Does squirel cage AC motor survive shaft removal from rotor?

[PekkaNF]

This might be a daft question, but how likely it is to press short shaft out of AC motor and press somewhat longer shaft home without degrading motor?

The motor is sandard squirel cage (induction) motor of 1,1 kW, three phase. I have several option and I'm very tempted to modify motor heavily and keep rest of the contraption simple.

I tried to google it but I'm not convinced.

Has anybody tried it and how did it go? Is there any tricks or something to avoid?

Pekka

[awemawson]

John Stevenson is the man to ask, as he is repairing and modifying motors all day long as his day job - no doubt he'll be along in a while 

[Manxmodder]

Pekka, I have done this type of modification to 2 motors and they both worked fine after.

One was for a small bench drill press and the original motor was burned out. I had another similar sized motor but the shaft rotated in the wrong direction,so I pressed the shaft out and reversed it relative to the rotor.

The second one I made a shaft for as I needed a much longer shaft nose than the standard one to mount a multi vee pulley on.

If the press fit doesn't feel tight enough when you re-assemble then use a bit of loctite retainer on the shaft just as the last couple of inches of pressing is being carried out.....OZ.

[awemawson]

I had always assumed that the rotor laminations had a keyway in the stamping - just shows what happens when you assume 

[mexican jon]

As Manxmodder has said it is perfectly doable we quite often do it with large motors in the oil industry, if the drive end of the shaft has been damaged. I've done it with small motors as well normally when I was skint or to tight to buy the correct motor 

[Manxmodder]

I had always assumed that the rotor laminations had a keyway in the stamping - just shows what happens when you assume 

If memory serves me correctly I think some large industrial motors do have a keyway through the rotor laminations,but I can't see why they wouldn't still be able to be separated from the shaft.....OZ.

EDIT TO ADD: Pekka,if you're going to give this a try then be aware that the pressing collar/tube you use to support the rotor on needs to be a close fit to the shaft size or you risk distorting the laminations on the side that the shaft exits through....OZ.

[mexican jon]

I had always assumed that the rotor laminations had a keyway in the stamping - just shows what happens when you assume 

If memory serves me correctly I think some large industrial motors do have a keyway through the rotor laminations

The large motors we use in the drilling industry (1100 -1250 HP ) do indeed have a keyway machined in the shaft and the rotor, and yes they do come apart as that is one of our 5 yearly inspections 

[lordedmond]

Yes done many when I did armature and stator winding

Make sure you use a tube to push close to the shaft

They are much easier than a DC one as the comm comes off the other way and needs desoldering and re soldering

 As has been said loctite is your friend

Stuart

[PekkaNF]

Thank you. Very nice to hear that.

I asked from the local group too and the consensus seemed to be that very old and import motors should be easy, but modern domestic made are "impossible"????? Something to do with manufacturing method.

Maybe there are some different flavors? I'll try one domestic one and if it does not work, big boohoo...I just have to find next cheap/free candidate (maybe italian import).

Pekka

[PekkaNF]

John Stevenson is the man to ask, as he is repairing and modifying motors all day long as his day job - no doubt he'll be along in a while 

I found this thread:
http://madmodder.net/index.php?topic=6096.0

Least it worked out for him!

Pekka

[PekkaNF]

aargh...got two motors and both are hard to modify:
1) Finnish made botor that apparenty has the rotor shrunk supertight (maybe used residula heat from aluminium casting).
2) Italian motori is a two piece design..Back bell is integral with shell.

Has anybdy modified AC motor bearings to angular contact bearings?

Pekka

[PekkaNF]

aargh...got two motors and both are hard to modify:
1) Finnish made botor that apparenty has the rotor shrunk supertight (maybe used residual heat from aluminium casting).
2) Italian motori is a two piece design..Back bell is integral with shell.

Has anybdy modified AC motor bearings to angular contact bearings?

Pekka

motor #1 flunked on insulation tester...one phase very low on 500V, low voltage measurement does not indicate anything too special. Bridges are off ie. coils are floating. This was the one that mechanically would disassemble easiest and would modification, but rotor is a bit of mystery.

Connection box has quite a bit of rust in there. I spayed it with first rust remover oil and CRC product I got my hands on. Then tipped it upside down, maybe it's just some gunk on connection box?

Motor #2 is nice and works, but can't work on it. It's awkward size and shape.

Probably should buy new italian motor and try it.

Pekka

[PekkaNF]

Motor #1 is a toast. Turned out that rust was not a conductor...it was an insulator.

All toasty inside. Now question about rotor on that motor is purely academic. Have to lug it around a bit, need a big press to coax it out, I don't care now how it survives.

Pekka