you do that 



> Having only one gear and forcing the car to finish the race at it's top RPM defintiely must hurt that car.


It was a comparative example. Both vehicles had only one gear. I address that in post #148.



> I'm curious what the optimal results would be for a setup with multiple gears allowing 'setup2' to reach it's top hp faster...


Again, this thread was not about multispeed transmissions. But what the H. Use that way if you want.



> Or maybe just one gear, but that would allow the 'setup2' car to reach 6000 rpm at mid-race and keep a constant speed from there..


Now this I am curious to know. When I asked Rich to run the example Bowser posted up, I asked him to set the GR so exit speeds would be 6000 RPM which seemed to be indicated as a maximum RPM for Bowser's example set-ups. Rich set the GR so 6000 was obtained at 1/4 mile. I think this yields the fastest ET for each, but I'm not sure. Let's see. And if it isn't optimum, adjust to optimum for both.

*



the only result we can generalize here is 'on a very short race with only one gear and with the rule of finishing the race at top rpm , having power in the lower rpm will win over having power in the higher rpm.

Click to expand...

*Yes, exactly. But, in my opinion, it was a fair comparison with a common platform in a common type race which also indicates acceleration capabilities for daily drivers. Everybody doesn't have to drive that fast, but we all accelerate from standstill and drive down the street. 

*



having power in the lower rpm

Click to expand...

* is just another way of saying *torque.* My point for drawing that plot back in post 61 was to show these guys that insist that area under the power curve means everything that a little extra torque in the right place can be useful. I keep being told torque is irrelevant. But clearly, the curve for #2 has greater area than #1, yet #1 wins. And I say the example was about as fair a comparison as it could be. Equal cars, equal conditions.

And I thought it was over 

major


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## bazou (Sep 11, 2009)

major said:


> Hi bazou,
> 
> [...]
> major


Wow, very documented reply  Sorry for bringing that thread, I have to admit I only skimmed the later posts.. 

Iguess I just have some (probably unjustified) hate toward torque... I mean, what can a torque curve tell you that a HP curve wont? Why even bother?

For the copy-pasting, all I did was copy-waste from excel to MsPaint, then upload as an attachment, nothing fancy.


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## major (Apr 4, 2008)

bazou said:


> Iguess I just have some (probably unjustified) hate toward torque... I mean, what can a torque curve tell you that a HP curve wont? Why even bother?


bazou,

Look at the curve in post #128. The Hp curve tells you nothing about performance at zero RPM. And it is cumbersome at very low RPM. But the torque curve shows everything you need to know. Including HP. All you have to do multiply torque and RPM to get HP at any RPM. The ICE guys don't worry about it because their engines don't make any torque at zero RPM. See that black line on there?

Another thing useful about the torque curve is that torque is the actual load on the motor. So using a torque curve, if you know the load (torque) you can tell for sure all the other parameters, such as RPM, power, current, efficiency, etc. However if you use power as a load for a power curve, there will be two points (except at peak power). So you can't be sure which you're at. If you are at a load of 150 kW on the blue curve, you could be either at 205 lb.ft., 5150 RPM or 80 lb.ft., 12,000 RPM.* Torque curves are a lot clearer for me.

*Values from the curve. I know they don't exactly yield 150 kW.

Regards,

major


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## major (Apr 4, 2008)

bazou said:


> Rich, I'm curious to try some stuff.. would you mind sharing your matlab code?


If you guys get to running calculations on that example, I am real curious to know which one used the most energy to go 1/4 mile. My bet is that #2 (the loser) used more energy.

major


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## bazou (Sep 11, 2009)

major said:


> If you guys get to running calculations on that example, I am real curious to know which one used the most energy to go 1/4 mile. My bet is that #2 (the loser) used more energy.
> 
> major


I'm working on an excel sheet that will allow us to try some stuff tonight 

brb


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## bazou (Sep 11, 2009)

Wow, that took longer than expected.

Anyway, the results are in, and they are interesting.


======================
First, let me compare my results with the previous ones :


Previous results :
The car with the step function:
gear ratio 5.2
0-60 in 7.95 seconds
quarter mile in 16.5 @ 84.44 mph

The car with the constant 200 ft-lbs:
gear ratio 4.45
0-60 in 9.95 seconds
quarter mile in 17.3 seconds @ 100.4 mph

Here's what my excel sheet gets. I must have made a mistake somewhere, but I'm definitely not far:
The car with the step function:
gear ratio 5.2
0-60 in *7.5* seconds
quarter mile in 
16,2 @ *85,8* mph

The car with the constant 200 ft-lbs:
gear ratio 4.45
0-60 in 9.9 seconds
quarter mile in 17.3 seconds @ 100.3 mph

Perfect match on the second car, not so perfect on the first car. I didnt calculate derivative: instead I calculated the power output every 1/1000's of second, and assumed it constant for the next 1/1000's of second. I guess that's what was done in Matlab as it doesnt allow derivative either to my knowledge.

======================
Second, knowing that my times arent too messed up, here are the results for the constant 200 ft-lbs car if it has a gear ratio of 5,6:
0-60 in 7.8 seconds 
quarter mile in 16.4 seconds @ 79,7 mph
(quickers times, lower end speed)

Obviously, the high low-speed torque car could be tuned to beat it, but this shows that peaking the RPM before the end of the 400m helps.


Attached: http://ceh.servehttp.com/torque curves.xlsgraphs for the 3 cars. I'll gladly share my excel file if requested. I just can't seem to be able to post it..


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## Drew (Jul 26, 2009)

Drew said:


> Unfortunately quite the opposite, my job roles of recent have moved away from this type of thing and its a bit rusty
> 
> I'll put up a spreadsheet a bit later, unfortunately I generally just hack around in excel and don't bother too much about collecting up sheets.


Whoops, got a bit side tracked today and I'm working tomorrow so I'll give it a crack in a couple of days


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## tomofreno (Mar 3, 2009)

> I think most of us really are on the same page...


 I think so. An approach something like Drew's might go like: Calculate the tractive effort as a function of vehicle speed. From this calculate the required wheel torque and power at the wheels. The required motor shaft power is then simply this required power at the wheels divided by the drive train efficiency. Compare this to a motor shaft power versus motor rpm curve to see what gear ratios will keep the motor running at an rpm that maximizes its shaft power over the range of vehicle speed considered, with the constraint that the maximum tractive effort cannot be exceeded. The latter being defined as the maximum tractive effort that does not exceed the product of the tractive mass and the coefficient of friction between the tires and the road (the normal force), nor damage drive system components. The motor shaft rpm is wheel rpm multiplied by the overall gear ratio. But you want motor rpm to remain at that which gives peak power, so knowing required power at the wheels as a function of vehicle speed, you can write an equation giving gear ratio as a function of vehicle speed which will do so. The required power at the wheels is the product of tractive effort and vehicle speed, v, and v = wr, where w is the wheel angular velocity, so the required wheel power is the product of 60, tractive effort, tire radius, drive train efficiency, and motor rpm, divided by the product of 2pi, and gear ratio. The product of the second two parameters is the required wheel torque. The required gear ratio is the product of 60, tire radius, drive train efficiency, and motor rpm divided by the product of 2pi, and vehicle speed. For motor rpm fixed at the value which gives maximum motor shaft power, gear ratio decreases linearly with vehicle speed. This gives some insight into a good sequence of gear ratios to use. 

Now of course the motor rpm will have to start from zero, so applying the maximum tractive effort or high power at the wheels at low motor rpm will require very large available wheel torque, since tractive effort is this divided by the tire radius, and wheel power is the product of this and w, which is small near the start. Qer and major will be quick to point out this can be obtained well with a series dc motor, high current controller, and sufficient Ah battery pack. But of course the Tesla shows it can also be obtained with an AC motor/controller. John Wayland uses two motors to obtain this high torque, and it goes on and on…

You might say what matters is how much motor torque you have at a given motor rpm, but then that's shaft power. As you've said, how can one parameter be important and the other not when power is the product of motor torque, shaft rpm, and some constants? For me David's comment on torque profile, torque versus rpm, being pertinent was most informative. His extreme case gedanken experiment illustrates this clearly, but of course it doesn't need to be that extreme. As he said, I think the problem is to find a closed form solution that gives the motor torque (or equivalently motor power) versus rpm curve that optimizes acceleration over a predetermined distance or time for a given gearing sequence.

Tom


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## Qer (May 7, 2008)

tomofreno said:


> Qer and major will be quick to point out this can be obtained well with a series dc motor, high current controller, and sufficient Ah battery pack.


Nonono and no. And no. No! I'd say it can be obtained with a motor, period.

AC, DC, 3-phase, Serial, SepEx, they all have advantages and disadvantages just like V8, inline, boxer, with or without turbo, manual or automatic transmission etc. Different technologies, similar tasks. That I "defend" DC is because there's some in this forum that has been drinking the AC cool aid and claim it's the best since sliced bread. I do agree that AC has some advantages, but it's not the ones that some people think it is.

Once again, from a performance point of view it's not that simple that "AC is better!", it has some different characteristics than DC but that doesn't make it automatically better. It all behaves a lot on circumstances and you have to compare SYSTEMS, not components. AC is, however, better in the aspect that there's no brush wear and it can be properly sealed to avoid dirt and water to get in, but on the other hand DC is more !/$.

Apples and oranges.


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## ZX-E (Aug 31, 2009)

Matlab definitely can do derivatives. Anyway, the reason yours are a little different for the step function is because my program had to make a polynomial to fit the function.

I'm glad to see our results are so close though bazou. The quarter mile times are within a 2% margin of error.


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## major (Apr 4, 2008)

ZX-E said:


> Matlab definitely can do derivatives.


Hey guys,

Glad to see you after this with an analytical approach. I'm sittin' in a hotel lobby far from home, so can't get into it much. But had time to think on the plane and in the car, for 12 hours. Torque is not the derivative of power as I have seen mentioned here. It is a factor. You want to hack that out. I'll be back next week.

Also, Any look yet at energy on that 1/4 example?

Later,

major


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## ZX-E (Aug 31, 2009)

We were saying torque is _a_ derivative of power in the way that power is derived or originates from torque. Not in the mathematical sense: _the_ derivative. 

In the last few replys with bazou we were talking about _the _mathematical derivative of velocity to find acceleration. I can see why that became confusing.


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## bazou (Sep 11, 2009)

ZX-E said:


> We were saying torque is _a_ derivative of power in the way that power is derived or originates from torque. Not in the mathematical sense: _the_ derivative.
> 
> In the last few replys with bazou we were talking about _the _mathematical derivative of velocity to find acceleration. I can see why that became confusing.


/me Agrees.

Major, here are your numbers:

Tesla 300-200-100 @5,2 16,155 seconds
total energy spent : 1 132 kJ

970 kJ of kinetic energy left (138,11 kmh (or 85,82 mph) with a weight of 1318 Kg( or 2900 pounds))
100 kJ spent against air resistance
62 kJ spent against rolling resistance.



Tesla 200-200-200 @ 4,45
17,25 seconds @ 128,3 km/h
total energy spent : 1502 kJ
1325 kJ of kinetic energy left
116 kJ spent against air resistance (due to higher top speed and resistance per meter travelled being proportional to the square of the speed)
62 kJ spent against rolling resistance (same thing -- phew. lol)

Tesla 200-200-200 @ 5,6
16,37 seconds @ 143,6 km/h
Total energy spent: 1 006 kJ
kinetic energy: 837 kJ
spent against air resistance: 108 kJ
spent against rolling resistance: 62 kJ




A gallon of gasoline contains 130 000 kJ ... but an ICE is what.. 25% efficient?


Here's how I built this:
From a starting kinetic energy of 0.0001 J , I calculate a starting speed. Then I calculate the rpm. Then I can get power generated at this instant. This power, minus the power needed to fight air resistance and air resistance is added to the car's kinetic energy at time T+1.

At time T+1, I start from the kinetic energy at time t+1 , and again calculate speed, rpm, power,air resistance and rolling resistance.

I am using torque because I fed the program the torque curve, but I might as well have fed it an HP curve..


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## bazou (Sep 11, 2009)

PhantomPholly said:


> A better example to explain why torque by itself is irrelevant would have been to describe two motors, A and B.
> 
> A generates 200 ft/lbs of torque between 0 and 6000 rpm
> B generates 100 ft/lbs of torque between 0 and 12000 rpm.


Just digging this up because it's a perfect example. Both arrive at the exact same time, car B always having a RPM twice as high.
Same power, half the torque at all time.


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## Drew (Jul 26, 2009)

ZX-E said:


> We were saying torque is _a_ derivative of power in the way that power is derived or originates from torque. Not in the mathematical sense: _the_ derivative.
> 
> In the last few replys with bazou we were talking about _the _mathematical derivative of velocity to find acceleration. I can see why that became confusing.


Torque is the mathematical derivative of power with respect to angular velocity, the same way that force is the derivative of power with respect to velocity and work is the derivative of power with respect to displacement.

As I said before, Torque is Nm, power is Nm/sec, work is Nm, force is N, rotation is 1/(2pi x sec) and velocity is m/sec so you can simply solve through from any system to any other system.


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## ZX-E (Aug 31, 2009)

Power is the product of torque and angular velocity. Torque is not the derivative of power with respect to angular velocity.


derived function: the result of mathematical differentiation; the instantaneous change of one quantity relative to another; df(x)/dx




bazou do you have matlab? I'll send you the code.


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## bazou (Sep 11, 2009)

ZX-E said:


> bazou do you have matlab? I'll send you the code.


Yes, will have to dig it up though.
Please send


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## evlowrider (Jul 23, 2009)

PhantomPholly said:


> _A better example to explain why torque by itself is irrelevant would have been to describe two motors, A and B.
> 
> A generates 200 ft/lbs of torque between 0 and 6000 rpm
> B generates 100 ft/lbs of torque between 0 and 12000 rpm._





bazou said:


> Just digging this up because it's a perfect example. Both arrive at the exact same time, car B always having a RPM twice as high.
> Same power, half the torque at all time.


Wait, while B doing twice the revs as A would result in the same power. With B having 1/2 the torque mean that its going to take twice as long just to get to 6000 revs??? A would leave B in its dust off the line.

(assuming the same gear ratios)


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## PhantomPholly (Aug 20, 2008)

evlowrider said:


> Wait, while B doing twice the revs as A would result in the same power. With B having 1/2 the torque mean that its going to take twice as long just to get to 6000 revs??? A would leave B in its dust off the line.
> 
> (assuming the same gear ratios)


Correct - but that's just the point. Changing effective gear ratios changes torque proportionately - which is why I was earlier maintaining that torque *by itself is meaningless. In this example if you gear B down by 2:1; or gear A up by 1:2; then the result between them will be identical even though motor "B" is identified as having "twice the torque."

Without knowing rpm range, torque alone is useless. Heck, you could have a motor with 5,000,000 ft/lb torque but an rpm range of only 0-1rpm. How useful is that?

Edit: Where are the icons for "whip" and "dead horse?"

*


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## bazou (Sep 11, 2009)

evlowrider said:


> Wait, while B doing twice the revs as A would result in the same power. With B having 1/2 the torque mean that its going to take twice as long just to get to 6000 revs??? A would leave B in its dust off the line.
> 
> (assuming the same gear ratios)


You said it - B will use double the gear ratio. ..
and here's the dead horse


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## PhantomPholly (Aug 20, 2008)

bazou said:


> You said it - B will use double the gear ratio. ..
> and here's the dead horse


Haw - nice photoshop job replacing the evil printer with the horse.

"What about the conjugal visits?"


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## ZX-E (Aug 31, 2009)

PhantomPholly said:


> Without knowing rpm range, torque alone is useless. Heck, you could have a motor with 5,000,000 ft/lb torque but an rpm range of only 0-1rpm. How useful is that?


 Ooooooh, thank you PhantomPholly. Here's a little food for thought. 5,000,000 _ft-lbs_ at 1 rpm is a 952 hp motor. You guys claim that you don't need to know rpm if you know the horsepower. So according to you horsepower nuts, that motor would be pretty damn useful right? Wow, almost 1000 hp! 

It just goes to show that you need all the information you can get. You still need to know at what rpm you get your power at. 



Also, Drew, you actually did start to confuse me there for a minute. But just look at this Tesla torque and power curve again.

If torque was _the_ derivative of power with respect to angular velocity, wouldn't you say that the torque should be zero at peak power? The slope of the power is zero at its peak, so the torque should be zero at the same angular velocity. I think you need to check your math again. Like I said before: torque is derived from power (in the literal sense), but it's not _the_ derivative of power.













Lolz


bazou said:


> and here's the dead horse


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## PhantomPholly (Aug 20, 2008)

ZX-E said:


> Ooooooh, thank you PhantomPholly. Here's a little food for thought. 5,000,000 _ft-lbs_ at 1 rpm is a 952 hp motor.


Hmmm, it was meant to be a silly example, but I wonder what the drag is on 5,000:1 gearing? That would reduce it to a "measly" 1,000 ft-lbs @ 5,000rpm...


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## ZX-E (Aug 31, 2009)

I know , I was being silly as well.


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## tomofreno (Mar 3, 2009)

> If torque was _the_ derivative of power with respect to angular velocity, wouldn't you say that the torque should be zero at peak power?


 The source of confusion is that torque itself is a function of motor rpm. So taking the derivative of power wrt shaft angular velocity, w, (or equivalently rpm) gives: dp/dw = d(T(w)*w)/dw = w*dT(w)/dw + T(w)*dw/dw = w*dT(w)/dw + T(w). So at max power T(w) = -w*dT(w)/dw. Torque is decreasing with w at this point so the term on the RHS is positive. Torque at this point is equal to the product of the shaft angular velocity and the slope of the torque versus angular velocity curve at this point.


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## PhantomPholly (Aug 20, 2008)

<head explodes>



I felt confident that someone in this group could provide the math...

There's a reason I went into the Air Force with my math degree rather than become a Mathematician.

I need a drink. Please bring one for my dead horse, too...


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## ZX-E (Aug 31, 2009)

tomofreno said:


> The source of confusion is that torque itself is a function of motor rpm. So taking the derivative of power wrt shaft angular velocity, w, (or equivalently rpm) gives: dp/dw = d(T(w)*w)/dw = w*dT(w)/dw + T(w)*dw/dw = w*dT(w)/dw + T(w). So at max power T(w) = -w*dT(w)/dw.


 
That makes sense. Product rule to expand d(T(w)*w)/dw into w*dT(w)/dw + T(w).

Way to go Tom!


So the derivative of power with respect to angular velocity isn't necessarily torque; but a first order differential equation involving the derivative of torque, torque and angular velocity.


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## tomofreno (Mar 3, 2009)

> So the derivative of power with respect to angular velocity isn't necessarily torque; but a first order differential equation involving the derivative of torque, torque and angular velocity.


 The result simply says that at max power the ratio of torque, T, to angular velocity, w, is equal to the change in torque with angular velocity or equivalently rpm. ie T(w)/w = dT(w)/dw. At lower rpm than where max power occurs the change in power with angular velocity is positive, so dp(w)/dw = w*dT(w)/dw + T(w) > 0 and dT(w)/dw < T(w)/w ie the change in torque with angular velocity is less than the ratio of torque to angular velocity. No surprise since angular velocity is small, torque is large and approximately constant over this range. At angular velocities greater than where power is max you have dp(w)/dw < 0, so T(w)/w < dT(w)/dw since torque is now falling off more rapidly with increasing w (due to back emf decreasing motor input voltage and current), and torque is smaller in magnitude and w is larger in this rpm range. No magic here.

The further out (higher rpm) the "knee" in the torque curve is the higher the rpm at which max power is reached. DC motors/controllers have a torque-rpm curve very much like the one shown for the Tesla since the torque is limited by the max current the controller can give at lower motor rpm. Available torque - the max the motor/controller can give - is then approximately constant at the value given by the max controller current until motor rpm becomes large enough to give significant back emf, where torque starts decreasing. So you get the same shape curve of torque versus rpm as for an AC motor/controller. 

The max in motor shaft power occurs at lower vehicle speed for lower gears since the shaft angular velocity is larger at a given vehicle speed for lower gears (large gear ratio) compared to higher gears (smaller gear ratio), so back emf is larger, decreasing torque. Wheel torque is larger, due to larger mechanical advantage with lower gears, but it falls off much more rapidly with increasing vehicle speed, due to the rapidly decreasing motor torque, compared to its decrease with vehicle speed in higher gears.

Tom


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## tomofreno (Mar 3, 2009)

I should have mentioned that you can of course move the "knee" of the torque-rpm curve out to higher rpm by going to a higher voltage battery pack. Torque is still limited at rpm below this higher "knee" to that given by the max controller current.


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## ZX-E (Aug 31, 2009)

tomofreno said:


> The result simply says that at max power the ratio of torque, T, to angular velocity, w, is equal to the change in torque with angular velocity or equivalently rpm. ie T(w)/w = dT(w)/dw. At lower rpm than where max power occurs the change in power with angular velocity is positive, so dp(w)/dw = w*dT(w)/dw + T(w) > 0 and dT(w)/dw < T(w)/w ie the change in torque with angular velocity is less than the ratio of torque to angular velocity. No surprise since angular velocity is small, torque is large and approximately constant over this range. At angular velocities greater than where power is max you have dp(w)/dw < 0, so T(w)/w < dT(w)/dw since torque is now falling off more rapidly with increasing w (due to back emf decreasing motor input voltage and current), and torque is smaller in magnitude and w is larger in this rpm range. No magic here.
> 
> The further out (higher rpm) the "knee" in the torque curve is the higher the rpm at which max power is reached. DC motors/controllers have a torque-rpm curve very much like the one shown for the Tesla since the torque is limited by the max current the controller can give at lower motor rpm. Available torque - the max the motor/controller can give - is then approximately constant at the value given by the max controller current until motor rpm becomes large enough to give significant back emf, where torque starts decreasing. So you get the same shape curve of torque versus rpm as for an AC motor/controller.
> 
> ...



You rule. Can I come down to Reno sometime? I have a lot of questions.


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## Drew (Jul 26, 2009)

Seems like I've been out of Uni for too long 

Oh well...


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## tomofreno (Mar 3, 2009)

It might also be interesting to note that dP(w)/dw = wdT(w)/dw + T(w) so on the "flat" (constant torque) part of the torque-motor rpm curve the derivative of power with respect to angular velocity IS simply the torque. So the slope of a power versus rpm plot in this rpm range is equal to the torque times some constants to convert from angular velocity to rpm.

Tom


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## alexcrouse (Mar 16, 2009)

All i have to say is one of the greatest car builders ever said:

"Horsepower sells cars, torque wins races."

-Carroll Shelby

Every driven a diesel truck? They have MASSIVE power in the 1k to 3k band, when your honda needs to be at 8000rpm just to embarrass it's self at the strip. 

Torque makes the drive more fun. Torque gives you that "performance car feel." I can't cite my source, (site is down right now)(http://phors.locost7.info/phors06.htm) 
but i sware it only takes like 24 horsepower to go 90mph. 

Everything else is pretty much useless on the road. ICE engines have massive horsepower, because they only make torque while spinning. DC series motors and AC inductions are actually better car motors than ICEs...

As for Mr. Shelby, I'm with him, no matter what the math says, because he won races.


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## major (Apr 4, 2008)

bazou said:


> Major, here are your numbers:
> 
> Tesla 300-200-100 @5,2, 16,155 seconds
> total energy spent : 1 132 kJ
> ...


Thank you bazou,

Looks like a valid analysis, from a quick look. Just got back home from a 5 day weird trip. 

So the slow guy with more HP uses more energy (which equates to less range from a battery) to do the same work (force times distance) in more time (which equates to less productivity). And some guys think hp is more relevant than torque. Go figure.

Regards,

major


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## Drew (Jul 26, 2009)

alexcrouse said:


> All i have to say is one of the greatest car builders ever said:
> 
> "Horsepower sells cars, torque wins races."
> 
> ...


A lot of people who don't actually design cars say thing like that... its probably why the misconception propagates so well...


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## Duncan (Dec 8, 2008)

The Torque V Power issue can be easily settled.

*Torque can be increased by suitable gear ratios 
Power can not!*

My old International tractor can out-pull any car I have driven with only 40 Hp
It is NOT fast!

Years ago I worked on the fuel systems for Ford Transit Diesels, 
the diesel version had 60 Hp
the petrol (gas) 100 Hp 

If you drove them the way most people do the diesel felt much stronger,
(available torque at 2000 rpm)

If you drove them as fast as they could go 
(changing gear at 4000 rpm diesel and 5500 rpm petrol (gas))

the petrol van was much faster

If you are in the correct gear more horsepower = more Torque at wheels

If your power band is narrow then you have lots of gear changes! 
A narrow power band also means your car is very unforgiving if you are in the wrong gear it will "bog down" 

A broad power band means less gear shifts - on the track this could mean the difference between having to change gear mid corner (a scary thing) and not


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## PhantomPholly (Aug 20, 2008)

Which is why, given a "perfect CVT," max horsepower will always win...

Now, where did I misplace my perfect CVT?



But this brings us full circle to the real world, where ICE motors have a very narrow rpm band over which they produce max hp, which would necessitate a lot of shifting (with each shift period of time X producing zero accelleration) to keep the motor at or near that max. Electric motors tend to be superior in that regard, generally increasing in hp up to around 1/2 to 2/3 max rpm, then holding hp nearly flat over the remaining rpm range (limited by current rather than available hp in that band).

The math whizzes have already posted the formulas. All you have to do is be smart enough (and masochistic enough) to use them to determine your "perfect motor."


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## major (Apr 4, 2008)

PhantomPholly said:


> where ICE motors have a very narrow rpm band over which they produce max hp, which would necessitate a lot of shifting (with each shift period of time X producing zero accelleration) to keep the motor at or near that max. Electric motors tend to be superior in that regard, generally increasing in hp up to around 1/2 to 2/3 max rpm, then holding hp nearly flat over the remaining rpm range (limited by current rather than available hp in that band).


Hi phantom,

I still don't follow you (and the other guys on this logic). Look at the hp curves for the electric motor (blue) and the ICE (black)*. Don't they both fall off similarly past RPM at which peak power occurs?

I still say, when you're looking a maximum output on electric motors, there is no such thing as constant power band 










Thanks to Rich for posting this graph about 100 posts ago 

Regards,

major

edit: * black curve is engine torque, not power. See post #206 & 207.


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## 2cycle (Jul 2, 2009)

CVT's work well up to a certain point. The style used on snowmobiles for the past 45 years work well with rpm lower than 11,000 rpm and less than 220 hp. The problems we face now are what the CVT uses to transmit the power from pulley to pulley. Snowmobiles use a rubber belt, the ZF CVT in my wife's Ford Five Hundred uses a steel chain/belt sort of thing. Both styles have their limitations. 
For general purpose use I think the CVT is a great addition to any electric vehicle that requires a lot of top speed that the single speed set up can't offer. I believe the Tesla would be able to keep it's quickness, maybe better it, and gain possibly 30 mph top speed if a proper CVT were used. Of coarse the CVT would need to be driven from a less rpm source to keep CVT rpm between 7000 and 8000 rpm for best efficiency.
Which reminds me, if anybody needs help with setting up a CVT for their project we can help design and get you the right parts to make it work. Projects like those are always fun.


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## PhantomPholly (Aug 20, 2008)

major said:


> Hi phantom,
> 
> I still don't follow you (and the other guys on this logic). Look at the hp curves for the electric motor (blue) and the ICE (black). Don't they both fall off similarly past RPM at which peak power occurs?
> 
> ...


Great chart, but it left out the ICE hp curve. You can calculate it from rpm & torque (and should, just to "see" it).

From about 6,000-11,000 rpm the electric motor stays within about 10% of max hp. That's awesome - almost a 100% increase in rpm once you get close to max hp before it falls off.

If you were to look at the ICE hp curve, however, you would typically see something different. In my recollection, the torque curve shown in the graph you presented is atypical of ICE motors. Here is one I found with a quick search which matches better with what I have seen over the years:










Note that in this chart the top 10% of peak horsepower is only achieved over about a 1,000 rpm band out of about 7,000rpm, or less than 15% of the available rpm band (while the electric held steady over almost 50% of it's functional RPM band). Also note that, although not shown here, we can expect torque (and hp) to drop off almost to zero just a few hundred rpm past where this chart ends.

It is this ability to hold peak hp over a wider operating range which gives electric motors one of their real advantages over ICE, because shifting is far less critical and not required nearly as often.

One last tidbit - I calculated the hp of the ICE engine in your example and, for grins, plotted it. By almost doubling (*1.95) the torque, I ended up with a chart where peak hp was almost exactly equal between the two. The curves are very similar up to 8,000rpm (ICE peak), with the ICE shifted left at the end about 1,000 rpm (peaks earlier than electric). But then in only about 1000 rpm hp drops to zero. It's like the back half of the hp "mountain" is simply "lopped off." To visualize it on the electric graph, simply draw a vertical line from peak hp on the electric hp line - and eliminate everything to the right. That's a bit of an exaggeration, but it gives you the idea - electric creates max hp over a much wider rpm band.


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## major (Apr 4, 2008)

PhantomPholly said:


> Great chart, but it left out the ICE hp curve. You can calculate it from rpm & torque (and should, just to "see" it).


 
Opps  I compared the electric power curve (blue) to the ICE torque curve (black). Sorry about that. Power curves will look different for the ICE having peak at higher RPM.

Thanks Phant.


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## PhantomPholly (Aug 20, 2008)

major said:


> Opps  I compared the electric power curve (blue) to the ICE torque curve (black). Sorry about that. Power curves will look different for the ICE having peak at higher RPM.
> 
> Thanks Phant.


No worries - the only real power stuff I had to study was related to THRUST. For example, I've known for over 30 years that the J-79 produced about 12,000 lbs of thrust at full military @ sea level while burning about 12,000lbs/hr of JP-4. But it doesn't do me a bit of good for land vehicles.

Horsepower and torque are far more confusing...


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## Duncan (Dec 8, 2008)

That Power/Torque chart is amazing

The first 6000 rpm (about 60 mph) is constant torque which means that if you have geared it to produce as much torque as your tires can take it simply accelerates as fast as it can!
Unfortunately its not one of Phantom's engines so it run out of puff and can't keep a constant acceleration! 
After 60 mph the Tesla is power limited and the torque (acceleration) drops but it still has 150 Kw at its governed top speed so its acceleration will have dropped to about a quarter of its initial 
Gearing the thing lower may (tyres permitting) increase its acceleration up to 40 or 50 mph but then it is power limited and that flat power curve means that adding gears could only help a little bit


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## bazou (Sep 11, 2009)

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## IamIan (Mar 29, 2009)

Interesting thread... sorry I came in late and took a while to read through it all.

I don't think it is a black and white either way.

but there are a few things that occurred to me that I didn't see mentioned I thought I would through out to get the point of view of others.

----------------
#1>
Equations represent relationships. 

F=MA is just as correct as M=F/A... it is deceptive to say power comes from torque when that is only true in one form of an equation... the equation can be re-written still be 100% accurate and make torque come from power .... etc.

In short The whole equation is expressing a relationship ... pulling out pieces of it makes that piece meaningless on its own.

Keep in mind the context of the relationship the equation represents... M=F/A does not mean that your mass disappears when the force applied goes to zero... or becomes infinite as acceleration goes to zero.

---------------------------
#2>
There is power at 0 RPMs.

It is just not expressed in the simple power torque rpm formula.
Just like your mass doesn't become infinite at 0 acceleration or go to zero at zero applied force.
Given the power applied to the motor... V*A... and the Power being dissipated by the motor as its less than 100% efficient ... most of the dissipated power goes out as heat... a bit as light , radio waves, sound , etc... but the remainder of the power is applied at 0 RPMs... 

The sum of the power losses from heat, sound, radio waves, etc... is less at 0RPMS than the total power applied to the electric motor... thus even at 0RPMs there is power.

-----------------------
#3>
While a a 1 HP or 1 kW motor with an ideal transmission can provide any amount of torque you want even over 2,000,000,000,000,000 Ft/Lb ... it is the real world limitations on parts, performance etc... thus power and torque can both be useful to varying amounts depending on the specifics of the application... specifics may effect priorities more toward one or the other but all of those things are still there in real world applications.

----------------

just my 2 bits / random thoughts.

Ian.!


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## major (Apr 4, 2008)

IamIan said:


> Interesting thread... sorry I came in late and took a while to read through it all.


Hi Iam,

Thanks for your input and thoughts. So what is your vote? Torque is irrelevant of relevant?



> There is power at 0 RPMs.


Gotta disagree with you here. On the shaft of a motor, even if there is torque, if it is stationary (zero RPM), the mechanical power is zero. Now there may be electrical power into the motor which produces torque, but the power output is zero. But there could also be a spring which produces that torque. Or a weight on a string around a pulley. Force (or torque) can exist without power.

Regards,

major


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## PhantomPholly (Aug 20, 2008)

major said:


> Gotta disagree with you here. On the shaft of a motor, even if there is torque, if it is stationary (zero RPM), the mechanical power is zero.


I don't think "power" is a physics term, so whether you are right or wrong on this depends on your subjective meaning of "power."

Torque is a force. At zero rpm, no WORK is done (horsepower is a measure of "work") but there is certainly a force. If the force is 10 ft/lbs and you balance a 10lb weight on the end of a 1 foot pole (of zero mass, for you perfectionists) with the pole horizontal to the ground and the plane of rotation vertical, no work gets done because the force of the motor exactly matches the force of gravity. Lighten the load by a few photons and it starts to move, accelerating away from the earth, and then you may calculate work done over some period of time "X". Make it heavier, and it will begin to descend, but more slowly than if it were in free-fall, and NEGATIVE work would be done (you give up your POTENTIAL energy stored in the form of altitude).



> Now there may be electrical power into the motor which produces torque, but the power output is zero. But there could also be a spring which produces that torque. Or a weight on a string around a pulley. Force (or torque) can exist without power.
> 
> Regards,
> 
> major


So, I think your intent was to say that the instantaneous hp rating is zero, which is true because hp (like "WORK") can only be measured over time.

The most confusing part of all of this is that in the real world our motors are hardly ever making a constant amount of power, unless we are at cruise and have balanced the forces (the instantaneous torque applied to the wheels at each instant is exactly equal to the opposing forces of wind and rolling resistance).

In MY personal vocabulary, "the power you are making" would mean the instantaneous measurement of force with the assumption that if you continued that exact force over a finite period of time you could then translate into horsepower. I tend to think in terms of thrust as power, which would be different from what Major is saying (where he is equating power to "work"). Neither is right nor wrong because they are simply English expressions, not physics terms.


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## IamIan (Mar 29, 2009)

major said:


> Thanks for your input and thoughts. So what is your vote? Torque is irrelevant of relevant?


I don't think it is a universal black and white relevant or irrelevant kind of thing ... I think it is a sliding scale depending on the application... where the value never completely reaches zero.... even if for some applications it can be so close to zero to be virtually the same thing... but depending on the application it becomes more or less relevant... kind of like aerodynamics on a large cement bridge, might be very minor concern at one application but in another they can become a major dominating concern.



major said:


> Gotta disagree with you here. On the shaft of a motor, even if there is torque, if it is stationary (zero RPM), the mechanical power is zero. Now there may be electrical power into the motor which produces torque, but the power output is zero. But there could also be a spring which produces that torque. Or a weight on a string around a pulley. Force (or torque) can exist without power.


I agree force even by another name of torque can exist without power... 

But I suspect there is more to it than one and only one simple equation.

__ Power goes in - ___ Power in heat , sound, radio waves, etc = __ Power remaining.

Just like F = MA ... M = F/A ... your Mass does not go to zero as the applied force goes to zero... the equation is just an expression of a relationship.

The relationship of the equation that relates power to torque and RPM is only one variation of that equation... there are others which are 100% equally as correct and accurate that do not include a RPM term at all... one such example is electrical power, among others.

The mechanical power out can not exceed the electrical power in... there is a direct relationship between them.

Although I guess that side of it is more academic and deviates a fair bit from the useful common application of the term power... so maybe it is best left for thought experiments just for fun.


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## major (Apr 4, 2008)

PhantomPholly said:


> I don't think "power" is a physics term, so whether you are right or wrong on this depends on your subjective meaning of "power."


Hi Phant,

In physics, *power* is the rate at which work is performed or energy is converted.

from: 

http://en.wikipedia.org/wiki/Power_(physics) 

That is what we are talking about 

major


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## PhantomPholly (Aug 20, 2008)

major said:


> Hi Phant,
> 
> In physics, *power* is the rate at which work is performed or energy is converted.
> 
> ...


Ah, I didn't remember that - I stand corrected.

At zero rpm, power is zero.


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## IamIan (Mar 29, 2009)

major said:


> Hi Phant,
> 
> In physics, *power* is the rate at which work is performed or energy is converted.
> 
> ...


Although I will agree in the common usage of the term as it has been used... and in that common usage sense the vast majority of people consider it to be 0 Power at 0 RPMs... 

but ... while it might be academic ... there is more to it...

Even in your own quote don't forget the 'or' part of that statement.

The next sentence you did not include from that Wikipedia article you quoted clarifies my meaning.



> In physics, *power* is the rate at which work is performed or energy is converted. It is an energy per unit of time.


as long as the 'or' statement of ,



> or energy is converted.


is included and as long as statements like ... 



> It is an energy per unit time.


 Statements are made

There very well can be power at 0 RPMs... even if that is not how most people have been taught to think of power.

Although I will agree that is a much more academic discussion on the nature of Power ... I will also continue to agree that the common usage of the term Power it would be zero... but there is more to it, if one wishes to delve into it... Although from an application point of view I doubt there would be any benefit in doing so.

Kind of like ... It is the electrons that move ... from the - or ground state up to the higher potential + state... the + protons do not move in electrical current ... it is only the - electrons that move... but while that is correct it doesn't change how we connect our batteries or motors ... and it doesn't change how people are taught electronics.

so there are many things that we could discuss ... like the nature of power... weather light is a particle a wave or both, etc ... but weather there is or is not power at 0 RPMs does not significantly change any ones application ... so it is a much more academic discussion.


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## DavidDymaxion (Dec 1, 2008)

I'd say it is not completely academic. If you know that you have zero output power at 0 rpm you won't use battery power to hold the car on a hill. You'd realize all the input power is going 100% into heat, and not overheat your comm bars and waste energy. You'll use your brakes instead to hold the car still on a hill.

Another practical consequence is you realize your efficiency is 0% at 0 rpm, even if it quickly climbs to 80+% at 1000 rpm, and that efficiency is poor at very low rpm. You'll avoid designing a big heavy direct drive truck, geared for 100+ mph, for slowly climbing steep hills -- you'd keep the tranny to minimize the near 0 rpm region.


IamIan said:


> ... ... but whether there is or is not power at 0 RPMs does not significantly change any ones application ... so it is a much more academic discussion.


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## IamIan (Mar 29, 2009)

DavidDymaxion said:


> I'd say it is not completely academic. If you know that you have zero output power at 0 rpm you won't use battery power to hold the car on a hill. You'd realize all the input power is going 100% into heat, and not overheat your comm bars and waste energy. You'll use your brakes instead to hold the car still on a hill.
> 
> Another practical consequence is you realize your efficiency is 0% at 0 rpm, even if it quickly climbs to 80+% at 1000 rpm, and that efficiency is poor at very low rpm. You'll avoid designing a big heavy direct drive truck, geared for 100+ mph, for slowly climbing steep hills -- you'd keep the tranny to minimize the near 0 rpm region.


The heat power produced by a electrical motor can be determined from the change in temperature of that motor over a defined period of time in a defined atmosphere such as air density, humidity, temperature, etc...

If you put a EV motor on a hill ... you can measure the electrical power going to the motor even if it is just enough to balance the EV so that it doesn't move up or down the hill... of againt a cement wall... of course one should be careful not to damage ones EV or motor.

The difference between the power applied to the motor and the dissipated / waste power to heat will show you what is left... it is a bit harder to quantify the radio waste power ,etc ... if it is zero there is no power at 0 RPMs... if there is still power unaccounted for there is still power at 0 RPMs.

Keep the power to the motor the same but vary the current ... then the voltage... the waste heat is produced by the current flow not the voltage... so when you half the voltage but double the current you have kept the power the same but you still might expect to get 4 times as much heat produced because you doubled the current even at the same power.... but if efficiency is 0% and all power is being converted to heat... than you would expect to get the same heat generated at any current level as long as the applied power was the same... and it would not change the amount of heat to have 10 amps and 1 V or 10V and 1 Amp... both are 10Watts of power and if there is no power than all power must be converted and we would expect the same heat generated either way... even though we already know that heat generated is only based on current or Amp flow and is independent of Voltage... which seems to contradict a 0% efficiency or 0 Power at 0 RPMs.

but feel free to do the experiment... carefully.

Either way there is energy converted ... which is a definition of power... and there is energy over time... which is another definition of power.

But I still think it is ... 99% just an academic discussion on the nature of power... I still don't see how it would effect actual application either way of a real world EV build.


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## DavidDymaxion (Dec 1, 2008)

Nah, there's a much easier test. First a little energy equation:

Ebattery = Eheat + Elinear motion + Erotationalmotion

Here's a power equation:

Pbattery = Pheat + Plinearmotion + Protationalmotion

All I have to do is draw some power from the batteries while holding the brakes, and observe the car didn't move -- therefore there can't be any energy put into linear or rotational motion; it is similar for power.

While it is correct that you could measure the heat and assume any missing heat goes to some other form of energy, in practice that is hard to do accurately. In this case it is far easier to observe there is no useful output power (motion).

Maybe there was confusion in saying there was no power. To clarify, you have electrical power going in, and power going out as heat, but no useful power in terms of motion.

If you vary the current, or voltage, or frequency, different things might get hot (possibly including air itself from arcing), but all that battery power is going to waste if the vehicle is not moving. Almost all of this loss is heat, a little bit might go into sound or flexing things.


IamIan said:


> The heat power produced by a electrical motor can be determined from the change in temperature of that motor over a defined period of time in a defined atmosphere such as air density, humidity, temperature, etc...
> 
> If you put a EV motor on a hill ... you can measure the electrical power going to the motor even if it is just enough to balance the EV so that it doesn't move up or down the hill... of againt a cement wall... of course one should be careful not to damage ones EV or motor.
> 
> ...


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## IamIan (Mar 29, 2009)

DavidDymaxion said:


> All I have to do is draw some power from the batteries while holding the brakes, and observe the car didn't move -- therefore there can't be any energy put into linear or rotational motion; it is similar for power.


very close.... but I think you missed a little bit .... there is still energy put into rotational motion... even if there is not a net motion... just because the energy put into the motion is not enough after losses to overcome the brakes does not negate the presence of the energy still being applied.

In short just because you put energy into doing something does not necessarily mean you actually will do something.

I put put forth my own personal energy but I will not be able to lift a skyscraper , not even a tiny bit... and even if there was no motion, there was still energy over time which is a definition of power ... and there was still energy converted which is another definition of power even if there was no motion at all.



DavidDymaxion said:


> While it is correct that you could measure the heat and assume any missing heat goes to some other form of energy, in practice that is hard to do accurately. In this case it is far easier to observe there is no useful output power (motion).
> 
> Maybe there was confusion in saying there was no power. To clarify, you have electrical power going in, and power going out as heat, but no useful power in terms of motion.


I would agree there is no apparent macro motion... which is a major reason why I think this kind of discussion is mostly academic ... people just want the car to go... exactly how the electrode works or the nature of electron drift may all be 100% correct things... but they are still 99% academic to the application for 99% of EV builders.

Macro motion is only one way of determining the presence or absence of power... remember power does not require motion... there is power any time there is energy converted...there is power any time there is energy over time.

Also ... although it is also an academic point... temperature is motion. 



DavidDymaxion said:


> If you vary the current, or voltage, or frequency, different things might get hot (possibly including air itself from arcing), but all that battery power is going to waste if the vehicle is not moving. Almost all of this loss is heat, a little bit might go into sound or flexing things.


Kind of... I was referring to a different angle...

It is already commonly known to most people who work with electricity ...that it is the flow of / movement of electrons that causes heat when it passes through a electrical resistance... Voltage is a current driver but voltage does not itself cause heat.

Although 10V @ 1 Amp and 1 V @ 10 Amps are both 10Watts... if you pass both of those through the same amount of resistance the 10 Amps will produce significantly more heat than the 1 Amp will... about 100x more heat actually.

This is one of the reasons higher voltage systems can use thinner wires to carry the same power.

If 100% of the power going into an electrical motor is all lost... where did it go?
If it went to heat than both the 10V @ 1 Amp and the 1V @ 10 Amps would both have to generate equal amounts of heat... when it is already known that they do not... If it was converted to something else... what was it? 

No matter what it is converted from or to... energy conversion is power... if it happens over time...energy over time is still power.

----------------

From a EV build perspective very little if any of this matters.

People care about the peak requirements and the continuous requirements.

Peak requirements of the motor , electronics, batteries, etc...

Continuous requirements of the motor, electronics, batteries, etc...

So a EV builder doesn't really care if there is or isn't power at 0 RPMs... at 0 RPMs he wants some specific things weather there is or isn't power.... he doesn't want to damage his EV components from heat , abuse , etc... he wants to be able to pull out from 0 RPMs at some rate of acceleration that he is happy with... that's it.

It doesn't matter if there is still 60% or more of the power than was applied... or 0% of the power applied.... as long as it does what he wants it to do the EV builder doesn't care.

As it was pointed out previously in the thread... there are methods of working out the acceleration and such of a build either form a torque or a power perspective.

If you are happy with the results of the build ... I don't see how it matters... do it which ever way you like to do it... either way gets you to a EV... so everybody wins


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## major (Apr 4, 2008)

IamIan said:


> If 100% of the power going into an electrical motor is all lost... where did it go?
> If it went to heat than both the 10V @ 1 Amp and the 1V @ 10 Amps would both have to generate equal amounts of heat... when it is already known that they do not... If it was converted to something else... what was it?


IamIan,

"If 100% of the power going into an electrical motor is all lost" then it would be a stall condition, meaning zero RPM, and zero mechanical power output. There could be torque on the motor shaft. In this condition, yes, the input energy (volts * amps * time) is converted to heat.

In your example, 10 volts @ 1 Amp, means the motor resistance is 10 ohms. And the input power is 10 Watts. And the energy converted to heat is 10 joules per second. Now how can you get this 10 ohm load to conduct 10 Amps at 1 volt?

Now if you allow the resistance to change, then 10 volts @ 1 amp will produce exactly the same heat as 1 volt at 10 amps.

The physics of this is clear. No motion, no mechanical power. Period. Now there may be power converted to heat or otherwise, but it is not mechanical power.

Just replace the motor with a torsion spring. It will have a torque on the shaft. Right? And it will stay there, essentially forever, without any power input, without any heat. So force (or torque) can (and does) exists without motion, and therefore without power.

Regards,

major


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## IamIan (Mar 29, 2009)

The Ohms has to stay the same.
So a 1 Ohm resistance ( not reluctance , or impedance, etc. ) when exposed to a 10 VDC electrical source can drawl up to 10 Amps... If we supply a conventional 100V electrical power source it would go up to 100 Amps... but Amps are just the average flow of electrons... so we use a PWM power supply to put out 100V at 1 Amp to the 1 Ohm circuit...

Now both are passing 10 Watts of power through the 1Ohms ... but it is well known and well documented that even at the same power ... the 10 Amps of higher current will always produce more heat at the same resistance... the 100V at 10 Amps will produce the same heat from that 1 Ohms of resistance as 10V at 10 Amps.

Amps of current drive the heat... Voltage effects power... but Voltage does not directly effect the heat at all... heat generation from electricity is a product of the resistance and the current... Voltage is not involved.

If 100% of the power was converted to heat than both the 1 Amp and the 10 Amps would both supply the same amount of heat as both have the same amount of power ... but that is not what happens... the heat is driven by the amps not the volts or the net power... which shows that more of the power is not lost to heat when one has higher voltage.... which turns out to be 100% correct... this is a very old very well known phenomenon of current and heat generation.

------------------


major said:


> Just replace the motor with a torsion spring. It will have a torque on the shaft. Right? And it will stay there, essentially forever, without any power input, without any heat. So force (or torque) can (and does) exists without motion, and therefore without power.


The major flaw with the spring example is that there is no energy conversion with the spring while it is held stationary ... and there is no energy flow over time while it is held stationary... if you had both of those with the electrical motor it to would have zero power at zero RPMs.

In the spring example... it is not because there is 0RPMs that there is no power... there is no power because there is no energy conversion ... and no flow of energy over time.

That same thing is not true for the electrical motor... In the electrical motor there is energy flow over time... and energy conversion... either of which mean you have power even at 0 RPMs.



major said:


> The physics of this is clear. No motion, no mechanical power. Period. Now there may be power converted to heat or otherwise, but it is not mechanical power.





major said:


> . Period.


That's allot of periods... 
But I still disagree.... even if I also still say it is just an academic discussion.

Now I will grant you... that if you want to just ignore the power at 0 RPMs for one reason or another... fine... but weather you want to ignore it or not... there is power there.

Even if you begin to exclude lots of things ... like when you say mechanical power you are also ignoring any perpendicular motion ... if at 0RPMs the electric motor caused the whole vehicle to move perpendicular to the rotational axis ... by the excluding rules of mechanical power that motion doesn't count and it would still give a result of 0 even if the whole EV is moved at any acceleration or speed you like, because as soon as you say mechanical power you exclude all perpendicular motion ... which just shows how silly it can get when you start to just exclude things... Mechanical power also excludes any vibration that is perpendicular , etc... it is just a way of ignoring lots of things that are actually there.

If you want to ignore it fine... but it is still there.

-----------------------

An other way to see that there is power at 0RPMs is the 'Instantaneous Power' ... Instantaneous Power is power with no time and no movement... ie 0RPMs because it is instantaneous and it would take at least some time to move, at any speed .... there is even 'Instantaneous Mechanical Power' ... or mechanical power without any motion and without any passage of time.

But that is even more academic than we have already been. 

----------------------

I still hold that... it doesn't matter... find the rating for your components under the conditions you will use them... including pulling out on a hill from a stop... use torque or power... whatever makes you happy... if you like it easier and just want to ignore the power at 0RPMs... go ahead... I don't see how it will effect 99% of the EV builders either way... do it however you want... if you don't know enough about it.. ask others who have done conversions and or read up and or pay someone to do it.


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## major (Apr 4, 2008)

IamIan said:


> Instantaneous Power is power with no time and no movement.


The quantity of power is an instantaneous value, just like velocity. It represents the work being done at that instant in time, just like velocity represents the rate of travel. As Tesseract said, this is one of the reasons Newton invented the calculus. To help us explain mathematically how his physics work.

You have said a lot, and if I have time, I'll try to expand more, because I find this interesting. But in short, I say you have nothing to offer here which would make me deviate from Sir Newton's view of our universe.

No offense, mate.  And I hope that I interpret Newton's Laws correctly. Any support or corrections from the sidelines is appreciated.

Regards,

major


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## major (Apr 4, 2008)

IamIan said:


> The major flaw with the spring example is that there is no energy conversion with the spring while it is held stationary ... and there is no energy flow over time while it is held stationary... if you had both of those with the electrical motor it to would have zero power at zero RPMs.


IamIan,

I think you said you agree with me 



> In the spring example... it is not because there is 0RPMs that there is no power... there is no power because there is no energy conversion ... and no flow of energy over time.


Energy flow over time???? Isn't that the definition of power? And it is exactly because there is no movement that the power, or "energy flow over time" is zero. Which came first, the chicken or the egg, the power or the motion?



> That same thing is not true for the electrical motor... In the electrical motor there is energy flow over time... and energy conversion... either of which mean you have power even at 0 RPMs.


Yeah, but the energy conversion is from electrical to heat, not mechanical. So it is no different from having a resistor and a torsion spring. No mechanical work is done, zero power (mechanical). There is torque on the shaft and heat from the resistance. But the vehicle does not move. Yeah things get hotter, but so what. That is not what we're after, is it?

Regards,

major


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## major (Apr 4, 2008)

IamIan said:


> The Ohms has to stay the same.
> So a 1 Ohm resistance ( not reluctance , or impedance, etc. ) when exposed to a 10 VDC electrical source can drawl up to 10 Amps... If we supply a conventional 100V electrical power source it would go up to 100 Amps... but Amps are just the average flow of electrons... so we use a PWM power supply to put out 100V at 1 Amp to the 1 Ohm circuit...
> 
> Now both are passing 10 Watts of power through the 1Ohms ... but it is well known and well documented that even at the same power ... the 10 Amps of higher current will always produce more heat at the same resistance... the 100V at 10 Amps will produce the same heat from that 1 Ohms of resistance as 10V at 10 Amps.
> ...


IamIan,

This is simply incorrect. I have argued with you on Newton's Laws. Hopefully someone else can help and explain Ohm's Law 

Regards,

major


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## DavidDymaxion (Dec 1, 2008)

Don't forget, if you PWM you get less average voltage. 100 Volts with a 10% on / 90% off PWM means you'll get on average 10 Volts. Armed with this knowledge, you'll see you get the same heat numbers and no mysterious differences.



IamIan said:


> The Ohms has to stay the same.
> So a 1 Ohm resistance ( not reluctance , or impedance, etc. ) when exposed to a 10 VDC electrical source can drawl up to 10 Amps... If we supply a conventional 100V electrical power source it would go up to 100 Amps... but Amps are just the average flow of electrons... so we use a PWM power supply to put out 100V at 1 Amp to the 1 Ohm circuit...
> 
> Now both are passing 10 Watts of power through the 1Ohms ... but it is well known and well documented that even at the same power ... the 10 Amps of higher current will always produce more heat at the same resistance... the 100V at 10 Amps will produce the same heat from that 1 Ohms of resistance as 10V at 10 Amps.
> ...


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## IamIan (Mar 29, 2009)

major said:


> IamIan,
> 
> This is simply incorrect. I have argued with you on Newton's Laws. Hopefully someone else can help and explain Ohm's Law
> 
> ...


I was aware of all your points so far on Newton's Laws before you posted them.... so you haven't said anything new to to me.

Nor has anything yet been said about Ohms laws that I was not already aware of.

But it isn't needed for us to 100% agree with each other... As I've have said from the beginning it's an academic point... and I don't see how it would effect a EV builder in real world application. 

----------------

You started saying there was no Power at 0 RPMs.

That statement is still incorrect.... even if as I have said from the beginning it is an academic issue and doesn't effect application... and even if you have sense silently abandoned that incorrect position.

Your own quote from Wikipedia disagreed with you on power.

Your own quote from Wikipedia disagreed with you about power and the stationary spring example.

You changed from your original position ... and instead of admitting there is power you claim that you just want to ignore any power that isn't 'mechanical power'.

I still say that is fine and the discussion is academic but point out some of the short comings of invoking 'mechanical power'... for instance Mechanical power also ignores more than just non-motion power... it also ignores any motion that is perpendicular to the applied force.

Even if you only care about 'mechanical power' that still doesn't mean that there aren't other types of power present that you just want to ignore.

------------

As easy as Newton's laws are ... don't forget progress has been made sense 1687 when he published them , and they are no longer considered to be scientifically 100% correct... they are simplified expressions of much more complicated interactions that do not always obey his 320+ year old understanding.

As easy as Ohm's laws are ... don't forget progress has been made sense 1827 when he published them... they are no longer considered to be scientifically 100% correct... they are simplified expressions of much more complicated interactions that do not always obey his 180+ year old understanding.

---------------

What I stated is correct, current and resistance are the drivers of electrical heat ... Voltage doesn't matter. It has been a very well known implication of electrical wiring for decades.

Here is another example that might help to illuminate this point about the power is not all converted to heat.

Make a Electric motor out of superconductive materials ... which has already been done at least on the research level... apply this EV motor with brake on to 100 kW of power... the brake may stop the motor from turning and there would be 0 RPMs... but there would also be almost none of that 100 kW of electrical applied power converted to heat... Where did the power go? ... Hint this is the same place a portion of the power goes from a normal electric motor with resistance used in this method.

If the idea that all the watts of power are converted to heat were true it would force the superconductor to heat up with that 100 kW ... but that isn't what happens.



DavidDymaxion said:


> Don't forget, if you PWM you get less average voltage. 100 Volts with a 10% on / 90% off PWM means you'll get on average 10 Volts. Armed with this knowledge, you'll see you get the same heat numbers and no mysterious differences.


That is a very good point ... and I agree my PWM example is obviously flawed.

It isn't mysterious ... It is just counter-intuitive.

---------------

Now using Ohm's laws ... consider a superconductor with 0 Ohms ... it can have a current even while there is no Voltage... 0 V = 10 Amps * 0 Ohms ... or that same superconductor can pass 1,000,000 Amps .... 0 V = 1,000,000 Amps * 0 Ohms.... the super conductor can carry electrical power ... there is still a flow of energy ... even if there is 0 V there can still be electrical power.

In short Ohms' laws and Newtons' Laws are very useful ... but neither one has been 100% scientifically correct for many many years.

We know more today than they did back then... so they and their outdated laws are sometimes wrong, or miss things.


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## ZX-E (Aug 31, 2009)

All major was saying is there's no _mechanical _power output at 0 RPM...


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## major (Apr 4, 2008)

ZX-E said:


> All major was saying is there's no _mechanical _power output at 0 RPM...


Well said, ZX-E. I don't see what is so hard to understand about that.

Thanks,

major

ps. BTW, this makes torque relevant.


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## Lordwacky (Jan 28, 2009)

This is probably stupid, but I'm going to weight in here. First let me say I haven't read this whole thread because its really long so if someone else has said these things already I'm sorry.

Horsepower = 1/C (Torque * RPM) where C is a constant. Horsepower is a function of torque. You cannot have horsepower without torque. Without getting into the physics of it. To say that torque is irrelevant is kinda absurd because you need torque to have horsepower.

for example in the fifties Chrysler built turbine powered cars. Even though they had ~200hp people didn't like them because they had poor acceleration. They had poor acceleration because turbines while high in horse power are low in torque, meaning they run at high RPMs to get comparable power to a conventional piston engines, meaning there was "turbine" lag, this is basically the same thing as a "turbo" lag you all know about already.

Another example is the good ol' transmission. We all know it is easy to get going in 1st gear then when you are in 4th. This is because the transmission applies a mechanical advantage to the drive train, in other words, it increases the torque on the drive train. In a way you can view an transmission as a horsepower to torque converter. If you have infinite torque you wouldn't need a transmission at all. Electric motors have a lot of torque hence all the direct drive conversions out there even though they have lower horse power rating then comparable piston engines that could never perform in a direct drive configuration.

I hope this makes sense.


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## Duncan (Dec 8, 2008)

IamIan

I don't know what you have been smoking but at human scales Newtons laws still work fine you have to be very small large or fast to detect the difference between Einsteinian mechanics and Newtonian

To your superconducting motor
While it is held at zero speed it will do zero work and consume zero power
As soon as you let it go it will do "mechanical work"and consume electrical power
If there is no power source the current in the coils will drop as work is done
No Magic!

The advantage of superconducting motors is that they should be able to be made much smaller
(Useful for a ship)

For my car I want mechanical power!

Other types of power will not move metal!

You can use the other types of power (Spiritual?) for your car if you want


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## major (Apr 4, 2008)

IamIan said:


> What I stated is correct, current and resistance are the drivers of electrical heat ... Voltage doesn't matter.


Hi IamIan,

So what you're saying is that voltage is irrelevant 

Just as I disagreed with Drew when he said that torque was irrelevant, I disagree with you that voltage is irrelevant. But maybe I should start another thread.

Ever notice the similarities between the expressions for electrical and mechanical power?

Pe = V * I or (Watts = Volts * Amps)

Pm = T * S or (Watts = Torque * Angular Velocity)

In the mechanical case, Drew chooses to use Power and Angular Velocity. Then says Torque is irrelevant. But when he defines the Power and Angular Velocity, he has defined Torque.

And you have done the same with your logic. Looking at "electrical heat", it is power. So when you say all you need is the current and resistance to determine power (electrical heat), you are correct, however by defining resistance and current, you have defined the voltage. You could have just as easily figured the electrical power (heat) by using voltage and current (making resistance irrelevant?) or by using voltage and resistance (making current irrelevant?).

My whole point here is that because you can have torque without power, it certainly cannot be considered irrelevant. And, as a sidebar, in your electrical heat example, you can have voltage without power, so it would be wrong to consider voltage irrelevant.

Regards,

major


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## IamIan (Mar 29, 2009)

Ok, Lesson learned... keep academic points ( like the nature of power ) to myself 

If it makes you happy ... say , write, and beleive anything you like.

I don't see a benefit to continue lengthy posts back and forth.

Ignore any type of power you like ... assume nothing has been learned sense Newton and Ohm... I am not a teacher and am not motivated to become one... or continue to point out mistakes, omissions, etc.

Count this as a personal win if you like ... 

My original point still stands 100% correct:

There is power at 0 RPMs... weather you like it or not... weather you like the type it is or not... weather major ever admits his claim was wrong or not.


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## ZX-E (Aug 31, 2009)

IamIan said:


> Ok, Lesson learned... keep academic points ( like the nature of power ) to myself
> 
> If it makes you happy ... say , write, and beleive anything you like.
> 
> ...


IamIan. Please go back and read what major wrote. He said there is no _mechanical_ power at 0 rpm... 

If you were a little clearer, I think major wouldn't even disagree with you. As far as power goes at 0 rpm. It depends on the situation, and what kind of power you're talking about. Major was clearly talking about mechanical power.


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## IamIan (Mar 29, 2009)

ZX-E said:


> IamIan. Please go back and read what major wrote. He said there is no _mechanical_ power at 0 rpm...
> 
> If you were a little clearer, I think major wouldn't even disagree with you. As far as power goes at 0 rpm. It depends on the situation, and what kind of power you're talking about. Major was clearly talking about mechanical power.


I will agree I am far from perfect and do not always word things perfectly.

Given the responses ( not just from major ) , I doubt it would have mattered how it was phrased... as I said from the beginning it was an academic point... and I shouldn't have even brought it up... In the future I'll try and bite my virtual tongue instead.

but ... as I also said from the beginning ... it doesn't matter.

Do I now move on to the other incorrect statements, and misinterpretations .... no ... it does not look to be worth the hassle... each time I've tried to explain one thing it has lead to other misinterpretations .... and it only looks to be building momentum and branching out to more and more things... that just isn't appealing to me... maybe some other time in a different format... But I am just not feeling that argumentative right now.


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## ZX-E (Aug 31, 2009)

IamIan said:


> I will agree I am far from perfect and do not always word things perfectly.
> 
> Given the responses ( not just from major ) , I doubt it would have mattered how it was phrased... as I said from the beginning it was an academic point... and I shouldn't have even brought it up... In the future I'll try and bite my virtual tongue instead.
> 
> ...



Well I'm sorry you feel that way. Please don't bite your virtual tongue. 

To be honest I really do think it would have mattered how it was phrased. You were saying that even if the motor's shaft isn't turning there can be power dissipated by the motor in the form of thermal energy. Right? Everyone can agree on that I think .


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## IamIan (Mar 29, 2009)

ZX-E said:


> To be honest I really do think it would have mattered how it was phrased. You were saying that even if the motor's shaft isn't turning there can be power dissipated by the motor in the form of thermal energy. Right? Everyone can agree on that I think .


Although I had hoped others would have seen it without been spoon feed. 

But, yes that one should be obvious... but it isn't just thermal power from the flow of and conversion to and from thermal energy... there are many many type of power and many many types of energy ... many many of which are still present at an electric motor at 0 RPMs... but not in a stationary spring.

Additionally ... it is often over looked that kinetic power is not the same as mechanical power .... kinetic power could be power from any type of movement.... mechanical power ignores any movement that is perpendicular to the applied force.

A crude example... yes it is flawed but I don't know off hand a better analogy...

A bolt and a nut ... you apply a force to turn the bolt ... the movement of the bolt in the direction of that applied force of rotation counts toward that mechanical power ... but the motion of the bolt toward or away from the nut does not count for that mechanical power because it is a motion that is perpendicular to the applied force.... Yes I can hear the masses screaming already... but its true... if you don't think so go look up mechanical power... Now the best you could do is that you could do with mechanical power is change your frame of reference ... the force and movement toward or away from the bolt is induced and in that frame of reference the rotational force and movement are ignored because they are now perpendicular.

In short... invoking mechanical power ignores allot of things ... to many for my tastes... and still does not change the presence of power at 0 RPMs.



ZX-E said:


> Well I'm sorry you feel that way. Please don't bite your virtual tongue.


but it has treed out so much... 

If this one rather simple concept was such a fight where am I for 

Duncan and his post with by my count... 4 points I disagree with.
Major and his most recent post by my count ... 5 points I disagree with.

or any of the older multitudes of points I disagree with.

I just see an steep uphill battle ... with very very little to be gained by the effort... and a very good chance they will never see it no matter what.


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## major (Apr 4, 2008)

IamIan said:


> A bolt and a nut ... you apply a force to turn the bolt ... the movement of the bolt in the direction of that applied force of rotation counts toward that mechanical power ... but the motion of the bolt toward or away from the nut does not count for that mechanical power because it is a motion that is perpendicular to the applied force.... Yes I can hear the masses screaming already... but its true... if you don't think so go look up mechanical power... Now the best you could do is that you could do with mechanical power is change your frame of reference ... the force and movement toward or away from the bolt is induced and in that frame of reference the rotational force and movement are ignored because they are now perpendicular.


Hi Iam,

Me again. Yeah, a bolt and nut. Good example. We all use those. And some of us use a torque wrench. When tightening a bolt and nut, what are you doing? Drawing the nut to the bolt head squeezing the material between the two. So there is a force parallel to the axis of rotation of the bolt and torque wrench. This force is translated into torque by the bolt thread radius and the thread pitch. So the force squeezing the material between the nut and bolt head (and the work done to move the nut or bolt, and the power associated with that work) is translated to the torque on the wrench (and the work done and associated power on the wrench). 

This is much the same as the rotation to translational mechanical power transformation which occurs in the EV via the wheel. Torque is applied to the axle and translated to linear force via the wheel radius.

We all know this. The linear motion, force, work, and power is considered and accounted for in the rotational coordinate system, namely the motor output torque.

What is your point? No force, power or energy is ignored, unless it is so insignificant it cannot be measured by reasonable means, meaning 10^-12%.

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> What is your point? No force, power or energy is ignored, unless it is so insignificant it cannot be measured by reasonable means, meaning 10^-12%.


....
Although I am 90% certain this effort I am about to make will still not be understood if it wasn't already... for the hell of it I'll give it a try. 
....

In regards to my point on invoking mechanical power.

By invoking mechanical power you ignore all motion perpendicular to the applied force... that is just how mechanical power works and is calculated ... look it up... look at the formulas and think about it.

I am not saying there isn't movement... I am not saying there isn't power... I am not saying the power was not converted from rotation force... I am not saying there is not a corresponding counter force or drag on the applied force that relates to the induced perpendicular force... I am not suggesting magic... I am not suggesting the perpendicular force comes from no where... I am not suggesting the perpendicular force does not originate from the applied force... I am not saying the perpendicular power can't be accounted for.

I'm sure I missed several other things I am also not saying.

I'm sure someone will focus on something I'm not saying either by one I missed in the list or by ignoring what I am saying.

Also I will repeat what I said from the beginning... I think this is at least 90% academic... if not 99%.

--------------------

There are two frames of reference.

The rotational frame of reference :
Apply a force in a rotational direction ... if that force causes movement in the rotational direction + or - movement mechanical power is present and + or - work is done in that frame of reference.

The perpendicular frame of reference:
Any motion that occurs perpendicular to the applied force... it is no accident that there is no term for this in RPM & torque power formulas ... mechanical power ignores any motion perpendicular to the applied force.

We can go back to what I am not saying if you like... or just page up.

If a motion occurred perpendicular to the axis of rotation the force of that motion still comes from the energy applied to the system... this motion might be experienced as a vibration, or sound, etc... 

A motor with energy flow has power ( several different kinds ) even while held stationary... If it is only stationary in the rotational frame of reference but is not stationary in the perpendicular frame of reference ... there is still no rotational frame of reference mechanical power no matter how much it moves in the perpendicular frame of reference... There is mechanical power in the perpendicular frame of reference while it moves in that direction but it is ignored in the rotational frame of reference ... If the motor is allowed to rotate any rotational movement is ignored and does not count as mechanical power in the perpendicular frame of reference.

In addition to all the other forms of power that are ignored when mechanical power is invoked ... you also ignore several types of physical movement as well depending on your chosen frame of reference that mechanical power conventions require you to pick one frame of reference.

-----------------

The several other points from older posts I will not even attempt to go into in this post... which is already long enough even after condensing it.


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## major (Apr 4, 2008)

IamIan said:


> ....Any motion that occurs perpendicular to the applied force... it is no accident that there is no term for this in RPM & torque power formulas ... mechanical power ignores any motion perpendicular to the applied force.


But there is a term. Radius. *T = r x F* This is a vector formula. See http://en.wikipedia.org/wiki/Torque 

Through the radius, and inclined plane, all translational quantities are accounted for in the rotational system.

If your "perpendicular motion" is a result of the motor, then it is accounted for in the torque and angular velocity of the output shaft.

Now if that perpendicular motion is a result of driving off a cliff, I guess I have ignored that back at the motor shaft 

Regards,

major


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## IamIan (Mar 29, 2009)

IamIan said:


> ....
> Although I am 90% certain this effort I am about to make will still not be understood if it wasn't already... for the hell of it I'll give it a try.
> ....
> 
> ...


I called it... maybe next time I should put money down to... 



major said:


> But there is a term. Radius. *T = r x F* This is a vector formula. See http://en.wikipedia.org/wiki/Torque
> 
> Through the radius, and inclined plane, all translational quantities are accounted for in the rotational system.
> 
> ...


Not Torque .... Mechanical power.... they are different things... you can't have forgotten this already you already came at least that far in previous posts.



major said:


> On the shaft of a motor, even if there is torque, if it is stationary (zero RPM), the mechanical power is zero....
> 
> Force (or torque) can exist without power.





major said:


> In physics, *power* is the rate at which work is performed or energy is converted.
> 
> from:
> 
> ...


Following your own link above on power under mechanical power when you read it you find:



> Note that only motion that is along the same axis as the force "counts", however; motion in the same direction as force gives positive work, and motion in the opposite direction gives negative work, while motion perpendicular to the force yields zero work.


When you invoke 'mechanical power' You bring with it the mandatory picking of a frame of reference and automatically in 'mechanical power' ignores all motion perpendicular to the applied force... in addition to all the other types of power invoking 'mechanical power' also ignores.


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## major (Apr 4, 2008)

IamIan said:


> When you invoke 'mechanical power' You bring with it the mandatory picking of a frame of reference and automatically in 'mechanical power' ignores all motion perpendicular to the applied force... in addition to all the other types of power invoking 'mechanical power' also ignores.


O.K. I see what you are saying. But what is the motion perpendicular to the frame of reference which is motor output to which you refer? Let's say our EV is an elevator instead of a car. All travel is up and down. This is accomplished with an electric motor, pulley and rope. Is there work done moving the elevator up 100 feet? Is there mechanical power delivered from the motor to lift it those 100 feet?

Is this the type of perpendicular motion to which you refer? 

Regards,

major


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## DavidDymaxion (Dec 1, 2008)

Major, you were on the right track.

We are used to seeing P = Tw (torque times angular speed) in high school physics. It is possible, however, to apply a torque about a different axis than the axis of rotation. We also need to keep in mind that power is a scalar, and hence is independent of the inertial reference frame. So we need a formula with vectors, that produces a scalar result.

P = T dot w = (r x f) dot w

We often think of rotational frequency as a scalar, but it actually is a vector -- it depends on the orientation of the axis.


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## PhantomPholly (Aug 20, 2008)

It seems to me that all the confusion comes from the fact that Physics does not consider that any "work" has been done unless something moves.

Thus, if you stand for an hour exerting a 100 lb upward force to hold barbells in the air, you have not done any "work." Tell that to your arms!


----------



## IamIan (Mar 29, 2009)

major said:


> O.K. I see what you are saying. But what is the motion perpendicular to the frame of reference which is motor output to which you refer? Let's say our EV is an elevator instead of a car. All travel is up and down. This is accomplished with an electric motor, pulley and rope. Is there work done moving the elevator up 100 feet? Is there mechanical power delivered from the motor to lift it those 100 feet?
> 
> Is this the type of perpendicular motion to which you refer?


I think it is easier to grasp the concept with the bolt and nut analogy ... if the only force you apply to the bolt is rotational force the movement of the bolt perpendicular to that rotation ... ie toward or away from the nut ... is automatically ignored when you invoke 'mechanical power'.... even if the induced force and movement in the perpendicular frame originates from the applied force in that rotational frame of reference.

In the elevator example ... yes work is done because there is motion ... but not just the up and down motion ... if the motor used to turn the cable spindle turns in the same rotational axis as the cable spindle does ... than any movement that results in the perpendicular direction to that applied force is automatically ignored when you invoke 'mechanical power'... not all motion is up and down ... some force and some motion will be front back and side to side ... some will be very small and fast and cause sound ... others will be extremely small and fast and cause heat... others will be larger and might be felt in a pull or jerk in a direction other than exactly 100% up and down.

Another example to see this is close your hand into a fist... put you hump up... the applied force and rotational frame of reference relate to the curve of your fingers ... the perpendicular is you thumb which is ~perpendicular to that rotation.



DavidDymaxion said:


> Major, you were on the right track.
> 
> We are used to seeing P = Tw (torque time angular speed) in high school physics. It is possible, however, to apply a torque about a different axis than the axis of rotation. We also need to keep in mind that power is a scalar, and hence is independent of the inertial reference frame. So we need a formula with vectors, that produces a scalar result.
> 
> ...


Yes.

Thus once you invoke 'mechanical power' you are forced to chose a frame of reference ... and any motion perpendicular to the applied force in that frame of reference is ignored in that frame of reference, along with all the other types of power invoking 'mechanical power' also ignores.... if you change your frame of reference to the perpendicular you now are ignoring the rotational movement instead.

It isn't to say it can't be dealt with one way or the other... but there are issues that come along for the ride once someone invokes 'mechanical power'.... often far more issues than the person who invoked it intended.



PhantomPholly said:


> It seems to me that all the confusion comes from the fact that Physics does not consider that any "work" has been done unless something moves.
> 
> Thus, if you stand for an hour exerting a 100 lb upward force to hold barbells in the air, you have not done any "work." Tell that to your arms!


Science is very specific about what it calls work ... power... energy ... etc... they are not the same thing ... you can move and consume energy but still do no / 0 Watts of work ... even if you have several Watts of power from the motion and conversion of energy... and you can completely depleat your battery pack and not have moved the EV at all one inch...consumed many kwh of energy but done no wh of work.

---------------

Thankfully EV building is far more forgiving ... the specific details are 99% of the time not significantly influential ... so less accurate , easier and simpler views of things can very often yield successful EV conversions.

That is why ... at least in my point of view ... on Torque vs Power ... there are ways to use either one to produce a good quality EV... Neither one is ever 100% irrelevant ... but given some specific build criteria one or the other might end up being only 0.00000001% of the process... and thus while not 0% ... it might be statistically very close to it.... and that can swing either way for Power or against it... or for torque or against it.... it just comes down to preferences and specifics exactly where the value between them falls and how someone wants to do it.


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## major (Apr 4, 2008)

IamIan said:


> I think it is easier to grasp the concept with the bolt and nut analogy ... if the only force you apply to the bolt is rotational force the movement of the bolt perpendicular to that rotation ... ie toward or away from the nut ... is automatically ignored when you invoke 'mechanical power'.... even if the induced force and movement in the perpendicular frame originates from the applied force in that rotational frame of reference.


Sorry IamIan,

I just can't make any sense out of this. A motor in the EV puts out 50 kW of mechanical rotational power at the shaft. It is connected thru gears and shafts to the wheel. The vehicle motivates with 50 (minus a few %) kW of mechanical translational power. I don't understand what is invoked, ignored or perpendicular about that. Seems simple to me.

O.K. Let's just leave it here. It is like we speak different languages. I started this thread, so I think that should give me some authority to request an end to this particular sidebar. 

I'd be happy to see the discussion continue about the relevance of torque. But no longer have an interest in perpendicular motion or acedemic powers.

Regards,

major


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## Duncan (Dec 8, 2008)

Hi Major
Back to your initial point
An electric motor has the advantage of producing torque at zero rpm
(no messing about with slipping clutches)
This goes through your gearbox and diff to the wheels to produce a wheel torque
The wheel torque goes through the tyre to produce a force against the ground

This will try and accelerate your vehicle

If you have geared it so that the motor torque to wheel torque to ground force are as much as the tyre ground interface will take the vehicle takes off smartly

(that Tesla torque graph)

As the motor turns it produces power - initially a small amount (5rpm)

For a constant torque the power delivered increases until the motor can no longer maintain the torque

So far the car has been accelerating as fast as its tyres will drive it

Now the torque and wheel torque and ground/tyre force will start to reduce reducing the acceleration

(the power will probably still be increasing)

The first part of the acceleration has been torque limited

The next part is power limited

Something like that Tesla is accelerating at something close to tyre limits until about 60 mph when it could use more power (if it was available)

You can gear any motor to produce that initial surge but with less power you will hit the torque reduction sooner,
The amount of power it takes to maintain a constant acceleration is directly proportional to your speed
(you need to overcome wind resistance as well so it is more than proportional to speed)

What most people mean by "a high Torque Motor"is really a broad power band so that the fact that they are a long way from the peak power revs when they throttle is less important

After a long walk around the bushes
More power is better *BUT*
It must be more power when you want it
If you are going to drive at 50% of max power revs then you want a power curve that reflects that
If you are willing to drop down a gear then you can have a pointier power curve

The electric motor curves that I have seen have been wonderful
The Tesla does not need any other gears - unless you want to go over 120 mph

As a final cut - nuts and bolts are not magic all of the simple laws of mechanics hold
The energy you put in from your spanner appears as heat and as strain energy in the bolt and threads


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## major (Apr 4, 2008)

Duncan said:


> Hi Major
> Back to your initial point


Hi Duncan,

Thanks for posting something I can understand and for getting back to the point.

I agree with everything except where you say this:



> What most people mean by "a high Torque Motor"is really a broad power band so that the fact that they are a long way from the peak power revs when they throttle is less important
> 
> After a long walk around the bushes
> More power is better


I know this is a long thread and the example was a while back, but please look at it. Post #25 is the simulated 1/4 mile from the post #22 example. The context which started the discussion was direct drive, no shifting, so that is the way they were run.

Equal cars, equal conditions. Fair race. Car #1 wins, even though it has only a peak of 152 hp against car #2 with 228 hp. The hp vs RPM plots can be seen in post #61/62. Car #2 obviously has a broader power band.

So, for this application, "More power is better" does not apply, does it? It is also interesting to note that car #2 used more energy going the same distance yet lost the race. Sown in a later post.

Now I haven't seen one power fan own up to the fact that torque is relevant even when this example clearly shows it is. I am not saying that power is irrelevant by any means. It is very important. In many applications, like top speed, power is the most important factor. But getting torque from the motor at the right times can be more important than peak power or a wide power band in some cases.

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> O.K. Let's just leave it here.


no problem at all... As I've said from the beginning it is only an academic point and I don't see how it would significantly effect any real EV builds either way.

I'm glad we can move on.





Duncan said:


> As a final cut - nuts and bolts are not magic all of the simple laws of mechanics hold The energy you put in from your spanner appears as heat and as strain energy in the bolt and threads


No magic was claimed or suggested ... and energy is not the same thing as 'mechanical power'... if you want it further explained start a new thread... or do further reading & / or study... further posts on this topic on this thread will be ignored.

---------------------



major said:


> I know this is a long thread and the example was a while back, but please look at it. Post #25 is the simulated 1/4 mile from the post #22 example. The context which started the discussion was direct drive, no shifting, so that is the way they were run.
> 
> Equal cars, equal conditions. Fair race. Car #1 wins, even though it has only a peak of 152 hp against car #2 with 228 hp. The hp vs RPM plots can be seen in post #61/62. Car #2 obviously has a broader power band.


I don't think it is quite equal ... if you wanted to make a equal comparison ... the work and post from #25 would have to be modified from the way it was originally done ... There was also several differences between the two ... including gearing which is a big one.

I think a better examination would be more involved ... maybe something along these lines:

Identical vehicles ( including gearing )

One is constant power... one is constant torque... what are the pros and cons? 

Things like:
1/4 Mile time ... 1/4 mile energy used ... 0 to 60 time ... 0 to 60 energy used ... max speed ... max torque for constant power ... Average torque for constant power ... max power for constant torque ... average power for constant torque ... those kinds of things.

Of course limits would have to be put in for the motors ... things like max torque the motor could do, max power, max RPMs , etc...

For the constant power chosen I would suggest the average power used by the constant torque motor.

After this base line is established you could make modifications ... how much more constant power is needed for this or that ... how much does a transmission help each option? etc...

Of course in the end I strongly suspect it would just come back to my position... but it could be quantified.


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## major (Apr 4, 2008)

IamIan said:


> I don't think it is quite equal ... if you wanted to make a equal comparison ... the work and post from #25 would have to be modified from the way it was originally done ... There was also several differences between the two ... including gearing which is a big one.


IamIan,

It was a fair example of the 2 torque profiles posted by Bowser. The gear ratio, which you call a "big one" was chosen to set exit speeds at the 6000 RPM which was considered the limit according to post #22. I requested that thinking that would optimize the times for each. If you read thru this thread, it was questioned by someone else and further examination proved that #2 could be improved with a gear ratio other than the original. But it made only a slight improvement and did not alter the results, namely, #1 wins.



> I think a better examination would be more involved ... maybe something along these lines:
> 
> Identical vehicles ( including gearing )
> 
> ...


Cool. Run these examples and post up the results and your conclusions. What I did with Rich's help was take a random example from Bowser and simulate a fair comparison of a fairly universally common metric, the 1/4 mile drag race. The 2 competitors have equal platforms, only a gear ratio and power plant difference. The guy with less power wins because he has more torque where it counts.

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> Cool. Run these examples and post up the results and your conclusions.


I don't have that same program... it will take a chunk of time and work for me to complete ... so don't expect it soon... but it might be useful / fun to quantify a bit more how the two play out in different ways.

I'll put it on my to do list


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## ZX-E (Aug 31, 2009)

One problem with constant power is you have infinite torque at 0 rpm.


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## ZX-E (Aug 31, 2009)

Tah Dah!


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## ZX-E (Aug 31, 2009)

Constant Power: *Setup #1*































Constant Torque: *Setup #2*


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## DavidDymaxion (Dec 1, 2008)

The plots are invisible for me -- looking forward to seeing them.

You can have constant power -- use a clutch or automatic tranny that lets the motor idle, avoiding that motor melting infinite power at zero rpm thing. For simulations, you could shift the torque curve left, so zero vehicle speed is at idle motor rpm.


ZX-E said:


> What can you tell from that plot? For one, that a constant power output is impossible. ...


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## ZX-E (Aug 31, 2009)

DavidDymaxion said:


> The plots are invisible for me -- looking forward to seeing them.
> 
> You can have constant power -- use a clutch or automatic tranny that lets the motor idle, avoiding that motor melting infinite power at zero rpm thing. For simulations, you could shift the torque curve left, so zero vehicle speed is at idle motor rpm.


It doesn't really effect the simulation . You just have really really fast acceleration until about 1000 rpm.


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## ZX-E (Aug 31, 2009)

Thanks for pointing out that the picture links weren't working. For some reason the website I usually host them on is down.


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## major (Apr 4, 2008)

ZX-E said:


> Both vehicles have exactly the same gearing and specs. Both vehicles finish the quarter mile at their top speeds.


Hi Rich,

Curious they both finished at 84 mph at 6000 RPM which looks like it was the speed limit. I suspect they each hit 84 mph before the 1/4 mile marker and ran the last part of the race at constant speed. Is that right? 

Interesting simulation, but not quite sure what it tells us, except getting going faster sooner results in faster ET.

Regards,

major


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## ZX-E (Aug 31, 2009)

major said:


> Hi Rich,
> 
> Curious they both finished at 84 mph at 6000 RPM which looks like it was the speed limit. I suspect they each hit 84 mph before the 1/4 mile marker and ran the last part of the race at constant speed. Is that right?
> 
> ...


You're right. I agree that all it really shows is the constant power setup has much better initial acceleration. 

The constant power car actually hits its top speed right at the end of the quarter mile. The constant torque motor reaches 84 mph 3 seconds before the end of the quarter mile. I thought it was a fair comparison, but if you think there's something I can change to get more out of it, I wouldn't mind


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## ZX-E (Aug 31, 2009)

Well actually what I think it really tells us is that if you have a power vs rpm plot, you still have little or no idea how that would effect the vehicle's performance other than from peak power. A constant power vs rpm graph is a great example of that. Torque vs rpm on the other hand gives you important motor characteristics over the entire range of rpm. You almost need torque to interpret the power vs. rpm plot. Just my two cents.


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## major (Apr 4, 2008)

ZX-E said:


> The constant power car actually hits its top speed right at the end of the quarter mile. The constant torque motor reaches 84 mph 3 seconds before the end of the quarter mile. I thought it was a fair comparison, but if you think there's something I can change to get more out of it, I wouldn't mind


Oh, I don't know. You can run these all day long and somebody will say it wasn't a fair comparison. I wasn't really saying that. But the loser wasn't using all his available power for the last 3 seconds. Gearing him to 6000 RPM at the 1/4 mile marker would increase his exit speed, but slow his acceleration, so I don't think it would get him a win. That monster torque blast off the line for the other guy would be tough to beat.

When it comes to electric motors, I hate the words "constant power". When you're talking peak power over the speed range, it is just a dream. Especially down to zero RPM. I notice you start him off at 1000 lb.ft. What's the matter? Won't your program handle infinite torque 

Regards,

major


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## IamIan (Mar 29, 2009)

ZX-E,

Thanks... you beat me to it... I had barely started coding and you are all done 

I agree use what ever works for you and you find the easiest to work with and understand ... if that is torque ... fine ... if that is power fine ... In the end its your EV only you have to like your finished work.

---------------

As for the two plots... I think it shows some rather nice examples of how both can be useful ... and have pros and cons.

It also clarifies I think a misunderstanding people had about the first one.

As long as the constant power graph is the same amount of power as the average power of the constant torque graph the net energy used should be the same between the two.

Despite this equal energy... the constant power graph clearly shows it is faster in the 1/4 mile and faster 0 to 60 MPH.

This is useful because the first graph I think gave people the opposite / backwards impression.

--------------

I also 100% agree with the point that a major issue with a constant power curve is that the initial torque at low RPMs is so crazy high that it is just not possible in the real world.

--------------

This brings us back to the sliding scale concept that I personally like to apply.

Depending on specifics of what you are trying to do and on what your preferences are... a good quality build can be had with either focus.

For myself I will focus more on one or the other depending on the specifics of what I am trying to accomplish ... Torque is often for many application very useful and sometimes very intuitive to use ... but I will admit sense so much of a EV is about energy flow , usage, etc ... kwh per mile ... usable kwh of battery capacity ... kw of heat generation / dissipation , etc... I do tend to lean a it more toward power most of the time.

---------------

I think a big reason the harder initial acceleration tends to win whoever has it... is because the other forces acting against the acceleration keep getting bigger and bigger and occupy a larger and larger % of the system force or power.

Although I suspect that is not the only factor I would suspect it is a significant player.


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## Duncan (Dec 8, 2008)

Hi Major
I didn't understand that either so I modeled it myself
I have ignored wind resistance - not relevant for a comparison

Dick Dastardly and Mutley have stolen Tesla's without the motors
Dick has the 300, 200, 100 lbft motor
Mutley has the 200 lbft motor

Because both motors are 6000 rpm the Tesla 8.28:1 ratio is changed to 4.1:1

http://www.diyelectriccar.com/forums/attachment.php?attachmentid=4808&stc=1&d=1257923457

My table should be in here!
As they start Dick is accelerating 50% faster than Mutley, at 2 seconds Dick has over twice the power 
At 4 seconds Dick loses his extra torque but because his revs are higher he still has 50% more power and continues to pull away
At 6 and 8 seconds Dick is still pulling away
At 10 second Dick loses his power advantage but he is still going faster and continuing to pull away
At 12 seconds Dick is still faster
At 14 seconds Mutley is now faster but behind
At 16 seconds - all over

Mutley had more power for the last six seconds 
Dick had more power for the first ten seconds

Mutley is going faster as Dick crosses the line - This represents more energy


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## Duncan (Dec 8, 2008)

I will get the hang of these attachments - eventually

Lets try with a gearbox!
And the Tesla Gearing

see table

As they start Dick is accelerating 50% faster than Mutley
At 2 seconds they have dropped to the same acceleration, Dick is 4.6 m in front
At 4 seconds Dick loses his extra torque and Mutley is catching him
Mutley changes gear at 4 seconds, Dick at 5 seconds
At 6 seconds Mutley catches Dick and is 6 mph faster
At 8 seconds Mutley is 5 m past Dick and pulling away
At 13 seconds Mutley must back off to avoid blowing his motor but its all over!


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## Duncan (Dec 8, 2008)

Mutley Verses a real Tesla


The Tesla is off like a scalded rat
At 2 seconds the Tesla is 9 m in front and 13 mph faster
At about 9.5 seconds the Tesla is maxed out 100 m in front of Mutley and 30 mph faster
At just over 11 seconds its all over


I enjoyed doing these simple models

The Tesla's huge rev range makes it simple,
At up about 60 mph it has constant torque, so much torque that it must be close to breaking traction
I am not sure if more torque could be used off a race track!

Above 60 mph it is power limited, with more power it could continue to accelerate that hard to a higher speed

Sticking a motor with more torque in a standard geared /tyred Tesla would probably not make it go faster as you would be tyre limited
A motor with more power would allow it to accelerate harder where the current Tesla is power limited

More power is always more important

But I would love something that delivered like a Tesla!


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## ZX-E (Aug 31, 2009)

Duncan said:


> Mutley Verses a real Tesla
> 
> 
> The Tesla is off like a scalded rat
> ...



Yea the Tesla really is a beast.


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## Duncan (Dec 8, 2008)

I got carried away with the Tesla!

What I intended to show was

In the single gear example the "more powerful"car (Mutleys) actually had less power for most of the run
And Lost!

With two gears Mutleys car had more power than Dick for most of the run 
And Won!

It is all about power BUT if you have not got a Tesla type huge power band then you need gears


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## electrabishi (Mar 11, 2008)

Duncan said:


> I got carried away with the Tesla!
> 
> What I intended to show was
> 
> ...



I don't have the Huge Power Band like the Tesla. But the Pinto with a single gear ratio will beat the Tesla in the 1/4 mile. Because I have so much more "torque" and can get 2 car lengths out in front at the start he has to use that extra power just to catch up. Like was mentioned earlier, by then its all over ;-)

I just read through this thread and will say without elaborating much that the person who said Torque is irrelevant must have never tried to drive his car around in 5th gear all the time with a little 4 cyl engine. Even with a hi power twin turbo 4 banger, taking off in 5th gear all the time really sucks. So torque IS relevant. Not much more to say on that except that there are several trade offs to consider when designing your car. Torque, Power, Dynamic Range, Gearing, Speed, Acceleration etc etc are all aspects....and Torque is one of those real aspects.


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## gor (Nov 25, 2009)

electrabishi said:


> ...
> 
> I just read through this thread and will say without elaborating much that the person who said Torque is irrelevant must have never tried to drive his car around in 5th gear all the time with a little 4 cyl engine. Even with a hi power twin turbo 4 banger, taking off in 5th gear all the time really sucks. So torque IS relevant. Not much more to say on that except that there are several trade offs to consider when designing your car. Torque, Power, Dynamic Range, Gearing, Speed, Acceleration etc etc are all aspects....and Torque is one of those real aspects.


this is been answered several times in this thread: 
for calculations "this person" made, he needed :
1. torque and rpm together, combined, torque*RPM (power); from here: 
2. his next step - to find out particular values of torque and rpm for each gear ratio, depending on power and torque curves; 
- so for his task, he needed only kilowatts, and for him it was irrelevant what are separate values of torque and rpm - exact numbers of each was yet to find out and will be relevant on next stage

depending on what you need to accomplish - you have several ways and same math. equation: power=torque*rpm/9549
- choose whatever approach you like and what works for you

p.s. the only relevant - is formula, irrelevantly to what we might call it, what really irrelevant - is semantics : ))))


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## Duncan (Dec 8, 2008)

What is this Pinto that can beat a Tesla with only one gear and less power??
Sounds Demon!


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## major (Apr 4, 2008)

Duncan said:


> What is this Pinto that can beat a Tesla with only one gear and less power??
> Sounds Demon!


http://www.diyelectriccar.com/forums/showthread.php/electric-crazyhorse-pinto-16474.html 

That thread has not had much activity lately. But Mike and his Pinto have. He has made the cover of a national magazine. Good press and good time slips. Maybe you can find his web site on that thread. Mike always seemed open about his builds and willing to show data. I give the guy a lot of credit


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## Bowser330 (Jun 15, 2008)

Duncan said:


> What is this Pinto that can beat a Tesla with only one gear and less power??
> Sounds Demon!


He also doesn't have "less" power....

http://www.evalbum.com/1093

360V sagged to ~260V @ 2000A = 520kw ~ 698hp


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## major (Apr 4, 2008)

Bowser330 said:


> He also doesn't have "less" power....
> 
> http://www.evalbum.com/1093
> 
> 360V sagged to ~260V @ 2000A = 520kw ~ 698hp


Hey Bowser,

Dyno tests showed just a hair over 300 HP at the wheels. 

http://home.gci.net/~saintbernard/Crazyhorse_Pinto_HP_Torque_06AUG08.pdf 

That is still a little more peak power than the Tesla, I think.

major


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## Bowser330 (Jun 15, 2008)

major said:


> Hey Bowser,
> 
> Dyno tests showed just a hair over 300 HP at the wheels.
> 
> ...


215kw peak for Tesla (289hp) at the motor not at the wheels....

Pinto has about 310hp @ the wheels....

If we consider a 5% loss for the Tesla drivetrain, then Tesla @ wheels is ~ 275hp...

35hp peak hp difference.


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## Duncan (Dec 8, 2008)

That Pinto is impressive

But it has more power than the Tesla - (5% reduction for transmission and tires is about what high pressure low rolling resistance tires will get - The Tesla has sportier rubber with higher losses)
Probably at least 45 Hp more

This translates into 0,2 seconds at the Quarter mile

Power is important
Torque is a resultant property - (power divided by rpm)

By using the correct gearing power will produce any torque you want
Changing gearing does not change power

Power band is also extremely important as it determines how may gears are needed


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## major (Apr 4, 2008)

Duncan said:


> Power is important
> Torque is a resultant property - (power divided by rpm)
> 
> By using the correct gearing power will produce any torque you want
> ...


Hey Duncan,

This whole thread was started discussing a direct drive, meaning a single gear reduction. Nobody has ever denied that you can alter the torque speed relationship by changing gears. That is not the point of this thread. But I lost control of it a long time ago, so talk about changing gears if you want. But both the Tesla and that Pinto run direct drive. And beat the pants off gassers with much more power and multi-ratio transmissions. So exactly how does this power thing trump the torque thing for the 1/4 mile ET?

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> And beat the pants off gassers with much more power and multi-ratio transmissions. So exactly how does this power thing trump the torque thing for the 1/4 mile ET?


Without more data ... my guess would be that ... the 'gassers' ... have more peak power ... they do not actually have equal output power in that race.

It doesn't matter what the peak power of the engine or motor is ... It matters what the applied power is... on a moment by moment basis... and as an overall average.

If a 500 Peak HP motor is only putting out 200 HP at one given time... than it is still only putting out 200 HP no matter what its peak might be under some other conditions.

200 applied/output HP from a gasser or an Electric will both produce identical results.



Duncan said:


> Torque is a resultant property - (power divided by rpm)


The equation is just as correct in either form.

One way Torque is the resultant.

equally as correct 

A second way Power is the resultant.

The equation only expresses a relationship between the two.


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## major (Apr 4, 2008)

IamIan said:


> Without more data ... my guess would be that ... the 'gassers' ... have more peak power ... they do not actually have equal output power in that race.


You have the data from Mike Pinto's dyno test. And I would think that that gasser data would be easily found.



> It doesn't matter what the peak power of the engine or motor is ... It matters what the applied power is... on a moment by moment basis.


Or in other words, torque. That is the point. The low speed (including zero) torque output of the electric motor is relevant. F=ma. The acceleration comes from force, not power. And when your prime mover is a rotary device, that is torque. I'll say it again, gettin' goin' faster sooner is the key  And that happens with launch torque.

Regards,

major


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## IamIan (Mar 29, 2009)

major said:


> Or in other words, torque. That is the point. The low speed (including zero) torque output of the electric motor is relevant. F=ma. The acceleration comes from force, not power. And when your prime mover is a rotary device, that is torque. I'll say it again, gettin' goin' faster sooner is the key  And that happens with launch torque.


Not what I was writing about... your seemed to have miss-understood.

I'll try again. 

It does not all boil down to either torque or power individually... just like you can't have a one sided magnet.

It is just as correct to say either:
#1>Torque comes from Power.

Also equally correct to say

#2> Power comes from torque.

They are related , not isolate things.

A gasser at 1 second is not outputting its peak power... its instantaneous power varies significantly over the power band.

Even if the gasser was rated at 500 Peak HP... it does not apply 500 HP all the time... sometimes as little as 100 HP.

You can correctly say that the electric motor has more torque at the low end of RPMS ... but that is just a rewording of an equally correct statement that the gasser has less power output at lower RPMs.

If the Gasser had equal power output it would have equal performance... just like it is equally correct to say if it had equal torque it would have equal performance.

It is not about peak ... it is about moment by moment and the over all average.

If you like to think of it as moment by moment torque and average torque ... that is just fine if you like it more go with it ... but it is just as equally correct to think of it as moment by moment power and average power.

I've never said either is irrelevant ... because they both matter... which one you happen to like working with depends on your specific personal preferences and the specifics you want to accomplish.

Large Power or Large Torque accelerate faster, than low amounts of either... that is true of any speed , low or high.

-------------

To save a repeat ... I recommend we avoid going back into the academic issue of power at zero speed ... so I recommend that we just skip that.


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## major (Apr 4, 2008)

IamIan said:


> #1>Torque comes from Power.


This is incorrect. What else can I say 

Good night.


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## gor (Nov 25, 2009)

"let the Force be with you" 
(or Power (based on Force - unfortunately, laws of physics - not the other way around ... unless it's "Power to the people", based on intelligence ... what is more irrelevant - hard to tell : ))))))))


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## gor (Nov 25, 2009)

if peak torque - first warning of "it's over" (acceleration decreases); peak horsepower- "it is over". power - result of force(torque), work done by force, if it start to go down - that's it...

while it's common sense what to do with peak torque, is there different approaches to using peak horsepower in transmission design and calculations?


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## gor (Nov 25, 2009)

Bowser330 said:


> Originally Posted by *Duncan*
> _What is this Pinto that can beat a Tesla with only one gear and less power??_
> _Sounds Demon!_
> 
> ...


are you comparing street car with 0-60 3.9(3.7)sec and range 244 miles
- and drag racers with 0.25 mile range, and consuming all its power in few seconds?


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## Bowser330 (Jun 15, 2008)

gor said:


> are you comparing street car with 0-60 3.9(3.7)sec and range 244 miles
> - and drag racers with 0.25 mile range, and consuming all its power in few seconds?


No, actually i was responding to the broad statement about which had more "power".

No one is comparing the overall statistics of each car but if you are going too there are few things in your comment we first need to correct...

First you cannot compare Tesla Roadster range of "244" miles which is met by driving moderately to the Pinto drag racing 

Second the Pinto's range is not only one quarter mile..
Per the Pinto's EVAlbum page, he gets 250wh/mile average...and his total battery pack is 60 12V 16AH batteries which equates to 11.5kwh, so that means 46 mile range to 100%DoD. I am referring to 100% DoD because thats what you started with when you mentioned 244miles for the Tesla....

Third, The pinto was about 30K$ to build and last time I checked the Tesla cost about 120k$ (for the 288hp model that we were talking about, the 3.7 sec 0-60 model)

To compare, lets give the pinto a comparable battery pack, so 250wh/mile means he would need 61kwh pack to get 244 miles per charge, so 61kwh of A123 cells @ 7$ each cell (3.3V&2.3AH) would be 56K$, but he will get a credit from his existing pack of 6K$, so total is 24K$+56K$ = 80K$....

My hat goes off to Mike for creating such a great EV with his Pinto. I also really respect the Tesla Roadster and think its a phenomenal performance machine.


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## IamIan (Mar 29, 2009)

major said:


> This is incorrect. What else can I say


You seemed to miss it again... here I'll try once more. 

P = ( T * 2 pi * RPMs ) / 60,000

Is a formula where power comes from torque... or said another way , in this equation Power is a function of torque.

It is equally correct to also write it as:

T = ( P * 60,000 ) / ( 2 PI * RPMs )

But written in the second form Torque comes from Power... or said another way in this equation Torque is a function of power.

Both are equally correct.

Welcome to Algebra.


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## major (Apr 4, 2008)

IamIan said:


> Welcome to Algebra.


Hey IamIan,

Stop your car on an inclined street. Put into park. Turn the engine off. Get out. Lock it. Leave it there. Look at it from a distance. There is no power. Zero. It is not moving. However there is torque on the shaft at the center of the wheel. You can calculate the magnitude of this torque using the slope of the street surface, the mass of the car and the radius of the wheel. You could also measure the torque with a strain type transducer on the axle. Torque is there, yet no power. Torque does not come from power.

Regards,

major


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## Tesseract (Sep 27, 2008)

IamIan said:


> ...
> 
> Welcome to Algebra.


ooo... nasty!

However you seem to have ignored the fact that, practically speaking, you can produce tremendous amounts of torque without doing a single horsepower's worth of work. For example, if an overhead crane is holding a load at a fixed elevation it might do so by pumping enough current through the motor to create enough torque to exactly balance the effect of gravity.

So, torque is not always created from power. It is alwaysa contributor to power, but not necessarily derived from it.

Conversely, the same can be said of RPM, though, realistically speaking, this corollary is only theoretical because while it is easy to create a real world situation where torque > 0 and power = 0, doing the same but with RPM > 0 is practically impossible (high vacuum, magnetic bearings and a levitating flywheel made of a superconductor would be some of the ingredients necessary to pull this off). 

Finally, a more pedestrian observation: the source of the EV grin is completely and totally from the much higher torque available at 0 rpm. Few people grin like that when, for example, a large turbine spools up on a plane prior to takeoff. Ergo, RPMs are boring while torque is exciting!


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## IamIan (Mar 29, 2009)

If I want to move a car talking about Zero RPMs means almost nothing.

I could supply 5 trillion N m of Torque at zero RPMs... but if that torque stops as soon as I have any non-Zero RPMS... even something as small as ... 0.000000000000000000000000000000000001 RPMs that torque at Zero RPMS is just about useless in terms of moving the car.

The same holds true with power ... even if I have 5 MW of power at Zero RPMs but only at 0 RPMs it is a nearly useless.

The only values I see in talking about power levels and torque levels at Zero RPMs is :

#1> In that tiny tiny fraction of a second it takes to break static friction and Rest Inertia.

#2> Don't break your components.

The above holds true for 1/4 Mile run times ... for 0 to 60 MPH run times ... for Fuel ranges ... for Top speeds ... etc... etc...

Talking about Zero RPMs is about as useful as talking about the electron drift rates.

------------

I doubt there is anything to be gained from getting back into a discussion on the nature of power or torque and what happens at Zero RPMs... As outlined above if you want to move ... Zero RPMS is almost useless... for Power or Torque.

Two vehicles at the same RPMs will accelerate and perform equally as long as they have equal power or equal torque.... because at equal RPMS having equal power means you have equal torque and having equal torque means you have equal power.

Even if one vehicles engine is rated at 500 HP and the other is rated at 200 HP... it doesn't matter what the engine is rated at... it matters what it is outputting.... If the 500HP rated engine is outputting less HP than the 200 HP rated engine than at that point it has less power and will perform less ... 

If you prefer, substitute the word Toque for Power in the above paragraph ... its the same result either way.

The reason EVs with less rated HP are able to keep pace with or beat ICEs that rated with higher HP ... is because the Electric motor of a EV has a very different performance curve than the ICE does... they do not produce the same Torque or Power at the same parts of their performance curves.... that's all it is.... If the EV has more torque at lower RPMs than it also has more power at lower RPMs ... They go together... both are equally correct.

----------

The basic point is this.

If you want to have a vehicle that moves ... you have both ... neither is inherently superior or inferior than the other... There are ways to do it either way... so whatever your preference is... have fun, and best of luck


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## major (Apr 4, 2008)

IamIan said:


> The reason EVs with less rated HP are able to keep pace with or beat ICEs that rated with higher HP ... is because the Electric motor of a EV has a very different performance curve than the ICE does... they do not produce the same Torque or Power at the same parts of their performance curves.... that's all it is.... If the EV has more torque at lower RPMs than it also has more power at lower RPMs ... They go together... both are equally correct.


So you agree with me that torque is relevant. That is what I said back at the beginning of this thread that you also have to look at torque, not just power. 

Neither I, nor anyone else here, has said that once motion has commenced that power and torque are not related by a simple mathematical formula. We all know that. But that power is dependant on torque, not the other way around. And the fact that there is torque at standstill proves it. Is there power without torque?

But this still does not answer the gasser-heads who claim they can manipulate torque with gear ratios. Those gassers have much more available horsepower and as many gear ratios as they want, but still lose to the electric with a single ratio. Yet they say torque is irrelevant. It seems to me with all those ratios and any number of shifts available, those guys could take that extra horsepower and convert it to torque in any part of the "power band" they want and beat the White Zoombie, or Crazyhorse Pinto, or Killacycle. What's holding them back?

Regards,

major


----------



## cutiepie (Dec 20, 2009)

Wow! After reading all this I got hungry. I think I'll have a squirm sandwich.
The last few pages about power at zero RPM reminded me of the discussion
over at the "hook a generator to your wheel" section where people couldn't
get it in their head that magnets are NOT doing any work just because
they "suck" all the time. Well, happy squirming everyone! And yes torque
is relevant! But it does not make the world spin around...I can't say what does because my wife will get mad...
Merry Christmas!


----------



## Batterypoweredtoad (Feb 5, 2008)

Major,
Plenty of gassers ARE beating the electrics. Pointing out who looses a particular race doesn't really prove the superiority of one or the other. We really haven't even had a good example of a really high horsepower low torque car competing with the electrics to use as a good example of which is better. IIRC Crazyhorse makes 1200ft lbs of torque and 300 hp. It would be interesting to see how a theoretical 300 ft lb of torque and 1200 hp car would do in comparison. Currently he is beating cars in the 350hp 350 ft lbs torque range. Pretty good, but not a world beater.


----------



## major (Apr 4, 2008)

Hi toad,



Batterypoweredtoad said:


> Major,
> Plenty of gassers ARE beating the electrics.


Obviously 



> Pointing out who looses a particular race doesn't really prove the superiority of one or the other.


That wasn't my point.



> We really haven't even had a good example of a really high horsepower low torque car competing with the electrics to use as a good example of which is better.


But Drew and those who side with him say that torque is irrelevant. All you have to do is choose the right gear.



> IIRC Crazyhorse makes 1200ft lbs of torque and 300 hp


Yep, according to the dyno test.



> It would be interesting to see how a theoretical 300 ft lb of torque and 1200 hp car would do in comparison.


Yeah, but that would be like 20,000 RPM, wouldn't it. Cool 



> Currently he is beating cars in the 350hp 350 ft lbs torque range. Pretty good, but not a world beater.


I think White Zoombie is less power and beats some guys with higher power than that. And KillaCycle blows away some bikes with high power engines and less weight. And then there is Dennis in the Current Eliminator. But hard pressed to get any power and torque figures from him.

I'm not here saying electrics are the best thing since sliced bread on the drag strip. The 1/4 mile race was just a good metric to use for performance when talking about power plant torque. If we were talking tractor pulling or hill climbing, we probably would have attracted a lot less attention 

major


----------



## IamIan (Mar 29, 2009)

major said:


> So you agree with me that torque is relevant. That is what I said back at the beginning of this thread that you also have to look at torque, not just power.


Kind of.

My own point of view is that I will sometimes use torque , and sometimes I use power... so for me personally torque is relevant.

Which one I use for a given situation and problem is a personal preference.

Due to relationships they can pretty much all be converted between each other.

A person who personally prefers power can manipulate the equations to be functions of power in all his equation to determine performance... including acceleration , top speed , distance per unit fuel , etc...

The same can also be true for a person who personally prefers torque... the equations can pretty much all be manipulated as functions of torque to determine performance ... including acceleration , top , speed , distance per unit fuel , etc...

I might personally prefer to use torque in some cases and power in others ... but that is just my personal preference ... I recognize that not everyone has my same preferences and other for some reason or another they might want to manipulate the equations to be functions of torque ... or functions of power.

As long as they manipulate the equations correctly and such the results should be the same either way.



major said:


> Neither I, nor anyone else here, has said that once motion has commenced that power and torque are not related by a simple mathematical formula.


Exactly why either can be used to get the same results.

Which is used in a specific situation is a personal preference.

Both are equally correct.



major said:


> But this still does not answer the gasser-heads who claim they can manipulate torque with gear ratios. Those gassers have much more available horsepower and as many gear ratios as they want, but still lose to the electric with a single ratio. Yet they say torque is irrelevant. It seems to me with all those ratios and any number of shifts available, those guys could take that extra horsepower and convert it to torque in any part of the "power band" they want and beat the White Zoombie, or Crazyhorse Pinto, or Killacycle. What's holding them back?


They run into problems because they didn't do it correctly... and the real world is more complex than they thought it would be.

We can get more into that if you like... but ... I'll leave it at that point there unless someone actually does want to read my 2 bits about that in more detail.



major said:


> But that power is dependant on torque, not the other way around.


Algebra can easily manipulate the formulas to make either the function of the other...

Yes written one way Power is dependent on torque.. but written another way Torque is dependent on Power.

That is just what it means to be a dependent variable... or an independant variable.

Both are equally correct.



major said:


> And the fact that there is torque at standstill proves it. Is there power without torque?


Torque and Power at Zero RPMS again.... 

Zero RPM conditions are still next to useless if you want to talk about a vehicle that moves.

Do we want our vehicles to move? 

If yes... there are only 3 reasons to discuss Zero RPMs... Static Friction , Inertia , Don't break components.

Power at Zero RPMs ... 
I don't see a benefit of getting back into that again.

Weather there is or not ... Zero RPMs are still next to useless... why keep focusing on this next to useless Zero RPM condition ... you already know my position on it... and I already know yours... and neither will effect a vehicle that we want to move.


----------



## major (Apr 4, 2008)

IamIan said:


> Algebra can easily manipulate the formulas to make either the function of the other...
> 
> Yes written one way Power is dependent on torque.. but written another way Torque is dependent on Power.
> 
> ...


Ian,

Just because the math is correct doesn't mean the physics are. In the rotational mechanical system power is the product of torque and angular velocity. Meaning that it is a resultant quantity of the 2 primary system variables, namely torque and angular velocity. Just because you can manipulate the equation and move torque to the left of the equal sign does not make it the resultant variable and power the primary variable in the physical world.

Do you look at the electrical system the same way? Voltage and current are the fundamental variables. Power is the resultant variable when you have voltage and current simultaneously. But who relies on electrical power to figure the voltage? Are you going to stick your hands into an electrical distribution box because you are told there is no power? Might be thousands of volts of potential. 

And look at it another way. Where does the power come from? In both the electric motor and the ICE, power results from a developed force inside the machine. Being rotational machines that force is translated into torque. Torque is the primary attribute which causes rotation resulting in power.

Regards,

major


----------



## IamIan (Mar 29, 2009)

major said:


> Just because the math is correct doesn't mean the physics are.


Actually ... yes it does.
The physics is the relationship.
The relationship is preserved as long as the math is correct.

Thus if the math is correct the physic is correct.

Just like ... V=IR ... I = V/R ... R = V/I ... all are equally correct ... the only time this is not true is for non-ohmic materials and effects that don't obey the basic V=IR formula to begin with.

Math is also very clear about what makes a term dependent, what makes a term independent , and what makes a term a resultant variable.



major said:


> Do you look at the electrical system the same way? Voltage and current are the fundamental variables. Power is the resultant variable when you have voltage and current simultaneously. But who relies on electrical power to figure the voltage? Are you going to stick your hands into an electrical distribution box because you are told there is no power? Might be thousands of volts of potential.


If there is no potential for power ... Voltage is next to meaningless.

Static electricity often is several thousands of volts ... but the total power is very low which is why you barely even get an electrical shock ... but if the total potential power is low enough than it could be billions of volts and still would pose no risk at all.

Actually I look at electrical in a similar way ... yes... but it is not identical... because it is not an identical situation.... but this is not the thread for a detailed look into the nature or interaction of different electrical concepts like voltage , current , power , etc...



major said:


> And look at it another way. Where does the power come from? In both the electric motor and the ICE, power results from a developed force inside the machine. Being rotational machines that force is translated into torque. Torque is the primary attribute which causes rotation resulting in power.


Although not the only path to take ... that would be an option ... but ... Even if we followed you path ... It is also not the start... where did you get that force from in the electric motor?... here's a hint... it was the conversion of energy... or power that gave you that force in the first place... same is true in the ICE.

----------- But ----------------

I seriously doubt that a discussion on which is more fundamental power or force has any significant usefulness in making a vehicle move... and talking about what is a more fundamental property is just going to get way off topic and ugly with obscure science very quickly.

It is even more useless than Zero RPM discussion.

Torque and Power are both there... if used correctly either can be used to determine acceleration , top speed , fuel used , etc... 

If you have a personal preference ... use either ... use both ... use exclusively one and not the other ... if done correctly the results are the same.


----------



## major (Apr 4, 2008)

IamIan said:


> P = ( T * 2 pi * RPMs ) / 60,000
> 
> Is a formula where power comes from torque... or said another way , in this equation Power is a function of torque.


Yes, this is always true.



> It is equally correct to also write it as:
> 
> T = ( P * 60,000 ) / ( 2 PI * RPMs )


No, this is incorrect because it is only true sometimes.



> But written in the second form Torque comes from Power... or said another way in this equation Torque is a function of power.


I spent an hour or two at this. Curious that all the text books and search engine results for a definition never mention power in the definition of torque. You'd think that if torque was a function of power, they might define it that way. BTW they all use torque to define rotational power.

In looking over some of those texts, I also notice that when calculating acceleration of rotational inertia they strictly use torque without ever mentioning power.



> It is even more useless than Zero RPM discussion.


I assume you think that it is useless because it blows your argument out of the water. This discussion and thread has used the drag race as example. So let's stick with it. Does not each race start with the vehicles at rest? Zero RPM at the wheels? And is not the launch (or hole shot) an important part of the race?

And beyond the race aspect, having torque at zero RPM can be useful. I find it quite handy in driving the EV in traffic on hilly terrain or negotiating ramps onto transport trailers.

Another thing bothers me about you insisting that torque is a function of power. If one didn't know better, they could infer that this means zero power is zero torque. And this is a DIY forum, so there could be someone reading this who would not know better. So to them, hey, it's not spinning. No power. No torque. Just cut it in half. Bingo! The shaft just sprung out and hit them in the head. 

Yeah, a long shot. The voltage thing worries me more. Oops, blew a fuse. Hey no power, no voltage, no worry. Wrong  

Regards,

major


----------



## Jan (Oct 5, 2009)

I know nobody cares about another point of view. Especially my even less educated one. But I’m going to share it anyway.

I never use torque in my calculations. And by that I mean the performance of my car I can expect with a certain motor setup. Performance like the maximum and cruising speed, range and acceleration. This is all easy to calculate out of the rated and peak power, and efficiency per RPM. 

About the power at zero rpm discussion: There is no mechanical power, but there is maybe some electric power. Depending of the fact why the vehicle is at zero speed. Is it because of the fact the brakes are on, or is it because of the fact the friction/resistance is greater than the electric power? In this last case there is energy consumed, but no speed. There is torque because of the electric power. But no mechanical power because of zero speed.

Either way, for my calculations it’s irrelevant. As soon the resistance becomes bigger than the max rated or peak power, I’ve found the max cruising and top speed. And if that’s at zero speed, the motor has a little to less power.

So, for me torque is pretty irrelevant. But I can understand that if you look at motors in a different way, it’s the other way around.


----------



## major (Apr 4, 2008)

Jan said:


> I know nobody cares about another point of view.


Sure we do (or at least I do). I'd like to see more. Thanks for posting.


----------



## Jan (Oct 5, 2009)

major said:


> Sure we do (or at least I do). I'd like to see more. Thanks for posting.


Thanks Major. At least someone reads me. Feels great!

Can you explain (dummy style) why the graphs for AC drives mostly are based on the RPM's and DC drives mostly on Amps in the X-axis? I find DC graphs hard to translate to my needs.


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## major (Apr 4, 2008)

Jan said:


> Can you explain (dummy style) why the graphs for AC drives mostly are based on the RPM's and DC drives mostly on Amps in the X-axis? I find DC graphs hard to translate to my needs.


Hi Jan,

I think that using torque as the x-axis is the proper way to do both AC and DC motor curves. I explain this (at least for the DC) in http://www.diyelectriccar.com/forums/showthread.php/dc-motor-graph-39649.html 

I was thinking about your prior post. You know, I'll bet most people go through life without ever thinking about torque. Ones that look at this site probably have run into a torque spec for tightening bolts. Now why is it that they do not use power to tell you how to properly apply that fastener?

Regards,

major


----------



## Jan (Oct 5, 2009)

major said:


> Hi Jan,
> 
> I think that using torque as the x-axis is the proper way to do both AC and DC motor curves. I explain this (at least for the DC) in http://www.diyelectriccar.com/forums/showthread.php/dc-motor-graph-39649.html


You make it clear how to read this graph. And you prefer this way, I understand, because you see how the motor behaves under increasing load. 

But, isn't that because you know how they work internally? 

I only want to know how much power is left at a certain RPM after overcomming the resistance to get the vehicle at the corresponding speed. With the remaining power I can calculate the accelaration. 

Is it maybe that in an AC drive the efficiency is less dependent on load?



> I was thinking about your prior post. You know, I'll bet most people go through life without ever thinking about torque.


A lot without ever thinking about the difference between power and energy too. 



> Ones that look at this site probably have run into a torque spec for tightening bolts. Now why is it that they do not use power to tell you how to properly apply that fastener?


This is rethorical, wright?


----------



## Tesseract (Sep 27, 2008)

major said:


> ...Ones that look at this site probably have run into a torque spec for tightening bolts. Now why is it that they do not use power to tell you how to properly apply that fastener?



Surely you can just spin the bolt faster to achieve the same clamping force, right?


----------



## major (Apr 4, 2008)

Jan said:


> But, isn't that because you know how they work internally?


I don't think so. The motor curves are drawn to help the users properly apply the motors.




major said:


> Now why is it that they do not use power to tell you how to properly apply that fastener?





Jan said:


> This is rethorical, wright?


No, it is actually a serious question for those that believe that torque is a function of power. So if most people are unaccustomed to using torque, why not specify the bolt tightening procedure in terms of horsepower, a term most people are more familiar with?

Regards,

major


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## Jan (Oct 5, 2009)

major said:


> I don't think so. The motor curves are drawn to help the users properly apply the motors.


OK, for DC, I understand: The voltage drop and the therefor increasing Amps is important to know. To understand the effect on your batteries. More amps on batteries mean a greater Peukert effect. 

But that's not the case with AC, or not? 



> No, it is actually a serious question for those that believe that torque is a function of power. So if most people are unaccustomed to using torque, why not specify the bolt tightening procedure in terms of horsepower, a term most people are more familiar with?


Becaus you can't measue it easy? I don't understand what you're trying to say.


----------



## major (Apr 4, 2008)

Jan said:


> OK, for DC, I understand: The voltage drop and the therefor increasing Amps is important to know. To understand the effect on your batteries. More amps on batteries mean a greater Peukert effect.
> 
> But that's not the case with AC, or not?


Hi Jan,

This is a bit off topic. I'd be glad to try to help you, or give you my opinions, but perhaps a new thread in the motor section would be appropriate.

If you have the AC motor powered by batteries (using an inverter, obviously), you will also see voltage droop and that will affect the motor output in a similar manner as it does with a DC motor.



major said:


> No, it is actually a serious question for those that believe that torque is a function of power. So if most people are unaccustomed to using torque, why not specify the bolt tightening procedure in terms of horsepower, a term most people are more familiar with?





Jan said:


> Becaus you can't measue it easy? I don't understand what you're trying to say.


I am trying to support my view that torque is not a function of power.

And how do we measure rotational mechanical power? Say for instance from an engine or motor? In most cases that would be with a torque sensor on the output shaft and a tachometer. I'd say further supporting my claim that power is a function of torque, but that torque isn't a function of power.

Got you thinking about it anyway.  All I have been doing with this thread is to try to get people to realize that torque is not irrelevant. I am not saying that power is unimportant. I use it all the time.

I'll add, I think that the fact that electric motors produce torque at zero RPM is a great attribute which makes them well suited for vehicle propulsion. And since there is no mechanical power on the motor output shaft at zero RPM, that alone makes torque relevant.

Regards,

major


----------



## major (Apr 4, 2008)

Tesseract said:


> Surely you can just spin the bolt faster to achieve the same clamping force, right?


Is that how you assemble those controllers?  I thought so.


----------



## Jan (Oct 5, 2009)

major said:


> Hi Jan,
> If you have the AC motor powered by batteries (using an inverter, obviously), you will also see voltage droop and that will affect the motor output in a similar manner as it does with a DC motor.


I didn't take this into account of my calculations. So, I've got to start a new topic.



> I am trying to support my view that torque is not a function of power.


I didn't deny that. I just say I can do my maths (until now, you got me worried) without the Torque concept.



> And how do we measure rotational mechanical power? Say for instance from an engine or motor? In most cases that would be with a torque sensor on the output shaft and a tachometer. I'd say further supporting my claim that power is a function of torque, but that torque isn't a function of power.


I would agree with you that the mechanical power that's focused at is somewhat of a function of torque. Although I don't like the function-of concept. It all depends of what you want and have. The tools, your background and situation. There is more power than just the mechanical power at the end of the line. In case of the bolt, you should define the musscle power that should be applied while thightening. That's nearly impossible to measure. So, the torrque that's easy to measure is the key. But to say it's a function off...?

I can live without it, because I don't calculate with the zero or negative rpm situations. 



> Got you thinking about it anyway.


Don't flatter yourself. That's very easy.



> All I have been doing with this thread is to try to get people to realize that torque is not irrelevant. I am not saying that power is unimportant. I use it all the time.


And I'm saying it depends. It's not absolute, it's relative. Actually the same thing you're saying. In other words.



> I'll add, I think that the fact that electric motors produce torque at zero RPM is a great attribute which makes them well suited for vehicle propulsion. And since there is no mechanical power on the motor output shaft at zero RPM, that alone makes torque relevant.


Mmmm... That's a way at looking at it. The ICE has the problem it can convert chemical power only when it's in operation. And it only operates when its rotating. Electromotors don't have that problem with converting electric power into mechanical power. They don't have to be in motion. The ICE that can start itself without the help of an electro motor has torque at zero RPM too. It's hard to build, but is theoretical possible. And it will be very little torque probably. Or power at low RPM's, whatever you prefer.


----------



## IamIan (Mar 29, 2009)

My apologize to others for the size of this post.

----------------



major said:


> Yes, this is always true.





major said:


> No, this is incorrect because it is only true sometimes.


I see one of three possibilities,

#1> You just don't like the results which are valid.

#2> I made a mistake in the math... if so please explain.

#3> Mathematics itself ... even if done correctly is still wrong.... in which case ~99% of science just went out with it.



major said:


> You'd think that if torque was a function of power, they might define it that way.
> 
> Another thing bothers me about you insisting that torque is a function of power.


Correction.

I am not making the one sided claim you are.

I am claiming it can go either way... one can define one in terms of the other.... this is something that is done all the time in science, mathematics, and engineering... as long as the mathematics are done correctly any resultant equation is equally true.

I can also just as correctly write:
M = E / C^2 ... E/M = C^2... and E=MC^2 .... all equally correct.... as long as the mathematics was done correctly and the original relationship E=MC^2 was correct.

You don't have to like the results... you don't have to understand them.

But if you want me to abandon these known principles of science and mathematics... your going to need more than just your own opinion that you don't like the results.

Otherwise don't ever solve for x to determine the unknown ... when you aren't accepting the validity of the mathematics used.



major said:


> I assume you think that it is useless because it blows your argument out of the water. This discussion and thread has used the drag race as example. So let's stick with it. Does not each race start with the vehicles at rest? Zero RPM at the wheels? And is not the launch (or hole shot) an important part of the race?
> 
> And beyond the race aspect, having torque at zero RPM can be useful. I find it quite handy in driving the EV in traffic on hilly terrain or negotiating ramps onto transport trailers.


You can of course assume anything you like.

Not that it will matter because after I show this flaw in your above statements it won't make a difference... you will still most likely still remain fixated on the Zero RPM next to useless condition.



IamIan said:


> If I want to move a car talking about Zero RPMs means almost nothing.
> 
> The only values I see in talking about power levels and torque levels at Zero RPMs is :
> 
> ...


I do not assume it is next to useless because it damages my case in any way... I assume it is next to useless because it is if we want our vehicle to move.

As soon as there is even 1 pm of movement you no longer have Zero RPMs.

At Zero RPMs the vehicle does not move at all.

Even to just break static friction and rest inertia requires you to leave the Zero RPM condition.

Do you want to have any acceleration at all? That requires you to move... which is outside the scope of Zero RPMs.

Do you want to move even 1 pm ? That requires you to move... which is outside the scope of Zero RPMs.



major said:


> This discussion and thread has used the drag race as example. So let's stick with it.


Sure .. lets stick with that... how fast is your 0 to 60 time or 1/4 mile time going to be as long as you only have Zero RPMs? ... hint... you will never move.



major said:


> And is not the launch (or hole shot) an important part of the race?


It can be yes... but that again ... yes you guessed it... requires you to move.

You are incorrectly equating Zero RPMs will low RPMs.

Once you have any movement even the 1 pm you don't have Zero RPMS anymore.



major said:


> And beyond the race aspect, having torque at zero RPM can be useful. I find it quite handy in driving the EV in traffic on hilly terrain or negotiating ramps onto transport trailers.


Sure lets go here too... as long as you had Zero RPMs you never moved at all.

You only were able to ... move ... in traffic because you no longer had Zero RPMs... and you were only able to go up ramps and hills because you moved... and again.... you gessed it... no longer had Zero RPMs.



IamIan said:


> If I want to move a car talking about Zero RPMs means almost nothing.
> 
> The only values I see in talking about power levels and torque levels at Zero RPMs is :
> 
> ...





major said:


> And this is a DIY forum, so there could be someone reading this who would not know better. So to them, hey, it's not spinning. No power. No torque. Just cut it in half. Bingo! The shaft just sprung out and hit them in the head.


It is any less safe for the person to doesn't know better to read you saying if there is Zero RPMs there is Zero Power... it doesn't matter if there was torque or not as long as there wasn't RPMs.... they then get electrocuted, or burned .... because they didn't think there was any power.

There will always be under informed people... no matter what you or I write or don't write.

Anyone involved with modifying , converting, or building something like a EV ... needs to either get informed ... or get someone else who is to do it for them.



major said:


> Yeah, a long shot. The voltage thing worries me more. Oops, blew a fuse. Hey no power, no voltage, no worry. Wrong


You are aware?
That fuses are not over voltage devices?
They blow from over current.

If you have zero power ... you can not blow a fuse... you can not feel a shock ... you can not be electrocuted or harmed from zero power .... no matter how many billions of volts there is.

Certain voltage levels are considered dangerous because they might be sufficient to induce a current across vital organs like the heart... which can lead to bad things ... the electrical resistance of the human body provides some protection but , that protection can be bypassed with high enough voltage.

The reason a Tazer and static electricity even with a much much higher voltage is not as lethal , is because the current and overall power is so much lower.

At Zero power ... any voltage is next to meaningless.


----------



## IamIan (Mar 29, 2009)

Jan said:


> But I can understand that if you look at motors in a different way, it’s the other way around.





Jan said:


> And I'm saying it depends. It's not absolute, it's relative.


 +1


----------



## major (Apr 4, 2008)

IamIan said:


> My apologize to others for the size of this post.


Apology accepted  on the behalf of the originator of this thread. Can't speak for others.

Again I grow weary of our argument and see no resolution unless a learned individual chimes in. So let's end it. You would not concede to torque's relevance if I twisted your arm until it broke. (just kidding , that is not a threat)

Good Bye and Merry Christmas.

major


----------



## Georgia Tech (Dec 5, 2008)

I'll Chime in??


----------



## electrabishi (Mar 11, 2008)

major said:


> Apology accepted  on the behalf of the originator of this thread. Can't speak for others.
> 
> Again I grow weary of our argument and see no resolution unless a learned individual chimes in. So let's end it. You would not concede to torque's relevance if I twisted your arm until it broke. (just kidding , that is not a threat)
> 
> ...


Funny you ended on that note. That is the exact reason (well one of the exact reasons) you actually need to use torque in the calculations. When using the stress and strain characteristics of the materials that make up the drive shafts and gears, you need to know the "forces", which in rotational terms is torque. Just knowing the power will not get you there. How much power can I apply to a 35 spline hardened drive shaft before I twist the teeth off, or rip the gear housing apart? 

The other exact reason is calculating how much traction you need to keep from spinning the tires during a launch. While a typical design for a street car may not approach the necessary torque to be traction limited on dry pavement, they still must do the due diligence and calculate the forces on their drive train components and so the relevancy is revealed ;-) 

Mike


----------



## major (Apr 4, 2008)

IamIan said:


> +1


Hey IamIan,

Does a discontinuity disprove a hypothesis? 

Just a last question I'd like your opinion on.

major


----------



## 88_2C_MIXAGE (Dec 22, 2009)

Guys,

I found this page and just had to post.. I haven't read every page but got a long way through from the beginning, now seeing that it never really got resolved at the end! Just as a bit of background, I am a design engineer for Designline USA, we build series HEV busses that use 3 phase induction traction motors for the propulsion and a micro turbine APU for the power generation.

First off.... Torque and Power are next to the same thing! Torque is the tangential force a shaft is putting out, the power is energy per unit time that the rotating shaft is carrying.... (1 Watt = 1 Joule/second).

The faster the shaft is spinning the more energy it has. The more turning force it is putting out the more energy it has. These are linked together by Power = Torque x Angular Velocity. Saying one or the other is irrelevant is totally rediculous, but the real issue is what is important when selecting an electric motor... the torque curve or the power curve??? The truth is if you have one then you have the other, you can use either power or torque to equal effect by manipulating the equations.

Now some specifics.. Drew keeps talking about tractive effort and that torque is irrelevant. What I believe he has done is use the limit of the tire adhesion (static friction coefficient) as his goal acceleration force, and plotted this against vehicle velocity to get the required power over a speed range (power = force x velocity same as power = torque x angular velocity), then matched up a motor power curve and selected an overall drive ratio so the motor is putting out a similar power over the speed range and finally, he worked out where the top speed of the setup is by taking the top motor speed and multiplying it by the ratio, (NOTE the tire diameter is included in this ratio!!!)

THE ALTERNATIVE... He could just as easily, if he knew what size tire he was planning on using, and most of the time this is already known, worked out what that tractive force equates to as a torque at the wheel. Now you have a desired max torque output at the wheel, take your max output torque from the motor and select a drive ratio to match them, then just as before take the max motor speed and multiply it by this ratio to get the wheel speed, you can equate this to get the vehicle speed from the diameter...

Which is the better way?? Much of a muchness.

How do I do it? I use Torque... We are always trying to get close to the output of the big diesels. I don't care what the power of the system is. When you are trying to push 42000lbs of bus you need a lot of starting torque, so that needs to be maximised, starting power is always 0 so doesn't help you, and due to the nature of induction motors the torque will remain constant for some time during acceleration. The next requirement is top speed, the bus needs to do 50mph..

A very real world example that I have worked on.
Motor 1 : dual 60kW rated, (total peak power = 240kW), max speed = 6000rpm, total max torque = 1354Nm
Motor 2: single 120kW rated (peak power = 240kW), max speed = 3750rpm, max torque = 1750Nm

Both can be geared down to the same max vehicle speed.. One has more starting torque when it is geared down to that speed. 

I don't need anything more to make a preliminary judgment call on which is better for acceleration, obviously more things come in to play such as how much each set up weighs, (one requires a summation gearbox), thermal operating range etc.

Sometimes it isn't the motor speed that limits the vehicle speed, sometimes it is the continuous torque output at high motor speeds. To work this out you need to know what the required torque is to move the object at speeds taking into account the drag, match this to the motor torque curve and hey presto you have a maximum theoretical speed, I could just as easily worked out the power required to move the object at this speed and compared that to the motor power curve to get the speed, in either situations the lines will cross over at some point.

In my opinion, Torque is the more fundamental unit of measure , it is torque you FEEL during acceleration (call it tractive effort if you want), you cannot feel power, you cannot measure power, you can only work out what the power is by measuring the torque and the speed!

Hope that helps!


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## IamIan (Mar 29, 2009)

major said:


> Again I grow weary of our argument and see no resolution unless a learned individual chimes in. So let's end it.


Fine by me... I'll just address your last posts that seem directed to me.



major said:


> You would not concede to torque's relevance if I twisted your arm until it broke. (just kidding , that is not a threat)




I admit I don't understand that last statement ... it doesn't agree with the posts I've made... or my position... I am not and have never been against the relevance of torque ... I have posted that there are plenty of times that I personally do prefer to use torque.

???

The most I ever posted about in regard to the relevance of torque is that it is subjective and a personal preference how much or how little any one specific person uses or doesn't use it ... there are alternatives that are still correct and able to produce EVs that perform as desired with or without Torque being used.

I have also said the other side of it as well... where a person could use alternatives to use more or less power based on their personal preference.

I am not against torque.

Sense you seemed to have missed it ... the end of this post includes some reminders.

---------------



major said:


> Hey IamIan,
> 
> Does a discontinuity disprove a hypothesis?
> 
> ...


It is a counter point of data... but not a complete proof by itself as a single piece of data.

There is data that the flat earth society still uses to support their belief in a flat earth ... just because they are wrong does not mean that they have no evidence at all... and nothing supports their position.

There are known flaws with Relativity ... that doesn't mean it is useless and not correct to some extent... there are some known flaws in Quantum Mechanics... and again that doesn't mean it is useless and not correct in some extent.

A Hypothesis does not have to be 100% correct to be useful... or partially correct.

A great deal of scientific progress has been made by the exploration of the exceptions to otherwise accepted hypotheses... that have lead to continuously refined and improved hypotheses that have fewer and fewer exceptions and or known flaws or problems.

------------



IamIan said:


> thus power and torque can both be useful to varying amounts depending on the specifics of the application... specifics may effect priorities more toward one or the other





IamIan said:


> I don't think it is a universal black and white relevant or irrelevant kind of thing ... I think it is a sliding scale depending on the application.





IamIan said:


> there are methods of working out the acceleration and such of a build either form a torque or a power perspective.
> 
> If you are happy with the results of the build ... I don't see how it matters... do it which ever way you like to do it.





IamIan said:


> I still hold that... it doesn't matter... find the rating for your components under the conditions you will use them... including pulling out on a hill from a stop... use torque or power... whatever makes you happy.





IamIan said:


> That is why ... at least in my point of view ... on Torque vs Power ... there are ways to use either one to produce a good quality EV... Neither one is ever 100% irrelevant.





IamIan said:


> I agree use what ever works for you and you find the easiest to work with and understand ... if that is torque ... fine ... if that is power fine ... In the end its your EV only you have to like your finished work.





IamIan said:


> I've never said either is irrelevant ... because they both matter... which one you happen to like working with depends on your specific personal preferences and the specifics you want to accomplish.





IamIan said:


> Both are equally correct.





IamIan said:


> If you want to have a vehicle that moves ... you have both ... neither is inherently superior or inferior than the other... There are ways to do it either way... so whatever your preference is... have fun, and best of luck





IamIan said:


> I might personally prefer to use torque in some cases and power in others ... but that is just my personal preference ... I recognize that not everyone has my same preferences and other for some reason or another they might want to manipulate the equations to be functions of torque ... or functions of power.
> 
> As long as they manipulate the equations correctly and such the results should be the same either way.





IamIan said:


> If you have a personal preference ... use either ... use both ... use exclusively one and not the other ... if done correctly the results are the same.





IamIan said:


> I am claiming it can go either way... one can define one in terms of the other.... this is something that is done all the time in science, mathematics, and engineering... as long as the mathematics are done correctly any resultant equation is equally true.


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## major (Apr 4, 2008)

IamIan said:


> I admit I don't understand that last statement -


I said I was kidding and used a smiley  It was just a torque joke.

major


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## gor (Nov 25, 2009)

IamIan said:


> OriginallyPostedby*Duncan*
> 
> Torque is a resultant property - (power divided by rpm)
> 
> ...


ok... following this logic: 
F=mA (force=mass*acceleration)
m=F/A 

"mass is a resultantproperty - (force divided by accel)

--------------------
(physical meaning: if force increases- mass increases; accel increase - mass decrease)
- how mass changes by I.I. logic

"The equation is just as correct in either form.
One way Force is the resultant.
equally as correct 
A second way Mass is the resultant." http://www.diyelectriccar.com/forums/showpost.php?p=156777&postcount=278


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## gor (Nov 25, 2009)

IamIan said:


> ... #1>Torque comes from Power.
> 
> Also equally correct to say
> 
> #2> Power comes from torque..


wrong, I.I. 

3. Power comes from RPM! 
...torque too 
: ))))))
though they both irrelevant... the only relevant - speed (rpm) : ))))))))))))))

p.s. I like I.I.'s Theory of Irrelativity - let's think out the box

anyway - in Relative Reality - any hypotheses how we use PeackTorque and PeakPower in drivetrain design?


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## electrabishi (Mar 11, 2008)

IamIan said:


> Originally Posted by IamIan
> I still hold that... it doesn't matter... find the rating for your components under the conditions you will use them... including pulling out on a hill from a stop... use torque or power... whatever makes you happy.


IamIan,
Could you answer me then how you find out how much power it takes to break a hardened 35 spline axle shaft? I mean typically a 500HP car can run 28 spline axles just fine, but a little old 300HP electric Datsun snaps them right off. If at the instant you launch a car, and the RPM of the axle is zero, then really you have no power yet transmitted to the wheels. What then will break the axle before the car even starts moving. Same goes for U-Joints, gears, the force of static friction of the tires to the pavement. How do you calculate the breaking points of parts by using the value of Power?

If as you say, you can at any time use either (power or torque - in calculation that is), then 'splain this to me. "How much power does it take to break an axle?" Because I can theoretically do it with zero power.

Mike


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## electrabishi (Mar 11, 2008)

gor said:


> wrong, I.I.
> 
> 3. Power comes from RPM!
> ....



It also comes from Volts times Amps ;-)

Say my tires get frozen in on an ice covered parking lot. This really happened to me in my ICE truck. But lets say for sake of argument it was my electric truck. When I mashed on the pedal to get unstuck, back wheels came lose and at the same time I heard a loud racket coming from the front end. I blew up the cheapo locking hubs I had in the truck. So lets just say it was my Pinto (which is not 4 wheel drive, and lets say its just the back wheels frozen down in the ice.) I jam my foot on the pedal. Being direct drive the motor does not move unless the tires do, and they are hopelessly frozen in the ice. Now say I hold my foot down for a little bit of time thinking maybe some constant pressure will break it free, but to no avail. Knowing what will happen if this state is maintained too long I let off the pedal.

Now tell me, did I consume any power in going nowhere? Of course I did. I pulled nearly 2000 amps of current through the small amount of resistance in the windings of the motor, until either I let off the pedal or the Zilla stall detect kicked in and stopped the experiment, or I broke an axle. Now try to calculate power from the torque times RPM of the wheel and you would get a value of 0. But look at the values of the battery voltage and current and you will find a real amount of power being dissipated. 

So when I hear someone say that:
1.) Torque is irrelevant - I say, "thats wrong".
2.) You can use *only* the values for Power to properly design an EV - I say, "thats wrong".

And all I have to do to prove my statement is give one example to the contrary where you cannot use the value for Power and you have to use the value for Torque. 

Torque is relevant, and there are some instances where you absolutely have to use the value of torque in a design calculation. Again - 

"...how much power does it take to break an axle?"

Mike


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## Jan (Oct 5, 2009)

electrabishi said:


> e use either (power or torque - in calculation that is), then 'splain this to me. "How much power does it take to break an axle?" Because I can theoretically do it with zero power.


No, you can't. It will happen when there is very little mechanical rotational (next to zero) output power and a lot of input power. Possibly electrical. Without the input power, nothing will happen.

I haven't read 10% of this discussion jet. And I'm not going to do it either. The problem with the last few pages is, that no one stated that Torque is always every time for everybody irrelevant. But that some are saying that those who do say that are wrong. And yes, those hypothetical people are wrong.

How does Torque measuring actually work on a non rotating axle?


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## Duncan (Dec 8, 2008)

Hey Guys

I use torque and power depending on what I am trying to do

My comment about torque being a secondary characteristic is because I would normally be interested in *Wheel Torque*
Which of course can be varied by your gear ratio

Power cannot be varied by your wheel ratio

This means that if I am comparing two vehicles (or two set-ups) I would use available power at those rpms

The zero rpm situation is easily handled for an electric motor without clutch slip but becomes more fun when you have clutch slip and the rotational inertia of the flywheel to think about

Anyway use what you need to get the job done,

I enjoyed working out and understanding the dynamics of some of the examples

Happy Hogmany


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## electrabishi (Mar 11, 2008)

Jan said:


> How does Torque measuring actually work on a non rotating axle?



I realize the fact that there takes input power to break an axle even if there is no movement of the axle.

I probably haven't read enough of this thread either ;-) its quite large. But the meat of what I have read is that someone stated that Torque is irrelevant. And there is someone else stating that it is true because you can always use a measured power to determine all the design criteria to build an EV. 

My contention that this is false, and that there are instance where you actually have to know the torque value. In particular where RPM is equal to 0. While some may contend that this is an unnecessary value to actually know a torque value, I would argue that it is the most necessary place to know the torque value. And further it is a place where a measured torque value is absolutely necessary. And therefore torque IS relevant. Which is the subject of this thread 

Mike


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## electrabishi (Mar 11, 2008)

Duncan said:


> Hey Guys
> Power cannot be varied by your wheel ratio


But average power can  If for instance you have 3-4 moving gears in a transmission you could delete some of the inefficiencies and go with a single ratio, direct drive. This wouldn't necessarily increase applied power, but it would increase available power.

And if you are trying to increase the applied power to say, increase your acceleration, then reducing the time spent shifting gears will also increase the time you spend accelerating. 0.1 second saved on the low end of a 1/4 mile decreases your top end time by 0.2 seconds. And an experienced racer typically loses 0.1 seconds of accelerating in shifting each gear. 

Mike


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## major (Apr 4, 2008)

Jan said:


> How does Torque measuring actually work on a non rotating axle?


Hi Jan,

I have used a torque wrench. But most would use a strain gauge. Or you could attach a moment arm and displace a load cell or spring scale.

For a rotational mechanical system, it is difficult to measure shaft power directly. So most times, torque and RPM are measured and the power calculated from those values. 

major


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## Jan (Oct 5, 2009)

Major,



major said:


> I have used a torque wrench. But most would use a strain gauge. Or you could attach a moment arm and displace a load cell or spring scale.


I'm not sure, becaus I've no idea what strain gauge means. But strain says -I think- enough: All those types of measurments you mention will measure no torque if there's absolutely no rotation. They need some and will translate the resistance they deliver to stop the rotation as torque. 

Which still doesn't mean that I think Torque is irrelevant. 

Just think that you can't measure torque at zero power. Unless you stop the rotation with your measuring device. But it must have initial rotation.

If I want to know the torque/strain on a blocked axis. I would measure the input power. Subtract the generated heat of the motor. The rest of the power is busy breaking the axle.

It's just a point of view. Reality doen't care how we do it: Trying to understand and predict what's going to happen. Reallity does it without our concepts anyway.



> For a rotational mechanical system, it is difficult to measure shaft power directly. So most times, torque and RPM are measured and the power calculated from those values.


I thought a dynamo or generator would do the trick? And you're able to recalculate the torque from the power and rpm. That is, if you need to know the torque.

Which doesn't mean I think Torque is irrelevant.


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## major (Apr 4, 2008)

Jan said:


> If I want to know the torque/strain on a blocked axis. I would measure the input power. Subtract the generated heat of the motor. The rest of the power is busy breaking the axle.


Jan,

If there is no shaft roation, then all input power to the device (such as an electric motor) producing the torque is lost to heat. 100% of it. There no power left over.

major


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## Jan (Oct 5, 2009)

major said:


> Jan,
> 
> If there is no shaft roation, then the all input power to the device (such as an electric motor) producing the torque is lost to heat. 100% of it. There no power left over.
> 
> major


The power of the complete system turns into heat. I agree. But this system is the motor and the axle. Booth will generate heat. 

The strain (trying to avoid Torque here. A bit.) on this blocked axle turns into heat after trying to break it first. 

So, you could also measure the temperature rise of the axle. Wait till its dropped again to the initial temp. Calculate the amount of energy that was. 

Recalculate that in the energy that was put into the axle during the time the motor was connected to power. 

So, you know the power that's put in the axle during that time. The time it din't turn.

Than try to calculate the Torque. And then I've got a little problem. At zero RPM Torque is always infinitive.

But at least I know the power.


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## major (Apr 4, 2008)

Jan said:


> I thought a dynamo or generator would do the trick? And you're able to recalculate the torque from the power and rpm. That is, if you need to know the torque.


Jan,

Dynamometers can use generators (dynamos) as loads and if you know a lot about the generator you could use the measured electrical power from it to characterize the output power from the tested motor. However this method is loaded with possibilities for error. So all which I have seen use a method to measure the torque on the motor output shaft. Modern equipment uses a shaft mounted torque transducer. In the olds days, the generator would be mounted on trunion bearings, have a moment arm attached and a load cell (force measuring device). 

Direct measurement of rotational power is difficult. Torque is relatively easy.

Regards,

major


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## Jan (Oct 5, 2009)

major said:


> Direct measurement of rotational power is difficult. Torque is relatively easy.


OK. I'm a noob about this subject anyway.


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## IamIan (Mar 29, 2009)

major said:


> I said I was kidding and used a smiley  It was just a torque joke.
> 
> major


sorry , my bad... I misunderstood.

I thought you were just joking about the breaking limbs thing... and serious about the other.

my mistake.


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## IamIan (Mar 29, 2009)

gor said:


> ok... following this logic:
> F=mA (force=mass*acceleration)
> m=F/A
> 
> "mass is a resultantproperty - (force divided by accel)


From a mathematics point of view yes , in that form as far as math is concerned the term 'mass' is resulting from the F/A equation... or the function ... F(m) = F/A ... thus in that form as far as mathematics is concerned Mass is a function of force and acceleration.

Look up what it means to be a dependent variable.

That form of that equation is used in order to solve a problem where the Mass is not known ... but you know how fast it accelerates when a specific force is applied to it.

Because that form of the equation is just as equally true ... one is able to calculate what the mass would be ... under those conditions of force and acceleration.

The equation is true for a relationship between the variables ... as long as the mathematics are done correctly the form of the equation does not effect its correctness.

If it did effect the correctness of the relationship that the equation represents you would not be able to use it to determine the unknown mass of an object even if you knew what its acceleration was under a known force.

Of course the original equation F=MA is also known for many decades now to not be 100% correct either.... but due to its greater simplicity than more accurate equations it is still used widely... in many cases it is accurate enough.



electrabishi said:


> If as you say, you can at any time use either (power or torque - in calculation that is), then 'splain this to me. "How much power does it take to break an axle?" Because I can theoretically do it with zero power.


There are several ways to look at this actually.

The first thing that comes to mind is that you can't actually break the axle without movement ... the way you describe there is movement and there is power ... it can move a certain amount under the elasticity of the metal where the metal deforms slightly but has not yet broken ... if it never moves at all you are never able to break it... a motionless axle is invulnerable to any torque as long as it remains motionless... as soon as it begins to move it has power ... and after it moves far enough then it can break.

Now as far as calculating the break point goes... there are several ways to do this.

The first that might be easy to follow would be... The atomic and molecular forces that keep the axle in the form you refer to as unbroken ... have properties... including limits on the attraction and binding , etc... It can be calculated what would be the minimum amount of energy pulse ( power ) that would be required to break this attraction and binding... and it can also be calculated under what time period this pulse of power would have to happen.

I personally wouldn't bother... allot of the harder work is often done for you by other people who tend to use torque for this application ... so while power could be used... I would not personally do so in that case as I suspect it would be significantly more work.

Why work harder to get the same result unless I had some great personal preference to use power or avoid torque?



Jan said:


> It will happen when there is very little mechanical rotational (next to zero) output power and a lot of input power. Possibly electrical. Without the input power, nothing will happen.


I agree.



Duncan said:


> Anyway use what you need to get the job done,


I agree.



major said:


> If there is no shaft roation, then all input power to the device (such as an electric motor) producing the torque is lost to heat. 100% of it. There no power left over.


Heat I would agree is most of it.

But there is also power in:
Vibration ( any motion not in the rotational direction ) , Light , Radio waves , Magnetic flux , Electrical currents , sound , etc...

--------------

Jan,

I get what you are saying about the torque measurement at Zero RPMs... if there is completely 100% true zero movement.

Most people do not consider Zero RPMs to be true Zero RPMs... most people tend to incorrectly think of very tiny movements as still being zero movement.

There are ways still to measure what it is without further movement even if there was initially movement ... although most conventional methods do require at least some type of tiny micro movement during the measurement process.


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## gor (Nov 25, 2009)

88_2C_MIXAGE said:


> Guys,
> 
> ...
> 
> ...


true, we can feel max torque (accelaration, g), rpm, speed; but we doesnt feel PeakPower - it is only known (theoretically or measured, say on dyno) number, multiplication ratio of torque and rpm where they meet ...

MIXAGE, do you use power (power curve) when setting gears?


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## Jan (Oct 5, 2009)

IamIan said:


> There are ways still to measure what it is without further movement even if there was initially movement ...


How does that work, Iamian? And is it also possible if there was no initial movement?


----------



## Jan (Oct 5, 2009)

gor said:


> true, we can feel max torque (accelaration, g), rpm, speed; but we doesnt feel PeakPower - it is only known (theoretically or measured, say on dyno) number, multiplication ratio of torque and rpm where they meet ...


I thought they say: Feel The Power!

And no, you don't feel power. You feel g-forces, you see some speed, notice some acceleration, and feel air resistance. Well, the last one in a topless car or motorcycle that is.

Torque, RPM's, Volts, Amps, Watts, Joules and horsepowers can only be observed with measerment equipment with a display on the dashboard. And Torque is the hardest to measure directly I recon. I would calculate it by measuring the RPM's and the Watts (=power). But that's just me. My knowledge about this subject is very limited.


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## gor (Nov 25, 2009)

88_2C_MIXAGE said:


> ...
> First off.... Torque and Power are next to the same thing! Torque is the tangential force a shaft is putting out, the power is energy per unit time that the rotating shaft is carrying.... (1 Watt = 1 Joule/second).
> 
> The faster the shaft is spinning the more energy it has. The more turning force it is putting out the more energy it has. These are linked together by Power = Torque x Angular Velocity. Saying one or the other is irrelevant is totally ridiculous, but the real issue is what is important when selecting an electric motor... the torque curve or the power curve??? The truth is if you have one then you have the other, you can use either power or torque to equal effect by manipulating the equations.
> ....


just want to add: 1 Joule= 1 N m, which is also measuring unit of torque (torque, Nm)


"you can use either power or torque to equal effect" 

close, but let's take ICE engines 4 example: peak torque usually about at 25000 rpm, peak power curve - about at 3600 rpm

how we use both curves to max.benefit setting up transmission gears ratios? (i'm using tq.curve, so Q.is - how to apply extra info given by power curve? range from before torque max to power ater max?)


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## major (Apr 4, 2008)

IamIan said:


> major said:
> 
> 
> > If there is no shaft roation, then all input power to the device (such as an electric motor) producing the torque is lost to heat. 100% of it. There no power left over.
> ...


IamIan,

I don't know what type of motors you're talking about. But DC motors I've tested this way do not vibrate (or move whatsoever), do not emit light or radio waves or sound. It is strictly a direct current, unchanging in magnitude or direction. No EMI that I am aware of. And what power is there in a steady state flux? None. Now, electrical currents. Yes. All the electrical input power goes into IsquaredR. 100% of it. So heat is it. 

Try it. You don't have to have large equipment. Use a toy motor and 1 or 2 volt battery. I have done this with large motors years ago to determine stall torque because the eddy current dynamometers we had would not take the motor down to zero RPM. More recently I used this technique to determine the performance characteristics of smaller motors used on bikes. 

Maybe some of those molecules are vibrating inside there, but I'd say no more than usual. And electrons flowing through the wires don't make much racket. Magnetic flux is silent as well.

Regards,

major


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## gor (Nov 25, 2009)

Quote: 
Originally Posted by *major*
You would not concede totorque's relevance if twisted your arm until it broke. (just kidding, that is not a threat)
--------------
I said I was kidding and used a smiley It was just a torque joke.
major


IamIan said:


> sorry , my bad... I misunderstood.
> 
> I thought you were just joking about the breaking limbs thing...
> my mistake


 
'cause that was torque joke and also an army joke


----------



## Jan (Oct 5, 2009)

major said:


> All the electrical input power goes into IsquaredR. 100% of it. So heat is it.


Major, I don't understand what you mean. You seem to imply that all the electric power that goes into a DC motor that's stalled is turned into heat inside the motor....?

Then there is no torque either. That implies that DC motor cvan never start turning under load. 

There must be internal strain and friction inside the axle that's suppose to turn. There must be some molecules fighting to maintain the structual order. There must be generated some heat.


----------



## major (Apr 4, 2008)

Jan said:


> Major, I don't understand what you mean. You seem to imply that all the electric power that goes into a DC motor that's stalled is turned into heat inside the motor....?


Yes, that is correct.



> Then there is no torque either.


There is torque. Torque is not dependent on power. Inside the motor, torque comes from the interaction of flux and current. If you had a superconducting motor with no resistance, then there would be no power loss, no heat at stall.



> There must be internal strain and friction inside the axle that's suppose to turn.


Strain does not require motion in equilibrium. There will be some motion as the components deform as the torque is applied, but then the system reaches equilibrium with no further motion yet stress (or strain) is still there. And no loss due to friction without motion.



> There must be some molecules fighting to maintain the structual order. There must be generated some heat


I don't think the molecules will fight any more than usual in the unloaded condition. You can find numerous examples of objects subjected to torque for years, or even centuries. Torque (and force) does not require power to exist.

Regards,

major


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## Jan (Oct 5, 2009)

major said:


> Strain does not require motion in equilibrium.


Equilibrium.. Pretty word. I think I'm starting to understand your point. The concepts of Force vs Power always confused me a lot. Still do. I think they will forever.

So, how do you measure torque at this equilibrium?


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## major (Apr 4, 2008)

Jan said:


> So, how do you measure torque at this equilibrium?


Torque wrench comes to mind


----------



## Jan (Oct 5, 2009)

major said:


> Torque wrench comes to mind


That only works towards to point of equilibrium. Not at it..?


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## major (Apr 4, 2008)

Jan said:


> That only works towards to point of equilibrium. Not at it..?


I disagree. I have torque wrenches which have a scale and pointer calibrated in oz.in. or the like. Put one of these on a bolt, tighten to 50 oz.in. Back off to 20 oz.in. There will be no movement. Clamp the handle of the torque wrench in place while it still reads 20 oz.in. Walk away. Come back in an hour. It still reads 20 oz.in. It is in equilibrium. Come back the next day. Still at 20 oz.in. Leave it for a year. Still at 20 oz.in.

Easy enough to try.

major


----------



## Jan (Oct 5, 2009)

major said:


> Easy enough to try.


I have a stalled motor. You come in and say: Ah no power, just torque. And I want to know how much. What do you do?


----------



## major (Apr 4, 2008)

Jan said:


> I have a stalled motor. You come in and say: Ah no power, just torque. And I want to know how much. What do you do?


Once it is in the stalled condition, you have lost the reference. You need two points. With the torque wrench example, that would be when the wrench is disconnected and then secondly when it is loaded.

So what I would do is to attach the torque wrench to the motor shaft and clamp the handle so there will be no movement of the handle. Then remove the load which was preventing the motor shaft rotation. Now the torque wrench is preventing motor shaft rotation and its scale will read the stall torque.

If it is not possible to use this method, then you need to affix a torque sensor to the motor shaft before you load it and stall it. Such sensors or transducers which work for rotating shafts also work perfectly well on stalled shafts.

Or if I knew the motor characteristics, I could tell you the shaft torque from the current (for a DC series or PM motor). 

Regards,

major


----------



## Jan (Oct 5, 2009)

major said:


> You need two points. With


In Holland we call the 'reference' between those two point: motion. 

Admit it major: You can not measure torque without motion. How little it is, you need it. And I will call this tiny little motion, just to annoy you: Rotation. Worse: RPM. Yes, I said it. You need RPM to measure Torque.

But I'm not saying Torque is irrelevant. Not me.


----------



## major (Apr 4, 2008)

Jan said:


> In Holland we call the 'reference' between those two point: motion.
> 
> Admit it major: You can not measure torque without motion. How little it is, you need it. And I will call this tiny little motion, just to annoy you: Rotation. Worse: RPM. Yes, I said it. You need RPM to measure Torque.
> 
> But I'm not saying Torque is irrelevant. Not me.


Show me where I ever said you could measure torque without a reference. And that reference may involve displacement. To get displacement, you have to move. So what?

My point is that you don't need RPM or power to have torque. Whether or not you measure it, it can exist.

Merry Christmas,

major


----------



## Jan (Oct 5, 2009)

major said:


> My point is that you don't need RPM or power to have torque. Whether or not you measure it, it can exist.


I agree. It can exist. But you can't measure it by itself. It's deducted by measuring power. OK, with very, very little RPM.

You to a merry christmas.


----------



## major (Apr 4, 2008)

Jan said:


> It's deducted by measuring power.


How much power is required to deduce you have 20 oz.in. of torque on the bolt in my example?


----------



## IamIan (Mar 29, 2009)

Jan said:


> How does that work, Iamian? And is it also possible if there was no initial movement?


Materials react to forces applied to them.
If the movement had stopped before I came along to study the situation but there was still a force being applied to prevent the elasticity of the object from reverting back to its initial state without an external force being applied to it. I would be testing for the variation between its current state and it's state if no force were being applied to it.

One easy way to see this... is a spring... I can come along after the movement that compressed it has already stopped ... and there is no current movement ... Once the springs composition and construction has been sufficiently determined I can then calculate backward from there to get the amount of force that was required to put the spring in the condition in which I found it .... I can also determine the amount of power sense I also know the distance the spring move through under that force... In that case the power is consumed from kinetic energy when moving the spring to potential energy when the spring stops moving... minus some losses sense nothing is 100% efficient you then get back negative power when the potential energy is converted back to kinetic energy.

Torque wrenches work by measuring the small amount of movement inside of its calibrated mechanism... All torque wrenches do this one way or another... most people don't think there is movement there because the torque wrench is usually celebrated well enough to only need very tiny amounts of movement to work accurately... usually too tiny to be detected by the unaided human senses.

True Zero initial movement is very different ... as it is very hard to actually have a force act on something and not have any kind of movement at all... every substance I know of , including solids ... all have some degree of elasticity... that would require some very very unusual setup ... I drawl a blank at the moment on one that would actually met the true Zero initial movement conditions... if you can at least move an incredibly tiny amount than maybe... but true zero initial movement?... that's a tough one.



major said:


> I don't know what type of motors you're talking about. But DC motors I've tested this way do not vibrate (or move whatsoever), do not emit light or radio waves or sound. It is strictly a direct current, unchanging in magnitude or direction. No EMI that I am aware of. And what power is there in a steady state flux? None. Now, electrical currents. Yes. All the electrical input power goes into IsquaredR. 100% of it. So heat is it.


I'll agree the majority ... and most likely the vast majority would go to heat.

No vibration at all????
No EMI at all???
No sound at all???


Are you just exaggerating or over simplifying? ... as in there is a small amount of EMI, a small amount of sound, a small amount of virbation?

Sorry that just doesn't seem to make sense to me.
I've never heard of or read of any electric motor of any of the variations ever built that do any one of those three... much less all three at the same time.

It also doesn't jive with what is going on inside and how electric motors work.

Please provide a specific motor reference for any motor company that I can still contact to verify this amazing claim.



major said:


> If you had a superconducting motor with no resistance, then there would be no power loss, no heat at stall.


No energy conversion is 100%... the conversion from electrical energy to a magnetic field around a wire with a current moving in it is not 100%... the conversion of the magnetic field to a different magnetic field... or to put it in flux is not 100% ... to convert the magnetic flux into physical torque is not 100%... even with no electrical resistance at all, even with a superconductor motor ... there would be losses to other things other than heat.

A super conductive motor is still not 100% efficient.


----------



## major (Apr 4, 2008)

IamIan said:


> A super conductive motor is still not 100% efficient.


It's Christmas Eve, so just a short note on this one. I was speaking "at stall" or zero output power. So efficiency is zero. Not 100%. 

Happy Holiday,

major


----------



## major (Apr 4, 2008)

IamIan said:


> No vibration at all????
> No EMI at all???
> No sound at all???
> 
> ...


Hi IamIan,

I meant what I said.


major said:


> I don't know what type of motors you're talking about. But DC motors I've tested this way do not vibrate (or move whatsoever), do not emit light or radio waves or sound. It is strictly a direct current, unchanging in magnitude or direction. No EMI that I am aware of. And what power is there in a steady state flux? None. Now, electrical currents. Yes. All the electrical input power goes into IsquaredR. 100% of it. So heat is it.





IamIan said:


> It also doesn't jive with what is going on inside and how electric motors work.


Please explain how this does not jive.



IamIan said:


> Please provide a specific motor reference for any motor company that I can still contact to verify this amazing claim.


What I have said would apply to any DC motor. Please do verify it. 

Now things will be different with AC motors at stall because you have time varying currents and flux. But with a DC motor in a steady state stall condition, there is no changing current, flux or motion. 

I mentioned it would be easy for you to test with a small motor. Here is another way. You can consider a simple relay a linear reluctance motor. Take a 12V automotive relay and apply 12V to the coil from a battery. The contacts close. You have a steady non varying current in the coil. You have a steady non varying flux in the core. How much vibration, EMI or sound is it emitting?

Regards,

major


----------



## electrabishi (Mar 11, 2008)

major said:


> Hi IamIan,
> You have a steady non varying flux in the core. How much vibration, EMI or sound is it emitting?
> 
> Regards,
> ...


My brushed DC motors do make a little bit of sound with the brushes sliding over the comms, and if you have any arcing set up (which there should be a very thin layer of plasma/patina reaction) between the comm bars and the brushes which will emit very small amount of EMI (haven't measured it though). Watch one in total darkness (real close up) and you'll see it. Especially if you change speed abruptly.

Mike


----------



## major (Apr 4, 2008)

electrabishi said:


> My brushed DC motors do make a little bit of sound with the brushes sliding over the comms, and if you have any arcing set up (which there should be a very thin layer of plasma/patina reaction) between the comm bars and the brushes which will emit very small amount of EMI (haven't measured it though). Watch one in total darkness (real close up) and you'll see it. Especially if you change speed abruptly.
> 
> Mike


Mike,

I am speaking specifically at stall, zero RPM. And not necessarily at high currents. I fully realize that under other conditions where there is rotation or changing current, things will happen.

Regards,

major


----------



## electrabishi (Mar 11, 2008)

major said:


> Mike,
> 
> I am speaking specifically at stall, zero RPM. And not necessarily at high currents. I fully realize that under other conditions where there is rotation or changing current, things will happen.
> 
> ...


Ahh yes, forgot where we left off. Yes at stall no sound, no motion no EMI ;-)
Unless the insulation breaks down somewhere, but then there would be no breaking of shafts ;-P

Mike


----------



## IamIan (Mar 29, 2009)

major said:


> Now, electrical currents. Yes. All the electrical input power goes into IsquaredR. 100% of it. So heat is it.





major said:


> Please explain how this does not jive.


You seem to be making some assumptions that I do not think hold as the absolute conditions you would need them to be in order for this to work ... 

In an effort to avoid extremely long post I'll not go into all of the issues but just highlight a few.

Nothing is 100% ... not storing energy ... not moving energy ... not any type of energy conversion.

I would agree that the vast majority of the electrical energy is probably converted to Heat and the magnetic field ... but I do not think the absolute assumption that Zero of any other form of energy is correct... and it would be in violation of nothing is ever 100% efficient... so there must be other forms of energy also present that are not heat or the magnetic field... Some are easy to understand.

I'm surprised you would even make such claim.... I would have sworn you knew better than that.



major said:


> What I have said would apply to any DC motor. Please do verify it.


Sorry , I don't see a need to confirm for myself that no form of energy conversion is ever 100% ... no form of energy movement is 100% .... etc.

If anything I think modern accepted science clearly disagrees with you ... and the burden of proof is on you to prove that you can actually reach 100% efficiency of energy conversion exclusively only converting the electrical current to heat alone.

Once you achieve this 100% efficient conversion ... go collect your noble prize for this major accomplishment.

You are inadvertently also making the secondary claim that after your have converted all 100% of the electrical energy to heat ... you have managed to produce a magnetic field and a force without using any energy to do it... because no energy is left after 100% is converted to heat ... which is another Nobel prize for you for this second equally major accomplishment.

You are inadvertently also making a third claim ... that what is known of inductors is wrong ... and the interaction between electricity being converted to and from a magnetic field is all incorrect ... because if 100% is converted to heat than none of the energy is stored in the magnetic field... so when the input current stops the inductive properties of the motor should not convert any of the magnetic field back into electrical power as any inductor will do... because 100% of the energy was converted to heat ... if we were to see an output of electrical energy it would push us over unity... which is a 3rd Nobel prize and a 3rd major accomplishment.

I don't think you intended to make these claims directly... but your 100% conversion claim does it anyway... weather it was intended or not.

I think you would be more accurate to write something like... The vast majority of the energy is converted to heat and the magnetic field... and abandon the 100% claim.



major said:


> But with a DC motor in a steady state stall condition, there is no changing current, flux or motion.


That is a simplified view... and functional in many ways... but is not 100% correct.

Electrons and charge levels are not actually ever 100% a steady state ... just like a room that reads 60 degrees F is not uniformly 60 degrees F ... the steady state current you refer to is an average ... individual quanta of energy and even larger electrons do not move and flow in this constant steady state you refer to... there is allot of changes and fluctuations going on all the time.


----------



## major (Apr 4, 2008)

You know IamIan,

I think this is the problem. You don't know nothing. Meaning you do not believe in zero as most of us do. This is a DIY forum. We are talking about electric motors and how they work. We can define zero RPM as the rotor speed when a direct drive motor in the EV is sitting there in a motionless vehicle. But you? No. There is no such thing as zero motion. There earth is rotating. The earth is orbiting around the sun. The solar system is moving in the galaxy. So on and so on.



IamIan said:


> Nothing is 100% ... not storing energy ... not moving energy ... not any type of energy conversion.


So it is not surprising you cannot accept 100%. And here I in fact agree with you that 100% energy conversion is not possible. However the case at point is not energy conversion since there is no motion. Yes, there is input energy converted to heat in the copper. 100% of the input energy. But the electric to magnetic to mechanical phenomena is all about force, not energy.



> so there must be other forms of energy also present that are not heat or the magnetic field... Some are easy to understand.


But you can't explain or quantify them.



> I'm surprised you would even make such claim.... I would have sworn you knew better than that.


And I would have thought you could see the discussion in context and not have to resort to quantum physics to describe a simple electric motor. 



> Sorry , I don't see a need to confirm for myself that no form of energy conversion is ever 100% ... no form of energy movement is 100% .... etc.


I thought you had asked me....


IamIan said:


> Please provide a specific motor reference for any motor company that I can still contact to verify this amazing claim.





> If anything I think modern accepted science clearly disagrees with you ... and the burden of proof is on you to prove that you can actually reach 100% efficiency of energy conversion exclusively only converting the electrical current to heat alone.


I don't have any idea why you say such a thing. I have never said there was 100% efficient energy conversion. I think your misconception between force and power leads you to believe I have.



> You are inadvertently also making the secondary claim that after your have converted all 100% of the electrical energy to heat ... you have managed to produce a magnetic field and a force without using any energy to do it... because no energy is left after 100% is converted to heat ... which is another Nobel prize for you for this second equally major accomplishment.


I think Ampere and Maxwell have taken credit for this already. But since you don't hold Ohm's and Newton's laws too highly, I guess you don't realize this either.



> You are inadvertently also making a third claim ... that what is known of inductors is wrong ... and the interaction between electricity being converted to and from a magnetic field is all incorrect ... because if 100% is converted to heat than none of the energy is stored in the magnetic field... so when the input current stops the inductive properties of the motor should not convert any of the magnetic field back into electrical power as any inductor will do... because 100% of the energy was converted to heat ... if we were to see an output of electrical energy it would push us over unity... which is a 3rd Nobel prize and a 3rd major accomplishment.


If you looked at my statements, you will note that I was speaking about a steady state condition. In other words, after the current in the coil has settled to a constant, therefore, the energy has been stored and no longer an issue. But wait, I would have probably have thought a couple thousand or a million time constants would have been long enough to reach equilibrium. And you will say that never happens. With inductance in the circuit the current is asymptotic never reaching the V/R value, right?



> That is a simplified view... and functional in many ways... but is not 100% correct.
> 
> Electrons and charge levels are not actually ever 100% a steady state ... just like a room that reads 60 degrees F is not uniformly 60 degrees F ... the steady state current you refer to is an average ... individual quanta of energy and even larger electrons do not move and flow in this constant steady state you refer to... there is allot of changes and fluctuations going on all the time.


Yes, I do have a simplified view. But I know how electric motors work, and do not need to use quantum mechanics to explain that to these DIYers. BTW, I did once take college courses in such things and think I can tell when such is pertinent to a discussion.

I'll say it again and try to keep from further response to you.

Good Bye, IamIan.

Regards,

major


----------



## IamIan (Mar 29, 2009)

major said:


> But you? No.


I'll agree... one of my personal faults/traits is my preference to be as reasonably accurate as I can be... It works for and against me depending on the situation.

0.00000000000000000000000000000000000000000000000001 to me does not equal Zero.

I full well understand that my way is not the only way ... and there does definitely exist things like ... good enough ... but I would still disagree with the person who claims that the above tiny number is equal to Zero... because it isn't... if they fail to see that ... oh well.



major said:


> So it is not surprising you cannot accept 100%. And here I in fact agree with you that 100% energy conversion is not possible. However the case at point is not energy conversion since there is no motion. Yes, there is input energy converted to heat in the copper. 100% of the input energy.


No energy conversion ??? 
You've claimed that 100% of the electrical energy input is converted to heat... how is that not an energy conversion?

Your 100% to heat claim is at the very least claiming a 100% efficient electric heater.

If as you post here you agree that 100% energy conversion is not possible... than I fail to understand how you can continue to insist on 100% of the electrical energy is converted to heat.



major said:


> But the electric to magnetic to mechanical phenomena is all about force, not energy.


  What 

I can't be the only person who sees the completely obvious faults with this statement / claim.

Is it even needed to explain why it is incorrect?
Would it just fall on deaf ears/eyes?



major said:


> But you can't explain or quantify them.


... ahahaha ... Nice of you to state so clearly for me what I am not able to do... ahahahaha... that was a good laugh.

You seem to have forgotten this part right at the beginning of the last message.



IamIan said:


> In an effort to avoid extremely long post I'll not go into all of the issues but just highlight a few.


I'm trying to keep my already long posts trimmed down... if you want me to explain or quantify it to you... despite your claims to the contrary I can... Although I have my doubts there would be much to gain from doing so... which is why I did not lengthen the last post by elaborating.



major said:


> I thought you had asked me....


And you never did provide a specific electric motor that does this 100% conversion of electrical energy to heat... that you claim... with no other output of any kind ... no sound, no EMI, no vibration, etc...

And you never will be able to ... because there is never 100% conversion... electrical energy to heat energy included.



major said:


> I don't have any idea why you say such a thing. I have never said there was 100% efficient energy conversion. I think your misconception between force and power leads you to believe I have.


 This discussion on the motor at stall not converting 100% of all the electrical input energy into heat... has nothing to do with our previous discussion... instead of trying to bring it back into this discussion ... Let it go and move on.

Oh and... Yes you have... and here are some reminders for you.



major said:


> Now, electrical currents. Yes. All the electrical input power goes into IsquaredR. 100% of it. So heat is it.





major said:


> Jan said:
> 
> 
> > Major, I don't understand what you mean. You seem to imply that all the electric power that goes into a DC motor that's stalled is turned into heat inside the motor....?
> ...





major said:


> Yes, there is input energy converted to heat in the copper. 100% of the input energy.


You have claimed multiple times a 100% energy conversion from electrical energy to heat energy.

That is what I am currently disagreeing with... And I honestly don't understand why you are trying to defend such obviously incorrect claims.



major said:


> IamIan said:
> 
> 
> > You are inadvertently also making the secondary claim that after your have converted all 100% of the electrical energy to heat ... you have managed to produce a magnetic field and a force without using any energy to do it... because no energy is left after 100% is converted to heat ...
> ...


Ampere and Maxwell ... either one ... have never made such a claim.



major said:


> But since you don't hold Ohm's and Newton's laws too highly, I guess you don't realize this either.


I endeavor to hold them accurately.

They have limits.. and flaws have been shown in both of them in the many many years sense there were put forth.

Science has made progress.... like it or not.

They are useful but not to be revered as gospel.


----------



## major (Apr 4, 2008)

IamIan said:


> Your 100% to heat claim is at the very least claiming a 100% efficient electric heater.


You're right, I stand corrected. I forgot about the electric heater. 100% of the electrical energy is converted to heat. All losses are heat, which is the desired output, so it is 100%. Silly me. I knew that, since I have electric heat in my house.



IamIan said:


> This discussion on the motor at stall not converting 100% of all the electrical input energy into heat... has nothing to do with our previous discussion... instead of trying to bring it back into this discussion ... Let it go and move on.


Oh, I thought that a machine which produced torque independent of power was at the heart of disproving your claim that torque is a function of power. How can torque be a function of power when something can produce torque with zero power? And you say there is never zero power. If all the power input to a motor at stall is converted to heat, then what power is left to produce stall torque?



IamIan said:


> Ampere and Maxwell ... either one ... have never made such a claim.


I think Ampere does exactly that. But you somehow believe that current is power and energy. Go figure.



IamIan said:


> That is a very good point ... and I agree my PWM example is obviously flawed.
> 
> It isn't mysterious ... It is just counter-intuitive.
> 
> ...


I'll remind you of this post a while back. First, we all make mistakes. Second, you and I don't speak the same language.

Good Bye again.

major


----------



## IamIan (Mar 29, 2009)

major said:


> First, we all make mistakes. Second, you and I don't speak the same language.


I will agree you and I do not think the same way... oh well.

I agree we all make mistakes... I'm no exception to that.



major said:


> But you somehow believe that current is power and energy. Go figure.


 *Does that mean that you do not?**
* 
------------

I guess we just disagree one several issues:

-----------
#1>
You claim 100% efficient energy conversion.


I do not... I hold that there is always some loss ... some form of EMR , vibration , etc... If carefully designed it can be very efficient ... 99.9999+ ... etc... but never 100%.
--------------
#2>
You think a Zero RPM condition still has vehicle movement.


I do not... its Zero.
--------------
#3>
You disagree with accepted principles of Mathematics... ( like Algebra , and what it means for x to be a function of y. )


I agree with accepted principles of mathematics... mathematics operations done correctly on a formula result in a form of that formula that is just as correct and the original... it doesn't matter if you like the result or not.
--------------

I'll say what I've said from the beginning ... as long as you do it right a finished resultant EV can be produced either way with equal abilities ... if you prefer Torque go ahead... if you prefer Power go ahead ... if you're like me , and prefer a mix of each do the mix instead ... If the result is the same I don't see how it would significantly matter if someone happens to prefer power or torque one way or the other... I like the mix of the two myself because I find it is often easier and faster than trying to convert everything into functions of either one, torque or power.



major said:


> And you say there is never zero power.


Where / When did I say there is ... Never ... Zero Power???? I do not recall making that claim... and it doesn't sound like the kind of thing I would claim ???

I've disagreed with some of your examples ... but to say there is never zero power??? That doesn't seem like me.

If I made such a claim... please provide me with a reference / link / post# ...


----------



## major (Apr 4, 2008)

IamIan said:


> I will agree you and I do not think the same way... oh well.





IamIan said:


> I agree we all make mistakes... I'm no exception to that.
> 
> 
> 
> ...


Yes, I do not. I believe that current is not power or energy. Without going into a lot of math, I believe that energy is power times time. And that power is voltage times current. So current by itself is not power or energy. Just as torque (or force) by itself is not power or energy.




> I do not... I hold that there is always some loss ... some form of EMR , vibration , etc... If carefully designed it can be very efficient ... 99.9999+ ... etc... but never 100%.


So you say that if I define my "device" as a simple resistor with 2 terminals and have as my desired output heat and the input as a direct current which does not vary, 100% of the electrical energy at the terminals to that resistor is not converted to heat? Would that not be a 100% efficient conversion device?



> #2>
> You think a Zero RPM condition still has vehicle movement.
> 
> I do not... its Zero.


Boy you turned this around. I have always maintained that zero RPM meant zero movement. You are the one who said there was always some perpendicular motion. 



> #3>
> You disagree with accepted principles of Mathematics... ( like Algebra , and what it means for x to be a function of y. )


I do not disagree with your math, just your use of it to infer unfounded functions or dependencies in physics.




> I'll say what I've said from the beginning ... as long as you do it right a finished resultant EV can be produced either way with equal abilities ... if you prefer Torque go ahead... if you prefer Power go ahead ... if you're like me , and prefer a mix of each do the mix instead ... If the result is the same I don't see how it would significantly matter if someone happens to prefer power or torque one way or the other... I like the mix of the two myself because I find it is often easier and faster than trying to convert everything into functions of either one, torque or power.


I have not argued with you about this have I?




> Where / When did I say there is ... Never ... Zero Power???? I do not recall making that claim... and it doesn't sound like the kind of thing I would claim ???


 

I don't really want to take the time to go back 10 or 20 pages in this tread to find it. But I am relatively certain it was when I first spoke of torque at zero RPM having zero power. I said there is no motion therefore no mechanical power. You disagreed and said there had to be motion because there had to be power. That's how I remember it. But we can always look back there.




> I've disagreed with some of your examples ... but to say there is never zero power??? That doesn't seem like me.





IamIan said:


> 0.00000000000000000000000000000000000000000000000001 to me does not equal Zero.


And then you go on to talk about some quantum stuff. Sounded to me like zero does not exist to you. I run into zero all the time. I thought you were immune to it. Sorry if I got the wrong impression.




> If I made such a claim... please provide me with a reference / link / post# ...


Sorry, but the above does sound kind of like you put a pretty tight tolerance on zero 

major


----------



## roflwaffle (Sep 9, 2008)

Gentlemen, gentlemen! Please. We're all out of dueling pistols, even tar and feathers. You'll have to be content w/ TP and honey.


----------



## Bowser330 (Jun 15, 2008)

This thread is one of the few that has brought about some serious intellectual discussion. Lets keep it at that level and continue the healthy debate shall we.


----------



## Jan (Oct 5, 2009)

major said:


> Sounded to me like zero does not exist to you.


Quantumrechnical speaking that's correct. There doesn't exists real zero power/energy situations in the universe.

But I don't think quantum effect are really relevant in this discussion. Although someone could start a thread with the question if quantum mechanics is relevant or not. And lets the circumstances unnamed.

Major, I remember you asked the question: what power is messured with a torque wrench. I think the power you as wrencher punt into it. You can spin vast or spin slow. The mechanisme of the wrench mechanical deducts the torque eitherway and displays it. Fact is: you can not measure torque without movement. So you need power to measure torque. 

Torque at real life zero rpm can only deducted from experience or by measuring the amps going into the stalled motor. Where there's amps, ther's volts. Where there is volts and amps there is power.



major said:


> This thread is one of the few that has brought about some serious intellectual discussion. Lets keep it at that level and continue the healthy debate shall we.


Mmmm.. That didn't stop me.


----------



## major (Apr 4, 2008)

Bowser330 said:


> This thread is one of the few that has brought about some serious intellectual discussion. Lets keep it at that level and continue the healthy debate shall we.


Bowser330 said this, not me.


----------



## Jan (Oct 5, 2009)

major said:


> Bowser330 said this, not me.


Copy error. Sorry. Just trying to break the ice.


----------



## major (Apr 4, 2008)

Jan said:


> Major, I remember you asked the question: what power is messured with a torque wrench. I think the power you as wrencher punt into it. You can spin vast or spin slow. The mechanisme of the wrench mechanical deducts the torque eitherway and displays it. Fact is: you can not measure torque without movement. So you need power to measure torque.


It was like this. Regarding measuring torque, you said:


Jan said:


> It's deducted by measuring power.


And I ask you:


major said:


> How much power is required to deduce you have 20 oz.in. of torque on the bolt in my example?


I was looking for a quantity from you. Like 3 Watts. Or 24.7 milliWatts. How much power is required to deduce you have 20 oz.in.?

Like that copy error, especially when threads get long, people will attribute things not said to individuals and forget things said. I never said power was not used to measure torque. All measurement we do requires reference. And in most cases, a displacement from that reference. That could be a displacement of an electron beam in an oscilloscope, the deflection of the pointer on an analog meter or the displacement of the pointer on the torque wrench. The displacement of a physical object like the pointer will require movement and therefore a force and motion which constitute power. I thought such was obvious to everyone, so I may not have mentioned it early on, but would have not denied it.

But you can have torque without measuring it. 



Jan said:


> Torque at real life zero rpm can only deducted from experience or by measuring the amps going into the stalled motor. Where there's amps, ther's volts. Where there is volts and amps there is power.


Outside of the superconducting realm, I agree with you. And I have not said differently. There is power, but the shaft torque is not dependent on that power. It is strictly dependent on the current.

Regards,

major


----------



## pgrovetom (Oct 6, 2009)

The question may not be relevant in a way. Since Torque x RPM = k x Power, the torque curve and power curve can be derived from one another. So both are relevant but not more relevant than the other. 

If you give a Torque versus RPM curve, the power versus RPM can simply be calculated and visa versa. The shape and area under the "curves" is important and relevant.

The confusion probably comes from the RPM ( and some constant) is used in the translation. If one just talks about Torque without regard to an RPM, then - how power and torque relate is confused.


----------



## IamIan (Mar 29, 2009)

pgrovetom said:


> the torque curve and power curve can be derived from one another. So both are relevant but not more relevant than the other.
> 
> If you give a Torque versus RPM curve, the power versus RPM can simply be calculated and visa versa.


+1 



major said:


> Sorry if I got the wrong impression.
> 
> Sorry, but the above does sound kind of like you put a pretty tight tolerance on zero


Very true... I put very tight tolerance on terms that carry absolutes ... things like Zero , Infinity, Never , etc.... Zero is Zero... close to Zero is not = to Zero... incredibly tiny, is not Zero.... etc.

Just one of my personal quirks. 



major said:


> I don't really want to take the time to go back 10 or 20 pages in this tread to find it. But I am relatively certain it was when I first spoke of torque at zero RPM having zero power. I said there is no motion therefore no mechanical power. You disagreed and said there had to be motion because there had to be power. That's how I remember it. But we can always look back there.


ok it was just a misunderstanding then... I did not make the absolute claim of ... 'there is ... never... zero power'... I was referring to that example/context did not have zero power.



major said:


> Boy you turned this around. I have always maintained that zero RPM meant zero movement.


I was referring to your claim about using Zero RPMs to initially accelerate off the starting line in a 1/4 mile race... I think you refereed to it as a 'launch' ... at Zero RPMs you are not launching at all... you are not moving at all... it is not until you have some small amount of RPMs that you can even start to flex tires and even start to 'launch'... 

So it is more accurate to claim at low RPMs and at very low RPMs Torque and power output matter for the 'launch' ... but Zero RPMs doesn't move the vehicle.

Maybe I mis-understood... and in that way I did not correctly depict your position... sorry.

But if you truly do hold that there is not vehicle movement at Zero RPMs ... than that just agrees with my position and claim from many pages ago.

As far as a vehicle that we want to move ... a Zero RPMs discussion is next to useless.



major said:


> Yes, I do not. I believe that current is not power or energy. Without going into a lot of math, I believe that energy is power times time. And that power is voltage times current. So current by itself is not power or energy. Just as torque (or force) by itself is not power or energy.
> 
> I do not disagree with your math, just your use of it to infer unfounded functions or dependencies in physics.


Interesting...

You are using the same algebra you disagreed with.

Remember when you previously gave this quote from Wikipedia for what Power is?

The original form of the equation is : Power = Energy / Time



Wikipedia said:


> In physics, *power* is the rate at which work is performed or energy is converted. *It is an energy per unit of time*. As a rate of change of work done or the energy of a subsystem


Above you used algebra to convert it into : Energy = Power * Time

Which I agree still holds the same relationship ... and as long as the math is done correctly is just as correct as the original ... 

But this is exactly the same thing you have argued against in terms of Power and Torque.

How do you justify disagreeing with math in one case and using the same mathematics techniques yourself in another?

Which is it? ... looks like you are playing both sides.

I myself still hold if done correctly the result of the math is just as correct... that applies as much to your current use of it above as it did to my use of it previously.

I recommend you agree with math... because you will have a very hard time in life and ever trying to build a functional EV as long as you reject the accuracy and correctness of correctly performed math... Find the error in how the math was used ... misplaced decimal point, etc.... or either accept it or reject it... but the flipping back and forth , when you fell like it or you like or dislike the results ... that's not good.

------------

The other oversight I see you making here is that you are overlooking what current actually is... the motion of a charged particle ( usually an electron ).

I also think you are either overlooking or trivializing what energy is ... there are a wide variety of types of energy... potential energy , kinetic energy , chemical energy , nuclear energy, thermal energy , electrical energy , etc...etc...

Even the tiny mass of an electron in motion has kinetic energy... even if it is just current and even if it is in a super conductor.

I can not think of even one example of there being any force that is not energy... even a stationary compressed spring is still potential energy of the tension stored in the elasticity of the springs molecular structure.

If you have force I don't see how you can escape from also having energy... and as far as I can tell most of science including physics considers energy to be more fundamental than force.

E=MC^2 ... for example ... there is no mention of force at all.



major said:


> So you say that if I define my "device" as a simple resistor with 2 terminals and have as my desired output heat and the input as a direct current which does not vary, 100% of the electrical energy at the terminals to that resistor is not converted to heat? Would that not be a 100% efficient conversion device?


Current passed though a resistor does not convert 100% of the energy ... even DC to heat... so even if the heat is your desired effect it still will not give you 100% efficiency.

I will agree you can get very high efficiency.... way up in the 99.99+ range... so high that I would understand why allot of people like to simplify it by just rounding up and just saying 100% ... one could easily argue that there is a insignificant difference between what it actually is and 100%... but it is not 100%.

Just like I would not agree that 0.0000000000000000000000000000000000000000001 is equal to or the same thing as Zero.... they are not the same thing... Very close yes ... insignificant difference , most likely.... but they are not the same thing.

If you could convert all 100% of the energy to heat and only to heat than yes in theory you could have 100% efficiency... but despite the appeal of simplifying and or rounding up to 100%... that is not the case... and it does not happen... in the real world there is always some other type of loss... you are always less than 100% efficient in any energy conversion.... even in an electric heater .... even using DC.

Although I would add even to setup a truly non-fluctuating DC would actually be exceeding difficult.... far more difficult than it might seem at first.


----------



## scarab (Jul 3, 2008)

Wot the ?

Can anybody tell me of upping the number of batteries i.e. volts will increase torque/rpm/hp from a ac55 motor which usually runs on 96 volts


----------



## major (Apr 4, 2008)

scarab said:


> Can anybody tell me of upping the number of batteries i.e. volts will increase torque/rpm/hp from a ac55 motor which usually runs on 96 volts


Hi scarab,

You would likely do better posting this question elsewhere like in the motor section of this forum. I wouldn't be surprised if a lot of folks avoid this thread.

But I'll give you an opinion. The ac55 is an induction motor, right? 96 volts is the battery voltage, right? It needs a controller or inverter which takes the DC battery to AC for the motor. In that process, the actual AC voltage to the motor is less than 96 by a factor of 0.707, IIRC.

With that out of the way, increasing the voltage available to the induction motor increases the base frequency. This means that maximum torque will be available at a higher speed which means the peak power will increase. This should be close to the proportion of increase in voltage. Higher voltage will not increase the magnitude of the torque. You'd need higher current and/or a bigger motor for that.

Now it is unknown if the controller will function with a higher input voltage. Or if it would need to be retuned. You need to check that out. And having more motor power available doesn't mean you will necessarily use it, but if you do, you may overheat and damage the motor.

Regards,

major


----------



## major (Apr 4, 2008)

IamIan said:


> You are using the same algebra you disagreed with.


Yes, I did. But I qualified my remarks as:


major said:


> Without going into a lot of math, I believe that energy is power times time. And that power is voltage times current. So current by itself is not power or energy. Just as torque (or force) by itself is not power or energy.


I was trying to avoid a long drawn out post and keep it simple. I am not saying or trying to imply that energy is a function of power. Another case where correct algebra does not make correct physics, wouldn't you say?

As for current and energy, again it may be a context thing here. I am talking about electrical energy. 




IamIan said:


> I was referring to your claim about using Zero RPMs to initially accelerate off the starting line in a 1/4 mile race... I think you refereed to it as a 'launch' ... at Zero RPMs you are not launching at all... you are not moving at all... it is not until you have some small amount of RPMs that you can even start to flex tires and even start to 'launch'...


So how does it start from zero? With torque it is easy to understand. With power, you have to resort to squirm, like Drew uses. That is way back in the first few pages of this thread. And then it becomes difficult to explain how steel wheeled vehicles launch when the tires can't flex. Starting torque is defined as torque at zero RPM. Without it, how do motors ever get started? Just an example of why torque is relevant with electric motors. Zero RPM torque means you don't need slipping clutches or torque converters like IC engines. Ever wonder why diesel locomotives use electric traction motors?

If initial acceleration does not start at zero RPM, at what RPM does it start, and how does the motor get from zero to that starting RPM?

Regards,

major


----------



## major (Apr 4, 2008)

IamIan said:


> I can not think of even one example of there being any force that is not energy.


Hey IamIan,

How many Joules are there in one Newton of force?

And, on the other subject, how many Watt-hours are there in one Ampere of current?

major


----------



## IamIan (Mar 29, 2009)

major said:


> I am not saying or trying to imply that energy is a function of power.


I'm getting the impression we are not meaning the same thing when I write or you write,

___ is a function of ___ .

When you use algebra as you did to write the equation as E = P * T .... That means E is a function of P * T ... if power becomes the determinant variable in P * T , than E is a function of P.

Science & Math use it the way I am here not the way you seem to be implying ... especially in calculus is very very clear about this... one of the first things they teach is what it means to be a function.

This is how I am using this expression .... ___ is a function of ___ .

If you are deviating from the mathematically and scientifically accepted method of usage ... please elaborate on your own personal usage... 

It occurs to me that this might just be a communication issue arising from a deviation in your own personal usage... where I was assuming you were using the accepted mathematics , and scientific usage instead.



major said:


> Another case where correct algebra does not make correct physics, wouldn't you say?


I would not say that... and I would not.

If the math is done correctly the science is also correct... if the science breaks down when correctly applied math is used... that is massive ... a very very large amount of our science depends on correctly applied math not invalidating the science.

A formula only represents a relationship among specific variables... when the math is done correctly the relationship is preserved and thus the resulting new form of the equation is just as scientifically correct as the initial form of the equation... the vast majority of the science we have developed depends on this.

Out of curiosity , do you have any reference to support this claim that correctly applied math invalidates or falsifies science?... or is this just an opinion of yours? ... seemingly because you don't like a specific result.

Unless this is explained somehow in your own personal variation/deviation in the usage of .... ____ is a function of ____ .



major said:


> With torque it is easy to understand. With power, you have to resort to squirm, like Drew uses. That is way back in the first few pages of this thread. And then it becomes difficult to explain how steel wheeled vehicles launch when the tires can't flex.


This is why I personally prefer to use a mix of power and torque... it isn't that you can't solve the same problem either way... I just think it is sometimes easier and faster to do it one way or the other... so depending on the context I might use torque or power.... but just because I chose to use torque in a particular context that doesn't mean it is impossible to use power instead ... and either method can produce equal results for our efforts to make our EVs that move.

Sure we all have personal preferences for one reason or another... and there is no harm at all in discussing those reasons and individual variation... many times there is a benefit in the collaboration of different points of view and experience etc.



major said:


> Ever wonder why diesel locomotives use electric traction motors?


It is because of the power that can be produced at low and very low RPMs... or it is just as correct to say the torque that is produced at low and very low RPMs.

Just because the current form of most of our combustion engines are not self starting does not mean that it is impossible to design one that would be... it is not an oversight from the engineers ... we design them the way we do for very good reasons ... in short the electric motor is the preferred option instead of designing , building, and buying a self starting combustion engine that can give power performance at low and very low RPMs like an electric motor does.

Electric motors are also more efficient at moving something than any heat engine I know of.... so less fuel energy is needed to do the same thing.

Electric motors also have better mean time of failure rates than combustion engines do.



major said:


> If initial acceleration does not start at zero RPM, at what RPM does it start, and how does the motor get from zero to that starting RPM?


This gets into the nature of static friction and inertia... without writing a book on either topic ... There is a minimum amount needed to break that rest condition ... there are equally correct ways to describe and look at that in terms of applied net force per unit time or in terms of energy per unit time ( ie power ).

It is not the force or the energy alone... but the time over which is acts... A pulse of force for a very short period of time might not be enough just as a very short pulse of energy might not be enough... otherwise there might not be any acceleration... of course there are cut off points too... where a pulse of force is large enough even at very short periods of time it might be enough... and the same is true for energy where there reaches a point where there is enough energy even at very short periods of time where it might be enough.



major said:


> IamIan said:
> 
> 
> > major said:
> ...


Does this mean you can think of even just one example of there being any force and no energy of any form?

I didn't think so... 

-------------

You are comparing different units... just because they are not the same units does not mean there is no energy in a given force.

In order to answer that question you asked I would need you to better define your question... but I doubt a specific number would make a difference here ... I also doubt you are actually interested in that ... You seem to be trying to imply that you disagree with my statement ... if I am reading you correctly and you disagree... go ahead.

Does this mean you can think of even just one example of there being any force and no energy of any form?

I didn't think so... 



major said:


> IamIan said:
> 
> 
> > major said:
> ...


You're comparing different units... and again I seems you are disagreeing with me... and I doubt you are actually looking to clarify the question to get to a specific number.

Can you think of even one example of how there can be current without any energy of any form? 

I didn't think so... 

Sense we already seemed to agree that P = E / T ... the only way I can see you reaching a claim of there not being power in current is if there is no time... which falls into the useless category, because there are finite lower limits on the minimum amount of time needed for energy... and there are finite lower limits on the minimum amounts of energy.

So if you are disagreeing with me...

Can you think of even one example of how there can be current without any energy of any form? 

I didn't think so...


----------



## major (Apr 4, 2008)

IamIan said:


> In order to answer that question you asked I would need you to better define your question... but I doubt a specific number would make a difference here ... I also doubt you are actually interested in that ...


IamIan,

I thought it was a clear, simple question from a simple guy looking for a simple answer. 


major said:


> How many Joules are there in one Newton of force?


I would like a number. You say force is energy. Energy has the scientific accepted unit of Joule. I have quantified the force value (one) in scientific accepted unit of Newton. What's the problem?

And on the second part: 


major said:


> ... how many Watt-hours are there in one Ampere of current?


Same here. A numerical value would helpful to the DIYers with range calculations, wouldn't it?

Happy New Year,

major


----------



## IamIan (Mar 29, 2009)

major said:


> I thought it was a clear, simple question from a simple guy looking for a simple answer.


And I thought it was a simple question for you to give just one example case ... just one ... but you were not able to give that were you?

So here it is again... take your time... google a bit... and you'll still come up with nothing and you know it.

#1>
Does this mean you can think of even just one example of there being any force and no energy of any form?

#2>
Can you think of even one example of how there can be current without any energy of any form? 

-----------------

I also thought it was a simple question for you to explain your own personal deviation / variation in your usage of the phrase:

___ is a function of ____.

It would be helpful in order to understand your rejection of accepted math and known principles accepted by most of the rest of the world ... if you are just not using the terminology in the normally accepted way by the rest of the math and science community.

---------------

I would not call you a simple guy... 

Yes it is a simple question... but not in the way you suggest here....you clearly seem to be disagreeing with what I said about the existence of some form of energy when there is a force or when there is current.

So ... can you think of even just one example ... just one?

You got nothing?

Yeah that's what I thought... 

-----------

Let me try it again.

Current by definition of the accepted scientific community ( maybe not by you ) is the flow of charged particles ( usually electrons ).

Do you think charged particle have energy?
The rest of the world says yes. ( maybe you don't? )

Do you think the flow of / movement of matter with mass has energy?
The rest of the world says yes. ( maybe you don't? )

Which leaves me a bit confused ... if you know what the terms current and energy mean.... how can you still insist there is no energy in 1 Ampere of current?

-----------



major said:


> You say force is energy.


Nope... not me.... try again.
I never claimed force is energy.

I claimed I can't not think of even one example where there is force but no energy... and I doubt there can be a force without some kind of energy... I never claimed that force and energy are the same thing.

You on the other hand have claimed that there can be force but no energy ... so by all means please provide at least one example , where there is force but no energy of any kind.

----------

I am happy to help DIYers with range calculations ... if you have the additional detail in that context then I can help.

So give me the rest of the data... 

If you want to be as simple as the energy content of the batteries and the energy used by the EV that will give us a range ... if the energy usage rate is in a per unit time format our range calculations will be in units of time... and if the rate of energy usage is in units of distance than our range calculations will be in units of distance.

If you want to go deeper and attempt to empirically calculate the energy usage rate ... in either units of time , distance, or both ... than we will need allot more information about the particular EV context... the vehicle and the route.

And yes we can do it .... if we have enough information about the context ... And the only variation changing in the calculations is a specific set amount of newtons that push with or against the car... we will be able to equate that into a change in the range ... and then using the rate of energy used we could also give that in an equivalent number of joules.

So yes... if you give the rest of the needed details I can give you such a number ... but allot more detail is needed.... which is what I already said.

---------------

But I still doubt you care about such a number ... you just seemed to be trying to use a round about method of disagreeing with me.

So if you continue to disagree.

Give just one example:

Of a force where there is no energy of any kind.

Of a current where there is no energy of any kind.

The meaning of the terms current and energy seem to clearly disagree with you... not that I expect you to see it.


----------



## major (Apr 4, 2008)

IamIan said:


> I never claimed that force and energy are the same thing.





IamIan said:


> I can not think of even one example of there being any force that is not energy.


Wonder why I thought you said force was energy? It sounds to me like you say all force is energy. I did not say you claim that all energy is force. But again, if force is energy, as you say, express one Newton of force in terms Joules for me.

major


----------



## DavidDymaxion (Dec 1, 2008)

For #1: A block on a table. The block exerts a force on the table. If maintaining this force took energy, eventually the energy would run out and the block would quit exerting a force on the table.

For #2: Imagine an isolated electron very very far far away, motionless, and very far from any other interactions. My motion due to the earth's movement makes it move relative to me, hence it is a current, yet in any practical sense I never have a hope of extracting energy from that electron.

For #2, part 2: I've heard the superconducting currents can go for weeks -- yep, go for weeks without a driving applied voltage. http://www.answers.com/topic/high-temperature-superconductors .


IamIan said:


> And I thought it was a simple question for you to give just one example case ... just one ... but you were not able to give that were you?
> 
> So here it is again... take your time... google a bit... and you'll still come up with nothing and you know it.
> 
> ...


----------



## major (Apr 4, 2008)

IamIan said:


> #2>
> Can you think of even one example of how there can be current without any energy of any form?


O.K. One Ampere. That is a current without any energy associated with it. So is two Amperes. I could go on all day.

I had already answered the question, and don't feel I need to repeat myself. But I will anyway. I do not believe current is energy. 

But you on the other hand refuse to answer my simple question.

Now certainly systems which have current flowing across a voltage for a time period will have energy. I said that previously. But current in and of itself is not energy, which you claim it is. So tell me how many Watt-hours is in one Ampere. Simple as that.

major


----------



## major (Apr 4, 2008)

IamIan said:


> .. if you know what the terms current and energy mean.... how can you still insist there is no energy in 1 Ampere of current?


I think I have a pretty good idea of what the terms current and energy mean. One Ampere is one Coulomb/second. It is a rate. Therefore it is a value existing at an infinitesimal time. How can it contain anything?

Saying there is energy in current is like saying there is mass in velocity.

I think the language difference between us is algebra and calculus.

You answer my questions with questions. When I agree with you, you tell me I'm wrong. I do not want to continue this nonsense.

Good bye.

major


----------



## IamIan (Mar 29, 2009)

major said:


> I think I have a pretty good idea of what the terms current and energy mean.


I begin to doubt.
It seems like you have a basic idea... good enough for some applications.

But you give the impression that you think you have a excellent nearly flawless idea... but your statements indicate some ( I would say significant ) flaws in your grasp of the concepts.



major said:


> One Ampere is one Coulomb/second. It is a rate. Therefore it is a value existing at an infinitesimal time. How can it contain anything?


Your example is incorrect.... look for a correct example of your position of current that does not contain energy.

How can the rate of one coulomb / second exist without any coulombs of energy?

The correct answer is... it can't... despite what you might think you know about 1 Ampere... if there are Zero Coulombs of energy ... by definition of what a Ampere is ... there must therefore be Zero Ampere.... unless you also have some personal deviation/variation on this from the rest of the accepted scientific community as well.

At best one could accurately say that the energy content of that current is undefined ... but to claim no energy ... is wrong.



major said:


> Saying there is energy in current is like saying there is mass in velocity.


I think I have a better analogy:

You claim force without energy... and you ask a question of how much energy in ___ amount of force.

The wind blows with 60 PSI of air pressure force.... how much energy is in that pressure (force)?

That is the same form of the force to energy question you asked and it is just as flawed... It does not have enough information... and you knew your question didn't have the necessary information from the beginning... but you formed it as a flawed /trick question anyway.

Until you have more information about the context ... over what size surface area ... over what period of time ... air density ... etc...etc... until you have more data you can not accurately determine the energy in that force.

To claim there is no energy or Zero energy in that wind is incorrect... it is undefined until you have additional detail... but there is still energy in that wind.

The flaw of your Ampere question can also be easily seen in a wind example.

The the wind is moving at 10 MPH how much energy is in that wind?

Again there is not enough data and the exact content of the energy contained in that wind is undefined.... but to claim that there would be no energy in that flow or movement of wind... would be incorrect.



major said:


> You answer my questions with questions.


When your question is not clear ... or was more of a trick/flawed question ... yes I asked questions in order to clarify... to which you refuse to clarify.



major said:


> I think the language difference between us is algebra and calculus.
> 
> I do not want to continue this nonsense.


fine by me...

Lets call an end to this one as well .... I think this the 3rd one now.


----------



## GerhardRP (Nov 17, 2009)

IamIan said:


> <snip>
> The flaw of your Ampere question can also be easily seen in a wind example.
> 
> The the wind is moving at 10 MPH how much energy is in that wind?
> ...


The amount of energy in a volume of air [calculate its mass] moving at 10 mph is well defined as 1/2*m*v^2. The more interesting question might be how much power can be extracted from 10 mph wind.. not much, see: http://eduhosting.org/windpics/wgwatts.html#doit

I will add to major's statements that if whatever you are talking about does not have the dimensions of power ie. watts, then you cannot ask how much power is involved. 
Now with current, you could say for example 100 amps is being pushed through 1 ohm, then the power is I^2*R or 10000 watts. Or maybe we could say that 100 amps was working against 100 volts of back emf in a dc motor, so the power is I*V or again 10000 watts.
The current is amperes, not watts and until you describe the interaction, you cannot calculate power. There is power disipated or transferred in the interaction, but not intrinsically existing in the current.
Gerhard


----------



## major (Apr 4, 2008)

IamIan said:


> ....but your statements indicate some ( I would say significant ) flaws in your grasp of the concepts.


As much I would have preferred not to respond, the above statement deserves a few more words from me.



IamIan said:


> How can the rate of one coulomb / second exist without any coulombs of energy?


So from this statement from you, you believe that electric charge is energy. This is incorrect. And something a lot of these DIYers can relate to. 

A Coulomb of charge is defined as one ampere-second. So in terms more familiar to the DIYer, 1 ampere-hour (Ahr) is 3600 Coulombs. Batteries or cells are rated in Ahr.

How often do we see a noobie chime in with the question "How many ampere-hour battery do I need to get 50 miles?" I've seen any number of members reply "Hey noob, it isn't Ahrs alone that get you the range. We need to know your battery voltage." 

I think it is obvious to most of us that charge (Ahrs) is not energy. You must know the potential (Voltage) associated with that charge to know the energy (watt-hours) of the energy storage system. Therefore I think it is safe to say that statement which includes "coulombs of energy" indicates a flaw in the grasp of the concept by the one making the statement.

I really do not care what IamIan thinks of me or my grasp of concepts. But I thought I'd put these last words on the subject up here and let the readers draw their own conclusions.



> Lets call an end to this one as well .... I think this the 3rd one now.


Yes, I agree. Please do not respond on this thread. If you wish to further explore the charge question, please take it over to the http://www.diyelectriccar.com/forums/forumdisplay.php/batteries-and-charging-35.html forum where it belongs.

Regards,

major


----------



## IamIan (Mar 29, 2009)

The lack of the needed information does not mean that an undefined property does not exist.

I think that sentence sums it up nicely. 



GerhardRP said:


> The amount of energy in a volume of air *[calculate its mass]* moving at 10 mph is well defined


Exactly... 

You need additional information ... in your example that would be , what is the mass related to that rate of flow of 10 MPH.

Without additional information the answer is undefined ... which is not the same as saying that there is no energy in that 10 mph wind.

And it would be silly for me to suggest there was no energy in the 10 MPH wind... or that there was no power in the 10 MPH wind.

If I do not give you all the needed information to define that amount of energy , or power ... asking for a specific value of energy or power in that 10 MPH wind is a flawed question at best and a intentional trick question at worst ... and needs additional information defined in order to accurately be able to answer the question.

You not being able to accurately give me an exact number for the amount of energy in the 10 MPH wind when I do not give you the mass or other needed information .... is not any kind of proof that there is no energy in that 10 MPH wind.

-------------

Here is a different example:

A super conductor has its electrical resistance go to Zero... if a 1 Amp current is known to be flowing in that super conductor ... we know that there is energy in that 1 Amp of current ... even though there will be no voltage drop across the superconductor ... even though we do not yet have the needed information in order to define exactly how much energy that 1 Amp of current has does not change that we already know that there is energy in it any way ... and we also know that energy has the potential to do work in the form of electrical power ... even if we do not yet know enough in order to define exactly how much this 1 Amp of current has.


----------



## GerhardRP (Nov 17, 2009)

IamIan said:


> The lack of the needed information does not mean that an undefined property does not exist.
> 
> I think that sentence sums it up nicely.
> 
> ...


Oh, for Pere's sake Google "mass of air" and you get 1.21kg/m3 at 20 deg C at sea level. You can do the math. But notice that the Energy is not 10 miles per hour, but 1/2*m*v^2.
Maybe we should start a Physics 101 thread somewhere. You need to learn some BASIC concepts about what various units specify: Current specifies moving charges. When current interacts with voltage, resistance or magnetic fields, there are interactions which can be described in terms of power and stored energy. Energy and power are properties of the interaction, not of the current. 
In your superconducting example, if the current is flowing a loop, there is energy stored in the magnetic field, it is NOT a property of the current, but of the field.


----------



## gor (Nov 25, 2009)

speaking of witch (that horse from early posts):
"Horsepower: Unit of rate of doing work. Defined as 550 foot-pounds per second. One horsepower is about 746 watts. 
A horsepower has also been defined as the amount of power needed to drag a dead horse 550 feet in 1 second, but this was not accepted by the international standards community."


----------



## gor (Nov 25, 2009)

Q.: what was the definition of Torque, not accepted by the International Standards Community?

since it has four legs and no arms (sorry, Major) - torque can be applied to the tail, but would it provide enough rpm?


----------



## Jan (Oct 5, 2009)

Hi Major,



major said:


> I was looking for a quantity from you. Like 3 Watts. Or 24.7 milliWatts. How much power is required to deduce you have 20 oz.in.?


I have to know how fast you turned the wrench. 

No, I can't tell. The wrench is constructed to show you the torque by measure power and speed. How? I have no idea. You could better explain to me how it works.



> The displacement of a physical object like the pointer will require movement and therefore a force and motion which constitute power. I thought such was obvious to everyone, so I may not have mentioned it early on, but would have not denied it.


I don't know anymore where we disagree upon.


----------



## major (Apr 4, 2008)

Jan said:


> I have to know how fast you turned the wrench.
> 
> No, I can't tell. The wrench is constructed to show you the torque by measure power and speed. How? I have no idea. You could better explain to me how it works.


Hi Jan,

I don't know how a torque wrench would measure power and speed either. I can almost envision an experiment to do this. But it would be cumbersome to say the least to use such a method for a torque wrench. Especially when the simple displacement of a calibrated spring works so well and is inexpensive, durable and reliable.

You told us that in Holland you used power to deduce torque. So I was simply inquiring as to how this is done.

Regards,

major


----------



## Jan (Oct 5, 2009)

major said:


> You told us that in Holland you used power to deduce torque.


I don't know exactly what I wrote, but it was something that if you need movement to measure torque, that movement and torque are called power. And yes, also in Holland. And we agree on that, I understand.

How this in reality works with a torque wrench? I don't know. 

I see torque without movement as a theoretical concept. We know it must exist. But we deduct it from other measurable phenomena. Like there is electric potential. But we can only measure it by releasing a few electrons, creating current. Very tiny. 

I guess measurement equipment needs power per definition. Or like the quantum mechanics say: Measuring is disturbing.


----------



## GerhardRP (Nov 17, 2009)

Jan said:


> I don't know exactly what I wrote, but it was something that if you need movement to measure torque, that movement and torque are called power. And yes, also in Holland. And we agree on that, I understand.
> 
> How this in reality works with a torque wrench? I don't know.
> 
> ...


Maybe part of the problem with this discussion is that measurements with a torque wrench are static. True that you apply a force to the handle and the arm of the wrench bends. During the time you are moving the handle you expend power to change the bend, but the measurement is made when you stop moving at the correct displacement[correct torque]. Then you have no more power being expended, but you do have energy stored in the bent arm of the wrench. 
The torque in the bolt is still there even though there is no movement. 
It is true that the total torque is zero IF you look at torques within the whole system including your arm, your legs and shoes coupling back to the workbench and then back up through your project to the bolt.
Gerhard


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## major (Apr 4, 2008)

scarab said:


> Can anybody tell me of upping the number of batteries i.e. volts will increase torque/rpm/hp from a ac55 motor which usually runs on 96 volts


Hey scarab,

Is this the ac55 you're talking about? http://www.azuredynamics.com/products/force-drive/documents/AC55_DMOC445ProductSheet.pdf 

If so, I read the minimum operating voltage at 100 VDC. 

major


----------



## PhantomPholly (Aug 20, 2008)

A friend sent this humorous bit. It does nothing to answer the question of this thread, but I thought you all might enjoy it anyway...


____________________________________________

One top fuel dragster 500 cubic inch Hemi engine makes more
horsepower than the first 4 rows of stock cars at the Daytona 500.

It takes just 15/100ths of a second for all 6,000+ horsepower of an
NHRA Top Fuel dragster engine to reach the rear wheels.

Under full throttle, a dragster engine consumes 1-1/2 gallons of
nitro methane per second; a fully loaded 747 consumes jet fuel at the
same rate with 25% less energy being produced.

A stock Dodge Hemi V8 engine cannot produce enough power to drive the
dragster's supercharger.

With 3,000 CFM of air being rammed in by the supercharger on
overdrive, the fuel mixture is compressed into a near-solid form
before ignition.
>

Cylinders run on the verge of hydraulic lock at full throttle.

At the stoichiometric (stoichiometry: methodology and technology by
which quantities of reactants and products in chemical reactions are
determined) 1.7:1 air/fuel mixture of nitro methane, the flame front
temperature measures 7,050 deg F.

Nitro methane burns yellow.. The spectacular white flame seen above
the stacks at night is raw burning hydrogen, dissociated from
atmospheric water vapor by the searing exhaust gases.

Dual magnetos supply 44 amps to each spark plug. This is the output
of an arc welder in each cylinder.

Spark plug electrodes are totally consumed during a pass. After
halfway, the engine is dieseling from
compression, plus the glow of
exhaust valves at 1,400 deg F. The engine can only be shut down by
cutting the fuel flow.

If spark momentarily fails early in the run, unburned nitro builds up
in the affected cylinders and then explodes with sufficient force to
blow cylinder heads off the block in pieces or split the block in half.

In order to exceed 300 mph in 4. 5 seconds, dragsters must accelerate
an average of over 4G's. In order to reach 200 mph (well before half-
track), the launch acceleration approaches 8G's.

Dragsters reach over 300 miles per hour before you have completed
reading this sentence.

Top fuel engines turn approximately 540 revolutions from light to light!
Including the
burnout, the engine must only survive 900 revolutions
under load.

The redline is actually quite high at 9,500 rpm.

Assuming all the equipment is paid off, the crew worked for free, and
for once NOTHING BLOWS UP, each run costs an estimate $1,000.00 per
second.

The current top fuel dragster elapsed time record is 4.428 seconds
for the quarter mile (11/12/06, Tony Schumacher, at Pomona , CA ).
The top speed record is 336.15 mph as measured over the last 66' of
the run (05/25/05 Tony Schumacher, at Hebron , OH ).

Putting all of this into perspective:

You are driving the average $140,000 Lingenfelter 'twin-turbo'
powered Corvette Z06.. Over a mile up the road, a top fuel
dragster
is staged and ready to launch down a quarter mile strip as you pass.
You have the advantage of a flying start. You run the 'Vette hard up
through the gears and blast across the starting line and pass the
dragster at an honest 200 mph. The 'tree' goes green for both of you
at that moment.

The dragster launches and starts after you. You keep your foot down
hard, but you hear an incredibly brutal whine that sears your
eardrums and within 3 seconds, the dragster catches and passes you.
He beats you to the finish line, a quarter mile away from where you
just passed him.

Think about it, from a standing start, the dragster had spotted you
200 mph and not only caught, but nearly blasted you off the road when
he passed
You within a mere 1,320 foot long race course.

...... And that my friends, is ACCELERATION!
Now don't you feel better just knowing that little bit of info?


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## Duncan (Dec 8, 2008)

Hi Major,
Measuring torque with a torque wrench is a pain because friction is such a large and variable part of what is wanted

What you are trying to do is to stretch the bolt 
(normally elastically but sometimes to the plastic zone (single use!))
to achieve a clamping load

For big engines (ships) you use a tool that stretches the bolts the desired amount and then you snug down a "nut" - normally round with holes for a tommy bar 

Totally irrelevant to the Power vs Torque but fun anyway


----------



## major (Apr 4, 2008)

Duncan said:


> Hi Major,
> Measuring torque with a torque wrench is a pain because friction is such a large and variable part of what is wanted


Hi Duncan,

I'd say measuring torque with a torque wrench is easy. Relating that to a clamping force is the difficult part, I agree. The use of the torque wrench example here was more about the wrench than about the bolt. 

Regards,

major


----------



## Dennis (Feb 25, 2008)

It has been forever since I have been here, but I decided I'll chime in here. Picking single value torque figures means absolutely nothing in racing. Why? Because it is one data point out of a vast array of data points of the TORQUE CURVE. What is important is the TORQUE CURVE, not some single value of torque. With the torque curve one can get an estimate of how the vehicle will perform from take off, till drag over comes the vehicle in which case the mechanical system becomes stable (i.e. no acceleration).

Also horespower simply describes torque values against RPM's. Rather than waste all that time doing horsepower calculations, it is much easier to simply look at what the torque is doing at various RPM's (the torque curve). One can even superimpose the load curve onto the torque curve to see how much acceleration that vehicle has and determine where the vehicle reaches its stabilized point, which is the point where the torque curve and load curve intersect and thus is the top speed of the vehicle.


----------



## gor (Nov 25, 2009)

good article : ))
torque&HP "arms race" http://craig.backfire.ca/pages/autos/horsepower


























"The Ricer's acceleration at low speeds is still very poor, but the Ricer has a trick up his sleeve. He is going to install a set of 5.67:1 gears in his axle without the ******* knowing:







The Ricer has pretty much completely caught up now, especially at speeds above 40mph. With those gears he put in, he has traded his higher revs for higher torque to the wheels. Now, for certain vehicle speeds, he can accelerate alongside the *******. The Ricer could narrow the gap even further if he changed the transmission gear ratios to better suit his power band.
...
If both cars were fitted with a Continuously Variable Transmission (CVT) that had an infinite ratio spread which can hold both engines at their horsepower peaks, the acceleration of both cars would be identical. "


Qestion: setting transmission, gear ratios - when we using torque curve, when HP curve?


----------



## major (Apr 4, 2008)

gor said:


> good article : ))
> torque&HP "arms race" http://craig.backfire.ca/pages/autos/horsepower


Hi gor,

Thanks for posting that. Curious how he seems to purposely avoid launch when talking about acceleration. His examples are at 70 mph or 35.7 mph. He says "The _torque method_ and the _power method_ will both produce the same results...." I'd like him to demonstrate that to me using the first 1/100th second from standstill when it is an electric motor doing the propulsion.

I'll avoid your gear question. Let's see what others have to say.

Regards,

major


----------



## electrabishi (Mar 11, 2008)

major said:


> Hi gor,
> 
> Thanks for posting that. Curious how he seems to purposely avoid launch when talking about acceleration. His examples are at 70 mph or 35.7 mph. He says "The _torque method_ and the _power method_ will both produce the same results...." I'd like him to demonstrate that to me using the first 1/100th second from standstill when it is an electric motor doing the propulsion.
> 
> ...


60 ft predictions would be nice. We have lots of data for electrics and otherwise to compare to calculations ;-)


----------



## LithiumaniacsEVRacing (Oct 9, 2010)

I was looking for a good explanation on how important torque is compared to hp. Torque is KING, but with added hp as a chaser you have the fastest car. HP with low torque is garbage, torque rules the road, track, etc.....



Qer said:


> Power = RPM * Torque, so yes indeed.
> 
> As I see it, and since my background is mainly from electricity, I tend to see it as torque is related to current and rpm is related to voltage. Both torque and rpm are potentially very powerful, but rpm without load or torque without movement won't make anyone happy, current without voltage or voltage without current are equally pointless. Of course.
> 
> ...


----------



## LithiumaniacsEVRacing (Oct 9, 2010)

This comment is only true if your motors start losing torque, then hp can maintain the speed with higher rpm's. BUT, if your motors continue to create torque till the end, then hp will be used at the very very end. It all depends on your drivetrains design, proper gearing can take the place of hp. 



paker said:


> This is about the best answer I've seen about torque.
> 
> *Torque is what accelerates the vehicle and horse power keeps it there. Just about any car can travel at 100 kph or 60 mph but how fast it can get there depends on how much torque the engine produces.*


----------



## Ravishankar (Jan 26, 2009)

major said:


> I was engaged in discussion with a member on another thread and the OP politely suggested we take it elsewhere. If interested that can be found here: http://www.diyelectriccar.com/forums/showthread.php/new-build-new-builder-ninja-250-36771.html
> 
> The other member claims
> 
> ...


Well, we need to understand what performance is: performance is usually described as the time to accelerate from 0-100 and the top speed of the vehicle. For performance what matters is power - as simple as that! What about the relevance of torque, you ask ? 
As is already mentioned, power=torque * speed for a rotating machine. 
So you may have the same power with low torque and high rpm - usually in case of a gasoline engine or high torque at low rpm - usually in case of a diesel engine. And electric motors provide the maximum torque at 0 rpm!! 

That makes for a different driving experience , but does not change the power of the engine! So for a gasoline engine you would have to rev the engine higher to get to the power required to for example pull up on a slope - by shifting to a lower gear. But for a diesel engine it pulls at lower speeds because of the torque at low rpm. This makes for different gearing of every engine based on its torque-speed curve. 

Finally, to end this note on the relevance of torque, consider the diesel-electric locomotive. The locomotive is so heavy and for a diesel engine to pull the train we would require a massive gearbox with huge gear-ratio! Which is why the diesel engine runs a synchronous generator which produces electricity that is then fed to the DC or AC Traction motors that produce the max torque at 0 rpm - enough to move the massive weight of the locomotive!


----------



## major (Apr 4, 2008)

Ravishankar said:


> ....performance is usually described as the time to accelerate from 0-100......what matters is power - as simple as that!


Hey Ravi,

You say that, and then contradict it with the statement below 



> Traction motors that produce the max torque at 0 rpm - enough to move the massive weight of the locomotive!


If your performance criteria involves launch from standstill, ie zero RPM, then torque is relevant. Afterall, there is no mechanical power at zero RPM.

Torque (or force) is the fundamental attribute or quantity responsible for the motion. Power is just the resultant measure of the system once motion is obtained 

Regards,

major


----------



## Ravishankar (Jan 26, 2009)

Major, I still go by my statement. Performance is determined by power or to be more exact the power/weight ratio. Thats why race cars are made lighter with advanced materials. Torque is the twisting force of a rotating machine. Its the tangential force vector multiplied by the radius of the axis of motion. That's why you are able to lift the car when the tire goes flat - because of torque multiplication.
Power is the rate at which work is done - whatever that work is.
For a rotating machine it happens to be the torque*speed. But if you think about a jet engine or a rocket engine, there is nothing rotating, but Newtons third law applies and the maximum velocity is determined by the propulsive power. So torque becomes relevant for rotating engines in this way: "At What Speed is the Max Torque available" since as you rightly pointed out the maximum torque is required from standstill (though not a performance criterion, its certainly a criterion for driveability!). If the max toruqe and power are available at higher speeds only - then the engine feels no better than a lower powered engine at low speeds. Many inexperienced drivers of race bikes and race cars say that they didnt feel anything different from normal engines!
So the relevance of torque is only one thing: Driveability! And in case of the locomotive, it in the extreme - whether we can start moving or not! We would require a massive gearbox and rev the diesel engine to around 4000rpm and then Bang! - clutch it to the wheels using a huge ratio to produce max torque.


----------



## major (Apr 4, 2008)

Ravishankar said:


> And in case of the locomotive, it in the extreme - whether we can start moving or not!


O.K. Ravi,

How much power is required to start moving your train?

Point is: Torque is relevant 

major


----------



## TigerNut (Dec 18, 2009)

> How much power is required to start moving your train?


The starting power requirement is the stall current times the applied voltage... over to you, Major 

My view (for what that's worth):
- A motor has zero efficiency when it's stalled. Talk of "power" at startup is meaningless except as I've noted above, since there is no output power at time zero.
- How well you can get away from the stalled condition depends on both the power handling capability of the motor and its maximum torque capability.
- From a system perspective, and assuming you're not mechanically torque limited, how well you can get away from the stalled condition depends on the power handling capability of the motor, the controller, and the battery pack. Whichever of these has the lowest power handling ability is what limits your conversion from battery energy to vehicle speed.


----------



## major (Apr 4, 2008)

TigerNut said:


> The starting power requirement is the stall current times the applied voltage... over to you, Major


So if I used a superconducting motor, it would require no power, right?


----------



## ken will (Dec 19, 2009)

TigerNut said:


> The starting power requirement is the stall current times the applied voltage...


The starting power requirement is the amount of force needed, where the tire touches the pavement!!...That's it.

Engine Torque is relevant in that it helps determine the most efficient gear ratio.


----------



## major (Apr 4, 2008)

ken will said:


> The starting power requirement is the amount of force needed,.......


Power is not force


----------



## Ravishankar (Jan 26, 2009)

major said:


> So if I used a superconducting motor, it would require no power, right?


Not really. With a superconducting motor, you will have zero I2R losses in the form of heat (since R = 0). Thus the efficiency of the motor is more. There will be other losses like eddy currents, hysteresis and others which are not understood yet. 
But how can we say that the motor does not require power ? The law of conservation of energy does not allow that. The electrical energy is converted to mechanical energy. 
Torque is produced in an electric motor as a result of the vector interaction of the electric current and magnetic field. This energy conversion is extraordinarily efficient

The question for the train is better framed as : how much power is required to move the train at 1kmph (which is to say: just moving!). There are equations and we can do the calculations given which I will not go into here. Lets say the power is X Mw (mega watts). This requirement will never change, but power=torque*speed. Speed = 1kmph and assuming a 1:1 gear ratio, torque is basically the power required.

Inasmuch I emphasize would like to summarize some points:
1) Torque is the basic motive force and is relevant. There is no question on that! That relevance is about Driveability! To give a simple example, image being stuck on the first gear of the manual transmission of your car. You have a lot of torque right ?. But what about the power ..no speed there..
2) But all physics of performance is based on power 
3) Power is very important for electric vehicle because
i) Electric motors already develop peak torque from 0rpm. The power transmission is accomplished by a single speed gear.
ii) Electric vehicles use batteries which have limited energy densities and using more power reduces their range drastically.


----------



## ken will (Dec 19, 2009)

If HP = ft-lbs * RPM /5250

You can not have HP without torque or RPM

zero Torque = zero HP

zero RPM = zero HP

Both RPM and Torque are absolutely relevant!!


----------



## major (Apr 4, 2008)

Ravishankar said:


> Not really. With a superconducting motor, you will have zero I2R losses in the form of heat (since R = 0). Thus the efficiency of the motor is more. There will be other losses like eddy currents, hysteresis and others which are not understood yet. .


Hi Ravi,

I've been thru this before on this thread. If motor at stall (zero RPM) has no motion and no changing magnetic field (as in a DC motor), then there are no other losses. Only resistive losses.




> But how can we say that the motor does not require power ?


If the resistive losses are eliminated and it has no rotational or magnetic induced loss, then it requires no power and produces torque from lossless current. ie. superconductivity. But this is just an academic example to demonstrate that the force (or torque in the case of a motor) is independent of power.



> The law of conservation of energy does not allow that. The electrical energy is converted to mechanical energy.


There exists force (or torque) without motion and therefore it does no work and requires no energy. And it is what gets the vehicle moving from standstill. Without it, everything would remain where it is at 




> Torque is produced in an electric motor as a result of the vector interaction of the electric current and magnetic field. This energy conversion is extraordinarily efficient


It is not energy conversion and in fact can be lossless if there is no motion or changing magnetic field.



> The question for the train is better framed as : how much power is required to move the train at 1kmph (which is to say: just moving!). There are equations and we can do the calculations given which I will not go into here. Lets say the power is X Mw (mega watts). This requirement will never change, but power=torque*speed. Speed = 1kmph and assuming a 1:1 gear ratio, torque is basically the power required.


Wait a minute. You can't change my question without permission  I said start the train moving----from zero speed. And again, torque is not power.



> 1) Torque is the basic motive force and is relevant.


Yes.



> 2) But all physics of performance is based on power


It is strange that Sir Newton did not have to even mention power in his 3 laws of motion.



> 3) Power is very important for electric vehicle


I never said otherwise  Just that torque is relevant.

Regards,

major


----------



## madmike8 (Jun 16, 2011)

If you read it entirely, this is a good read.

http://www.vettenet.org/torquehp.html

And a ET Calculator...

http://www.stealth316.com/2-calc-hp-et-mph.htm


----------



## major (Apr 4, 2008)

I want to reply to Mr. McRat's post in John's DCPlasma thread, but don't want to hijack that thread any further, so I figure why not stick it here 



McRat said:


> Turn 460rwhp at 0 rpm into calories, and apply it to 12 lbs of steel. It would fail, since steel softens starting at 500°F.


Turn 460rwhp at 0 rpm into torque, and apply it to 12 lbs of steel. It would fail, since infinite torque breaks everything.

If you have a shaft or wheel at 0 RPM, then the power is zero. Also, calorie is a unit of energy ( = 4.184 J ), so you cannot convert 460 hp into calories.


----------



## Arlo (Dec 27, 2009)

major said:


> I was engaged in discussion with a member on another thread and the OP politely suggested we take it elsewhere. If interested that can be found here: http://www.diyelectriccar.com/forums/showthread.php/new-build-new-builder-ninja-250-36771.html
> 
> The other member claims
> 
> ...


 Major Just think about it this way at 0 rpm no matter how much torque you have you are not making any HP so... To launch a car fast would you rather have 600 ft/lbs at 0 rpm or 60 ft/lbs even though they both give you 0 HP! Trust me torque is very important. Having a Torque vs RPM curve is the most important curve for a car. Having a HP curve is very handy but you might think its really good because you have some big HP numbers then realize you need 2 stages of reduction to make use of the hi rpm required to make the HP So if you had a torque vs rpm graph as well it will show this in an easier to understand way.


----------



## McRat (Jul 10, 2012)

Naw, Major wants to play Clutches don't Multiply Torque with me. 

As someone who has broken more driveline parts in my clutch cars than automagics, it's either multiplying torque BETTER than a TC, or clutches have magic torque.

Since on a car, peak torque occurs at less that 5252 rpm, your best launches would be at under that RPM. I can tell you that as you increase the launch RPM the launch gets more and more violent. With a manual you are often limited by how much torque the tires will take, hence this is limits your launch RPM. Too high, and you just blow off the tires.


----------



## Arlo (Dec 27, 2009)

McRat said:


> Naw, Major wants to play Clutches don't Multiply Torque with me.
> 
> As someone who has broken more driveline parts in my clutch cars than automagics, it's either multiplying torque BETTER than a TC, or clutches have magic torque.
> 
> Since on a car, peak torque occurs at less that 5252 rpm,


You proly just cant make a clutch as smooth as a Torque converter.

At 5252 torque = HP yes But peak torque is not always below 5252.

I dont belive in the terms torque multiplication from a TQ or a clutch. Another thing you maybe doing is letting the clutch out in such a way you are pulling the motor rpm down a touch and using stored energy of rotation to get a burst of torque above the actual torque output of the motor! This is common espicaly in ICE's.


----------



## major (Apr 4, 2008)

McRat said:


> Naw, Major wants to play Clutches don't Multiply Torque with me.
> 
> As someone who has broken more driveline parts in my clutch cars than automagics, it's either multiplying torque BETTER than a TC, or clutches have magic torque.
> 
> Since on a car, peak torque occurs at less that 5252 rpm, your best launches would be at under that RPM. I can tell you that as you increase the launch RPM the launch gets more and more violent. With a manual you are often limited by how much torque the tires will take, hence this is limits your launch RPM. Too high, and you just blow off the tires.


It is due to more torque being delivered though the clutch from the moment of inertia of the high revving engine and flywheel, not a multiplication by the clutch. When you engage the clutch there is a change in the rotational velocity of the engine parts and flywheel. This amounts to angular acceleration. That angular acceleration times the moment of inertia equals torque which is delivered to the wheels though the clutch. *The higher the engine speed; the higher energy from the moment of inertia; the greater the torque.* The faster the clutch is engaged; the greater the angular acceleration; the greater the torque.

*__* I changed the sentence. The moment of inertia is independent of the speed. However the higher speed increases the kinetic energy of the rotating parts and allows for a greater change in angular velocity and therefore greater angular acceleration.


----------



## GerhardRP (Nov 17, 2009)

McRat said:


> Turn 460rwhp at 0 rpm into calories, and apply it to 12 lbs of steel. It would fail, since steel softens starting at 500°F. 6000HP?


Lets do the calculation:
1) It take 460 Joules to heat 1 kg of steel 1 degree Celsius.
3) 500 degrees F is 260 degrees Celsius
3) 12 pounds is 5.44 kg
4) therefore it takes 460 * 260 * 5.44 J = 650 kJ to soften your pressure plate.
5) 460 hp equals 335 kW
6) Therefore, you would need to completely slip your clutch for 650/335 = 1.95 seconds.


----------



## McRat (Jul 10, 2012)

major said:


> It is due to more torque being delivered though the clutch from the moment of inertia of the high revving engine and flywheel, not a multiplication by the clutch. When you engage the clutch there is a change in the rotational velocity of the engine parts and flywheel. This amounts to angular acceleration. That angular acceleration times the moment of inertia equals torque which is delivered to the wheels though the clutch. *The higher the engine speed; the higher the moment of inertia; the greater the torque.* The faster the clutch is engaged; the greater the angular acceleration; the greater the torque.
> 
> *__* I am incorrect in that statement. The moment of inertia is independent of the speed. However the higher speed increases the kinetic energy of the rotating parts and allows for a greater change in angular velocity and therefore greater angular acceleration.


Drive any manual trans car down the freeway at it's torque peak RPM, then nail the throttle.

Now, do the same thing, but when you nail the throttle, slip the clutch to peak HP rpm and watch what happens. This is not engine inertia that is doing it. In any case, the tires wheel and brakes have far more rotational inertia than the engine does. The crank and flywheel dia is small, and it weighs less than the large dia wheels and tires. Oddly enough, a lightweight reciprocating assy will accelerate quicker off the line with a clutch. It is routine to lighten the flywheel to improve ET's.

Two strokes are famous for this. A stab of the clutch when you need some instant acceleration works pretty well. You are trading the torque for HP.

Like I said, it's an agree to disagree kind of thing. I know what works for me, and how the clutch behaves. A TC has nothing over an educated clutch foot. If it really could multiply torque, a TC would win every time.


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## McRat (Jul 10, 2012)

GerhardRP said:


> Lets do the calculation:
> 1) It take 460 Joules to heat 1 kg of steel 1 degree Celsius.
> 3) 500 degrees F is 260 degrees Celsius
> 3) 12 pounds is 5.44 kg
> ...


Your flywheel is about 150-200°F (100C) when you pull up to the line. It's about what the transmission temp and engine oil temp is. When you hot-lap it, it's a lot higher. I know I ride the clutch for >1.5 seconds on a launch if the tires hold. Dumping it will bog the engine.

Now do that with 6000HP, the TF clutches don't weigh a bunch either. 460 is street car output.


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## tomofreno (Mar 3, 2009)

McRat said:


> Drive any manual trans car down the freeway at it's torque peak RPM, then nail the throttle.
> 
> Now, do the same thing, but when you nail the throttle, slip the clutch to peak HP rpm and watch what happens. This is not engine inertia that is doing it.


 Not sure why you say that. You slip the clutch while nailing the throttle, correct? Then the application of torque by the engine to the transmission is greatly reduced, or eliminated, no? If so, then the vehicle decelerates due to the remaining forces, drag, rolling and friction, operating on it, and the engine rpm increases. When the rpm reaches that for max power, you release the clutch to again apply torque from the engine to the transmission. The engine rpm is now greater than the transmission rpm due to the vehicle slowing and the engine rpm increasing, so the rotational energy of the engine and flywheel do work to accelerate the car as the transmission, wheels, etc, become part of this now larger rotating mass, all now turning at some rpm in between the earlier engine and wheel rpms when the clutch is released, with the result that the vehicle is accelerated by this transfer of rotational energy as well as by the now re-applied engine torque.



> In any case, the tires wheel and brakes have far more rotational inertia than the engine does. The crank and flywheel dia is small, and it weighs less than the large dia wheels and tires.


 May be, but they are decoupled by the depressed clutch pedal, no?



> Oddly enough, a lightweight reciprocating assy will accelerate quicker off the line with a clutch. It is routine to lighten the flywheel to improve ET's.


 Generally referred to as equivalent mass - the translational mass the rotating mass is equivalent to, energy-wise. See for example: http://hpwizard.com/rotational-inertia.html


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## McRat (Jul 10, 2012)

tomofreno said:


> ... Then the application of torque by the engine to the transmission is greatly reduced, or eliminated, no? If so, then the vehicle decelerates due to the remaining forces, drag, rolling and friction, operating on it, and the engine rpm increases. When the rpm reaches that for max power, you release the clutch to again apply torque from the engine to the transmission. The engine rpm is now greater than the transmission rpm due to the vehicle slowing and the engine rpm increasing, so the rotational energy of the engine and flywheel do work to accelerate the car as the transmission, wheels, etc, become part of this now larger rotating mass, all now turning at some rpm in between the earlier engine and wheel rpms when the clutch is released, with the result that the vehicle is accelerated by this transfer of rotational energy as well as by the now re-applied engine torque.
> 
> ...[/URL]


All I can say is give it a try. The reciprocating mass isn't very much. I doubt you'd feel more than a mild jerk in a 3000+ lb car. You aren't "dumping" the inertia, you are abusing the clutch. The radius of the reciprocating parts is small, it doesn't store much energy. Watch a new clutch driver sometime. They constantly kill the engine. The inertia isn't enough to accelerate the car significantly. Or? Sitting still, take your engine to 6000, then shut off the ignition, and instantly open the throttle so there is little resistance. It stops pretty quick, eh? Certainly not enough force to move a car.

Another simple test. Typical V8 car makes peak torque at 3000 rpm. If you are in a big arse hurry, don't ride the clutch at 3000, ride it at 6000 and observe the difference. With a well prepped track, I can leave at 7000 rpm, and pick the tires up. But 7000 is way past peak torque. It should take off slower at 7000 since there is much less torque generated than at 3k, but the opposite is true.

With the same gearing, a manual trans will take off from the line as quick (if not quicker) than a torque converter does, but only if you ride the clutch hard.


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## major (Apr 4, 2008)

> Torque multiplication does not occur with a manual transmission clutch and pressure plate. This necessitates the need for heavy flywheels, high numerical gear ratios, and high launch rpm.


This is a quote from Jefferson Bryant in his book "How to Build a Killer Street Machine", p55, paragraph 4. I found it here: http://books.google.com/books?id=fo...nepage&q=clutch torque multiplication&f=false


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## Jan (Oct 5, 2009)

Since it's back alive, I'll give it a shoot again:

It seems to me that to some of the posters, including you Major, that torque is a 'real' thing. Something that you can feel and almost see if you look carefully. OK, that’s exaggerated. But still, I read between the lines as if they are real substantial things. 

They’re not. They’re just names for formula’s. Formula’s that do not describe thing for what they are, but are just (but never the less very important) tools which helps you predict what can be expected. 

A force, like torque, or gravity is just a theoretical concept. It does not say what reality is, or not even how it works. It only helps you predict. 

Up till an certain level we can imagine something about the ‘nature’ of reality. And can particles, behavior, flow, current etc really exists in our head. But it’s just an illusion. We can never grasp with our minds nature really. How well and accurate mathematical formula’s predict the future. 

Since the chaos theory and especially quantum mechanics it’s even better to give imagining up at all. We can’t imagine with our very limited mind stuff like a Higgs boson, or the fact that an electron e.g. is a wave and a particle at the same time. 

Reality is what reality is, and physics can only discover mathematical formula’s that predict outcomes, or better outcomes than the previous theory.

And in this light torque and power and energy and all other physical concepts are only relevant in context of the question. What do you want to know? Then you know how relevant torque is. At zero RPM power calculated with the formula P=T*2pi*RPM is pretty irrelevant. Calculated with P=U*I*Eff it might be relevant.


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## McRat (Jul 10, 2012)

major said:


> This is a quote from Jefferson Bryant in his book "How to Build a Killer Street Machine", p55, paragraph 4. I found it here: http://books.google.com/books?id=fo...nepage&q=clutch torque multiplication&f=false


Really? My KTM clutch weighs less than Paris Hilton's purse puppy. (and is more useful).

I've raced a lot of clutch and automagics over the years, and it puzzles me why most the time, if a car has the manual option I can click off better ET's. Note that many bleeding edge automagics are going clutch. Mine has 1 T/C yet 5 clutches. And you can feel it jump when the clutches in the converter do their soft-engage.

Heavy flywheels are NOT necessary. In fact, many are now "dual mass", where only the contact surface(s) are steel. Heavy flywheels (which aren't all that heavy) are for those without a well educated foot. A torque converter weighs a bunch more than a race clutch.

But how does this apply to EV's? It would be interesting to see if an EV accelerates harder if you can launch it at higher RPM. I dunno to tell you the truth, I'm still goofing off with little motors so far.

PS - Thanks for all your posts. I've learned a lot.


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## major (Apr 4, 2008)

McRat said:


> Really? My KTM clutch weighs less than Paris Hilton's purse puppy. (and is more useful).


I never said clutches weren't useful, or that torque converters were better than clutches for you. All I am saying is that clutches do not multiply torque as you would have us believe. You can use a clutch to get torque to your wheels, but that torque must come from the input to the clutch if it comes out of the clutch.


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## ruckus (Apr 15, 2009)

Not getting in the middle of this and arguing either way, but just wanted to clarify that clutches DO allow very temporary pulses of extra power by harnessing the rotational mass of the (over) revving motor when engaged suddenly. As soon as it is hooked up that energy is gone so it is very transient. This "extra" energy is available for both electric and gas and is purely determined by the rotational mass and rpm.

Arguing auto vs. manual is kinda like all those gas vs. electric arguments. It is very hard to separate what COULD be done from what HAS been done historically. 

As for the relevance of torque, I say it is PARAMOUNT. HP cannot exist without torque. Anyone who argues otherwise should have an elephant sit on their chest. It is exerting zero hp and yet you will still die. Force without power is not trivial.


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## major (Apr 4, 2008)

Jan said:


> ......gravity is just a theoretical concept......


Jump off a bridge and keep telling yourself that on the way down


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## McRat (Jul 10, 2012)

There is no gravity. The earth sucks...


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## ruckus (Apr 15, 2009)

Ok, watch what you say about my mother.

What does this have to do with torque? 

We are all in agreement then that torque is the essential ingredient. Hp is just a measure of how fast you got your torque to work. This is an important side-note, but does not exist without having the torque in the first place.


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## Jan (Oct 5, 2009)

major said:


> Jump off a bridge and keep telling yourself that on the way down


Newton did not invent gravity. What makes you fall doesn't give a shit about our theories. Einstein just made a better working formula, and didn't bent space time either. Reality is what it is, and we do not know more than some smart formula's to predict a bit of what will happen. And that last part (bending space time) is just a trick we use to visualize the formula's. Reality still gives a fuck. Imagining that torque is a real thing is scientifically wrong. Reading the last reactions, my assumption was right. You do believe it is real. It is not. You will never find torque, nowhere. You made out of a simple useful formula a believe. Torque is nothing more, and nothing less than a symbol in a formula that has great value to us.


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## ruckus (Apr 15, 2009)

Ummm.. Sorry, but the whole "nothing exists cause you can't prove anything" philosophy is beyond BS malarky and irrelevant. Go back to college and take a class in Bayesian Epistemology. Sure you can't prove anything and you don't know if you are just in a dream. Get over it. You can only deal with the reality that presents itself and that you can sense. It doesn't matter if anything is "real" or not. If you fall off a cliff and die, then gravity HAS to be treated as real. If I can put 500 ft lbs on a bar and squish your toe into liquid then it HAS to be treated as real. If I spin the bar to 5000 rpm then that too has to be treated as real. 

Nobody said HP wasn't REAL. It is just TOTALLY a factor of torque and rpm with torque being the prime component.

It is just a simple basic obvious fact that hp is DEPENDENT on torque, while torque is completely INDEPENDENT of hp. 

In layman's terms this means you can calculate torque without hp, but to calculate hp you MUST know torque.

Hp is NEVER present without torque. Therefore it is a dependent variable.

This is high school math.

ohhh, wait, there aren't really numbers and words don't exist...


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## Jan (Oct 5, 2009)

ruckus said:


> Nobody said HP wasn't REAL. It is just TOTALLY a factor of torque and rpm with torque being the prime component.


Beside of missing my whole point, there is a mutual depedency. If you know the torque and rpm you can calculate the power. And vice versa. It is only a miracle that someone knows the torque before the power. Torque or forces in general are even more abstract than power. Because of the simple fact you can not measure torque. No, there are no torque measurement instruments. They can only measure power, and the torque is deduced out of the measured power. Only power can be transformed. From rotational power to electricity or in springtension etc.


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## ruckus (Apr 15, 2009)

Jan said:


> Because of the simple fact you can not measure torque. No, there are no torque measurement instruments. They can only measure power, and the torque is deduced out of the measured power.


???? I think you have it backwards. A simple spring scale can measure torque in a steady state with no movement which all agree has no power. 

Let's put it this way, if I twist your nose but you hold your head still I have applied torque. If you give in to the torque and rotate your head then I have applied power. The torque HAD to be applied before power could be measured, but power can NEVER be applied without torque.

I can supply you with all the calculations used by an engineer to design a vehicle. Power is a derived and final calculation. Torque is the root and basis of movement and fundamental to the design of a vehicle. If torque was not paramount there would be no such thing as a torque multiplier (transmission) If hp was relevant it would be unnecessary. Your engine has ALL it's hp in 5th gear. Why don't you start in 5th?? Because hp is worthless. It is a magnitude of torque that is needed for movement. Once it is applied and you have movement you can measure it as power if you so desire, but that movement could never occur without sufficient torque. This is why all engineers start with torque calculations.

Sure these arguments are a bit moot because they are EQUAL at 5250 rpm. This might fool you into thinking one is more or less the same as the other. But this is not so. AGAIN, you can have torque without power, but never can you have power without torque. And yes, torque is easily measurable. Stick your nose out...


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## LithiumaniacsEVRacing (Oct 9, 2010)

*Enzo Ferrari

"Horsepower sells cars, Torque wins races"

http://www.physicsforums.com/showthread.php?t=153996
*


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## ruckus (Apr 15, 2009)

Repeating that worn quote is easy. Understanding it is a bit harder.

I believe he was saying that even a novice can spout a hp number, but exiting a corner, grabbing a gear a bit too tall (assuming the next gear down is a bit too low), that is where torque will win the race.

Hp requires perfect gearing. Gearing is NEVER perfect. Thus it is torque that pulls you through the gaps.

My interpretation. Also, it sounds good.


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## Jan (Oct 5, 2009)

ruckus said:


> ???? I think you have it backwards. A simple spring scale can measure torque in a steady state with no movement which all agree has no power.


It's hard to believe for me you really mean this: That there is no movement... I'm not going to tell you to go back to school, because the root of the problem might be there. No, you can not measure torque. And not only you. No one.


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## Jan (Oct 5, 2009)

Actually I am wrong. Power can be converted, what's necessary for measuring. That's correct. But you need/consume energy to make the measurement. The spring scale not only move, but it consumes a certain amount of time as well. That energy is stored in the spring as potential energy. Very little of course, but that's what instruments like. So, you do not measure power, but energy. Power and torque are both calculated.


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## DIYguy (Sep 18, 2008)

crap, now I have to throw out all three of my torque wrenches...


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## Jan (Oct 5, 2009)

DIYguy said:


> crap, now I have to throw out all three of my torque wrenches...


Come on DIYguy, you've never used them without moving. If you did, you would have trown 'm away already.


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## ruckus (Apr 15, 2009)

A master of Science was all I could stand. Blame the internet for the rest.. 

If I put a 1' lug wrench horizontally on a very tight lug and stand on the lug wrench, but the lug does not move I have applied 165 ft-lbs of torque but there has been no measurable movement and thus no horsepower. Torque is the INDEPENDENT variable.

Never can you have horsepower without BOTH torque and movement. That is why it is a DEPENDENT variable.

The cart does not push the horse up a hill.


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## rochesterricer (Jan 5, 2011)

Torque is a measure of force. It exists independent of work(movement or displacement).

Horsepower is a measure of power, or the rate at which work is done over time. 

Ruckus is correct here, although some of you may just be misunderstanding what he is saying.


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## McRat (Jul 10, 2012)

To make it more confusing, rear wheel torque is what accelerates a RWD car.

However, if you leave the RWTQ the same, and change to a smaller tire, you accelerate faster with no other changes. At least at first.

Did you make Magic Torque? Isn't 1000ftlb at the axle always 1000ftlb at the axle? No, it's just that torque isn't anything by itself. It must always be just one the variables in a driveline.


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## ruckus (Apr 15, 2009)

McRat said:


> To make it more confusing, rear wheel torque is what accelerates a RWD car.
> 
> However, if you leave the RWTQ the same, and change to a smaller tire, you accelerate faster with no other changes. At least at first.
> 
> Did you make Magic Torque? Isn't 1000ftlb at the axle always 1000ftlb at the axle? No, it's just that torque isn't anything by itself. It must always be just one the variables in a driveline.


No, you have decreased the tire radius which DOES increase the torque at the ground, thus the faster acceleration. It is not magic, it is called gearing.

Your tires are your final gear ratio. (and the easiest to adjust)


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## McRat (Jul 10, 2012)

ruckus said:


> No, you have decreased the tire radius which DOES increase the torque at the ground, thus the faster acceleration. It is not magic, it is called gearing.
> 
> Your tires are your final gear ratio. (and the easiest to adjust)


But the axle torque (wheel is secured to axle) remains unchanged. Torque is not changed. The force at the contact patch changes, but not measured output torque.

When I play with chassis dynos, if I do not give it an RPM feed, I do get HP from across the range, and it's accurate. What I don't get is torque. Why? It has no idea what the tire diameter is, it just knows the MPH acceleration.


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## MalcolmB (Jun 10, 2008)

Look what you've gone and done now Major, worms everywhere...


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## DIYguy (Sep 18, 2008)

ruckus said:


> A master of Science was all I could stand. Blame the internet for the rest..
> 
> If I put a 1' lug wrench horizontally on a very tight lug and stand on the lug wrench, but the lug does not move I have applied 165 ft-lbs of torque but there has been no measurable movement and thus no horsepower. Torque is the INDEPENDENT variable.
> 
> ...


ya, what u said.  I was going to say that a different way and try to use my torque wrench in the example. . . just so they don't feel completely useless anymore.


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## rochesterricer (Jan 5, 2011)

McRat said:


> But the axle torque (wheel is secured to axle) remains unchanged. Torque is not changed. The force at the contact patch changes, but not measured output torque.
> 
> When I play with chassis dynos, if I do not give it an RPM feed, I do get HP from across the range, and it's accurate. What I don't get is torque. Why? It has no idea what the tire diameter is, it just knows the MPH acceleration.


Thats because you are using a Dynojet(based on what you just described), and a Dynojet does not actually measure torque or horsepower. It extrapolates by measuring how long it takes to accelerate the drum, which is of known mass. 

This is why you can fool a Dynojet into thinking there is more horsepower by just lightening the flywheel. You don't actually gain hp by doing this, but the Dynojet thinks you do because it changes how quickly the driveline accelerates. You don't get this effect with dynos that actually measure force, like a Dynapack or Mustang dyno. 

Reducing tire diameter improves acceleration simply because you are changing the gear ratio. This is why it also reduces your top speed.


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## McRat (Jul 10, 2012)

rochesterricer said:


> Thats because you are using a Dynojet(based on what you just described), and a Dynojet does not actually measure torque or horsepower. It extrapolates by measuring how long it takes to accelerate the drum, which is of known mass.
> 
> This is why you can fool a Dynojet into thinking there is more horsepower by just lightening the flywheel. You don't actually gain hp by doing this, but the Dynojet thinks you do because it changes how quickly the driveline accelerates. You don't get this effect with dynos that actually measure force, like a Dynapack or Mustang dyno.
> 
> Reducing tire diameter improves acceleration simply because you are changing the gear ratio. This is why it also reduces your top speed.


I've used Mustangs, SuperFlows, and a few different Dynojet models. Odd thing about diesels, is that they have no sparkplug or coils to put the RPM pickup on, hence sometimes I must test without RPM.

And yes, a non-retarded Dynojet is the least reliable of dyno types. Superflow is my personal favorite.


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## DIYguy (Sep 18, 2008)

McRat said:


> To make it more confusing, rear wheel torque is what accelerates a RWD car.
> 
> However, if you leave the RWTQ the same, and change to a smaller tire, you accelerate faster with no other changes. At least at first.
> 
> Did you make Magic Torque? Isn't 1000ftlb at the axle always 1000ftlb at the axle? No, it's just that torque isn't anything by itself. It must always be just one the variables in a driveline.


Actually, you have changed the torque. Torque is force at distance, often expressed in ft-lbs. In your example, the distance is reduced with the shorter wheel/tire.


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## GerhardRP (Nov 17, 2009)

Jan said:


> Since it's back alive, I'll give it a shoot again:
> 
> It seems to me that to some of the posters, including you Major, that torque is a 'real' thing. Something that you can feel and almost see if you look carefully. OK, that’s exaggerated. But still, I read between the lines as if they are real substantial things.
> 
> ...


I remember an experiment in freshman physics in 1962: I turn a crank attached to a drum which had a resistance band attached and to a spring scale. We turn at a chosen rotational velocity and note the load from the scale. Given the drum radius, resistance, rotor mass and its specific heat capacity, we can say what is its expected temperature rise. Not surprisingly, they agreed.


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## McRat (Jul 10, 2012)

DIYguy said:


> Actually, you have changed the torque. Torque is force at distance, often expressed in ft-lbs. In your example, the distance is reduced with the shorter wheel/tire.


So when I apply 100ftlb to a 1" bolt, it's different than if I apply 100ftlb to a 1/2" bolt? Am I really torquing the 1/2" to 200ftlb? If I twist an axle with 1000ftlb torque, does it have to have a tire on it? Could it have a propeller? Or a bolt-on eddy current dyno?


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## tomofreno (Mar 3, 2009)

McRat said:


> So when I apply 100ftlb to a 1" bolt, it's different than if I apply 100ftlb to a 1/2" bolt? Am I really torquing the 1/2" to 200ftlb? If I twist an axle with 1000ftlb torque, does it have to have a tire on it? Could it have a propeller? Or a bolt-on eddy current dyno?


 The tractive effort - the force the tires apply to the road tangent to its surface - is what makes the car accelerate. That's the F in F = ma for acceleration, a, of a car. So say you apply 100 ft-lb directly to the shaft the wheels are on. The tractive effort the wheels apply to the road is 100 ft-lb/dynamic tire radius. Smaller dynamic radius, greater tractive effort or force, and greater acceleration.


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## Jan (Oct 5, 2009)

ruckus said:


> A master of Science was all I could stand. Blame the internet for the rest..
> 
> If I put a 1' lug wrench horizontally on a very tight lug and stand on the lug wrench, but the lug does not move I have applied 165 ft-lbs of torque but there has been no measurable movement and thus no horsepower. Torque is the INDEPENDENT variable.
> 
> ...


I said: You can not measure Torque. In this newexample; if the lug really really didn't move a fraction of a micron, you did not measure any increase in torque. You calculated it. Just like I said.

This will be my last response in this topic for a while, because of the weird emotional responses. Torque looks like some kind of a sacred word in americano.


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## poprock (Apr 29, 2010)

" horsepower sells cars, torque wins races " Who said that?


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## DIYguy (Sep 18, 2008)

McRat said:


> So when I apply 100ftlb to a 1" bolt, it's different than if I apply 100ftlb to a 1/2" bolt? Am I really torquing the 1/2" to 200ftlb? If I twist an axle with 1000ftlb torque, does it have to have a tire on it? Could it have a propeller? Or a bolt-on eddy current dyno?


Think of it like a transmission. In first gear, you under drive. This multiplies torque at the expense of speed. This is why transmissions are often called torque multipliers. It's the same with the wheel. It's effect at the ground is greater and the ultimate speed is less. 

Or maybe think of a teeder-todder (sp?). If you have a board 20 feet long and pivot at the 10' point.... now put a load of X at one end. To balance, you have to put the same load of X at the same distance on the other side. If you move one of the loads X, closer to the pivot point, that side will go up, but it's path (elevation travel) will be less. It becomes an unequal "force at distance". Now if you think of the bolt, or the axle, as the teeder-todder pivot point and the diameter of the bolt, or wheel, as the distance the weight is exerted at. . . you have a comparable situation.


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## McRat (Jul 10, 2012)

poprock1 said:


> " horsepower sells cars, torque wins races " Who said that?


A guy who was in charge of building F1 cars, which have very little torque. Oddly, his team won an awful lot of races without significant torque.


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## McRat (Jul 10, 2012)

DIYguy said:


> Think of it like a transmission. In first gear, you under drive. This multiplies torque at the expense of speed. This is why transmissions are often called torque multipliers. It's the same with the wheel. It's effect at the ground is greater and the ultimate speed is less.
> 
> Or maybe think of a teeder-todder (sp?). If you have a board 20 feet long and pivot at the 10' point.... now put a load of X at one end. To balance, you have to put the same load of X at the same distance on the other side. If you move one of the loads X, closer to the pivot point, that side will go up, but it's path (elevation travel) will be less. It becomes an unequal "force at distance". Now if you think of the bolt, or the axle, as the teeder-todder pivot point and the diameter of the bolt, or wheel, as the distance the weight is exerted at. . . you have a comparable situation.


I have race tires from 25" to 33" inches in dia for different applications. I use tires for both gearing and to optimize traction for the track.

To alter the torque, I don't use tires though. I have surplus HP at low speed, and actually launch in 2nd gear quite a bit. To alter the torque characteristics, I change turbochargers and fueling tables. I "detorque" as much as I can. Motorcycles and F1 cars have very little torque, yet they accelerate violently.


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## McRat (Jul 10, 2012)

To go back on topic, I was looking around and saw a 536HP (400kw rating continuous) 460vac motor that put out max power at over 10,000 rpm with a 20,000 redline. It's 27" long which is the longest dimension, with an aluminum case. So it's not the size of a normal 500HP electric motor.

So there are electric motors that don't need torque to make big HP numbers.

http://www.synchrony.com/products/h...vagen-novadrive-400-oil-less-drive-train.aspx

No, that is not affordable or useful, but if that company can do it, what's to stop others from making similar high HP, low torque EV motors.


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## DIYguy (Sep 18, 2008)

McRat said:


> I have race tires from 25" to 33" inches in dia for different applications. I use tires for both gearing and to optimize traction for the track.
> 
> To alter the torque, I don't use tires though. I have surplus HP at low speed, and actually launch in 2nd gear quite a bit. To alter the torque characteristics, I change turbochargers and fueling tables. I "detorque" as much as I can. Motorcycles and F1 cars have very little torque, yet they accelerate violently.


I'm sure you have much experience and u know what works for you. Hp is Hp and the same level can be achieved in different ways. Hi RPM and low torque can generate the same hp as low rpm and high torque. Typically though, very high rpm is geared back down (torque multiplication) through the drive train in order to do useful work.


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