Effect of keeping clutch on Electric motor

Technical discussion on converting internal combustion to electric
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Martin
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Effect of keeping clutch on Electric motor

Post by Martin »

While checking the adapter plate requirements for a conversion which was intending to keep the clutch,

it became obvious that the pressure delivered 'lengthways' from the thrust bearing (~500kg), is eventually forced up against the flywheel. Thankfully in an ICE the flywheel is bolted to the crankshaft (which has very large heavy bearings).

Now for the conversion, where the electric motor is replacing the ICE, and the flywheel is adapted to the electric motor's shaft...

Is this likely to damage the electric motor bearings as it forces 500kg+ of pressure on the shaft - trying to push it out the other side of the motor?

If the electric motor's bearings were 'tapered' this may be an non-issue, but why should they be? If they are only designed for radial forces... maybe something needs to be added in to protect them.

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acmotor
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Effect of keeping clutch on Electric motor

Post by acmotor »

Martin, the thrust bearing only supplies maybe 200Newton of force to the release springs of the clutch pressure plate (not the total pressure plate force as there is a lever action at the plate). That is 20kg if you think of it as a weight. This is only applied to release the clutch (during gear change).

In an ICE this is taken by the crankshaft bearings that are typically only white metal (forced oil lubricated) plain bearings.
On a emotor, the bearings are ball bearings easily capable of this amount of axial force continuously. Most good emotors state the axial loading capacity in the specs so you can confirm this.

To remove any guesswork, measure the release force of the clutch you intend to use and check the emotor data.

I am assuming here that you intend to mount the complete flywheel/clutch plate/pressure plate assembly to the emotor shaft.
You may wish to machine away some of the flywheel if it is a massive one as you won't need its inertia, just the clutch function.
i.e. ring gear can come off etc.
Do take the effort to machine with minimal runout and consider a dynamic balance for a smooth future.

Some people will talk you out of keeping the clutch, however, you will not regret keeping it, even though it may be more work to fit. Yes, you can 'get away' without the clutch, but get on better with it !
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Martin
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Effect of keeping clutch on Electric motor

Post by Martin »

Thanks acmotor, the difference between 500 and 20kg is considerable, so I'll check what the thrust bearing is capable of and hopefully keep the clutch assembly.

Of course you're right about not needing the inertia of the flywheel, but I may leave it alone to save time for now.

I haven't viewed the specs on the motor's axial loading, hopefully the manual will mention something, if not, at least the bearing type perhaps.

As this axial consideration was the reason for dropping the clutch so to speak, it looks like now it will be acceptable to retain it - I would prefer it stays myself...
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evric
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Effect of keeping clutch on Electric motor

Post by evric »

The other consideration when keeping the clutch is ensure that it will handle the increased torque available fron the electric motor. Many people upgrade the clutch plate when keeping the clutch.
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acmotor
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Effect of keeping clutch on Electric motor

Post by acmotor »

Good point.
Can I throw another in though.... if the standard clutch (in good condition !) slips then the emotor torque is likely too much and gearbox will be stressed, maybe break. (assuming clutch slips before it breaks by design !) You may be tempted to fit a new plate while you are there though.
Anyhow, these are all numbers in data sheets and can be checked before you proceed.
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