It is incredible how the smallest details in the manufacture or repair of electric motors can cause dramatic failures. We recently worked on a customer’s motor which had obvious signs of incorrect bearing housing tolerance. This motor’s bearing housings were too tight causing an internal preload on the opposite drive end bearing. Basically, once the motor gets hot, the balls in the bearing are being compressed. The heat generated from this added friction caused the inner race to thermally expand and become loose on the shaft. Because the bearing became loose, it started spinning on the shaft causing damage to the shaft.

It is difficult to take a picture of the internal preloading wear on the inner race, but we are able to share an illustration from of internal preload from the book “Rolling Bearings Handbook and Troubleshooting Guide” by Raymond A. Guyer, Jr.:

 

This picture helps to show what the wear looks like to the human eye. In addition to relying on engineering books to make our team smarter when it comes to motor repair, our technicians have an average of 16+ years of electric motor repair experience. This long tenure, coupled with strict standards for motor repair specifications helps us ensure the longevity of your motor repair. Check out our Machining Capabilities here.

This motor user fortunately stopped the motor before the rotor could drop on the stator windings. A destroyed winding would have caused a much more expensive repair or replacement decision.