"klm" wrote in message
...
On Tue, 25 Nov 2003 22:50:26 GMT, klm wrote:


The mechanism is as simple as it gets with a 1/2HP electric motor
turning a squirrel cage fan via a pulley and belt. Tried to be a bit
too clever when it was new and added grease to the bronze bearings for
the squirrel cage axle. That grease dried up fast, probably wore the
bronze bearings to give a dirty dark abrasive crud (oxidized bronze.)
I had to change the bearings twice within 3 years before I wised up
and figured that the bearings were meant to run dry. The damaged
bearings were ovalled so that the axle could flop around and the
furnace gave a loud clunk everytime it started up or stopped. It
squealed like a stuck pig when the fan was turning. The furnace had
been running fine for more than 10 years since I omitted that grease.

The ovalling of the bearings part bugged me. Finally recalled the old
(10 year) sequence of what happened.

A newspaper story on prepping for winter caught my eye. It was to
check the furnace for clean filters, etc. plus check the fan belt
tension. So tightened the belt.. After some time the furnace fan
started to squeak so added some grease and 10/30W lube oil. Tensioned
the belt again. That grease dried up so added more and tensioned the
belt again. Recurring problem and now the fan started to clunk every
time it started or stopped. After two seasons the squirrel cage fan
and the floor of the furnace was spattered with grease and lube oil.
So decided to take out the assembly to clean. Found the bearings
ovalled and the fan shaft scoured. Replaced those.

The above same problems developed over time again. By my third
service effort figured that the bearings were not meant to be lubed.
More important the belt tension should be just what the motor weight
is as mounted on its hinge.

Ok..first, wrong oil. 20W MAX turbine oil. Period.
Second, belt tension is not set that way...I have motors that weigh enough
that the belt would be overtensioned if you allowed it to set with its full
weight on it.
A properly tensioned belt, to the average layman, would look to be far too
loose to run properly.
Oval bearings? LOL...easy enough...wrong belt tension.

Oh..oil impregnated bronze sleeves normally dont have oil ports...and 10W30
oil, wont harden..oil, isnt grease.

No problem since.