source of vibration?, car vibrates at ~ 3k RPM Options

[astronomerdave]

My 914 was converted to an electric vehicle; other than having an electric motor instead of a gasoline engine, the drivetrain is the same as you're familiar with. The electric motor has a hub adapter which matches the bolt pattern of the original flywheel. Then I'm using the orig flywheel, clutch, and transmission. The problem is that somewhere around 3000 RPM the car starts to vibrate (and gets worse with increasing RPMs).

Now at least two or maybe three other guys who did this same conversion had similar vibrations and all of them found that they had troubles with their transmissions. So I jumped to conclusions and thought the same. But I just discovered that I get the same vibration whether driving, sitting in neutral, or sitting with the clutch disengaged.

I have my own new theories now but want to hear what some of you other people think.

Thanks,
Dave

p.s. images of the car, including some parts such as the motor, flywheel, etc. can be found here: http://www.halestorm.us/evconstruction.htm

[charliew]

Are you sure the pressure plate and the flywheel are balanced? The flywheel can be checked out of the car on the motor for trueness but the balance can't be. Just put a dial indicator on the back surface then on the od and turn it slowly to check for trueness. A flywheel shop can check the pressure plate and flywheel for balance, they should be balanced individually and checked together also then marked so they are a matched set.

The only thing spinning at the engine speed is the motor and flywheel and pressure plate in neutral setting still and the clutch pushed in. The clutch disk and input shaft will turn from some internal friction but probably not at the same speed. The bearings in the motor won't last long with a vibration.

Is there a input shaft bearing in the crank hub in the picture? If there is no bearing push the clutch in while spinning up to 3k and if it gets better the clutch disk may be floating around inbetween the pressure plate and the flywheel and not centered with the clutch out. You gotta have a input shaft bearing to support the input shaft on the clutch disk end. If all else fails check the trueness of the adapter.