"Han" wrote in message ...

"anon" wrote in
ng.com:

Han,

I've never seen a bad bearing in these small motors cause a fire, but
I suppose it is possible. The usual risk from hot bearings is thermal
breakdown of insulators within the motor windings and wires, possible
causing a electrical hazard.

If the bearings races or ball are pitted (not that you can see them
without destroying the the bearing set), replacing the bearings is a
very good solution for that type of motor. They will be ball bearing
sets, not sleeve bearings. When you get the replacements try to get
the "ZZ" type which have both sides sealed, as your device is
apparently used in a dusty environment.

Sometimes you get lucky and the bearings stay on the rotor which makes
them easier to remove using a bearing puller. A bearing press is
handy for reinstallation but I've also used a heavy drill press (off)
with makeshift jig. Brinelling is a risk when approaching these with
a hammer, especially if the fit is tight.

Light machine oil was suggested for a temporary fix, and it indeed can
prolong the life of the bearings considerably if they've simply dried
out, if you can get the oil into the bearing set casing. However,
there is a popular canned spray that should be avoided, marketed as a
"lubricant" and is often touted as the fix-all for everything.
However, around sealed, greased bearings, the stuff is a nightmare
since it is a powerful degreaser, which liquifies the packed grease.
It's name begins with WD - don't fall for the hype.

Check for loose mounting as suggested since the cage is fairly
lightweight and would squeak if given the chance.

(The opinions and suggestion expressed above are my own and do not
reflect current enginieering or electrical standards in any way.)
Scott in Dunedin, FL

This is very close to a post-mortem, as predicted by Puckdropper.

I took things apart. This is a 7.7 Amp motor for 1050 rpm. It was
rather solidly mounted, so that wasn't the problem.

It was an interesting experience. There was 1 loose long bolt that
attached a grounding wire between outer housing and motor itself. If
there ever was a nut on the other side it is now lost. I can't get the
bearing covers (?) off unless I go out and buy something. So I am going
to ask a plumber friend whether he might know of a squirrelcage fan and
motor that is looking for a new home. Otherwise, I may just go and get
another one on eBay.

-
Han,

It sounds as if the bearings are tightly pressed onto the rotor and into the
end caps, preventing you from separating the motor. A seated bearing set
will only move if pressure is applied evenly and straight along shaft
direction. Prying with one screwdriver is futile; you would need at least
two large screwdrivers applied at the same time directly across from each
other, torquing in opposite directions. Even this is doubtful to work on
the tough nuts to crack.

Sometimes I'll use the weight of the stator to my advantage, being very
careful to protect the shaft, and raise the motor assy and strike (gently at
first) the shaft end of the rotor (traveling in a straight line with the
shaft) onto the (carpetted) bench until the weight of the stator drives the
front end cap off of the bearing (or the front bearing off the shaft).
Unfortunately removing the rear end cap is more difficult without the mass
of the stator to help and the end caps tend to be a brittle cast metal that
dont like repeated banging.

Regarding the nutless screw, if one of the adjoining screws were at all
loose, one of the end caps could have skewed slightly, binding the bearing
up, creating increased friction, higher heat, etc.. If the motor could be
hand turned, find a nut to fit the bolt, tighten it all up making sure the
end caps seat tightly and evenly into the stator frame. Having all of the
screws tight may make the difference.

(The opinions and suggestion expressed above are my own and do not
reflect current enginieering or electrical standards in any way.)

Scott in Dunedin FL