# Alternative to Flywheel/Clutch Coupler



## RE Farmer (Aug 8, 2009)

As a suggestion, consider something like a magnetic or electric clutch.

Or, how about adapting the torque converter lockup mechanism present in all recent automatic trannies, admitting beforehand that I don't know exactly how they operate.


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## Woodsmith (Jun 5, 2008)

A sprag clutch (freewheel or one way clutch) would seem to be a great option as it would allow up changes while the motor slowed down and down changes while the clutch slipped faster then the motor.
It would also remove the risk of over speeding the motor when coasting down hill.

However, finding one suitable for automotive use, able to handle the torque and is cheap is the difficulty.
I thought about the PTO freewheel adaptor used on some tractor impliments but they are like big course ratchets and so no good for an EV.
Proper Sprag clutches are costly and need accurate alignment to handle the torque at low speed apparently.

Magnetic clutches, like those on AC compressors are also good but I haven't found one yet that would handle the torque or the power transmission of an EV motor.


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## RE Farmer (Aug 8, 2009)

I'd considered the sprague clutch, but since I'm installing an AC, I wouldn't be able to regen.

OT: Since you are a tractor person. I've thought of converting my 9N to electric, but I think making ethanol with a solar still would be much more cost effective. I think Ford originally envisioned burning alcohol in his tractors built during WWII era.


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## EVfun (Mar 14, 2010)

Here is an idea. Since an EV doesn't really need to slip the clutch a solid splined engagement may work. It is designed to release for shifting and it is small diameter and light.


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## madderscience (Jun 28, 2008)

Any spline type clutch is going to have to handle the shock force of engagement and disengagement. Without some sort of give or a synchronization mechanism, it is going to be really easy to damage the clutch or what it is connected to (either the motor and/or transmission); whichever is weakest. There's a reason for all the springs and the friction engagement mechanism of modern automobile clutches. If you only use such a locking mechanism as a range selector switched at low speeds it might work, but under those circumstances you don't need a clutch at all anyway. 

Here is something that might work but would be an advanced fabrication job. Assuming you are using a small vehicle like a geo, etc. Find a synchronizer out of a large manual truck transmission, and use it as the coupling mechanism. You would need to modify it for momentary disengaging, and find a way to run it bathed in transmission fluid, and attach the locking splines to both the motor shaft and tranny shaft.. The larger size should be able to handle the shifting loads and it would provide the positive locking with less rotating mass than a flywheel would.

Simpler option (working for me): A high performance automotive clutch coupled with an aluminum flywheel and pressure plate can knock about 1/2 the weight off of a standard clutch and flywheel assembly (easily around 10lbs of the highest speed rotating weight in the car), and still retain full function (if not better) vs. stock. If you drive anything relatively modern and japanese, or even slightly popular with the performance crowd, then chances are you can order one off the shelf for not too much money relatively speaking.

Of course in any EV application you can knock the ring gear off the flywheel since there is no need for the starter motor. that will be about 1 or 2lbs of rotating weight right there. Any machinist can also shave several pounds off an otherwise stock flywheel though it will probably be up to you to research how much weight is safe to remove, and from where.


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## Woodsmith (Jun 5, 2008)

How about cone clutches or multiplate clutch packs from motorbikes?


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## RE Farmer (Aug 8, 2009)

MAD: I have located AL. flywheel (Fidanza), but I've never seen AL. or light weight pressure plates. Any sources?

Yes, I was already planning on loosing the ring gear.

WOOD: I've also found 5" multiplate (similar to motorcycle), racing clutches (expensive and I'm not sure they're any lighter), but they add several more inches of length to the drive line which I don't have room for.


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## DavidDymaxion (Dec 1, 2008)

Kennedy Engineering Products makes lightweight pressure plates, I have one in my car (and a Fidanza flywheel, it saved about 10 lbs of geared, rotating weight, the best kind to lose!). Another benefit is the KEP pressure plate has much high clamping force. Downside: I have already had to replace a clutch cable! For many cars you might be better off with a grabbier clutch disk rather than higher clamping force.

Some folks have gone to small diameter racing clutches, too. There are Chevy V8 to many other car adapter kits.


RE Farmer said:


> MAD: I have located AL. flywheel (Fidanza), but I've never seen AL. or light weight pressure plates. Any sources?
> 
> Yes, I was already planning on loosing the ring gear.
> 
> WOOD: I've also found 5" multiplate (similar to motorcycle), racing clutches (expensive and I'm not sure they're any lighter), but they add several more inches of length to the drive line which I don't have room for.


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