"Han" wrote in message ...

"anon" wrote in
ng.com:

"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.

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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 don€„¢t 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

Thanks, Scott, but I have indeed given up on this thing. Chalk one up
for experience and in favor of the disposable society. I wonder what the
town's recycling division is going to do with it ...

-
Aye, the ease of disassembly usually offers a taste of the reassembly.
Good luck then,
Scott in Dunedin FL