# DC Motor Charts for EV performance spreadsheet



## major (Apr 4, 2008)

maxvtol said:


> And is this how a controller works if the controller is rated at 1000amps with the batteries limited to 500amps? And which controllers can do this?


Hi max,

When you have a battery current limit, that region is constant power. So I think that portion of the curve is curved, not linear. Hyperbola??

I believe Qer has done software for this and maybe the Zilla has it.

I don't know why you guys take a perfectly nice motor speed torque curve and turn it sideways 

Regards,

major


----------



## maxvtol (Nov 11, 2009)

Thanks for responding major.


major said:


> When you have a battery current limit, that region is constant power. So I think that portion of the curve is curved, not linear. Hyperbola??


MAN your good! Yes, hyperbolic, that make more sense, torque inversely proportional to rpm for constant power, don't know what I was thinking. The AC50 motor efficiency behind max power falls off as it approaches 0, would any curve fit that? I guess those 2 curves would need to be multiplied for mechanical power out. 

And do the other curves look right, being proportional to volts and motor amps? 

And I know the torque falls off after peak power due to back emf. I was going to use a couple of linear lines to approximate those, or is there a curve that would make sense?



major said:


> I don't know why you guys take a perfectly nice motor speed torque curve and turn it sideways


I was thinking the same of you DC motor guys . All in what you're used to I guess. It would make it easier for us mechanical guys if everything were based on rpm, not just the torque. Efficiency based on torque? I still don't get that one .


----------



## major (Apr 4, 2008)

maxvtol said:


> Yes, hyperbolic, that make more sense, torque inversely proportional to rpm for constant power,


Hi Max,

The battery current limit makes the motor input a constant power. You're plotting motor output, so it ain't exactly right. But pretty close because motor efficiency is fairly constant over that range.



> The AC50 motor efficiency behind max power falls off as it approaches 0, would any curve fit that?


I'm sure some curve (mathematical expression) would fit it, but no simple curve of which I am aware.



> And do the other curves look right,


Look pretty good to me, except sideways 



> being proportional to volts and motor amps?


Over the midrange, it is a close approximation to consider RPM proportional to motor voltage. And current and torque are a unique relationship, but not completely linear. For series motors, prior to saturation, torque is proportional to the square of current, after saturation, approximately proportional. 



> And I know the torque falls off after peak power due to back emf. I was going to use a couple of linear lines to approximate those, or is there a curve that would make sense?


You lost me here. You plotted a series motor on a PWM having a current limit. Unless you have a real high current limit, peak power will be at the power where the PWM goes full on. After that power is linear, for approximation. Prior to that, the power curve is the motor power curve from the motor speed torque curve which kinda resembles a parabola when plotted against torque. Turned sideways, don't know what it looks like. 



> Efficiency based on torque? I still don't get that one


Torque is the load. It makes perfect sense to use it as the independent variable (x axis). The motor speed, current, power output and efficiency all depend on the motor load, when the motor is supplied a particular voltage.

What do you plot efficiency against? Time of day, phase of the moon, or speed or something 

I end up explaining motor curves to quite a few of you guys. Like this: http://www.diyelectriccar.com/forums/showthread.php/dc-motor-graph-39649.html You want to take that information and transpose it over to some other format, fine, but I think you lose some of the basic understanding of the characteristic behavior of the motor.

Regards,

major


----------



## maxvtol (Nov 11, 2009)

major said:


> The battery current limit makes the motor input a constant power. You're plotting motor output, so it ain't exactly right. But pretty close because motor efficiency is fairly constant over that range.


That's cool, if the efficiency is relatively contstant at constant power, close enough. 


major said:


> You lost me here. You plotted a series motor on a PWM having a current limit. Unless you have a real high current limit, peak power will be at the power where the PWM goes full on. After that power is linear, for approximation. Prior to that, the power curve is the motor power curve from the motor speed torque curve which kinda resembles a parabola when plotted against torque. Turned sideways, don't know what it looks like.


I think I got it, found a curve that looks pretty good. 


major said:


> What do you plot efficiency against? Time of day, phase of the moon, or speed or something


Speed, on Thursdays at noon .


major said:


> I end up explaining motor curves to quite a few of you guys. Like this: http://www.diyelectriccar.com/forums...aph-39649.html You want to take that information and transpose it over to some other format, fine, but I think you lose some of the basic understanding of the characteristic behavior of the motor.


I appreciate you taking the time to explain it again. I see it might make the motor easier to understand (if that were my goal at this point). I just want as few equations as possible to describe a motor curve, and I think I have it now. Look for a spreadsheet shortly. 

I'll use the updated attached chart.


----------



## maxvtol (Nov 11, 2009)

Didn't read your linked post, major, before my reply. 


major said:


> I think the thing which confuses people about these motor curves is they compare it to stepping on the throttle in the car. The motor speeds up and produces more power as it speeds up. But remember, as you increase the motor speed in the car, you are increasing the motor voltage with the controller. These graphs show the motor output at a constant voltage. The motor factory makes the motor for the rated voltage and does not know what controller you will put on it. They give you the motor graph to tell you how the motor will perform at that rated voltage.
> 
> Hope that explained it for ya,
> 
> major


Gonna have to get my head wrapped around that one. So, is the curve I'm making going to represent what torque the motor is producing in the car?


----------



## major (Apr 4, 2008)

maxvtol said:


> So, is the curve I'm making going to represent what torque the motor is producing in the car?


Yeah, if you got the pedal to the metal


----------



## maxvtol (Nov 11, 2009)

Spreadsheet (zipped, Excel format) is attached to Post #1. I'll keep editing Post #1 so you won't have to search the thread for the latest corrected spreadsheet. 

Feedback is appreciated. I'll add other motors if desired.


----------



## Thaniel (May 25, 2008)

Thank you for putting this together. I find all the formulas a little confusing on how to translate to different amps and voltages. 

I put in some data for my setup and it shows the torque falling WAY off after 1000 RPMs. IS that right? Interesting information if it is.

Thaniel

Think I found my error. I was putting in the wrong voltage in "cell Volts Each". Torque is now flat until 4500 RPM.


----------



## maxvtol (Nov 11, 2009)

Thanks for the feedback Thaniel. Let me know if there is something I can make more clear. I probably shouldn't have interchanged cell and battery, that might be confusing, maybe I should just call them batteries. 

Also, if there is any real world data that might confirm if the spreadsheet is close, that would be appreciated.


----------



## tomofreno (Mar 3, 2009)

Joe, this guy needs your spreadsheet: http://www.diyelectriccar.com/garage/cars/215


----------



## maxvtol (Nov 11, 2009)

Yeah, he's using something else to get those numbers or he left off the JATO rocket engines in the Accessories section.


----------



## DavidDymaxion (Dec 1, 2008)

Maybe he confused km/hr with mph?



tomofreno said:


> Joe, this guy needs your spreadsheet: http://www.diyelectriccar.com/garage/cars/215


----------



## maxvtol (Nov 11, 2009)

Just updated the spreadsheet (get from post #1). 

Added the WarP 8, ImPulse 9, WarP 11, and the AC50/1238-75 to the WarP 9, just chose the number and all the relevant info will pop in. 

Added 1/4 mile (user selectable distance in miles) speeds and times. Max speed is 100 mph, so may not be useful for the super serious drag racers. 

Just changed wording a little so hopefully it will be more understandable. 

I don't anticipate more changes unless anyone wants me to add another motor or finds errors. 

Enjoy.


----------



## tomofreno (Mar 3, 2009)

Nice! The lookup for motors is slick! And warning max amps exceeded. Well done.


----------



## tomofreno (Mar 3, 2009)

> Maybe he confused km/hr with mph?


 The top speed and 0 - 60 numbers would then make sense, and ranges also if he assumes 100% discharge.


----------



## Thaniel (May 25, 2008)

Have you considered adding the HP line to the RPM torque curve like in Dyno plots for ICE?


----------



## maxvtol (Nov 11, 2009)

Thaniel said:


> Have you considered adding the HP line to the RPM torque curve like in Dyno plots for ICE?


No, but it would be very easy to do since it's just a function of torque and rpm. How would you use it?

Have you compared the spreadsheet to your performance, is it close?


----------



## Bowser330 (Jun 15, 2008)

Thaniel said:


> Have you considered adding the HP line to the RPM torque curve like in Dyno plots for ICE?


Is this data just an example or are you really pulling enough amps to give you 200ftlbs of torque from a warp9 and 4500+ rpm??? Isn't that like 800-1000A?? If it's real data then thats great to hear.


----------



## Duncan (Dec 8, 2008)

Hi Max
I have just had a quick look at your spreadsheet
Did you do it all in Imperial units?
If so then I am impressed - 
The only way I can do anything serious with Imperial is by converting it to Metric and then converting the answers back

Slugs -- Ughhhh


----------



## maxvtol (Nov 11, 2009)

Duncan said:


> Hi Max
> I have just had a quick look at your spreadsheet
> Did you do it all in Imperial units?
> If so then I am impressed -
> ...


Thanks Duncan, yes, all Imperial. Slugs did seem to cause some grief in engineering school back in the day. Seems most of the charts I looked at were in ft lbs, so I just stayed with it. I also have a better sense of units in Imperial so if something seemed out of whack, I would more likely notice it.


----------



## Thaniel (May 25, 2008)

maxvtol said:


> No, but it would be very easy to do since it's just a function of torque and rpm. How would you use it?
> 
> Have you compared the spreadsheet to your performance, is it close?


I use the HP curve same as I would for an ICE engine. Want to make gear changes so it stratles the HP peak (most area under the curve). Torque is good for pulling stumps but HP is for accelerating quickly 

Sorry I haven't had a chance to do real world comparisons yet as I still haven't licenced my car. I do have G-Tech and will do some accel tests when it's on the road.



Bowser330 said:


> Is this data just an example or are you really pulling enough amps to give you 200ftlbs of torque from a warp9 and 4500+ rpm??? Isn't that like 800-1000A?? If it's real data then thats great to hear.


The data is from setting the nomial voltage to 156 and current to 1000A in the spread sheet. Zilla says it's good for 1000A and my batteries should do that as well (for a few seconds) Don't see why the warp9 couldn't do it then. Time will tell I guess.

Thaniel


----------



## maxvtol (Nov 11, 2009)

Thaniel said:


> Want to make gear changes so it stratles the HP peak (most area under the curve).


How do you determine how wide the rpm band should be?



Thaniel said:


> I do have G-Tech and will do some accel tests when it's on the road.


 Cool! please post or put a link to your results here.


----------



## Thaniel (May 25, 2008)

maxvtol said:


> How do you determine how wide the rpm band should be?
> 
> Cool! please post or put a link to your results here.


In our cases the RPM drop per gear is already fixed by the gear box design. Well Could skip gears but doubt that's going to make it faster. Your spread sheet is pretty handy for predicting when to shift and if skipping gears would help.

I'll definitly post the G-tech numbers. The EV is progressing slowly. Sometimes I feel I'm almost done and other times so far away.


----------



## maxvtol (Nov 11, 2009)

Thaniel said:


> In our cases the RPM drop per gear is already fixed by the gear box design.


Just wanted to make sure I hadn't missed any tricks in shifting gears. I know the hp curve is used in ICE engines to help in shifting, the C4 Corvette had the tach in shape of the power curve for that reason. But available torque at the wheel is what you need for acceleration. In a lot of ICE engines, the torque curve looks a lot like the power curve, maybe just not as accentuated which is probably why they used the power curve. 

Power * rpm (area under the power curve ie. ft lbs/sec^2) doesn't give anything meaningful that I'm aware of. OTOH, F=ma and Torque=F*distance, so a=F/m or a=T/md, so acceleration depends on available torque at the wheel. So unless I'm missing something, I don't think the hp curve will help much for shifting on electric motors.


Thaniel said:


> I'll definitly post the G-tech numbers. The EV is progressing slowly. Sometimes I feel I'm almost done and other times so far away.


That would be great, thanks. And I know what you mean, 80% done, 80% to go. I'm enjoying your build thread. Keep up the good work!


----------



## DavidDymaxion (Dec 1, 2008)

If you have a constant power mode, it doesn't matter which gear you are in (provided that gear is in the constant power region). Suppose you have a constant power mode from 3000 to 6000 rpm. You could go 6000 rpm in 2nd, then 4000 to 6000 rpm in 3rd, and then 4000 to 6000 rpm in 4th. It would be faster, however, to go to 6000 rpm in 2nd, and then go 3000 to 6000 rpm in 4th. You accelerate at the same rate at each speed, but you save the time of one shift. Some NEDRA racers have found that a 2-4 shift pattern gives them their best 1/4 times.

It's a little counter intuitive. Power = torque * rpm. For constant power, if you down shift you get more rpm, but less torque, but more torque multiplication through the tranny. The net result is you get the same rear wheel torque for a constant power mode for any gear that is in that constant power rpm range.

If you can spin the wheels, try going up a gear. For instance, if 1st gear just produces tire smoke, starting in 2nd might be faster by saving the shift time.

Naturally, real life doesn't have perfectly flat, constant power modes. Some good simulations or experimentation can find which gears and which shift points make you fastest.

Finally, it can be faster to be on the falling side of the torque curve. This gives a natural form of traction control -- if rpm increases suddenly due to wheel spin, then torque drops, helping regain traction. So even though you might be in a lower power region, sometimes it makes the car enough easier to drive you wind up being faster as a driver (especially if curves are involved).



maxvtol said:


> Just wanted to make sure I hadn't missed any tricks in shifting gears. I know the hp curve is used in ICE engines to help in shifting, the C4 Corvette had the tach in shape of the power curve for that reason. But available torque at the wheel is what you need for acceleration. In a lot of ICE engines, the torque curve looks a lot like the power curve, maybe just not as accentuated which is probably why they used the power curve.
> 
> ... OTOH, F=ma and Torque=F*distance, so a=F/m or a=T/md, so acceleration depends on available torque at the wheel. So unless I'm missing something, I don't think the hp curve will help much for shifting on electric motors....


----------



## maxvtol (Nov 11, 2009)

DavidDymaxion said:


> Some good simulations or experimentation can find which gears and which shift points make you fastest.


I agree, and that's the point of my spreadsheet. And it's consistant with your point for the constant power region. I was surprised to find my fastest 0-60mph was 1, 3, 5th gear. However, using a 1000amp controller limit and 500amp battery limit gives me a fairly wide constant power range. Thaniel, on the other hand, if he can achieve the torque curve he plotted, won't have much of a constant power region. He'll problably be fastest with the lowest gear that doen't cause wheel spin, up through each gear. 

I do find it interesting that the maximum area under the power-rpm curve in my case does seem to give a close approximation of the best shift points. Though, looking at the units, I'm not exactly sure why (especially since maximum acceleration is a near 0 hp in 1st gear, so I don't know if the units would give any clue.) Maybe it's just a good rule of thumb.


----------



## DavidDymaxion (Dec 1, 2008)

That's a neat result from your spreadsheet.

I think you have backed into something interesting here. Suppose you plotted RW torque vs. distance. The area would give you energy, and that could be used for giving the car the greatest energy in the shortest distance (what most racers want). If you plotted Power vs. time, the area would be energy again, but this time it could be used to get the greatest energy in the shortest time (if you wanted to brag about the 0 to 60 number). RPM is a proxy for time (not perfect, but rpm is correlated to time).


maxvtol said:


> I agree, and that's the point of my spreadsheet. And it's consistant with your point for the constant power region. I was surprised to find my fastest 0-60mph was 1, 3, 5th gear. However, using a 1000amp controller limit and 500amp battery limit gives me a fairly wide constant power range. ...
> 
> I do find it interesting that the maximum area under the power-rpm curve in my case does seem to give a close approximation of the best shift points. Though, looking at the units, I'm not exactly sure why (especially since maximum acceleration is a near 0 hp in 1st gear, so I don't know if the units would give any clue.) Maybe it's just a good rule of thumb.


----------



## Thaniel (May 25, 2008)

maxvtol said:


> And I know what you mean, 80% done, 80% to go. I'm enjoying your build thread. Keep up the good work!


When I read that I laughed and laughed. Yes it totally feels that way. 80% done 80% to go.



maxvtol said:


> Just wanted to make sure I hadn't missed any tricks in shifting gears. I know the hp curve is used in ICE engines to help in shifting, the C4 Corvette had the tach in shape of the power curve for that reason. But available torque at the wheel is what you need for acceleration. In a lot of ICE engines, the torque curve looks a lot like the power curve, maybe just not as accentuated which is probably why they used the power curve.
> 
> Power * rpm (area under the power curve ie. ft lbs/sec^2) doesn't give anything meaningful that I'm aware of. OTOH, F=ma and Torque=F*distance, so a=F/m or a=T/md, so acceleration depends on available torque at the wheel. So unless I'm missing something, I don't think the hp curve will help much for shifting on electric motors. That would be great, thanks.


Sorry such ablong delay to reply. Life just seems to get busier as the kids get older and the weather gets warmer. 

I'll try to expound on my statemet but it's been years since I've done the math but it doeswork out. I'd like to look up formulas and all but I know myself if I wait until I do that I'll never get it done.

As some have mentioned what we really want is the most power put into the system as quickly as possible. Torque is basically a static measure. What we want to look at for acceleration calcuations is power (I think your sheet does this). So what we need to find the way to put the MOST power to the GROUND (if not using rockets or jets  ). 

We could have a high torque motor say 1000 ft lbs that can only turn 1 rpm or a motor that turns 1000 rpm with 1 ft-lb of torque. Both will put out the same POWER output. Neglecting losses we could put them through a transmission and have the exact same RPM and torque out of either motor. Or in other words either motor could put the same power to the ground. 1000 ft-lbs of torque @1 rpm is no better than 1 ft lb and 1000 rpm. 

This is why looking at the HP curve to me is important. It's easier for me to see where that HP peak is. We want to keep the motor as high on the curve as possible at ALL times. If not using a constantly variable transmission it'll fall over one side going to Hi RPM or be on the low side to low RPM. Swapping back and forth as the shifts happen. If the torque stayed constant regardless of RPM then we'd want to spin the motor as fast as it would allow and shift at redline. This is one reason why race engines are designed for high RPM. Usually costs more as better materials have to be used to keep it from flying apart but they get more HP out by just turning it more RPM. 

I had a rotary engine car and it's torque didn't fall off at high rpm. There was never that lul in power that gives one the urge to shift the motor like most cars give. Wind thing up to red line and it' would put out more and more power. No suprise the biggest gauge on the dash was the Tach and a rev buzzer would go off at high RPM. I thought the Electric motors would be like that but looks like the controler and battery limitations cause the high RPM performance to drop off. As the sheet suggests with my 89 volts I'm currently using to just play with the car there is a definite HP peak.

Im I making any sense?

Let me take a stab at the spining tire issue too. We know static friction (not spinning tires) is higher than sliding friction (spinning tires). Let's say a spining tire has 1/2 the grip of a non spinning tire. If you spin the tire twice as fast then you are putting down the same power as keeping it barely from spinning. Spin it more than twice as fast and you would be quicker to spin the tires. Lots of factors involved in making the best Launch and zero to 60 times. Type of tire, HP curve of the motor etc.

While we are talking about it, not that it applies much to ev's, if launching while slipping the clutch, as one would when normally starting from a stop in an ICE car, the clutch is SLIPPING when starting. So we have sliding fricition and not static friction. So might as well spin the tires as opposed to slipping the clutch. Trick is getting the RPM right so that the most power is put down and things "hook up" at the right RPM to keep the most power coming out. Of course this does shock the driveline and could break things and causes lots of noise and attention. But I'm strictly speaking about best performance. However, is it's a lot easier to change the tires when they wear out than a clutch  And too much slipping the clutch will "burn" the clutch and cause it not to grab. Sorry probably more about launching a car from a dead stop then you wanted to hear. Perhaps it is stuff you already know.

Hope this makes sense. If not perhaps someone can explain it mathematically.

Thaniel


----------



## major (Apr 4, 2008)

Thaniel said:


> Torque is basically a static measure.


Hi Thaniel,

I don't think this is true at all. It is just that torque is a quantity which can be measured statically whereas power is not. But that does not in any way infer that torque is not dynamic. It relates to the disagreement I had with IamIan in the thread http://www.diyelectriccar.com/forums/showthread.php/torque-irrelevant-relevanti-36904.html

Regards,

major


----------



## maxvtol (Nov 11, 2009)

Thaniel said:


> Im I making any sense?


 Well, most people talk about torque and hp in a state of equilibrium, in which Torque = How Much You Can Haul, HP= How Fast You Can Haul It. When you talk about acceleration, you add another element, it’s now a dynamic issue. My spreadsheet uses torque to calculate acceleration, but it’s the torque in excess of what’s required for a particular speed (which is hp). To really be meaningful, you also need to establish an increment over which the acceleration is to occur. So to say torque or hp is = to acceleration is really not right. 

Your analysis on static and dynamic friction with respect to force on the ground makes sense (for motors that can deliver significant amounts of power over the amount required for wheelspin). So my spreadsheet is really only for finding the fastest times where the wheels don’t spin. For most EV’ers I suspect this won’t be a problem, but the acceleration curve can show if you’re approaching 1 G, which is where I think most wheels would spin. 

Your using maximum area under the hp curve for shift points is what interested me the most. I thought (being a bit anal about making units match) that electric may be different than ICE. I think David’s explanation of “pseudo” units for energy is pretty close to why it would still work for electrics.


----------



## Thaniel (May 25, 2008)

Sorry guys for slow replys. This moving thing is a killer.

Let me say again I think your sheet is great. We can get into the symatics of it all but over all the formulas can predict where the best shift points are on the curve (Other than the spinning the wheels or slipping the clutch part). 

I promised to report back on real world data From my car. Getting ready to move I've put plates and insurance on it so I can drive it to it's new house but I have only 7 of the 12 volt batteries hooked up. I drove it around a bit saturday to show it off and have some fun. NONE of the roads around my house are flat enough to really do any G-Tech measurements but the predicted flatening out of acceleation at speed seemed to match the predictions. 

Thaniel


----------



## Kelmark (Oct 26, 2009)

maxvtol said:


> I'm trying to find out what performance I can realistically expect for my EV project and am trying to fine tune my spreadsheet. I need to approximate a DC motor torque curve and have attached some figures to see if I have understood what I have read.
> 
> Chart 1 is just the torque curve from Netgain for a 9" motor formatted how I'm used to looking at torque curves. It seems that torque is very proportional to motor amps, and I just assumed that the 334 amps at maximum torque is the controller rating and the Red torque curve is just flat from 0 rpm to 2158 rpm.
> 
> ...


Could you post this in an unzipped file? I can't open the file but I really would like to see what you done. Maybe its Vista causing problems again!


----------



## maxvtol (Nov 11, 2009)

Kelmark said:


> Could you post this in an unzipped file? I can't open the file but I really would like to see what you done. Maybe its Vista causing problems again!


Do you have Excel? I think this version is 2003. You can also use OpenOffice.org, they have a spreadsheet that works. 

I can't post anything but a zipped file, but if you PM me, I'll email you an unzipped Excel file, it's not very big.


----------



## Bowser330 (Jun 15, 2008)

Thaniel said:


> ....
> We could have a high torque motor say 1000 ft lbs that can only turn 1 rpm or a motor that turns 1000 rpm with 1 ft-lb of torque. Both will put out the same POWER output. Neglecting losses we could put them through a transmission and have the exact same RPM and torque out of either motor. Or in other words either motor could put the same power to the ground. 1000 ft-lbs of torque @1 rpm is no better than 1 ft lb and 1000 rpm.
> 
> This is why looking at the HP curve to me is important. It's easier for me to see where that HP peak is. We want to keep the motor as high on the curve as possible at ALL times. If not using a constantly variable transmission it'll fall over one side going to Hi RPM or be on the low side to low RPM. Swapping back and forth as the shifts happen. If the torque stayed constant regardless of RPM then we'd want to spin the motor as fast as it would allow and shift at redline. This is one reason why race engines are designed for high RPM. Usually costs more as better materials have to be used to keep it from flying apart but they get more HP out by just turning it more RPM.
> ...


absolute sense, i agree 1000%

We need results that show...

For a certain setup, e.g.

Warp11HV
Zilla 2K
300V
2000A capable pack

What is max rpm this setup can hold 2000A?
What is max rpm this setup can hold 1500A?
What is max rpm this setup can hold 1000A?
What is max rpm this setup can hold 500A?

If lets say say, for example, the data is.....

2000A = max 1500rpm
1500A = max 3000rpm
1000A = max 4000rpm
500A = max 5000rpm

And note that a 11" DC motor makes 300ftlbs torque @ 1000A, using linear assumption...

Then the max torque at a specific rpm would be...

600ftlbs @ 1500rpm
450ftlbs @ 3000rpm
300ftlbs @ 4000rpm
150ftlbs @ 5000rpm

So then the max horsepower at a specific rpm would be...

171hp & 600ftlbs @ 1500rpm
*257hp & 450ftlbs @ 3000rpm PEAK HP in this example*
228hp & 300ftlbs @ 4000rpm
143hp & 150ftlbs @ 5000rpm

All of this in a curve provided by the manufacturers of controllers and motors would be really cool...and would make the data more understandable...


----------



## maxvtol (Nov 11, 2009)

I can put a WarP 11HV in the spreadsheet (if anyone has a link to the table values) and certainly a HP curve is easy. But I think there may be another limitation in the calculations. 

If the coefficient of friction is _roughly_ .8 for a standard tire (from a post in another forum, sounds reasonable), and for example say my car is 3000lbs with a 50/50 weight distribution, and I'm driving the front wheels. So 1500 lbs * .8 = 1200 lbs, is there any point in putting more than 1200lbs at the tire patch? Dynamically, a front wheel drive won't have this much force on the front wheels, and a rear wheel drive would have more on the rear, but you get the idea. 

So in rough theory, I don't know if there is any point in me trying to accomplish more than 1200lbs/3000lbs = .4 g's or 12.9ft/sec^2 in the spreadsheet for my application. Just from playing around a little with this limitation, looks like an Impulse 9 with higher voltage would give me better performance. 

Ideas, comments, any experience on this?


----------



## maxvtol (Nov 11, 2009)

Tom,
Can you spin tires on the SwiftE in 1st gear by flooring it on a flat dry surface (not popping clutch if you have one)? And it's front wheel drive, right?

I'm playing around with traction force on the drive wheel and I'm seeing some real limitations for my car if my calculations are correct.


----------



## tomofreno (Mar 3, 2009)

> Can you spin tires on the SwiftE in 1st gear by flooring it on a flat dry surface (not popping clutch if you have one)? And it's front wheel drive, right?


 The few times I floored it to test 0 - to 60mph they did not spin. But max torque is only about 90 lb-ft and tire radius is about 22" so max force is about 98 lb. Yes it is front wheel drive. About 20 - 30 lb heavier in front than stock.


----------



## maxvtol (Nov 11, 2009)

tomofreno said:


> ...so max force is about 98 lb.


Huh? I thought your 1st gear was 13.45 ratio and diameter was 22" (not radius), so 13.45*90ft lbs/(.9167)ft = 1320 lbs. 

Do you know your front/rear weight ratio, and what's your wheelbase?
Edit: Oh, and do you have any limits on the battery or controller?


----------



## tomofreno (Mar 3, 2009)

> Huh? I thought your 1st gear was 13.45 ratio and diameter was 22" (not radius), so 13.45*90ft lbs/(.9167)ft = 1320 lbs.


 Yes, that is correct. I'm not thinking well lately. No limits on battery or controller. Front to rear weight ratio is about 1:1. Wheel base is 93.1 inch.


----------



## DavidDymaxion (Dec 1, 2008)

If you want race levels of acceleration, a race tire would have significantly more grip than a street tire. Also, many tracks have prepped surfaces that you can launch even harder on. If you want enough torque to do a tire warming burnout, then you need even more available force. With batteries you might be able to get the weight lower, and have less weight transfer to the rear. 


maxvtol said:


> ... If the coefficient of friction is _roughly_ .8 for a standard tire (from a post in another forum, sounds reasonable), and for example say my car is 3000lbs with a 50/50 weight distribution, and I'm driving the front wheels. So 1500 lbs * .8 = 1200 lbs, is there any point in putting more than 1200lbs at the tire patch? Dynamically, a front wheel drive won't have this much force on the front wheels, and a rear wheel drive would have more on the rear, but you get the idea.
> 
> So in rough theory, I don't know if there is any point in me trying to accomplish more than 1200lbs/3000lbs = .4 g's or 12.9ft/sec^2 in the spreadsheet for my application. Just from playing around a little with this limitation, looks like an Impulse 9 with higher voltage would give me better performance.
> 
> Ideas, comments, any experience on this?


----------



## maxvtol (Nov 11, 2009)

DavidDymaxion said:


> If you want race levels of acceleration, a race tire would have significantly more grip than a street tire. Also, many tracks have prepped surfaces that you can launch even harder on. If you want enough torque to do a tire warming burnout, then you need even more available force. With batteries you might be able to get the weight lower, and have less weight transfer to the rear.


Not race levels, my targets are 0-35mph in <6 seconds, 0-60mph in <15 seconds, which isn't even the current ICE performance, but enough for me to keep the fun factor.

I should have thought about tire static friction when I made the spreadsheet originally, so I'm working now to put it in. For my application, the WarP 9 and a 1000 amp controller, torque at the front wheels in 1st gear is twice what the tire static friction can handle. But it looks like I can just drive around in 3rd gear and meet my performance goals, shifting into 5th around 40mph if I need to.

I've been trying to verify tire static coefficient and looks like a value of 1 seems to be reasonable, but even at that, looks like Tom in his SwiftE should be able to spin a little in 1st gear. That's pretty low sample, so I put in all the Tesla Roadster info, and a value of 1 works. And my spreadsheet calculated 0-60mph in 3.85 seconds, Tesla's number is 3.7 seconds, so I feel pretty good about the numbers.

I'll probably spend a little time to put in a few more features, HP curve, watt hours/mile and range at different speeds, maybe a battery table and cost per mile. If you want any other features, let me know.


----------



## gor (Nov 25, 2009)

Max, why curve shifts down under 750a?
should be like this?

calc. from porsh thread


----------



## gor (Nov 25, 2009)

also - by HP wiz f-las, rotational inertia adding >50% eqv. mass on low gears http://hpwizard.com/rotational-inertia.html
you adding ~6%, they ~60% - which killing me: i need to double my power to have <50% better accel; so, i like you calc. better 

and btw. very nicely put together and neet calculator
(lets just find out how to put this rot. m. inertia)


----------



## drgrieve (Apr 14, 2011)

Hi Max,

Found a dyno chart of 4 gears for the warp 11 hv. Not sure if this is usable.

http://jackrickard.blogspot.com/2011/11/elecobra-thrill-of-victory-and-agony-of.html 

I'm making some changes to accomodate pack resistance and c rate and hopefully cells in parallel (to play with headway cells).

Hope to post them soon.


----------



## John Metric (Feb 26, 2009)

Not sure if you can use these. These were two charts I made for comparing Stock Netgain Warp9 to netgain Impulse9.

These are the "GROSS" torque and power calculations based upon input power to the motor and rpm. For net motor output you need to multiply these by the estimated motor efficiency and net rear wheel horsepower by the drive train efficiency. I have found that an everage of about 85% for the motor and 90% for the drive train give very good results in my acceleration modeling software.

I also have some charts of Field Weakening versus stock. If anyone is interested.

For a single Warp 9" you should be able to cut these figures in half.
Other points: 2000 Motor amp limit, 170V Motor Voltage Limit, no battery limitations, these are based on real Zilla Data Aquisition data.

Note the Impulse9 has less torque (but you could make that up with gearing) but the Impulse9 makes more HP much farther into the rpm range.
(Waylunds pack was slightly battery limited here)


----------



## major (Apr 4, 2008)

drgrieve said:


> Found a dyno chart of 4 gears for the warp 11 hv. Not sure if this is usable.
> 
> http://jackrickard.blogspot.com/2011/11/elecobra-thrill-of-victory-and-agony-of.html


Hi drg,

Interesting charts. Thanks for posting the link. Do you know why the mph vs RPM trace (brown) isn't linear? Is there a non-locked torque converter on the car?

major


----------



## tomofreno (Mar 3, 2009)

gor said:


> also - by HP wiz f-las, rotational inertia adding >50% eqv. mass on low gears http://hpwizard.com/rotational-inertia.html
> you adding ~6%, they ~60% - which killing me: i need to double my power to have <50% better accel; so, i like you calc. better
> 
> 
> ...


There may be some confusion. The reference defines the equivalent mass as the sum of translational and rotational mass so that the ratio of equivalent mass to translational mass of a part is always greater than 1. As stated there, the usual definition of equivalent mass is just the rotational part, the product of moment of inertia, I, and n squared, where n is the ratio of angular velocity of the part to the vehicle speed. The percentages stated in the reference are based on the ratio of _this equivalent mass to mass of the rotational part_. 

I used the simple equation, m sub e = m(1 + 1.04 + 0.0025*G*G) (Edit: 1.04 is a typo, should be 0.04 as gor pointed out) in the reference (and also given on page 99 in the second edition of "Build Your Own Electric Vehicle" by Bob Brant as C sub i which is m sub e divided by m) in a spreadsheet to estimate acceleration time from 0 to 60 mph from the difference in required and available wheel torque. It gave a result of 13.2 sec compared to the result from maxtvol's spreadsheet modified for my car of 13.26 sec, both without time included for shifting twice. May well be just coincidence for this one result, but agreed amazingly well considering the approximation of the simple equation. The simple equation is very easy to use in a spreadsheet because you just have to calculate C sub i for a given vehicle's overall gear ratios then include it in the acceleration calculations, which then apply for any vehicle with those overall gear ratios. I hadn't included the effect of rotational mass at first and had something like 11.5 sec IIRC. If I assume 0.4 sec per shift, then the result including rotational inertia is about 14 sec, which is about 13% less than the measured time of 16 seconds using a gps data logger:
View attachment Swift, 0 to 60 mph test, graph.pdf


This is the time starting from zero mph and zero motor rpm. If I rev'ed the motor a bit and popped the clutch I would likely do better. I found by accident (foot slipped) that if I pop the clutch this way the tires do chirp and the car jumps forward. Not sure what the motor rpm was in this case, but it wasn't more than several hundred rpm.


----------



## gor (Nov 25, 2009)

tomofreno said:


> There may be some confusion. The reference defines the equivalent mass as the sum of translational and rotational mass so that the ratio of equivalent mass to translational mass of a part is always greater than 1. As stated there, the usual definition of equivalent mass is just the rotational part, the product of moment of inertia, I, and n squared, where n is the ratio of angular velocity of the part to the vehicle speed. The percentages stated in the reference are based on the ratio of _this equivalent mass to mass of the rotational part_.
> 
> I used the simple equation, *m sub e = m(1 + 1.04 + 0.0025*G*G)* in the reference (and also given on page 99 in the second edition of "Build Your Own Electric Vehicle" by Bob Brant as C sub i which is m sub e divided by m) in a spreadsheet to estimate acceleration time from 0 to 60 mph from the difference in required and available wheel torque. It gave a result of 13.2 sec compared to the result from maxtvol's spreadsheet modified for my car of 13.26 sec, both without time included for shifting twice. May well be just coincidence for this one result, but agreed amazingly well considering the approximation of the simple equation. The simple equation is very easy to use in a spreadsheet because you just have to calculate C sub i for a given vehicle's overall gear ratios then include it in the acceleration calculations, which then apply for any vehicle with those overall gear ratios. I hadn't included the effect of rotational mass at first and had something like 11.5 sec IIRC. If I assume 0.4 sec per shift, then the result including rotational inertia is about 14 sec, which is about 13% less than the measured time of 16 seconds using a gps data logger:
> View attachment 11707
> ...


Me = M(1 + *0.04* + 0.0025*G*G)

if 1.04, Me>2.04

with 3:1 diff and 3:1 first gear, overall G= 9 (1:9)
0.0025*9*9=0.2025; 1+0.04+0.2025= 1.2425 (24%+)

with 3:1 diff and 4:1 first gear, overall G= 12 (1:12)
0.0025*12*12=0.36; 1+0.04+0.36= 1.4 (40%+)

with 4:1 diff and 4:1 first gear, overall G= 16 (1:16)
0.0025*16*16=0.64; 1+0.04+0.64= 1.68 (68%+)

http://hpwizard.com/rotational-inertia.html

Max Me ~+6%
p.s. i love 6 more than 60, but... x10 difference...


----------



## drgrieve (Apr 14, 2011)

major said:


> Hi drg,
> 
> Interesting charts. Thanks for posting the link. Do you know why the mph vs RPM trace (brown) isn't linear?
> 
> major


I had a second look, seems that the RPM chart points are not an even increment. Which is a little weird - maybe the issue?

Updated the spreadsheet with the ability to add cells in parallel and to determine max c for acceleration by inputing pack IR and voltage to sag to from a defined voltage (eg 3.3 to 2.7).


----------



## major (Apr 4, 2008)

drgrieve said:


> I had a second look, seems that the RPM chart points are not an even increment. Which is a little weird - maybe the issue?


Yeah, didn't notice that. Pretty strange but does account for the shape.


----------



## tomofreno (Mar 3, 2009)

These percentages look correct to me, and agree with what the reference says. Sorry about the 1.04 typo.



gor said:


> Me = M(1 + *0.04* + 0.0025*G*G)
> 
> if 1.04, Me>2.04
> 
> ...


----------



## tomofreno (Mar 3, 2009)

Not sure, but looks to me like maxtvol forgot to square the radius of gyration, the wheel radius, and the gear ratio in the calculation of equivalent mass. The reference defines equivalent mass as the sum of static mass of the part plus I*n*n, but says that normally people call I*n*n the equivalent mass, which is what it appears Maxtvol is doing. Edit: I is the moment of inertia, and n is as defined in the reference, the ratio of overall gear ratio to tire radius.

Maxtvol calculates the product of the radius of gyration and the mass, and divides this by the tire radius. I think these radii need to be squared (since the product of mass and the square of the radius of gyration is the moment of inertia). Then you would have the product of mass and square of the radius of gyration, divided by the square of the tire radius. Multiplying this by the square of the gear ratio for the “before transmission” components gives I*n*n. Calculating it this way I get 16.0 for the “before transmission” equivalent mass for second gear. Doing the same for the “after transmission” equivalent mass, but not multiplying by the square of the gear ratio since these parts are spinning at the tire rpm, I get 3.12 for the “after” equivalent mass. So the ratio of equivalent mass to vehicle mass estimated this way is about 100*19.12/93.727 = 20.3% for second gear. Keep in mind the radii of gyration are just guesstimates specific to his vehicle. I am not familiar with how “equivalent mass” is normally defined. I am just going by the reference, the physics of which certainly appears correct to me since one half I*n*n*v*v is one half I*w*w (w equal angular velocity) which is the kinetic energy of a rotating object. It makes sense that I*n*n would be defined as an equivalent mass. I apologize if I have misunderstood something here maxtvol.





gor said:


> also - by HP wiz f-las, rotational inertia adding >50% eqv. mass on low gears http://hpwizard.com/rotational-inertia.html
> you adding ~6%, they ~60% - which killing me: i need to double my power to have <50% better accel; so, i like you calc. better
> 
> and btw. very nicely put together and neet calculator
> (lets just find out how to put this rot. m. inertia)


----------



## gor (Nov 25, 2009)

tomofreno said:


> Not sure, but looks to me like maxtvol forgot to square the radius of gyration, the wheel radius, and the gear ratio in the calculation of equivalent mass. The reference defines equivalent mass as the sum of static mass of the part plus I*n*n, but says that normally people call I*n*n the equivalent mass, which is what it appears Maxtvol is doing. Edit: I is the moment of inertia, and n is as defined in the reference, the ratio of overall gear ratio to tire radius.
> 
> Maxtvol calculates the product of the radius of gyration and the mass, and divides this by the tire radius. I think these radii need to be squared (since the product of mass and the square of the radius of gyration is the moment of inertia). Then you would have the product of mass and square of the radius of gyration, divided by the square of the tire radius. Multiplying this by the square of the gear ratio for the “before transmission” components gives I*n*n. Calculating it this way I get 16.0 for the “before transmission” equivalent mass for second gear. Doing the same for the “after transmission” equivalent mass, but not multiplying by the square of the gear ratio since these parts are spinning at the tire rpm, I get 3.12 for the “after” equivalent mass. So the ratio of equivalent mass to vehicle mass estimated this way is about 100*19.12/93.727 = 20.3% for second gear. Keep in mind the radii of gyration are just guesstimates specific to his vehicle. I am not familiar with how “equivalent mass” is normally defined. I am just going by the reference, the physics of which certainly appears correct to me since one half I*n*n*v*v is one half I*w*w (w equal angular velocity) which is the kinetic energy of a rotating object. It makes sense that I*n*n would be defined as an equivalent mass. I apologize if I have misunderstood something here maxtvol.


also - hp.wiz weight distribution M/wheelM/rot.m (0.04;0.0025)- based on 1994 stats; which is - generic car, average drivetrain - assumption - heavier car - heavier drivetrain; rwd. fwd or awd(4x4)
drivetrain losses distributes ~~ 15% fwd, 18 rwd, 23-25 4wd; - should be a correlation with M to rot.M too
what would return digging into weight comparison of 2wd vs. 4wd same motor versions of same car - rav4, saturn, volvo, etc?

p.s. in fwd the only thing which spins faster than wheels (0.04 koef -4%) - short transmission shaft and two small gears - 4% vs 60% - simms a bit steep...
... rwd driveshaft ~2-3 times (?) heavier than 2 halfshafts, spins 3-4 times faster, what it gives us (fwd vs rwd eq.m)?


----------



## gor (Nov 25, 2009)

here calc. for saturn Vu - 2.2L vs. ev vs. hybr (fwd + e.motor stuck into rear diff from awd)
as you see - by hp.wiz f-la, more than double the torque at wheels brings only 20% better accel on low gear (0.5g vs 0.4) - and this is with 0.002, not 0.0024G^2 ... demit... : ))


----------



## DIYguy (Sep 18, 2008)

Very nice indeed. Warp 13 addition would awesome.


----------



## maxvtol (Nov 11, 2009)

gor said:


> Max, why curve shifts down under 750a?
> should be like this?
> 
> calc. from porsh thread


As best I understand how the controller works with the motor, the flat part at the top is the amp limit of the controller to the motor. The first curve in the 1000a and 1500a curve is the constant power curve or the power limit to the motor (and as the motor speeds up, torque decreases). The last curve is due to the back EMF (I think. Hopefully major will correct me if I'm wrong )

But yes, the curves look correct base on the way I used the equations.


----------



## maxvtol (Nov 11, 2009)

Tom, gor, anybody, give my your thoughts. 

Walk with me through a thought experiment and see if you think my thoughts on rotational mass are correct. I’m not sure if my Equivalent Mass is the same as Bob Brant’s, but I’ll show how I’m coming up with mine. 

We are looking for the “_a_” from _F=ma_ so, _a_=_F/m_. Radius of Gyration is the “point mass” where all the mass of the tire would act if it were at this point, or radius. 

We have a magic tire, 1 slug in mass, which we are going to accelerate with 10lbs of force. 

In the first case, we are going to apply a force to the tire on a frictionless surface such that the tire doesn’t spin. Now _a_ = 10lbs/1 slug, so _a_ = 10ft/sec^2. In this case, it really doesn’t matter where the Radius of Gyration is because the tire doesn't rotate. 

In case 2, we are going to apply a force of 10lbs with a mass-less tread or belt applied at distance R, but the tire is only going to spin, not move in any direction. In this case, we’re going to assign the Radius of Gyration at R, and I want the acceleration of the tread, which is also at R. Again we should have _a_ = 10lbs/1 slug, so _a_ = 10ft/sec^2. 

In case 3, we are going to apply the force of 10lbs such that the tire moves and spins at the tangential speed at R, as you would expect a tire to travel. Rad of Gyr is at R as in case 2, and we want the acceleration at R. We should have _a_ = 10lbs /(1 + 1)slugs or 5ft/sec^2. In my spreadsheet, I figured it would be much easier to calculate acceleration if I could figure out how set all the rotational masses at distance R (what I'm calling Equivalent Mass) and all the speeds to the tangential speed of R (same as the vehicle speed). 


Now, let’s change the Rad of Gyr to ½ R using the same 1 slug mass. 

In case 4A, let’s apply a force to a tread as we did in case 2 at R. It’s easier to accelerate the mass, but I want to find the acceleration of the tread. So it should be like accelerating ½ the mass at radius R. We should have _a_ = 10lbs / (1/2 * 1slug) or 20ft/sec^2. My Equivalent Mass would be the ½ slug. This is similar to how I calculate the rotating mass after the transmission (B23 in the spreadsheet). For case 4B, if we accelerate the tire on a conventional surface where it moves and spins, _a_ = 10lbs / (0.5 + 1) slugs or 6.67ft/sec^2. 

In case 5, let’s apply a force to a tread at R as in case 4A, but we’re going to gear up the speed of the Equivalent Mass of ½ slug to 3. It’s going to be harder to accelerate the Equivalent Mass to 3 times the velocity, so in this case 3_a = F/m_, or _a = F/(_3_*m)_. _a_ = 10lbs/(3 * 0.5slugs), or 10lbs/(1.5 slugs) or 6.67ft/sec^2. My Final Equivalent Mass in this case is the 1.5 slugs. In the spreadsheet, I’m just multiplying the Initial Equivalent Mass (B38), times the gear ratio to get the Final Equivalent Mass (which starts at R44) for the parts before the transmission. 

Then all we have to do is add up all the masses and equivalent masses, and given a given amount of available force, we can find acceleration.


----------



## gor (Nov 25, 2009)

tanks, Max
while i'm translating imperial logic to mundane kilogramo-banano-meters (to not get piled-up under stones, slugs, pounds and weights), a few thoughts:

why don't come back to basics and re-check weights and speeds of rot.masses:
wheels+hubs+ halfshafts + diff gears: overall gear rat speed;
prop.shaft+ tranny gears: gear speed;
- and see if we can come to some percentages or proportions 
if it 6% - good, if 60 - bad, but so be it...

could correlate with drivetrain losses(fwd, rwd, awd)
- waterdrum dyno measures hp by how fast wheel accelerates it; lighter flywheel mod would show increase of hp ("fake hp increase")


----------



## maxvtol (Nov 11, 2009)

gor said:


> tanks, Max
> while i'm translating imperial logic to mundane kilogramo-banano-meters (to not get piled-up under stones, slugs, pounds and weights), a few thoughts:
> 
> why don't come back to basics and re-check weights and speeds of rot.masses:
> ...


Ok, but percentages of what?
Assuming a 1 slug flywheel with a radius of gyration of .5ft and a tire radius of 1 ft, gives an Initial Equivalent Mass of 1/2 slug. With a final gear drive of 6 in first gear, that would be a Final Equivalent Mass of 3. On a 100 slug vehicle, that's 3%. For the ratio to the Final Equivalent Mass of the flywheel to its actual mass, it's 3 to 1.


----------



## gor (Nov 25, 2009)

maxvtol said:


> Ok, but percentages of what?
> Assuming a 1 slug flywheel with a radius of gyration of .5ft and a tire radius of 1 ft, gives an Initial Equivalent Mass of 1/2 slug. With a final gear drive of 6 in first gear, that would be a Final Equivalent Mass of 3. On a 100 slug vehicle, that's 3%. For the ratio to the Final Equivalent Mass of the flywheel to its actual mass, it's 3 to 1.


 that's fine - nothing wrong with percentage of vehicle mass - as we did before, let's just check it all again, one-by one, and whatever it is - it is


----------



## maxvtol (Nov 11, 2009)

gor said:


> that's fine - nothing wrong with percentage of vehicle mass - as we did before, let's just check it all again, one-by one, and whatever it is - it is


If you check the spreadsheet in column R starting at row 44, in 1st gear it's almost 7% of the vehicle mass, in 5th gear it's over 3% for all the components before the transmission. 

For all the components after the transmission, it's about 4% (B23 in the spreadsheet).


----------



## tomofreno (Mar 3, 2009)

I've attached my thoughts on this since I can't write equations here very well. It appears to me maxtvol's method is correct, but his calculations are incorrect. Edit: fixed some things that got messed up when the docx document was converted to a doc.
View attachment equivalent mass of rotating part.doc




maxvtol said:


> Tom, gor, anybody, give my your thoughts.
> 
> Walk with me through a thought experiment and see if you think my thoughts on rotational mass are correct. I’m not sure if my Equivalent Mass is the same as Bob Brant’s, but I’ll show how I’m coming up with mine...


----------



## tomofreno (Mar 3, 2009)

Maybe this additional comment helps:
View attachment equivalent mass, additional comment.doc


----------



## tomofreno (Mar 3, 2009)

By the calculation in the attachment I gave, the flywheel equivalent mass is 160 kg. The car without rotational considerations is 1700 lb or 773 kg, so the flywheel equivalent mass is 100*160/773 = 20.7% for second gear. Sorry gor.



gor said:


> that's fine - nothing wrong with percentage of vehicle mass - as we did before, let's just check it all again, one-by one, and whatever it is - it is


----------



## gor (Nov 25, 2009)

tomofreno said:


> By the calculation in the attachment I gave, the flywheel equivalent mass is 160 kg. The car without rotational considerations is 1700 lb or 773 kg, so the flywheel equivalent mass is 100*160/773 = 20.7% for second gear. Sorry gor.


sorry about what? 
you doing good  - let's just come with f-la more discretive than general for all 1994 cars 1+0.04+0.0025G^2


----------



## gor (Nov 25, 2009)

maxvtol said:


> If you check the spreadsheet in column R starting at row 44, in 1st gear it's almost 7% of the vehicle mass, in 5th gear it's over 3% for all the components before the transmission.
> 
> For all the components after the transmission, it's about 4% (B23 in the spreadsheet).


Max, you have your slugs xG (gear rat) - should be G squared, G^2 

thus, your effect 6 times lower


----------



## gor (Nov 25, 2009)

mom. of inertia f-las and real effect on dyno (30 lbs stock flywheel vs 10 lbs) 
p.s. derivation, where G^2 comes from


----------



## gor (Nov 25, 2009)

exactly, Tom - that's my thinking too: from your doc: 
"The discrepancy boils down to g, rg, and rt must be squared." - i agree


----------



## tomofreno (Mar 3, 2009)

I already did. Just plug the masses and radii of gyration of the rotating parts of your vehicle drive train along with the appropriate gear ratios into the equations in the attachment. It does not use that "rule of thumb" equation.



gor said:


> sorry about what?
> you doing good  - let's just come with f-la more discretive than general for all 1994 cars 1+0.04+0.0025G^2


----------



## maxvtol (Nov 11, 2009)

It's nice to see engineers keeping up their skills. I shall cave to superior minds! 

But let me get may head wrapped arround this one at a time.

And I see the error of my thinking in case 4A. But I think the ratio of rg to R should be squared, not just square rg. And squaring the ratio jives with HPWizard then. Just squaring just rg makes no sense to me. So where the point mass is at R/2, the equivalent ratio should be .25 (as HPWizard calculators show) instead of .5 as I thought in case 4A, right?

Edit: I see you're squaring rt also, so that works. 
That's done. 

Now just square the gear ratio, and we're done, right?


----------



## tomofreno (Mar 3, 2009)

maxvtol said:


> It's nice to see engineers keeping up their skills. I shall cave to superior minds!
> 
> But let me get may head wrapped arround this one at a time.
> 
> ...


Yes. So it is easy to fix in the spreadsheet.


----------



## gor (Nov 25, 2009)

maxvtol said:


> It's nice to see engineers keeping up their skills. I shall cave to superior minds!
> 
> But let me get may head wrapped arround this one at a time.
> 
> ...


 

skilled engenders, my ... i don't even know why you need so much slugs an stones in you car, but hey, its your vehicle, carry as mach as you want !
: )))

G^2 hopefully would work - if not - painstakingly rechecking all estimations - all over again
HPwiz f-la gives too long 0-60 times, even published in magazines for regular cars; it's could be outdated - would be great if we could come with better rule of thumb (to find exact masses and radii of components, like in diff, gearbox - hardly possible)


----------



## tomofreno (Mar 3, 2009)

gor said:


> sorry about what?
> you doing good  - let's just come with f-la more discretive than general for all 1994 cars 1+0.04+0.0025G^2


gor, maybe this helps:

Accounting for rotational effects, the acceleration of the vehicle is a = F/M where M is the effective vehicle mass including rotational effects, or the vehicle mass plus the sum of the equivalent masses of all the rotating parts. Then if a is the vehicle acceleration without the effects of rotation and A is the acceleration with these effects, A = amv/M. The acceleration will be slower by the amount mv/M due to the increased effective mass of the vehicle due to rotation effects. Including just the effects of maxtvols flywheel in second gear, me = 160 kg, mv = 773 kg and A = 773a/(773+160) = 0.83a. Acceleration is about 17% slower due to the rotational inertia of the flywheel.


Oh, and sorry as in sorry the effect is larger than you would like.
I didn't think the effect was this big, so I hadn't bothered to look at it before.


----------



## tomofreno (Mar 3, 2009)

gor said:


> skilled engenders, my ... i don't even know why you need so much slugs an stones in you car, but hey, its your vehicle, carry as mach as you want
> : )))
> 
> G^2 hopefully would work - if not - painstakingly rechecking all estimations - all over again
> HPwiz f-la gives too long 0-60 times, published in magazines for regular cars; it's could be outdated - would be great if we could come with better rule of thumb (to find exact masses and radii of components, like in diff, gearbox - hardly possible)


Do you mean the simple "engineering rule of thumb" equation? The 1 + 0.04 +...? I used it in a spreadsheet because I don't know the masses and radii of gyration of the rotating parts in my car, and I figured that equation would get me as close as if I just guessed at the values. I guess you are saying it does not? Darn.


----------



## gor (Nov 25, 2009)

tomofreno said:


> Do you mean the simple "engineering rule of thumb" equation? The 1 + 0.04 +...? I used it in a spreadsheet because I don't know the masses and radii of gyration of the rotating parts in my car, and I figured that equation would get me as close as if I just guessed at the values. I guess you are saying it does not? Darn.


yea... i been using 0.002 instead 1+ ... 0.0025 - just to get closer to published 0-60 times...


----------



## gor (Nov 25, 2009)

affect not that big when numbers are low - but the feather you're go - the worse it gets (more a, more ft-lbs, more hp; the more accel - the greater inertia, the greater force you need)
as they say - tire on the wheel = 2 in the trunk... true when it's 1 or 2 tires ... 2+2or 2x2 or 2^2, but when you have 4 tires ... 4^2 and 4x2... : )))) 8 or 16 tires in the trunk - big difference : ))))


----------



## gor (Nov 25, 2009)

Tom, do you have accel data say 20to40 on different gears?
torque on your ac50 should be clean flat say at 1500-2500 rpm

f=ma, if we know F(torks & gears) and measured a - we'll have M on different gears (Meqv, Mstat +Minetia)


----------



## tomofreno (Mar 3, 2009)

gor said:


> yea... i been using 0.002 instead 1+ ... 0.0025 - just to get closer to published 0-60 times...


Are you saying you are using 0.002 as the coefficient of G^2 rather than 0.0025? When I do this for the example I did for maxtvol's flywheel I get A = 0.88a, which is close to the 0.83% I calculated in the example (post #74).


----------



## tomofreno (Mar 3, 2009)

gor said:


> Tom, do you have accel data say 20to40 on different gears?
> torque on your ac50 should be clean flat say at 1500-2500 rpm
> 
> f=ma, if we know F(torks & gears) and measured a - we'll have M on different gears (Meqv, Mstat +Minetia)


No I don't. Could do it though. We would just be assuming the torque is the peak obtained in the dyno tests - 92 ft-lb for the Curtis test. The error should be small I guess. Peak torque is out to a bit under 4000 rpm I think, though Jack R's dyno data indicated out to about 4100. So maybe accelerate from 1500 to 3000.

Yes, I agree we could then calculate M, the effective mass including rotational effects, for different gears, then fit an equation of the form M = m(1 + c + dg^2) to determine the constants c and d. I'll try it when I get a chance. Good idea!


----------



## maxvtol (Nov 11, 2009)

Just a test version for anybody that wants to play with it. If you find issues, let me know. I'm going to play around with it for a few days then publish the final version in post #1. 

Changes to Equivalent Mass done. Added Batteries in Parallel feature, and some changes to the battery table posted by drgrieve. I limited Motor Volts to the max allowed by the motor, no matter what the battery volts are. I think the only thing it would really change would be the C rate drawn from the batteries, but it's a circular reference since the voltage is calculated based on the C rate drawn. If the voltage is limited to the motor anyway, it won't matter on any other calculations. 

I'm going to play around with the motor charts supplied earlier (Rickard's charts). It does seem the HV is different than the WarP11, at least different than the Netgain chart.


----------



## DIYguy (Sep 18, 2008)

maxvtol said:


> Added the WarP 8, ImPulse 9, WarP 11, and the AC50/1238-75 to the WarP 9, just chose the number and all the relevant info will pop in.
> 
> 
> I don't anticipate more changes unless anyone wants me to add another motor or finds errors.
> ...


Warp 13? )


----------



## tomofreno (Mar 3, 2009)

maxvtol said:


> Just a test version for anybody that wants to play with it. If you find issues, let me know. I'm going to play around with it for a few days then publish the final version in post #1...


Joe, 

What is "Continuous Peukert Factor"? It's obviously not the exponent. Are you using it in your $/mile estimate to account for energy dissipation in the battery during charge/discharge? This is significant for lead acid, especially at higher discharge currents and lower temperatures. 

Nice job on the battery table - taking account of life Wh and life cost! How did you arrive at your expected life cycle factors? 

I also like the calculation of cell voltage based on C rate during acceleration. 

I guess Steady State Force Required is the force required to move the vehicle at constant speed?

It is not clear to me how Drive Wheel Force Available can be greater than Lbs Force Available, since the latter seems to be the force available for acceleration based on available wheel torque. Oh, the former depends on fwd/rwd, is it the max force the tires can apply to the road with static friction, before the tires would spin? Oh, looks like it is from "Traction Test".

If the vehicle is rear wheel drive, then technically there would need to be another gear ratio, that of the differential, to estimate equivalent mass of the drive shaft. Can leave that for gor to do since he wants accurate expressions for fwd, rwd, and 4wd. 

Looks like you gained a couple seconds in 0 - 60 time with the equivalent mass correction, still well within your requirements though.

Boy, getting to be a lot of stuff in there! I've learned some tricks from your spreadsheet wizardry!


----------



## maxvtol (Nov 11, 2009)

tomofreno said:


> Joe,
> 
> What is "Continuous Peukert Factor"? It's obviously not the exponent. Are you using it in your $/mile estimate to account for energy dissipation in the battery during charge/discharge? This is significant for lead acid, especially at higher discharge currents and lower temperatures.


Just a fixed amount for LA to modify the AH for range calculations (which I didn't put in yet), kind of a guess based on what I read somewhere. Since it's for LA only, I didn't want to get it too complicated because I don't consider LA cost effective for my purposes. 



tomofreno said:


> Nice job on the battery table - taking account of life Wh and life cost! How did you arrive at your expected life cycle factors?


Thanks! Just a guess really. From things I've read, it seems LA really lasts maybe half what it's rated at in EV's, don't really know for sure. For Lithium, it's just a guess, and a fudge factor if you have to replace a couple of batteries, maybe. 




tomofreno said:


> I guess Steady State Force Required is the force required to move the vehicle at constant speed?
> 
> It is not clear to me how Drive Wheel Force Available can be greater than Lbs Force Available, since the latter seems to be the force available for acceleration based on available wheel torque. Oh, the former depends on fwd/rwd, is it the max force the tires can apply to the road with static friction, before the tires would spin? Oh, looks like it is from "Traction Test".
> 
> If the vehicle is rear wheel drive, then technically there would need to be another gear ratio, that of the differential, to estimate equivalent mass of the drive shaft. Can leave that for gor to do since he wants accurate expressions for fwd, rwd, and 4wd.


Yes; yes; yes; I hope no one would notice , it should be very small though; and yes let's let gor figure that out for us! 

Since wheels, tires and flywheels would be the most likely things someone could change to make a change in acceleration based on rotating mass, it'd be nice to leave just those in the spreadsheet and have the other rotating components Eq Mass based on vehicle mass, like in HPWizard. Maybe a future revision. 



tomofreno said:


> Looks like you gained a couple seconds in 0 - 60 time with the equivalent mass correction, still well within your requirements though.


 I must have changed a few things on my car from my sheet in post # 1. I'm showing a loss of about 0.3 seconds if I'm only using 3rd gear for starts. I think I found 1st gear had too much wheel spin. 



tomofreno said:


> Boy, getting to be a lot of stuff in there! I've learned some tricks from your spreadsheet wizardry!


Cool! It's nice to have someone checking these things out. Hopefully it can be helpful to others.


----------



## gor (Nov 25, 2009)

"If the vehicle is rear wheel drive, then technically there would need to be another gear ratio, that of the differential, to estimate equivalent mass of the drive shaft. Can leave that for gor to do since he wants accurate expressions for fwd, rwd, and 4wd"
--------------
"and yes let's let gor figure that out for us! "
----------------

yea, right : ))))) - you don't wanna know... the more i digging there - the less i like it
for now - hp wiz f-la - just fine  (mid. of drivetrain: diff-gear box ~ most constant % - less affected by gears like top and bottom) 
i guess i'll put it in separate thread - too much info
----------------

"Since wheels, tires and flywheels would be the most likely things someone could change to make a change in acceleration based on rotating mass, it'd be nice to leave just those in the spreadsheet and have the other rotating components Eq Mass based on vehicle mass, like in HPWizard. Maybe a future revision." 

- right (+ clutch & propshaft),- just take word "guesstimate" out - it's estimate, examples and links can be added for reference in the bottom

p.s. again - very nice spreadsheet, Max, congratulations


----------



## tomofreno (Mar 3, 2009)

Couple things...I used the C sub i parameter in the "porsche" version of Joe's spreadsheet and it gave a 0 to 60 time a couple seconds longer (10.20 versus 9.26) than that predicted by the calculation using equivalent masses. 

I also tried reducing 0.0025 to 0.002 in the equation using C sub i in my spreadsheet and it further underestimated the 0 to 60 time, so wrong direction. It gave 9.75 sec in Joe's sheet.

It's easy to use the C sub i parameter in Joe's spreadsheet since a = F/(C sub i)m, where m is the total translational mass of the car, M1, in Joe's "porsche" version. So for example entry S44 becomes Q44/(M$1*J$31) in place of Q44/(M$2+R44). 

I wonder if the 0 to 60 times reported in articles are achieved by reving the engines and popping the clutch, which makes it different than my time which was recorded by starting from zero mph and zero rpm, though not as different as it would be if my car had an ice.

Gor, what discrepancies are you seeing for the 0 to 60 times you pulled off the net? Are they over or under estimated, or a mix? How do the predictions compare for front wheel drive versus rear wheel drive? How do you know the numbers are accurate? Edit: Also, how are you using the C sub i parameter or equivalent mass to calculate acceleration, do you have torque-speed curves for the cars?

For my car the C sub i parameter gave 0 to 60 time about 13% less than measured, which I figured was good enough considering the uncertainties, but it may just have been coincidence for that one result. I think +/-15% agreement for a number of different cars would be very good considering...


----------



## gor (Nov 25, 2009)

tomofreno said:


> Couple things...I used the C sub i parameter in the "porsche" version of Joe's spreadsheet and it gave a 0 to 60 time a couple seconds longer (10.20 versus 9.26) than that predicted by the calculation using equivalent masses.
> 
> I also tried reducing 0.0025 to 0.002 in the equation using C sub i in my spreadsheet and it further underestimated the 0 to 60 time, so wrong direction. It gave 9.75 sec in Joe's sheet.
> 
> ...


for EV performance calc, i make donor perf. model (with ice torque curve) to have data before and after conversion 

w/o inertia accel times are less than published, with MOI - more;

true, on the magazines testing - they do revving engine, slipping clutch, using tire slip etc - whatever works to get better time, abusing tested vehicle just shy from braking it
this would take care of MOI on low gear, isn't it? : ))
but i don't have enough data to come with fwd, rwd, awd MOI numbers 

launch 0-20 mph - gray area, too many things will vary, with clutch or with torque converter in AT...
many performance calc. don't even want to get blamed and start count from 30 mph : )))) 

http://vlsicad.ucsd.edu/~sharma/Potpourri/perf_est.html


----------



## tomofreno (Mar 3, 2009)

gor said:


> for EV performance calc, i make donor perf. model (with ice torque curve) to have data before and after conversion
> 
> w/o inertia accel times are less than published, with MOI - more;
> 
> ...


 I think so...and that is where the effect is largest. For example, the C sub i parameter (1 +0.04 +0.0025g^2) for my car is 1.49 in first gear, 1.17 in second, and 1.10 in third, so only a 10% effect in third. In my car, starting in second gives worse performance than starting in third, despite the lower effect of moi, because the decrease in mechanical advantage, 1.88, and resultant wheel torque is greater than what you gain in reduced moi, 1.27.


----------



## tomofreno (Mar 3, 2009)

It occurred to me that I had included drive train efficiency in the calculation of range, but not in the calculation of available acceleration. Using the value suggested by Bob Brant, 90%, (since I don't know what it would be), it increased my calculated 0 to 60 mph time from 13.2 sec to 14.8 sec. If I add 1 sec for shifting twice it gives 15.8 sec versus the measured time of 16 sec. May well be serendipity, but you couldn't ask for much better agreement than that!

I did the same for the AC31/Curtis 1238-7501 in my car and got 15.25 sec, but I have to shift three times rather than 2 so pick up an additional about 1/2 sec, so 15.8 versus 16.75 sec total, AC50/AC31. Doesn't seem to be much difference between them.


----------

