I have this old squirrel cage induction motor (nameplate below) that I just replaced the bearings on. When it runs, there is a rattling noise that gradually gets louder and then softer, repeating every ~5 seconds. Here's a video of it in action. I don't think the motor made this noise before replacing the bearings, but I'm not sure. (I just bought it and the only time I ran it was briefly at the seller's house.) Does anybody know what might be the source of this rattle? I've put pictures of the motor and the rotor below, as well. Thanks! motor

nameplate rotor


1 Answer 1


I listened to the recording and I suspect there's a loose bearing in the motor. Here's how to test it:

With the motor OFF, grab the end of the shaft and pull up and down on it as hard as you can. There should be NO wiggle at all in the shaft when you do this.

  • $\begingroup$ Thanks for taking the time to listen! I suspect that the front bearing is moving in the housing then. That bearing was in very bad shape when I removed it, and it looked a little bit like there was a tiny bit of wear on the race when I disassembled the motor with the new bearing last night. I'll check for any tiny bit of wiggle with a dial indicator tonight, and select your answer if there is play. Then I'm gonna loctite it in place and use the motor until it dies :D $\endgroup$
    – user278411
    Commented Aug 13, 2019 at 15:04
  • $\begingroup$ very good! by the way, boogered-up bearing lands can be built up and returned to service with epoxy paste into which fine metal shavings have been blended as thickener. you extract the bearing, glob the epoxy into the land, insert the bearing, and spin the shaft to get things lined up, then let the epoxy cure. $\endgroup$ Commented Aug 13, 2019 at 21:54
  • $\begingroup$ Indeed there was play in the shaft near the front bearing, small but discernible even without an indicator. I'm going to put some Loctite 660 liquid metal bearing retainer on it tonight and get it back running. Thanks again for yr help! $\endgroup$
    – user278411
    Commented Aug 14, 2019 at 13:43

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