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Growling ST 3000 Watt generator head

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BruceM:
My ST 3000 watt head makes a strange grrrr noise when loaded.  It increases with load.  It's loud enough to mask some of the engine mechanical noises.  The unit does not run hot, and the output is good under load.  I did not repack the bearings yet, but they feel smooth.

Any thoughts about the source of this sound?  Could it be the "dog house"?

Bruce

SHIPCHIEF:
Could be either or both.
My doghouse was flimsey and falling apart, so I replaced it with a smaller good J box, and remote mounted the volt meter and pilot light, with a hobbs meter and the control rheostat (which crapped out and I disconnected) In a cool looking grey steel box on the wall.
Nonetheless, noises continued. I dismounted and disassembled the gen. The bearings were not damaged, but they did not have grease in them, in my opinion, they still had cosmoline preservative in them, that's what it smelled like to me. The hotter they ran, the drier it got. it was beginning to form a shellac like coating that I had to scrub off in gasoline or diesel fuel (standard parts cleaner around here). After that, I blew the bearings out with air, inspected them, and hand packed them with some good grease. They did not have bearing shields on the outside, so I didn't worry about overpacking. When I ran it again I just wiped up the excess that was pushed out the generator ends!
Oh, and my generator was rattling on the base. I engineered a slide so I could adjust it while it was running, but the clearance needed to allow sliding allowed a hellaceous rattle, so I had to build hold down straps as an afterthought (ugly spot!) >:(
Scott E

quinnf:
Scott,

I'm glad to hear my genny wasn't the only one that leaked grease after I repacked the bearings.  Thought I had broken a seal.  Didn't recall seeing one, but figured there must have been something there.

First thing I did when I got my ST-5 was take it apart and remove and re-pack the bearings.  Was planning to replace them, but they were of nice quality, so I left them in there.  I have the Timken number so if they get rough, I can always replace them later.

As far as growling noise goes, that usually indicates either a dry bearing or one that is under an improper load, such as if the bearing is twisted in one of the end housings.  The fact that the growl increses under load is consistent with a bad bearing. 

Best thing to do is pop the ends off and inspect the bearings.  Mine were packed with something that had the consistency of warm roofing tar.  Very stiff creamy yellow goop.  I washed the residue out with paint thinner and a brush, then blew the solvent out with air, then packed with moly grease. 

Reassembled genny, then hooked it up to the dizzle.  After running about an hour, I had about a tablespoon full of grease that extruded out one end. 

The genny now spins easier and is silent except for a barely audible hysteresis hum once it gets up to speed.  No mechanical noise at all.

Hope this helps.

Quinn

Doug:
Good Bearings are cheap by some Fags or SKF, avoid Nachi poor heat treating(as of 94 when I worked in the motor shops and used them in quantity). Get a C3 clearence bearing of course and in my opinion 2RS sealed are better. If you must use 2Z fill the inside of the end bell with NLG1 grease (Moly type not a bad idea). 2Z sheilded bears will to a degree pump grease from the resevor you made and lube themselves to a point.
If you like to add a greas fitting thats fine but also add a purge port so you can pump out the old grease when you regrease. Leave the purge port open and run the generator untill its warm to allow for expansion before you replace it. they could be to tight loose egg shaped...
The bearing manufacture should be able to provide you with proper shaft and housing size limits for the bearings I would check this before instaling new ones in case you have a problem. Or alternatively an EASA member electric motor shop will have proven dimensions for shaft size end end bell clearences.
When putting bearings on a generator shaft preheat the bearing in an oven to about 200-225 F(best do this when the wife is not home) it should slide on the shaft easy but be quick about it.
Never hammer on a bearing this causes brinelling and bearing failure. This much said you will most likely hammer on a bearing so make sure you only hit the inner race at least.

Over greasing is bad for bearings a couple of shots a year for bearings without a purge port is probaly enough...

Brushes.... thats a hole lot of information for me to type. In a nut shell ask the guy you got the head from for spares. Failing this make what you buy is meant for slip rings and not DC coms, although it not a huge deal they are different the slip ring types use a harder matrix more graphite than carbon black, Some have sinter copper in the mix..... Huge debate where I work over types of matrix mix and hardness...

Hope this can help
Doug

BruceM:
Gentlemen, My sincere thanks for your sage wisdom and advice.  I'll pull the bearings and check them out carefully.

I was hoping to get a 3KW PM generator from George B soon, he's got 120volt ones now, but I need the 220 volt which is still in the works.

Bruce

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