Re: Repairing cracked castings


Guy Fawkes wrote:
> John Stevenson wrote:
>
> > First off I thought it was powered by a Lister D so where does Diesel
> > engine driven come into it.
>
> ok, I thought it was a diesel, doesn;t really make much difference
> though what the prime mover is
>
> >
> > Secondly I have spend a greater part of my working life repairing
> > rotating electric motors, generators and the like.
> > Many have been to my workshops and see the variety that passed thru
> > here so the following is fact, hands on dirty work, no text book
> > reading.
>
> good
>
> >
> > Many items come to me for repair damaged to the point that this
> > casting is but the owners / users had no idea. People don't strip
> > stuff that 's working just to look so there are many applications out
> > there in the same boat.
> > No excuse, just pointing out the potential bombs you walk by every day
> > but I never read about these, do you ?
>
> world of difference between not knowing something is US and dangerous
> and bodging something so it is US and dangerous.
>
> sure, the former is negligence, people SHOULD take more care, but it's
> still hugely preferable to people who have reason to believe something
> has a problem and stll ignore it
>
> at least the former will listen if you buttonhole them
>
> >
> > Now lets take this one stage further, we have a cracked bearing
> > housing on one side on the tail end of a generator. As our esteemed
> > am/was marine engineer points out motors and generators have a small
> > air gap between rotor and stator.
>
> yup
>
>
> > So what happens in PRACTISE when a housing lets go, and it has to be
> > severe is that the rotor touches the stator with a loud grinding noise
> > and it is either stopped if attended or get gradually worse until it
> > stalls or seizes.
> > The rotor doesn't fly out as it's retained by the drive bearing.
> > Even if both ends were to explode it would take an axial force to
> > shear the drive coupling and push the rotor at least 8" whilst trapped
> > in the confines of the stator.
>
> generally speaking I agree, that is usually what does happen.
>
> >
> > In extreme case I have seen large driven end shields with three cast
> > spokes to support the bearing housing crack and then snap.
> > Result is as above, a lot of damage but all confined to rotor and
> > stator fields INSIDE the motor.
> > The cast legs that fail were not rotating and so have no kinetic
> > energy to fly out, hit anyone or stir their tea for that matter.
>
> generally speaking, I would agree with you, but on one occassion I saw
> (or rather heard from outside) an exception where the rotor delaminated
> and sent several shards of steel flying, again, I would agree with you
> that this should also stay inside the housing, but on this occassion
> one piece didn't, which we only discovered when the standy refused to
> allow injection because there was no oil pressure, pull the stick, no
> oil, which was odd because it was a constant fill sump with external
> tank etc, that shard of laminate, size of my palm, had punched clean
> through the sump of the other generator.
>
> one in a million?
>
> mebbe
>
> but I haven't seen / inspected the OP's kit, so I don't make ANY
> assumptions about the state it is in, and while I take the point YOU
> are making here, you too will do a 180 and take MY attitude the moment
> the OP asks you for a fixed price quote over then net, and mumble
> something about crystal balls.


John everyone here knows you dont know WTF you are on about, so no need
to keep rubbing it in!

k

Ps: dont think the new medication is worrking that
well....................lol

.