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radkins
09-26-2015, 05:31 PM
I already have this fixed but thought it a bit interesting, last year I bought a NEW 5 HP 3PH GE motor still wrapped in plastic and strapped to a small chip-board skid so it had zero time on it. This was used for nothing but an idler motor for my 3 PH converter and as such has never had a load of any kind on it, now after an estimated 200 HRs (probably less) the rear armature bearing went out! I had noticed when I switched it on a couple of days ago it didn't sound exactly right but it seemed to start and run normally, after an hour or so it started making a kind of low-key squealing noise that went away when I tapped on the back housing plate but when I shut the power off and it started to spool down it suddenly went into a shriek mode and stopped a LOT faster than normal! I removed the armature and sure enough the rear bearing (an NSK) was rough when turned by hand, this is just a common 6203 bearing that I keep on hand for lawn mowers and automotive belt idlers so I installed a new one and all is back to normal now. I just thought it odd that a brand new motor would K-rap out like that in such a short time with no load at all on it? Of course I suppose the failure here was the NSK bearing but aren't those supposed to be a reputable brand?

lakeside53
09-26-2015, 06:02 PM
Unusual.. maybe someone bashed the motor shaft while it was strapped to the pallet and damaged the bearing? Idlers are a bit rough on bearings if not mounted on rubber feet, but I'd expect a lot more time than that.

btw.. 6203 (15mm shaft) sounds awfully small for a 5hp motor.

Bruce Griffing
09-26-2015, 06:16 PM
Where did you get the motor? I suspect that some ebay and craigslist deals come from employee smuggled rejects. If it came from a reputable dealer, that should not be the case. Just a thought.

JoeLee
09-26-2015, 07:50 PM
It sounds like the grease just dried out and caused the bearing to fail. Motor manufacturers some times order bearing from the bearing manufacturer and specify the type of grease they want the bearing loaded with depending on the application. The mfg. loads the bearing with the specified grease and some may have slipped through with out getting greased.

JL.................

radkins
09-26-2015, 07:56 PM
It was surplus from a large auto parts factory near here (Denso) so I'm sure it was not a reject. That bearing is the rear bearing and the front one is a lot bigger, the 6203 is the only bearing I keep on hand (seems like everything has one of those in it somewhere!) otherwise I would have replaced the front one too. I wouldn't have been at all surprised if the motor had come from Harbor freight or such but I just thought it odd that a brand new GE motor would fail so soon especially under no load, in any case the motor is again running smooth and quiet.

Mcostello
09-26-2015, 09:54 PM
Any one can make a bad part occasionally, it is when it becomes a habit that it hits the fan.

EddyCurr
09-27-2015, 12:04 AM
It was surplus from a large auto parts factory near here (Denso) so I'm sure it was not a reject. ...

but I just thought it odd that a brand new GE motor would fail so soon especially under no load, ...Perhaps an instance of False Brinelling ?

.

Paul Alciatore
09-27-2015, 01:09 AM
Virtually all parts exhibit an "S" shaped curve of failures vs. time. There are always a few initial failures in the first minutes or hours of operation. That number diminishes and stays low for most things until some point in the life cycle where wear of one form or another takes over and the curve starts to rise again. It rises to a peak and then starts to drop again due to the fact that there are fewer units left to fail. When the last one fails, the curve hits zero and stays there.

Anyway it is no surprise to find a few early failures in any product. It is a fact of life.

ikdor
09-27-2015, 04:11 AM
Perhaps it was stored in such a way that the rotor pushed the non locating bearing. If the bearing then got stuck in place the preload spring would not work. Operating the motor without anything attached might not break the bearing free either.
The lack of preload would kill the rear bearing first as the sliding balls cause surface damage, the front will have a bit of damage as well but being much larger it will take more abuse.
The infant mortality theory is also likely as bearing life is a numbers game, for all the brands.
Igor