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motor bearing problem

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I bought my ADC shunt motor used on ebay. I put the car together and got it running. The motor made a sound like a loud wheel bearing which, since I'm not that familiar with large electric motors, I didn't know if it was normal or not.

I had the bearing replaced and it sounded much better, much quieter.

Now, about 3 months later, the motor is making the same loud bearing noise that it did before.

My questions are:

Could I have received a bad bearing?

Could the shaft be bent and put undue stress on the bearing causing it to be louder?

Could the bearing be improperly seated in the front motor mounting plate?

Could the motor and trans be out of alignment to such an extent that the bearing is overstressed?

Could there be some other reason or cause for this bad bearing noise?

I am using a Lovejoy spider coupling with a plastic insert that should compensate for a small misalignment.

To fix the problem, I've got to take most of the system apart. I would like to replace the bearing but I'm afraid that the new bearing will also fail.

Thanks for your ideas.

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· Registered
1,033 Posts
If the motor shaft is bent, then it will probably be difficult or impossible to turn by hand, and/or it will probably vibrate badly when run up under no load.

based on the photographs I am going to go with the inadequate adapter plate theory. With a large amount of standoff like that, held together by bolts it won't take a lot of force to push things out of alignment under load enough to damage stuff.

Unless of course the 2nd bearing that failed was the /other/ bearing in the motor. Always replace in pairs :D

Good luck, and stick with it. You'll get it.
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