[F16bmathis]

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. The rotational weight is around a 7:1 ratio, so a clutch and flywheel is like 300 lbs more you have to "push" as you accelerate.

All I can find on rotational weight is anywhere from a 1:2 to a 1:10. I'm not sure how badly it affects the acceleration of the truck / car, it seems to gather rpm's rather quickly in nuetral, and I love driving it with a clutch. I don't have to wait for the motor to spin down to match my next gear.

So would I get so much more range, it would be worth it to take it out and go clutchless?

[MJ Monterey]

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

[Overlander23]

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.

Originally Posted by F16bmathis

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.

[Stunt Driver]

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

Originally Posted by Overlander23

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

[Overlander23]

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.

Originally Posted by Stunt Driver

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.

[DONEAL]

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.

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

[automd]

Originally Posted by DONEAL

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.

[frk2]

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!

[O'Zeeke]

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. Formulas 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
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