Clutch - leave in or not?

Have you made or bought a converted vehicle if so this is for you
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geekygrilli
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Clutch - leave in or not?

Postby geekygrilli » Wed Jul 09, 2008 7:29 pm

Hi

As you know I have just finished my Cinquecento, from which I removed the clutch assy and pedal assy. The motor, gearbox and current settings I have mean I need to use 2nd gear when pulling away on hills in order to fit in and keep up with teh flow of traffic. Top speed in 2nd is 32mph, so I then require a change into 3rd.

My feeling is that life would be a bit easier if I had left the clutch in. The car would be a lot more user friendly, its fine as it is I can cope with it, but when friends and family use the car it might put them off a bit having to match the motor speed to gearbox speed so not to crunch the gears.

Obviously the clutch would not be used when pulling away from standstill.

Maybe I could have a relay switch on the clutch pedal so that when it is depressed the trottle pedal doesn't work, just to discourage the use of the clutch.

The reason I removed the clutch in this build was because most people do it, and I think the reason most people do it is because they worry about people over revving the motor and/or burning out the clutch.

Any thoughts or experience on this subject would be greatly appreciated. After experiencing my car without a clutch, I think my opinion is that it would be better to leave it in next time.

Many thanks

Christopher

jonathan jewkes
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Postby jonathan jewkes » Sat Jul 19, 2008 9:29 pm

I have experienced both, and I think it is good to keep the clutch. Of course you only have to use it when changing gear on the move, not when starting or stopping.
I had a Rover Metro EV conversion which had no clutch. Like you I needed to change up from 2nd to 3rd when going much above 30mph. That wasn't too difficult but I always had difficulty changing back down to 2nd while moving - because you can't hear the electric motor it is hard to match the motor speed to the road speed. Was't made any easier by the fact that when I took my foot off the throttle pedal the regen kicked in and so as I went through neutral the motor would be slowed right down (so I needed to keep the throttle depressed just enough but not too much - I never really got the knack even after 10 years).
I now have an Elcat van which actually requires more gear changes, but because it has a clutch it is much easier to drive.
Jonathan
Jonathan Jewkes
Daily EV user for 10years - an enthusiast and also a realist

social misfit
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Re: Clutch - leave in or not?

Postby social misfit » Thu Jul 24, 2008 10:37 am

geekygrilli wrote:Hi

As you know I have just finished my Cinquecento, from which I removed the clutch assy and pedal assy. The motor, gearbox and current settings I have mean I need to use 2nd gear when pulling away on hills in order to fit in and keep up with teh flow of traffic. Top speed in 2nd is 32mph, so I then require a change into 3rd.

My feeling is that life would be a bit easier if I had left the clutch in. The car would be a lot more user friendly, its fine as it is I can cope with it, but when friends and family use the car it might put them off a bit having to match the motor speed to gearbox speed so not to crunch the gears.

Obviously the clutch would not be used when pulling away from standstill.

Maybe I could have a relay switch on the clutch pedal so that when it is depressed the trottle pedal doesn't work, just to discourage the use of the clutch.

The reason I removed the clutch in this build was because most people do it, and I think the reason most people do it is because they worry about people over revving the motor and/or burning out the clutch.

Any thoughts or experience on this subject would be greatly appreciated. After experiencing my car without a clutch, I think my opinion is that it would be better to leave it in next time.

Many thanks

Christopher
has any one tried it with a automatic gearbox probably not the best idea but would be interesting

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geekygrilli
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Postby geekygrilli » Wed Aug 13, 2008 8:06 pm

I thought of that, or maybe even a CVT box like in the Micra, but I don't know how the massive torque will affect things when pulling away...

Does anyone know?

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EVguru
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Postby EVguru » Wed Aug 13, 2008 9:17 pm

Automatics can be done, but you either have to keep the torque converter and idle the motor to maintain hydraulic pressure, or run an external oil pump and pressure accumulator.

Most automatic gearboxes are pretty much as efficient as a manual, it's the torque converter that's lossy.

CVTs are friction drive devices and often have quite high losses. Their ability to keep an ICE in a better efficiency range makes them worth while in that application. You've got to look at average system efficency, not focus too much on one component.

In both cases the real trick can be 'tuning' the ratio selection to match your motor.
Paul

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Richard Ward
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Postby Richard Ward » Thu Aug 14, 2008 12:35 pm

Hi, I'm a bit new to EVs, but there's something I don't quite understand about including the clutch in a conversion.
Surely this would mean also including the original flywheel, which would have to be mounted on the end of the motor shaft. What about the huge extra rotational inertia this would add, also how would the motor bearings cope with the weight, and the end thrust of the clutch release bearing?
I suppose you could machine down the flywheel, removing the ring gear flange, right down to the clutch cover diameter, but it would still be quite a lump to spin around.

Richard
Bristol

hyve
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Postby hyve » Mon Aug 18, 2008 10:51 am

Like you Richard I'd like to know what people who've retained the clutch do here. The absence of a response is interesting.....
Extra mass of any sort is the enemy of the EV builder and I agree, you don't want the old flywheel in there. By the time it's adapted to the motor, machined down to a minimum etc you may as well start with a steel disc. Warpage due to heat will not be a problem since the clutch is not being used for start-off, only gear synchronisation.
Again, since the clutch has only this function, and the E-motor has most likely significantly less power than the ICE it replaces, a smaller clutch could be used. But the combined mass of both clutch and drive plate will still be a fair bit which we could well do without.

I think you'll find that ball bearings will cope with the kind of brief end loads which occur during gear changes; as to extra radial loads: I expect there must be increased wear, though how it affects bearing life depends on how much surplus the motor designer has allowed. Most likely it will not be a problem.

It really would be useful to hear what others have done to resolve this issue.
Peter Ph

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ChrisB
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Postby ChrisB » Mon Aug 18, 2008 11:14 am

Can only post my findings and ownership of the Fiesta which didnt have a clutch either.

I must admit that around my area I rarely needed to change gear, top speed flat out in second was about 35mph and the motor was at its most efficaint at that so as my local area speed limit was 30 or 40mph it use to stay in that gear 99% of the time.

Yes it did take folks a few gearchanges to work out how to change gear without a clutch but not many, the harder problem I saw was when they came to rest as they would be frantically pressing a non existent clutch pedal and that seemed to un-nerve them far more.

As for retaining a clutch then as others have said you would need to keep some sort of a flywheel etc for the presure plate to attach to which does seem somewhat wasteful.

My own feeling is you have to remember its a retro fit and hence the vehicle will be different :? and so people need to remember this when they are driving it. It also helps them understand that they are not in a normal car that has a range of 500miles and they have to drive it far more carefully.

ChrisB
I reject reality and substitute my own !!!!!!

GregsGarage
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Postby GregsGarage » Mon Aug 18, 2008 2:01 pm

Both of my conversions are clutchless. 2nd and 3rd gear are used almost exclusively. With the Volvo, 2nd gear is good for up to 45mph and 3rd pulls nicely from 5 to 65mph. So I can leave it in third unless I come to almost a complete stop. At slow speeds downshifting from 3rd to 2nd isn't much of a problem.

The Fiat is good for around 35mph in 2nd and just over 50mph in third although I am changing the tyre size from 135/70R13 to 135/80R13 to try and gain a little more top speed in 3rd and also the later size has Low Rolling Resistance options for tyres.

Up shifts without a clutch is normally a little slower due to having to wait for the motor to spin down and match gearbox speeds. With the Fiat I have found that I can downshift by "blipping" the throttle in neutral. This spins the motor up and helps to match motor/gearbox speeds. NOTE:You must not use this technique with a series wound dc motor as you are likely to damage the motor and cause injury to people if the motor flies apart! :evil: The Fiat uses a permant magnet motor who's rpm is limited by voltage even without a load, a series wound motor without a load will continue increasing RPM till it flies apart!

Keeping the clutch means easier downshifting, but sacrifices weight and complexity.

Losing the clutch makes for a simpler motor to gearbox connection and less weight, but sacrifices some driveability particularly if the motor/controller is a bit undersized and you find you need to downshift quite often. Also if you have regen, it can make shifting difficult in some cases. My Fiat has regen activated by the brake switch, so changing gears with the brake on is not possible as the regen stops the motor.
Greg Fordyce

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MalcolmB
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Postby MalcolmB » Mon Aug 18, 2008 2:35 pm

Greg

When you say that 3rd pulls nicely from 5 mph, is it possible to pull away in 3rd and if so what sort of current does this take? I'm just trying to get a feel for how practical it would be to do away with the clutch and gearbox entirely, and run a single reduction. Your Volvo weighs around twice as much as my mini, so if you can pull away in 3rd I should be OK (assuming roughly same torque at wheels)...


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