# Clutch or no?



## MJ Monterey (Aug 20, 2009)

Not sure of your base vehicle, are lightened flywheels available for your clutch?

That's kinda middle ground. Less weight still "normal" shifting?

Is automatic an option for you?

MJ


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## Overlander23 (Jun 15, 2009)

I'm skeptical of this. Race cars use lightened fly-wheels because it reduces shift times, etc. The weight of the clutch can affect how quickly an amount of power is delivered to a drivetrain (ie. acceleration), but I'm pretty sure your 42 lb flywheel weighs 42 lbs in the end. 

You could ask it this way. At what rotational speed does the flywheel weigh seven times more than when its not rotating?

Overall vehicle weight and frictional losses are what accounts for energy consumption or range, not acceleration. You will consume more energy accelerating faster than slower, but you will also attain your target speed faster, so will have accelerated for less overall time.

If you were so inclined to remove the clutch and flywheel you'd save the energy required to move the static weight of the clutch and flywheel. Depending on how heavy your vehicle is, the 50 pounds, or so, in the clutch and flywheel may not affect range by a whole lot. You have to determine whether it's a good tradeoff.

Personally, I like the clutch for all the reasons you do, including safety. If you're OK with the acceleration, I see no reason to get rid of it.




F16bmathis said:


> Both my Ev';s have the clutch installed. Was talking to Bryan at evamerica?, and he says I'd get more range by removing the extra weight of having a flywheel and clutch assembly.


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## Stunt Driver (May 14, 2009)

I am planning to pull mine out, since I don't use it anyway.





Overlander23 said:


> If you were so inclined to remove the clutch and flywheel you'd save the energy required to move the static weight of the clutch and flywheel.


Sorry, you are wrong.


Next time when you'll be on service with your car up on the lift - try to spin your tire wtih your hands as fast as you can (hardly 1000 rpm). Then ask someone to stop it by brakes. Then spin it up a few times again.

While static weight doesn't move anywhere - do you feel exausted?


Energy of rorating body is proportional to square of angular velocity. http://en.wikipedia.org/wiki/Kinetic_energy


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## Overlander23 (Jun 15, 2009)

I'm unsure what this proves? I'm not claiming that weight doesn't affect acceleration. I'm claiming that weight is weight. Equal amounts of weight require the same amount of energy to move a given distance. Just because some of that weight is spinning doesn't mean anything for overall consumption.

In the case of the flywheel... it acts like a battery, storing energy within its mass. As the flywheel spins down it releases that energy. In most driving cases, the flywheel will spin down as the car comes to a stop adding to momentum gained by the car moving. The net loss is zero (barring frictional losses, etc.)

If you were to accelerate the flywheel up to speed and then depress the clutch... allowing the clutch to slow on its own, then yes, you'd leach energy away uselessly (from the friction slowing the flywheel). But that's not how one typically drives.

With your example, let's assume a zero friction scenario (impossible, but let's get irrelevant variables out of the way.) Spin the wheel with no flywheel connected and bring it up to a constant speed. Now do the same with the flywheel connected. At the same constant speed, the wheel will require the same amount of force to move it (actually in a zero friction situation this would be zero force to maintain rotation at a constant speed.)

The amount of energy required to spin each setup to speed will be different, more being required for the flywheel system. But the flywheel system will also return that energy when it stops.

Take the clutch/flywheel to an extreme. Say you have a 1000lb flywheel on your car. It will take a huge amount of energy to accelerate the flywheel (and thus the car), but when you stop accelerating, the car will coast forever. Not just because it's a 1000lb flywheel, but because of the stored energy within the flywheel. Same thing works for a light flywheel but high rpm. A light flywheel spinning a million RPM will store quite a bit of potential energy.






Stunt Driver said:


> Next time when you'll be on service with your car up on the lift - try to spin your tire wtih your hands as fast as you can (hardly 1000 rpm). Then ask someone to stop it by brakes. Then spin it up a few times again.


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## DONEAL (Sep 10, 2008)

F16bmathis
Not sure what you mean? 
>I don't have to wait for the motor to spin down to match my next gear.<
For a ICE, yes, you have to time your shifts, but on my EV, there is no motor spin down, I just shift( I don’t have a clutch) and there is no grinding, no nothing. It goes in gear with ease.
About >So would I get so much more range< I’ve read several post about rotational weight and I would be inclined to think that it would.


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## Guest (Feb 6, 2010)

I doubt you'd have any noticeable difference in range without the clutch vs with the clutch. If you were racing I'd still say keep it because you may just need to get that one extra gear and you'd want that clutch for that. Only if you don't have a transmission would you go clutchless. Keep the clutch. It can't hurt and you already have it in. Go clutchless and you must do some changing on how you connect your motor. Just leave well enough alone. You made a fine choice to keep the clutch. 

Pete


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## automd (Feb 5, 2010)

DONEAL said:


> F16bmathis
> Not sure what you mean?
> >I don't have to wait for the motor to spin down to match my next gear.<
> For a ICE, yes, you have to time your shifts, but on my EV, there is no motor spin down, I just shift( I don’t have a clutch) and there is no grinding, no nothing. It goes in gear with ease.
> About >So would I get so much more range< I’ve read several post about rotational weight and I would be inclined to think that it would.


Hmm.. Based from my friend's experience & based on what you have right now, I guess that you won't have any noticeable difference too.


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## frk2 (Jan 2, 2009)

I can confirm there is no noticeable difference with or without the clutch in terms of acceleration or range in my 72v setup though i did heavily shave off my flywheel even with the clutch. However I have been driving clutchless for 2 months and am definitely going to get the clutch put back in since its really bothers me having to wait that 2 or 3 second between shifts. I live in a crowded city and people behind me get really pissed when i start slowing down to make shifts. Also shifting down is a Big issue and i almost always grind gears doing that.

I would also recommend keeping the clutch!


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## O'Zeeke (Mar 9, 2008)

This is from a previous thread where I did the math. There is a gain in range but depends on the weight/rotational mass of your clutch setup, mine was very heavy compared to most. No stats but acceleration "feels" better and as far as increased range, the math tells the story. The 525Wh/mile is actually a little less as no accounting for the charge inefficiency was incorporated 
Quote:
Originally Posted by *O'Zeeke*  
_I recently removed the clutch/flywheel setup from my 0.0 mustang and went direct for several reasons, not the least of which eliminating 65 pounds of rotating mass (78 lbs with t.o.b., fork) which has made a noticeable difference in acceleration (no stats yet) and I expect some increase in range as well. Not concerned about synchro wear as it will drop right in with a little practice and a lot of the time i just leave it in 3rd anyway. Also someone here has a thread on thrust/lateral load exerted on the rear motor bearing while depressing the clutch and that got me thinking. Just my 0.02$_

I'm no mathematician but I did some calculations of the rotational energy used to get the 33kg, .35m dia. flywheel/clutch assembly spinning to 4000 rpm. [wiki=673]Formulas[/wiki] from Wikipedia http://en.wikipedia.org/wiki/Rotational_energy

K(rotational) = 1/2 x (k) x mass(kg) x radius2 x angular velocity(rad/sec)

K = 46274 Joules 

My 20 mile commute involves an average of 22 stop lights requiring 22 x 46274 = 1,018,028 Joules or 0.283 KWh. 

Charging uses 10.5 KWh (525Wh/mile) so about 2.7 percent of the total charge was used just to get the mass of the flywheel/clutch spinning so for my Mustang this translates into about 0.6 miles for a 20 mile trip (maybe a little more because of the 78 less pounds to haul around). Not a huge increase but in a heavy car I'll take all I can get and its free.

Also interesting is doubling the speed increases the energy requirement by a factor of 4. No guarantee on the math, just my $0.02 
__________________
Zero point Zero
http://www.diyelectriccar.com/garage/cars/47


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## Overlander23 (Jun 15, 2009)

OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?



O'Zeeke said:


> I'm no mathematician but I did some calculations of the rotational energy used to get the 33kg, .35m dia. flywheel/clutch assembly spinning to 4000 rpm. [wiki=673]Formulas[/wiki] from Wikipedia http://en.wikipedia.org/wiki/Rotational_energy
> 
> K(rotational) = 1/2 x (k) x mass(kg) x radius2 x angular velocity(rad/sec)
> 
> K = 46274 Joules


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## KiwiEV (Jul 26, 2007)

The energy savings in clutch vs clutchless are minimal. Any tiny savings would be lost as soon as someone pulls out in front of you and you have to hit the brakes.
I fear the only noticable gain would be from a clutchless EV having reduced weight - to which there are lightened flywheels available anyway, so I admit it's not much of an argument!

Ultimately for most converters the clutch vs clutchless argument comes down to conversion simplicity. Simplicity means saving time, but more importantly saving money on engineering or fabrication.


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## F16bmathis (Jun 6, 2008)

As far as a lightened clutch goes, I could pull it, grind it down, but from all I've read here, and testing driving it without the clutch, there's no way I'm getting rid of the clutch. I had the same effect as the other poster who said it takes too long to shift. I'm running around with huge "ELECTRIC VEHICLE" stickers on the sides and rear to promote EV's, and so getting up and going is a big concern, can't do it fast enough without the clutch. Every day I have someone pull up behind me, obviously read the EV sign, and try to go around as we leave the intersection, and every time, I keep up with the guy in front of me, shifting as fast as I can! Most of my driving is a constant highway speed, so accelerating isn't such a big problem. I suppose if I drove in stop and go traffic, I might consider clutchless.

I'd love to go automatic if I could figure it out. Every application is different, and the wiring diagrams I get from Chevy doesn't help figure out shifting gears. I suppose I can simulate everything, engine rpm's, speed, temperature to the ECM, but I'm pretty darn stupid! But I am watching that thread!


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## F16bmathis (Jun 6, 2008)

I'm going to have to agree with you. Getting a few lbs of metal to rotate doesnt seem like much when compared to getting all the metal you can't get rid of to rotate, plus pushing ALL the weight of the entire vehicle, makes the clutch weight minimal. And if I have a manual tranny, I have to have the speed of shifting with a clutch.


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## F16bmathis (Jun 6, 2008)

Overlander23 said:


> OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?


If this is all correct, I used an online calculator and came up with 771 watts, which I can produce on my bike generator in a minute or two, so not really much of a drag on my truck?

I can spin the clutch, motor, all that in nuetral with minimal pedal travel / amps / time, so I'm just guessing it isn't much power used to do it once. Stop and go traffic may be different in doing it multiple times can add up.


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## green caveman (Oct 2, 2009)

Anyone have any advice on machining down the flywheel? I'm about at that stage with the Sidekick and it seems that you can loose a bunch of weight, rotating or otherwise. 

Maybe that advice is "just don't bother", but decreasing the rotating mass would seem to be good for a number of reasons, not least that any imbalance should be minimized.

Seems that the advantage would be to take it of the outside - that is, the part furthest from the center. The current flywheel is about 1.25" thick. Since the clutch doesn't get as much of a workout, it would seem that you could easily be able to cut that down, but where's the limit? Would 1/2" be too thin? The center has to stay at about the current thickness to accommodate the pilot bearing so it could be thinned gradually as it goes outwards. I'm thinking it would be good to leave a "rim" on the outside to stiffen the whole plate, but maybe that isn't necessary.


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## F16bmathis (Jun 6, 2008)

Stunt Driver said:


> I am planning to pull mine out, since I don't use it anyway.
> 
> 
> 
> ...


Yeah, but I feel exhausted pedalling a bike generator that I can produce a measly 75 watts on (for a short time). I understand what you're saying and found some calulations for it, but some say 10:1, others got as low as 2:1, and when it comes out in the long run, isn't the rotating weight keeping the truck going at that same weight calculation as you slow down?

I wish I had two vehicles I could test side by side!


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## Overlander23 (Jun 15, 2009)

Yes!! This is my point. Any energy used to spin the flywheel will be returned to the drivetrain for a net zero energy loss.

Everyone is worried about how much energy it takes to spin the flywheel, but no one is considering that the energy has to go somewhere. It goes back into moving the vehicle.

The "ratios" people are quoting for lightened flywheels refer to the amount of energy needed to spin the flywheel through a transmission, usually through first gear. In this case, 10 lbs off the flywheel is torque multiplied by the first gear ratio. The ratios are always quoted differently because not all transmissions have the same first gear ratio.

The amount of energy needed to spin a flywheel to, say, 4000 rpm changes depending on the mass of the flywheel and its diameter. That's the angular momentum calculations. And due to the laws of conservation of energy, any energy used to spin the flywheel remains in the flywheel. Angular momentum calculations can be used to determine the amount of energy stored in a rotational mass. As the flywheel slows, it gives its stored potential energy up to the drivetrain. The car will "coast" longer.

If people have found that their range is reduced after installing a flywheel and clutch to a formerly direct coupled transmission, it's because full advantage of the flywheel's storage capabilities isn't being taken advantage of. In other words, a longer coast time is being overridden by the frictional application of brakes more than necessary.

The only situations the energy used to spin the flywheel would be wasted would be during the application of friction to convert the flywheel energy to useless heat (braking), or the slowing of the flywheel while it was disengaged from the drivetrain.

For those that think that rotational mass somehow is heavier than static mass, think of it this way. Take a 50 lb flywheel... measure the weight of the car when the flywheel is stationary. Now spin the flywheel to a million rpm. The weight of the car doesn't change! If the weight of the car doesn't change then rotational mass is no different from static mass and range isn't affected. Think of rotational mass as "energy storage" mass.





F16bmathis said:


> Yeah, but I feel exhausted pedalling a bike generator that I can produce a measly 75 watts on (for a short time). I understand what you're saying and found some calulations for it, but some say 10:1, others got as low as 2:1, and when it comes out in the long run, isn't the rotating weight keeping the truck going at that same weight calculation as you slow down?
> 
> I wish I had two vehicles I could test side by side!


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## EV-propulsion.com (Jun 1, 2009)

Green, I would be careful as to what you are taking off the flywheel-remember thats spinning upwards of 5000 rpm, _very_ ugly if it comes apart.
Also, overlander is correct in that when driving an EV we should be using the long coasting ability to your advantage-I think that's the best way to increase range. Anticipating stops ahead of time (stop signs and such) can save alot of energy. Kind of a learning curve involved in EV driving.......
Mike
EV-propulsion llc


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## green caveman (Oct 2, 2009)

EV-propulsion.com said:


> Green, I would be careful as to what you are taking off the flywheel-remember thats spinning upwards of 5000 rpm, _very_ ugly if it comes apart.


Yep, that's why I ask. Nonetheless, there is undoubtedly a bunch of weight there that the ICE needs and the EV doesn't. For example, it seems to me that you could remove the starter motor gear ring without any disadvantage at all.



EV-propulsion.com said:


> Also, overlander is correct in that when driving an EV we should be using the long coasting ability to your advantage-I think that's the best way to increase range. Anticipating stops ahead of time (stop signs and such) can save alot of energy. Kind of a learning curve involved in EV driving.......
> Mike
> EV-propulsion llc


Craig Vinton with his Chevy Tracker claims that machining 12lbs off the flywheel improved his range. If the stored energy is really 700+W, then that's more than a mile of range every time you stop that without recoverying the energy. For a 3000lb car moving at 30mph that's about 25% of the kinetic energy of the car stored in the flywheel - a significant chunk, but as you say, that only comes into play when you stop it with the brakes.

Since we have a Sepex/Regen system, it should be possible to recover energy from the 5000 RPM hunk of very heavy steel even on a quick stop - so long as you remember to push out the clutch.

I still tend to think that some amount of material can reasonably, and cost effectively, be removed from the flywheel without any danger to the structure and that it would be an advantage to do that.


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## Stunt Driver (May 14, 2009)

Overlander23 said:


> In the case of the flywheel... it acts like a battery, storing energy within its mass. As the flywheel spins down it releases that energy



I guess you never-ever use brakes on your car? Others go long ways to invent regenerative braking and such Just wonder why 


ps


> Everyone is worried about how much energy it takes to spin the flywheel, but no one is considering that the energy has to go somewhere.


You are right, It goes right back to heating your disk brakes.
I wish I was living in a city where i can take off from my house and nEveR touch brakes till I reach my work. And during last mile, while I am waiting for the speed to come down to zero, I would not have angry people behind be, wondering, what's up with speed? Or at 90 degree turns - i would have to coast in a way, so I slow down from my 40mph to 10mph, so I can make the turn. Oh people behind me would be happy   

So, *Overlander23*, if all you are saying is that if you don't use brakes ever - flywheel doesn't affect your range - I would 100% agree. But if we get back to real world - that doesn't fly.
Some one did calculation for average distance between red light - numbers were real, allthou not killing.


For my car being a low cost convertion - I can't go above 40mph, and do not have to shift out of 2nd gear, but every time red light pops up - I transfer energy from flwheel and pressure plate to my front brake pads. That is why i'd remove it, if I can find time. My tranny never grinds upshifting, and on downshift I have to give a small kick to gas pedal to shift smooth. But again, I rarely need this. Only if on a long straight I want to get higher than 40Mph speed, but it comes at higher AMPs, and probably only hurts my range.

Now, if my convertion would be higher voltage - I would actually need the clutch.

Clutch or No Clutch debate - does not have a universal answer.


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## Overlander23 (Jun 15, 2009)

Sorry, I just realized this is responding to a couple of other responses, not just Green Caveman's.

I don't disagree that using the brakes will kill the energy in the flywheel leading to total system efficiency losses. I'm right there with you on that. But how much energy is that?

I don't know how you think you're using the figure 700+W. And where do you get the idea that the flywheel stores over a mile of energy every time it spins up? There seems to be a lot of confusion over power/energy/units. Do you really think that people with clutches and flywheels are losing over a mile of range each time they come to a stop? You can test it yourself, spin the flywheel to 4000 rpm with the clutch depressed, then dump it and see how far you get. That's pretty much how much range you'll save by removing it if everything survives. _<note: this last sentence is hyperbole>_ 

(Yes, I know that accelerating a vehicle consumes far more energy than just maintaining its speed. The point was to give you an idea that there isn't much energy stored in a conventional car flywheel.)

Here are the numbers.

Firstly, watts is a unit of how much power is flowing at any given time. You need to have a time component for it to be an amount of energy. In the case of O'Zeeke's conversion, he calculated 46274 Joules of energy to spin his 33kg flywheel/clutch combination to 4000rpm. That comes out to (http://www.unitconversion.org/energy/joules-to-watt-hours-conversion.html): 46274 Joules = 12.854 watt-hours (700+ watt-mins, actually more like 770 watt-mins.)

Luckily, we gauge EV efficiency in watt-hours. An efficient EV may consume 200 watt-hours/mile (a very efficient EV, I might add). That's 1/15th of mile in flywheel energy consumption (5%), but only if 100% of the energy in the flywheel were bled off uselessly. 

Unless you're in the habit of braking hard enough to stop the vehicle instantly, therefore insuring that 100% of the stored energy in the flywheel was converted to heat, then the larger 5% figure starts to go down to 0% (a non-braked coast to a stop).

As KiwiEV points out, there are so many other variable involved, such as a sudden braking maneuvers. Obviously, if your EV is more inefficient the effects of the flywheel will be even less. The effects of vehicle speed will play a factor since the EV will not use 200 watt-hours/mile all the time. The flywheel will be spinning at different speeds so will not always be storing the same amount of energy... etc. You stand more of chance of getting back the 0-5% energy loss by changing your driving behavior.

So yes, I agree with you, the clutch/flywheel combination will technically be more inefficient, but practically it won't be very significant, IMO. 

I even machined the ring gear and a raised portion off of my flywheel, but knowing it was to save overall vehicle weight. Even then it didn't amount to much, but I had it piggybacked onto some other machine shop work I was having done.

I'd be curious to know just how much more range Craig Vinton got due to the 12lb flywheel shave (not even something like a 33kg loss), as opposed to his aerodynamic aids... or merely different driving behavior. 

Of course, what do people mean when they say significant? 

_*Edit:*_ I realize now, that Green Caveman's use of 700+W was probably from F16bmathis' report of 771 watts in converting 46274 Joules to Watts (correct me if I'm wrong). What's confusing is that while watt usage is typically assumed to be usage for an hour, sometimes it isn't. If he then claimed that he could "generate the 771 watts in a minute or two _(not verbatim)_" then he'd be generating 771 watt-minutes of energy (or 700 watt-"two mins" for the latter, to be esoteric), or divided by 60 mins, about 12 watt-hours. This only works if the 771 watt figure was quoted for a minute, though.

In a later post, his real-world experience of being able to maintain 75 watts of power on his bike generator is probably accurate. If he were able to cycle at that rate for an hour he would produce 75 watt-hours of energy, or 4500 watt/mins (75w*60mins). Assuming F16bmathis' abilities on the bike generator, the equivalent amount of energy in the flywheel could be generated by him in around 10 seconds. Now that does seem small, doesn't it?

Hmmm, that was supposed to clarify things... 

OK, one more analogy. Remember that 46000 Joules? That's equivalent to about 11 nutritional calories. Now that really seems small.




green caveman said:


> Craig Vinton with his Chevy Tracker claims that machining 12lbs off the flywheel improved his range. If the stored energy is really 700+W, then that's more than a mile of range every time you stop that without recoverying the energy. For a 3000lb car moving at 30mph that's about 25% of the kinetic energy of the car stored in the flywheel - a significant chunk, but as you say, that only comes into play when you stop it with the brakes.
> 
> Since we have a Sepex/Regen system, it should be possible to recover energy from the 5000 RPM hunk of very heavy steel even on a quick stop - so long as you remember to push out the clutch.
> 
> I still tend to think that some amount of material can reasonably, and cost effectively, be removed from the flywheel without any danger to the structure and that it would be an advantage to do that.


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## O'Zeeke (Mar 9, 2008)

Overlander23 said:


> OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?


As stunt driver correctly pointed out it is converted to heat when the brakes are applied. There are a lot of hear say and subjective comments about this as "I doubt if it would make much difference" or "it's probably insignificant" but if we stay objective and stick with the math the numbers tell the story. There is an energy savings because it does take energy to spin that flywheel but it is up to the individual as to how "significant" it would be for them. For me It's all about range. I have a lot of stop and go on my commute and although my ev shifts easily, I almost always just leave it in 2nd, so for my circumstances, clutchless makes sense


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## Jan (Oct 5, 2009)

Overlander23 said:


> OK, you've calculated it takes 46274 joules to spin your 33kg flywheel to 4000 rpm. Where does that energy go then?





F16bmathis said:


> If this is all correct, I used an online calculator and came up with 771 watts, which I can produce on my bike generator in a minute or two, so not really much of a drag on my truck?


If the 46274 joules is correct. That eqauals 46274 Watt seconds. 

(c) http://en.wikipedia.org/wiki/Joule

If you accelerate upto that speed in lets say 10 seconds. It will cost you an _extra_ 4.6kW those 10 seconds, you'll never get back. The faster you want to accelerate, the more it will cost. And visa versa.

I personaly find 4.6kW significant. But I haven't checked if those 46274 joules are correct. I wouldn't know how.


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## O'Zeeke (Mar 9, 2008)

Jan said:


> I personaly find 4.6kW significant. But I haven't checked if those 46274 joules are correct. I wouldn't know how.


Here's the formula 
Wikipedia http://en.wikipedia.org/wiki/Rotational_energy


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## Overlander23 (Jun 15, 2009)

46274 joules is "close enough". I say that because the inertial moment is hard to determine exactly from a flywheel/clutch/clutch plate combo. It should be in the ballpark.

Give me an idea of how significant you find 4.6kw-s to be? 46274 watt-seconds is equivalent to 4627.4 watt-ten seconds, not 46274 watts of energy for each second of 10 seconds. You're mixing terms. Power vs energy.

Using your example, what if you wanted to accelerate to the same speed but over a period of 100 seconds? Have you used 100s x 4.6kw? No. You've used 4.6kw-s of energy stretched out over 100 seconds.

By your figuring, the harder you accelerate the less energy you use.

If that's not what you mean, then I apologize. One thing is for sure, though... you will use 4.6kw-s of energy to spin the flywheel. 

EDIT: Turns out that's not what Jan meant. I believe Jan was talking about the loss of power incurred by the flywheel.



Jan said:


> If the 46274 joules is correct. That eqauals 46274 Watt seconds.
> 
> (c) http://en.wikipedia.org/wiki/Joule
> 
> ...


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## Jan (Oct 5, 2009)

Overlander23 said:


> Give me an idea of how significant you find 4.6kw/s to be?


It's not 4.6kW/s. During those 10 seconds you have e.g. 40kW of power available from your motor and controler system. power is timeless. 

Of these 40kW you'll loose besides all other resistance an extra 4.6kW to the flywheel.



> 46274 watt/seconds is equivalent to 4624.5 watts per ten seconds, not 46274 watts of energy for each second of 10 seconds. You're mixing terms. Power vs energy.


1 joule is 1 Ws, not 1 W/s. I really don't think I'm the one who confuses them now.


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## Overlander23 (Jun 15, 2009)

You are correct, that's my nomenclature mistake. A joule is indeed one watt-second.

But a joule is a unit of energy. A watt is a unit of power. You are correct, you will lose power to the flywheel, but you will not lose much energy, and the discussion thus far has been about the effects of the flywheel on range... which is about energy consumption, not power.

No one has claimed that the flywheel would not absorb power.



Jan said:


> It's not 4.6kW/s. During those 10 seconds you have e.g. 40kW of power available from your motor and controler system. power is timeless.
> 
> Of these 40kW you'll loose besides all other resistance an extra 4.6kW to the flywheel.
> 
> ...


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## Jan (Oct 5, 2009)

Overlander23 said:


> You are correct, that's my nomenclature mistake. A joule is indeed one watt-second.
> 
> But a joule is a unit of energy. A watt is a unit of power. You are correct, you will lose power to the flywheel, but you will not lose much energy, and the discussion thus far has been about the effects of the flywheel on range... which is about energy consumption, not power.
> 
> No one has claimed that the flywheel would not absorb power.


That's true. It will have an insignificant effect on range if you accelerate once or twice during a long trip. But more than 10% loss during acceleration, I find significant.


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## DC Braveheart (Oct 12, 2008)

Overlander23 said:


> Everyone is worried about how much energy it takes to spin the flywheel, but no one is considering that the energy has to go somewhere. It goes back into moving the vehicle.


Actually I think you'll find that all that stored energy goes into heating up your brakes when you stop.

Now if you put your clutch in before you brake, the flywheel (and motor rotor) will continue spinning for a while until the stored energy is again transferred to heat in the various bearings due to friction. If, after stopping, you try to move off again then you'll need to slip the clutch a bit as you pull off, as the motor/flywheel is still spinning faster than the transmission and you'll transfer some of the stored rotational energy to heat in the clutch, again due to friction. I doubt much of the energy stored up in the flywheel ever actually makes it to the wheels. 

In any case, I doubt anyone with a MT EV uses the clutch that way - I'm pretty sure that the clutch only get used when changing gears NOT to keep the motor spinning when stopped.


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## green caveman (Oct 2, 2009)

Overlander23 said:


> _*Edit:*_ I realize now, that Green Caveman's use of 700+W was probably from F16bmathis' report of 771 watts in converting 46274 Joules to Watts (correct me if I'm wrong).


You're right and I should have questioned that conversion - and I reused it in a later calculation. Thus the error propagated.

Probably a better guide as to how much energy is stored in the flywheel is to consider that if you stop a 3000lb car from 30mph you have about 125000 joules. Kinetic energy is 0.5mv^2 (so my son tells me - I've long ago forgotten my high school physics) v is 13.5 m/s m is 1360kg so you have

13.5*13.5*1360 = 123930

I don't know whether that really helps, except to tell you that if the 46kJ is a significant number when compared to the kinetic energy of the car. Now when you stop suddenly you loose the 120kJ and the 46kJ. Without the flywheel you'd only loose the 120kJ. Whether that really translates to a significant loss of range probably depends on many other factors.

However, it seems unlikely that the 46kJ is at 30MPH since it was calculated at 4000rpm. Since the energy stored in a flywheel seems to be a v^2 relationship (I'm just taking O'Zeeke's word for that) it seems likely that the the flywheel would be going less that 4000rpm in stop-go traffic. It also seems to be a very heavy flywheel - 33kg.

Actually, I'm tending to agree with O'Zeeke's math/logic that there's probably only a few percent lost in the clutch, and then only if you have a bunch of stops (I don't think that there are 22 traffic lights in town here).

O'Zeeke do you have any real-world range numbers yet?


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## O'Zeeke (Mar 9, 2008)

green caveman said:


> However, it seems unlikely that the 46kJ is at 30MPH since it was calculated at 4000rpm. Since the energy stored in a flywheel seems to be a v^2 relationship (I'm just taking O'Zeeke's word for that) it seems likely that the the flywheel would be going less that 4000rpm in stop-go traffic. It also seems to be a very heavy flywheel - 33kg.
> 
> 
> 
> ...


No I don't other than the math, as it sits in my garage while I am switching over to LiFePO4, however after removing the clutch I could burn the tires on my driveway where before it could never do that, every thing else being the same. As far as the flywheel It was the very heavy stock cast iron flywheel - clutch - disk setup, and the 4000 rpm is about the highest rpm I would use but usually lower, depending on amp draw


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## F16bmathis (Jun 6, 2008)

Overlander23 said:


> Yes!! This is my point. Any energy used to spin the flywheel will be returned to the drivetrain for a net zero energy loss.
> 
> Everyone is worried about how much energy it takes to spin the flywheel, but no one is considering that the energy has to go somewhere. It goes back into moving the vehicle.
> 
> ...


And to contradict myself, my motor/flywheel in nuetral will rather quickly spin down to nothing. I don't mean like an ICE's engine rev's down, but yet, if I'm doing even as slow as 30 mph and throw her in nuetral, the motor will be spun down to 0 before I'm doing 20 mph. So, usually if I want to coast, I'll toss it in nuetral and then rev her back up a little when I re-engage. Though I don't believe it really helps, as just a touch of the juice pedal gets it back up to speed without some agonizing amount of KWH used.


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## F16bmathis (Jun 6, 2008)

Overlander23 said:


> Sorry, I just realized this is responding to a couple of other responses, not just Green Caveman's.
> 
> I don't disagree that using the brakes will kill the energy in the flywheel leading to total system efficiency losses. I'm right there with you on that. But how much energy is that?
> 
> ...


Thats a great idea! I'll go flat surface, rev her up to about 5K and ease out the clutch, enough to get the most speed and break some of that rolling resistance, but not so fast I rip the clutch apart. Will post results.

The pedal generator is not going to do much if I'm pedaling. I can do 75 watts (max) for about 30 seconds! Solar is so much easier! I bought that wattsviewer program, pretty neat, shows the V,A, Watts, and Watt hours all in pretty guages or graphs. Only problem is I can produce about 40 watts steady, but my laptop uses 40 watts, so I get tired getting nowhere. My homemade solar panels bring in 300 watts and I can just sit back and watch from my chair!


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## F16bmathis (Jun 6, 2008)

F16bmathis said:


> Thats a great idea! I'll go flat surface, rev her up to about 5K and ease out the clutch, enough to get the most speed and break some of that rolling resistance, but not so fast I rip the clutch apart. Will post results.
> 
> The pedal generator is not going to do much if I'm pedaling. I can do 75 watts (max) for about 30 seconds! Solar is so much easier! I bought that wattsviewer program, pretty neat, shows the V,A, Watts, and Watt hours all in pretty guages or graphs. Only problem is I can produce about 40 watts steady, but my laptop uses 40 watts, so I get tired getting nowhere. My homemade solar panels bring in 300 watts and I can just sit back and watch from my chair!


5000 rpm, flat and level, let out the clutch pretty steady, I got about 1.5 ft. I'm going with the "clutch weight isn't squat" theory!


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## samborambo (Aug 27, 2008)

green caveman said:


> Yep, that's why I ask. Nonetheless, there is undoubtedly a bunch of weight there that the ICE needs and the EV doesn't. For example, it seems to me that you could remove the starter motor gear ring without any disadvantage at all.
> 
> 
> 
> ...


You hit on an interesting point with a regen capable motor. If you have the electronics know-how, you could do away with the clutch and flywheel, put an rpm sensor on the motor, tap into the speedo sensor on the differential and use something like a PIC based PI control loop to synchronise the motor speed to the next gear being shifted to. I've done some calcs on this before when looking into for my own conversion. For a typical AC motor (considering its angular moment of inertia) you could synchronise the speed in less than 100ms with regen under 30kW.

Sam.


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## green caveman (Oct 2, 2009)

samborambo said:


> You hit on an interesting point with a regen capable motor. If you have the electronics know-how, you could do away with the clutch and flywheel, put an rpm sensor on the motor, tap into the speedo sensor on the differential and use something like a PIC based PI control loop to synchronise the motor speed to the next gear being shifted to. I've done some calcs on this before when looking into for my own conversion. For a typical AC motor (considering its angular moment of inertia) you could synchronise the speed in less than 100ms with regen under 30kW.
> 
> Sam.


As long as you have the controller, you might as well also control the amount of regen as you brake. Nothing could possibly go wrong with that idea, no way it'll interact with the anti-lock brakes - right?

Actually, I think you have an interesting idea, but I would seriously be a little afraid of allowing software to control the speed of the car. Even though it's only supposed to make minor adjustments if something goes wrong it seems to have the possibility for either a sudden stop of a runaway. Neither of these sound particularly pleasant.

Maybe a different scheme would be to control the gear change, so you have a computer controlled manual. The driver would still have to play with the accelerator to match the speeds, but the change could occur very quickly once the match is made - even if it's transient.


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## Overlander23 (Jun 15, 2009)

But all modern PWM controllers control the motor with software. That's all it is. With the correct fail-safe modes in place, I don't know how controlling the throttle between gears is any different from Nissan's shift matching control on the 370Z... or the way the throttle works on pretty much all solid-state controllers with regen.

I don't know how it would interact with ABS since ABS is determined by the four wheels, not what the motor/engine is doing.

A healthy fail-safe is controlling the maximum amount of regen allowable by the system to prevent lockups.

Didn't Etischer do a rev matching system like this on his regen-capable AC controller?



green caveman said:


> Actually, I think you have an interesting idea, but I would seriously be a little afraid of allowing software to control the speed of the car. Even though it's only supposed to make minor adjustments if something goes wrong it seems to have the possibility for either a sudden stop of a runaway. Neither of these sound particularly pleasant.


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## green caveman (Oct 2, 2009)

Overlander23 said:


> I don't know how it would interact with ABS since ABS is determined by the four wheels, not what the motor/engine is doing.


Reference was to Toyota recent Software Patch for problems with Regen/ABS interaction.


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## samborambo (Aug 27, 2008)

Overlander23 said:


> But all modern PWM controllers control the motor with software. That's all it is. With the correct fail-safe modes in place, I don't know how controlling the throttle between gears is any different from Nissan's shift matching control on the 370Z... or the way the throttle works on pretty much all solid-state controllers with regen.
> 
> I don't know how it would interact with ABS since ABS is determined by the four wheels, not what the motor/engine is doing.
> 
> ...


Did he? Someone poke Eric please and get his input.

I totally agree - every modern controller I know of has a microcontroller at the heart of it with human produced, fallible software. The good thing with microcontrollers is that you can implement some very sophisticated fail-safes that would otherwise not be possible or easy with an analog or discrete digital circuit.

How did the Nissan shift matching control work? They must have had a brake on the crankshaft or flywheel.

Sam.


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## Overlander23 (Jun 15, 2009)

Pretty sure it's only good for blipping the throttle to match revs for downshifts... but apparently it's very adept at getting it exactly right.



samborambo said:


> How did the Nissan shift matching control work? They must have had a brake on the crankshaft or flywheel.
> 
> Sam.


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## DavidDymaxion (Dec 1, 2008)

2nd try on this post!

There are some other factors that will lessen the clutchless energy savings advantage, and could even make it have worse efficiency. This is even more pronounced for some of the points for a direct drive (single gear) freeway capable conversion.


Without a clutch, you are more likely to lug the motor rather than shift, and be running it at a lower efficiency rpm.
You lose more speed while shifting clutchess, that you'd have to reaccelerate to get back. This would be especially bad up a hill.
With clutchless you'll be more likely to take off in 2nd gear rather than first, extending the time you are in current multiplication mode, which is not as efficient as higher rpm. Lesser motor efficiency at low rpm compounds this problem.
You can get back a little bit of energy if you keep the motor spinning until you need to take off again
Regen can be increased by downshifting
A clutch can let the motor idle. There is a well respected EVDL EVer (Roland) that claims to get better range idling the motor when stopped! While I'm not sure about that myself, but it is interesting food for thought.
Most of these events would be brief and clutchless could be more efficient. At the moment the clutch lets you run in a lower gear (or downshifting isn't worth the trouble clutchless), though, then the clutched car could get better efficiency. It would depend on your driving cycle, if you have hills, if you have regen, etc.


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## Overlander23 (Jun 15, 2009)

Here's the rev matching regen thread... though there's not much info in it.

http://www.diyelectriccar.com/forums/showthread.php?t=37764



samborambo said:


> Did he? Someone poke Eric please and get his input.


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## martymcfly (Sep 10, 2008)

If you are concerned with the weight of the clutch, there are companies that manufacture light weight clutches. I had a Goldstar in a mini-stock that weighed in at 12 pounds. There are other light weight clutch options too. Some guys used a ram coupler. I have often thought about using an electric clutch, like off of a a/c compressor, or a air activated clutch like the radiator fan off of a Kenworth. Clutch weight can make a big difference in performance. Not only the weight, but the diam.


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## Guest (Feb 20, 2010)

> Clutch weight can make a big difference in performance.


If you are concerned about that 1/100th of a second time in a 1/4 mile run.  For going to work or to get some groceries the weight of the clutch will make no difference in performance and distance. 

Pete


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## Dave Koller (Nov 15, 2008)

gottdi said:


> If you are concerned about that 1/100th of a second time in a 1/4 mile run.  For going to work or to get some groceries the weight of the clutch will make no difference in performance and distance.
> 
> Pete


I second that too


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## dtbaker (Jan 5, 2008)

Dave Koller said:


> I second that too


I'll 'third' it... having a clutch makes it a lot easier for 'untrained' drivers too. I'd much rather replace a clutch disc than a tranny chewed up from bad shifts.....

Unless you are doing lots of accelerations, where speed is critical, that weight will not be noticable.


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