Genset bearing end cap failure - what caused this???

[Ashton Crusher]

There are 12 photos here

showing a genset that has failed twice the same way after only several dozen hours of running, most of that just to start it periodically each week to make sure it's working. In the photos there is a round gray generator/alternator and you can see the end cap on it. If you look at the small round holes in the end cap you see that the screws that hold it to the frame don't seem to be there. You can see the broken screws (look like Allen head to me) laying on the baseplate. As far as I can tell this end cap holds the end bearing for the common centershaft that goes thru the middle of the generator/alternator and is direct coupled to the propane powered engine that powers it. These small screws have sheared like this twice now. The only reason I can think of is that the bearing in the end cap seized. It's my sister and brother in laws backup generator and the company didn't really want to fix it under warranty the first time, trying to claim "abuse" and is less thrilled about it going out a second time. The company claims they have never seen this happen before, much less twice on the same genset.

Thoughts on why it failed????

[Ed Pawlowski]

Speculation on my part, but I doubt abuse has anything to do with it. I'd think some sort of misalignment of the bearing and/or shaft. Under normal running or even constant full speed operation, bolts don't break unless stressed beyond capability and intended use. A very small but constant whipping of the end shaft due to misalignment can cause bolts to break from the stress. I'm talking thousandths of an inch, not even visible, but at 3000 rpm, it is a bit problem.

Rather than try to weasel out of the fix, the manufacturer should be doing more investigation.

[The Daring Dufas]

When I was installing and servicing a lot of Generac units, I had the phone number of the vice president of the company who was in charge of service. Whenever some strange thing like that came up, the boss was very interested in finding out what was up so it didn't happen on a lager scale. I would see if I could get hold of someone up the company ladder about the problem you're having since it's possible a defect got past Quality Control or the unit may have been damaged by mishandling somewhere down the line and you have a bent shaft. o_O

TDD

[harry]

Agree with above. Or they have got a batch of faulty bolts. Or the rotating bit is out of balance. But in any event not the fault of the user.

In the UK they could legally demand money back/new generator as the generator was not fit for purpose.

[David L. Martel]

Ash,

What does this end cap do? Looks like just a cover. Is there a gasket between the end cap and the gen.? Is vibration excessive when you run the gen.? Have you run the gen. for an extended period (several hours)?

Dave M.

[Ashton Crusher]

All I know at this point is what I've seen in the pictures, it's not my genset, it's my sisters back east. The last time I was there the electric was out and the genset ran for about 12 hours and seemed fine.