On Mon, 20 Jul 2009 08:55:17 -0700, Robert Macy wrote:

On Jul 19, 6:56*pm, Jeff Liebermann wrote:
On Sun, 19 Jul 2009 17:42:43 -0700 (PDT), Robert Macy

wrote:
This may not be a clutch by design, but rather a rubber 'alignment'
shaft. *When new, the press fit kept the fan and motor locked
together, but with age and rubber deteriorating from actions of oil,
some clipped

The 'light grinding' noise comes when the motor shaft starts slipping in
the rubber transfer to the fan. It seems there are four small ridges
on the metal to help 'bite' into the rubber. So, when it starts
slipping it makes a noise.

Here is the failure scenario to date: System does run fairly cool at
around 60C [This is based upon my experience at not being able to hold
my finger on metal above 60C for more than 10 seconds]. All bearings
are smooth and oiled, also running cool. Fan whether hot or cold turns
easily coasting slowly to stop. Oil however migrated from the motor
bearing, along the shaft, and into the rubber transfer and that is now
slipping.

I tried to remove the fan from the motor shaft, but could not. I
completely lifted the motor/fan out of the unit, yet the rubber won't
slide off the end of the motor shaft allowing access to clean all out.
If there is a retaining clip of some kind, I can't see it, and worse,
not be able to get access to it. Since the fan is squirrel cage, there
is no way to gain access to a clip inside the 'cylinder' with my tools.


But, transmission fluid is a high temperature oil isn't it?

Robert

Yes transmission fluid is a grade of oil and is safe for neopreme Orings
not regular rubber.

Your Oric sounds a lot like some Sears branded electrostatic cleaners that
I had once the fan was what is refered to as a reever style about 8 inches
long and mounted in a bronze bearing block on one end and a heavy rubber
grommet on the other. The rubber is simply to allow easy alignment between
the motor and fan, A flex coupler if you think about it so that the case
alignment is not critical.

The bearing on the end of the fam was what failed since it was quite small
7/16" ID (had I known this before it failed oiling would have saved it)
Like your case the fan would run at low speed for a short period before
locking up but woul not run at any speed higher than low.

You probably have a bad beaing on the end of thr fan away from the motor
Robert. Here is what happens with sleve bearings that are "oillite" bronze
used in most places. They exhaust the actual impregnated lubricant and
gall. This is not apperent until the friction heats up the bearing or the
fan tries to run beyond the point where friction balances torque. ( this
effect is most often seen in chesp computer cooing fans that rev up to
about haf or less of rated speed and start squealing and slow down).