Bearing replacement and clean up of electric motors

[Bobby Robbinett]

So I am rebuilding a 1990’s era machine that has 4 electric motors. I want to break down the motors, clean them and install new bearings. The motors are 3 phase so not much to them. The machine did get rained on tor several hours transporting it back to my shop. So it has a lot of rust. This is my first time reworking an electric motor. I have rebuilt many machines but never did the motors myself. I am fully competent wrt bearing replacement. My question to you guys is, what else should I look for or do to the motors while I have them apart? They all run fine so the windings seem ok. That is something I know would be best done by an electric motor shop. Assuming the windings are good, what else do you guys suggest I do while replacing the bearings?

[Carl Beckett]

Clean out dust and debris from the windings. Blow it out with air (I have washed before but recommend simple air blow out). Look for any loose 'bindings' and get some cord and rebind. Look for any damaged insulation that could arc to ground. I also give the end windings a fresh coat of motor winding lacquer.

If it has a start cap, there may be a cutout switch that runs on centrifugal momentum (single phase do, I do not know about 3 phase). Clean inspect and relube.

And sometimes I put a new capacitor, for good measure.

Many youtube videos on it - look there for some tips.

Unless windings degrade should run for many many more years with new bearings

[Matt Day]

Carl - there are no capacitors, it’s 3 phase.

I’d take it apart and make sure it’s completely dry. Clean out all the old sawdust and crud that builds up around the windings (air compressor and/or old toothbrush). Replace the bearings, check the wiring isn’t cracking or anything, and that’s about it really. Not much to 3 phase motors as you said.

[Mike Kees]

I have a phase converter at my shop (Big three phase motor) that I purchased used. After it was all hooked up and running I noticed one day that the bearings made quite a bit of noise on wind down. I switched off the breaker powering it and just pulled it apart. On mine the cleanup part was blow out the mouse terds and then I used my shop vac to suck anything loose up. Went to town and picked up new bearings and put it back together. I still think that three phase is magic.:D

[Bill Dufour]

Three phase is dead easy to do the bearings. No switches no centrifugal switches no caps. A quality motor will have bearing size listed on the nameplate. Use sealed bearings for dust. Easy to pull apart since both ends are free of wires.
I agree dust it off inside and add some extra varnish if it looks like it may help stop vibration of the windings.
Bill D

[Jerry Bruette]

Be sure to mark your end bells so they go back on in the same position, and make sure you don't swap ends with the end bells and the rotor or your motor will run backwards DAMHIKT.

[Frank Pratt]

Be sure to mark your end bells so they go back on in the same position, and make sure you don't swap ends with the end bells and the rotor or your motor will run backwards DAMHIKT.

At least there's an easy fix for that.

[Jerry Bruette]

At least there's an easy fix for that.

You still feel stupid until you figure out what you did wrong.

[Bill Dufour]

For small fan motors that are not reversible you can remove the fixed windings and flip it around to reverse the motor.
Bill D

[Mike Henderson]

For small fan motors that are not reversible you can remove the fixed windings and flip it around to reverse the motor.
Bill D

For a 3-phase motor. you just reverse two of the three wires to reverse the motor. But I assume you were referring to a single phase motor.

Mike

[Bobby Robbinett]

Thanks for all of the replies fellows!

[Bobby Robbinett]

Three phase is dead easy to do the bearings. No switches no centrifugal switches no caps. A quality motor will have bearing size listed on the nameplate. Use sealed bearings for dust. Easy to pull apart since both ends are free of wires.
I agree dust it off inside and add some extra varnish if it looks like it may help stop vibration of the windings.
Bill D

Bill do I have to disconnect any wire or the power cord to pull the rotor out?

[Bobby Robbinett]

Carl - there are no capacitors, it’s 3 phase.

I’d take it apart and make sure it’s completely dry. Clean out all the old sawdust and crud that builds up around the windings (air compressor and/or old toothbrush). Replace the bearings, check the wiring isn’t cracking or anything, and that’s about it really. Not much to 3 phase motors as you said.

Matt, any suggestions on how to clean up the shaft? I pulled the pulleys off the other day and the shafts look a little rough. I figure that I could just take some degreaser and white vinegar/baking soda to it with a Scotch Bright pad and give it a good cleaning, just want to get sone more opinions.

[Carl Beckett]

Does it look like the bearing could have been spinning on the shaft? The inner race of the bearing needs to be tight on the shaft - if the bearing got sluggish sometimes the race spins on the shaft and becomes a problem.

[Jerry Bruette]

Bill do I have to disconnect any wire or the power cord to pull the rotor out?

Nope. There's no wires connected to the rotor. One of the bearings will be a "held" bearing, the one nearest the output shaft. Might be held with a bolt on keeper or possibly a snap ring in the end bell.

[Jerry Bruette]

Matt, any suggestions on how to clean up the shaft? I pulled the pulleys off the other day and the shafts look a little rough. I figure that I could just take some degreaser and white vinegar/baking soda to it with a Scotch Bright pad and give it a good cleaning, just want to get sone more opinions.

I used to use steel wool and citrus cleaner/degreaser. That's all you should need unless there's galling where the sheave was, then carefully clean that up with a file/abrasive paper. You don't want to change the dimensions of the shaft where the bearings or sheave mount.

[Rod Sheridan]

Use C3 clearance bearings for electric motors and after cleaning the debris from the windings gently with a soft paint brush and low pressure air, perform an insulation resistance test…….Regards, Rod.

[Frank Pratt]

You still feel stupid until you figure out what you did wrong.

A feeling I'm very familiar with :)

[Marc Fenneuff]

Matt, any suggestions on how to clean up the shaft? I pulled the pulleys off the other day and the shafts look a little rough. I figure that I could just take some degreaser and white vinegar/baking soda to it with a Scotch Bright pad and give it a good cleaning, just want to get sone more opinions.

Try the blue scotchbrite pads on shafts first, not the green. The green ones will leave visible scratches on the shaft surfaces (of course you could then polish that out too). Too much abrading and too much polishing will start to mess with the tolerances as well.

3-phase motors are a dream to work on and run, provided you can power them. On some smaller 1-phase motors I have had to desolder a single lead to get the end bell off.

472377

[Bobby Robbinett]

Thank you guys so much. I plan to start disassembling the motors next week. Will do one at a time. There are a total of 4 motors but I only plan on breaking down 3. These go on a shape and sand machine. I have the entire machine pulled apart and am doing a full rebuild/restore on the whole thing. It has 1 shaper spindle and 2 sanding spindles.

I am taking the base and all of the parts of the shaping and sanding heads to get sand blasted and powder coated next week too. Only thing is that my powder coating guy is a month out to to my job.

With that said, I have toyed around with the idea of either sanding then prime and painting myself or buy a Harbor Freight sand blasting kit and priming and painting afterwards. That is a whole other topic though.

I have all of the worm gears, shafts, guide tubes, gears, sprockets and chains to disassemble and derust before I start sanding. I am also replacing all bearings, pulleys, belts, conveyer pads, rollers and gold downs. Should have a pretty nice machine when done.

[Jerry Bruette]

You could save a few dollars by not replacing the pulleys. I would check them for wear before spending unneeded dollars.

[Marc Fenneuff]

With that said, I have toyed around with the idea of either sanding then prime and painting myself or buy a Harbor Freight sand blasting kit and priming and painting afterwards. That is a whole other topic though.

If you sandblast at home, be sure to use the proper PPE, regardless of the media you use.

[Bobby Robbinett]

You could save a few dollars by not replacing the pulleys. I would check them for wear before spending unneeded dollars.

The stock pulleys are in horrible shape. I am not the original owner so I don’t know for sure but the pulleys look like they have been beaten to death. New ones for just the two sanding heads are $700 aftermarket that includes two motor pulleys and two spindle pulleys because there are 2 sanding stations. Haven’t priced the shaper head pulleys yet.

[Bobby Robbinett]

If you sandblast at home, be sure to use the proper PPE, regardless of the media you use.

Absolutely! I have to get a few more ppe items to even consider it.

[Charles Coolidge]

Seems like there was a motor shop here in town that did this work, including soaking/baking the windings. It was NOT cheap but the place did an excellent job.

[Bobby Robbinett]

Seems like there was a motor shop here in town that did this work, including soaking/baking the windings. It was NOT cheap but the place did an excellent job.

Yes I spoke with my local electric motor shop and for just the bearing replacements and no clean up or any additional services they quoted me $360 minimum for the big motor and $260 for the 3 smaller motors. I just figured that I could easily replace the bearings my self and do a good cleaning and inspection for far less. Like I stated above the pulleys for just the sanding heads are like $700 so I need to save money where ever I can.