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Old 03-21-2008, 01:10 PM   #1 (permalink)
Nomadic Chicken
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How Clutches Work

I've seen in threads that most electric vehicles have some type of clutch issue.
Either the car is left fixed in a certain gear or there is forced shifting - which implies to me shifting without using the clutch to disengage the motor(engine).

I know crap about cars.

I've tried howstuffworks.com and it seems kind of vauge to me. other than demonstrating that it uses a pressure/friction plate, it doesn't show where the engine and transmission tie into it.

Can someone explain to me why clutches seem to be an issue with EVs?

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Old 03-21-2008, 04:32 PM   #2 (permalink)
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I would imagine the clutch is often left out because not only does it save weight to leave it out, but you don't have to figure out how to attach the flywheel to your electric motor, and the flywheel is used as part of the clutch (it's one half of the pressure plate) it also allows for a simpler flex coupler (lovejoy coupling)

so you are simply connecting one shaft to another shaft, and have some leeway for some misalignment... altho you should always make sure shafts line up as perfectly as possible! but if you can figure out a way to get your motor shaft perfectly aline to your tranny, and attach the fly wheel to it, then go for it.

how a car clutch works is: you have 3 layers, attached to the engine is the fly wheel with a smooth steel surface, then you have a double sided clutch disk/friction disk of stuff simaler to brake pads that will "grab" the smooth metal on the flywheel surface that it's pressed agenst, then you have another pressure pressure plate that is simaler to the steel to the fly wheel, that is held to the fly wheel with a weird type of spring fingers, this sandwich squeeze the middle friction layer between the two smooth steel layers, simaler to if you were to pinch either side of a spinning disk your hand would want to travel around with the disk, when you press the clutch pedal it takes the tension off the springs and lets go of the center disk, that center disk is attached to the transmission shaft.

Last edited by Ryland; 03-21-2008 at 04:49 PM..
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Old 03-21-2008, 04:53 PM   #3 (permalink)
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I can't tell you why, if, or how clutches are an issue in electric cars.
I haven't built an electric or had the opportunity to work on one.
If you will allow me to spew here I can explain how most automotive clutches work.
Remember that you must dis-engage the engine from the transmission in order to stop the car.[ wheels stop--motor doesn't]
You must also dis-engage the engine & transmission to shift.[engine and trans spinning at different speeds]
The clutch in your car has several components to allow it to accomplish these tasks.
Flywheel - Directly attached to the engine
Driven Plate - Directly attached to the trans input
Pressure Plate - Bolted to the flywheel and sandwiching the Driven Plate to the Flywheel
Release Bearing - Attached to the clutch pedal
The Driven Plate is squeezed between the Flywheel & Pressure Plate.
It spins when they spin
as you push on the clutch pedal it pushes the Release Bearing into the Pressure Plate to force the Pressure Plate off of the Driven Plate.
As the Pressure Plate moves away from the Driven Plate the Driven Plate is allowed to spin free [or at speed with the trans]
so to recap
three plates
inner & outer go to engine
center goes to trans
squeeze & they all move together
un-squeeze & the two engine spin independent of the trans
It would be easier to illustrate with pics or a video.
Maybe someone can find you one, I don't have any on this computer,[ and I'm to lazy to look for them on the web]
I hope this helps you understand a little better.

When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity.
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Old 03-21-2008, 08:09 PM   #4 (permalink)
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Thank you guys.
I find that extremely helpful.
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Old 03-25-2008, 11:34 PM   #5 (permalink)
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Hey Waxy,

I had the exact same question about 2 weeks ago.

Then I took the Metro apart and figured it out!

Yeah, the first thing I did too was go to "How Stuff Works" - makes a lot more sense when you can see and touch the parts.

My Metro clutch looks EXACTLY like the diagram Ryland posted.

I am not sure if I will use the clutch or not in my EV. That question comes up about EVs all the time!!!

What I did was save the flywheel when I sold the engine, that way I still have it available if I do want to use the clutch with the finished EV.


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