How to lubricate fan bearings in furnace?
So in our 27-year-old Winnebago Warrior, we have a Suburban NT30KLT furnace. In the last couple of years, the first time it fires up you can hear the fan bearing squalling a bit and then it quiets ...
Forum Discussion
Really amazing -
Small ball bearings are not at all expensive. The motor case would cost more to manufacture but with a decent non Chinese bearing, a small motor bearing would last one hundred years.
The soy-sauce sintered-bronze (If you think oil-lite quality bushing, you dream) bushings in today's junk does not respond well to lubing. Me and an expensive Harbor Freight (Well, it cost EIGHTY dollars!) rotary squirrel cage fan had a toe-to-toe knock down drag out fight about ten years ago. I was determined to ventilate a four room house and it was determined to commit seppuku. The fan had a few thousand hours of use. But what the heck it was a matter of lubrication.
The fan upon startup began to make neighborhood dogs howl.
I substituted a pair of Fantastic Endless breeze fans and went to work.
Off came the squirrel cage and out came the fan motor. The Chinese thought it essential to demand use of a foot long tiny mm set screw allen wrench to get to the screw - don't ask.
Out popped the armature. I spent a half-hour examining its windings to make sure I wasn't flogging a dead horse. All OK in the copper dept.
The armature shaft was not shiny chrome looking. The school of hard knocks later showed that the "staining" was actually smeared bushing material but at the time I use fingers to determine the shaft was good to go as far as no grooves, taper or roughness.
The bushing under a strong light, after alcohol, Q-tips and patience was used to clean out the interior of the knob-line sheet metal protrudence revealed the same smearing glaze that I saw on the armature shaft. Nothing to do but rub harder. I used brake cleaner but that did not remove the glaze. The Q-tips after rubbing came out shiny.
Now it was time to lube. Being neurotic, I do not inventory just any oil, no, it has to be the "best" for sintered bushings
Wait a minute! Wait a minute! I am not going to go through this again!
I held the housing up high and drilled a 1/16" hole from the bottom up right in the center of the bushing knob.
Then spent even more time flushing and cleaning out the inside of the "bore". I found only couple of good size chip residue with the Q-tips
Then, I plastered a piece of oil proof adhesive patch on the outside of the sheet metal. Let it dry overnight.
Then used an absurd amount of oil to fill the hole.
Placed the armature shaft into the bushing bore and spent the next hour reassembling the fan.
Plugged it in, tapped the rocker switch and TAH-DH, noise gone. Silent and powerful blast of air.
Two weeks later I woke up in the middle of the night to a squealing fan. This time I smelled hot electrical.
WHY!
Back apart it went. Got to the bushing and shaft. The staining on the shaft was worse. Same with the shaft only this time the shaft did not feel mirror smooth.
That oil I used was lab grade turbine oil. And there ain't no better lube for a slow speed bushing.
MORAL OF THE STORY
Never Again!
PS: I was a hundred miles from the nearest store that sold larger fans. Harbor Freight? Make a left and don't take your foot off the gas for a thousand miles.
PPS: Your mileage may vary
Small ball bearings are not at all expensive. The motor case would cost more to manufacture but with a decent non Chinese bearing, a small motor bearing would last one hundred years.
The soy-sauce sintered-bronze (If you think oil-lite quality bushing, you dream) bushings in today's junk does not respond well to lubing. Me and an expensive Harbor Freight (Well, it cost EIGHTY dollars!) rotary squirrel cage fan had a toe-to-toe knock down drag out fight about ten years ago. I was determined to ventilate a four room house and it was determined to commit seppuku. The fan had a few thousand hours of use. But what the heck it was a matter of lubrication.
The fan upon startup began to make neighborhood dogs howl.
I substituted a pair of Fantastic Endless breeze fans and went to work.
Off came the squirrel cage and out came the fan motor. The Chinese thought it essential to demand use of a foot long tiny mm set screw allen wrench to get to the screw - don't ask.
Out popped the armature. I spent a half-hour examining its windings to make sure I wasn't flogging a dead horse. All OK in the copper dept.
The armature shaft was not shiny chrome looking. The school of hard knocks later showed that the "staining" was actually smeared bushing material but at the time I use fingers to determine the shaft was good to go as far as no grooves, taper or roughness.
The bushing under a strong light, after alcohol, Q-tips and patience was used to clean out the interior of the knob-line sheet metal protrudence revealed the same smearing glaze that I saw on the armature shaft. Nothing to do but rub harder. I used brake cleaner but that did not remove the glaze. The Q-tips after rubbing came out shiny.
Now it was time to lube. Being neurotic, I do not inventory just any oil, no, it has to be the "best" for sintered bushings
Wait a minute! Wait a minute! I am not going to go through this again!
I held the housing up high and drilled a 1/16" hole from the bottom up right in the center of the bushing knob.
Then spent even more time flushing and cleaning out the inside of the "bore". I found only couple of good size chip residue with the Q-tips
Then, I plastered a piece of oil proof adhesive patch on the outside of the sheet metal. Let it dry overnight.
Then used an absurd amount of oil to fill the hole.
Placed the armature shaft into the bushing bore and spent the next hour reassembling the fan.
Plugged it in, tapped the rocker switch and TAH-DH, noise gone. Silent and powerful blast of air.
Two weeks later I woke up in the middle of the night to a squealing fan. This time I smelled hot electrical.
WHY!
Back apart it went. Got to the bushing and shaft. The staining on the shaft was worse. Same with the shaft only this time the shaft did not feel mirror smooth.
That oil I used was lab grade turbine oil. And there ain't no better lube for a slow speed bushing.
MORAL OF THE STORY
Never Again!
PS: I was a hundred miles from the nearest store that sold larger fans. Harbor Freight? Make a left and don't take your foot off the gas for a thousand miles.
PPS: Your mileage may vary
