I have an ancient GE 1/2hp 66 frame single phase motor on my 1949 South Bend, and lately it has started making a noise I don't like. Actually, I like dead silence out of motors, any noise I don't like, but this is an annoying buzz. It doesn't vibrate, it just buzzes. It sounds like single phase motors often do while starting, but once they spin up the noise stops.
When it's slowing to a stop, I can very clearly hear the centrifugal switch clicking back closed.
If this were a 56 frame motor, I'd just replace it and toss this battleax. I have the feeling that trying to replace a 66 frame motor would be spendy. (Buying *any* motor when you need one is spendy, the only way to get them cheap is to buy them when you don't need them.) I probably have about 4 56 frame motors sitting around anyway.
I suppose this problem is either that the centrifugal switch is failing to open at speed, or the start cap is drying out, probably the former. I don't think it's a cracked rotor bar or end ring, as those usually vibrate. I also don't think the stator windings came loose, this normally causes vibration too.
It happens regardless of spin direction. The noise doesn't change any at all if I put oil in the oil cups. It's nothing to do with my lathe, I've tested it without the belts. The mounting bolts are tight, and the motor ran very quietly for many years and I didn't change anything about the setup.
It isn't a bearing noise. Anyway, the bearings are nice and smooth and silky when I turn the shaft by hand.
Anyone?
Grant Erwin Kirkland, Washington