Any centrifugal fan that is secured to the fan motor shaft with only one bolt will eventually become loose and begin to hit the fan cage. This is especially so for fans that are heavy and operated horizontally. A fan that is hitting its cage will cause the temperature cut-out to trip and will eventually burn-out. These types of fans are usually found in furnaces. It may be possible to avoid this by drilling and tapping a second hole perpendicular to the first one on the fan for another bolt to better secure it to the motor shaft or check to make sure your fan is not secured by only one bolt before buying it.
Centrifugal fan design flaw.
Jan 04, 2011
10 Replies
Surely any fan with just one bolt will have the threads cut in the opposite direction to the motor's rotation, so that the motor's turning will have a tendency to tighten the bolt rather than loosen it? Or have you seen designs where this isn't the case?
cheers
Jules
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Gmm, Never happened to me. Use some locktite for the bolt thread.
Millions of them around that have not failed seems to contradict your theory.
Many commercial designs have 2 set-screws...one on top of the other. (same tapped hole)
Yep, I'd expect some kind of thread sealer in conjunction with properly torquing down the bolt would do the job - unless the fan was allowed to get so choked with crap over time that vibration became significant (but that's what periodic maintenance is for, right? :-)
(re. your other comment about a hose - you're lucky, my outside faucets are about 3' beneath the snow and will be for another few months :-)
cheers
Jules
I've never heard of one coming loose ever. It's usually the opposite, you can't remove the dam things with a jackhammer.
Ain't that the truth :-)
I recently took the squirrel cage from a centrifugal blower off of the motor shaft (it was from an ancient oil burning furnace). It was attached with
*one* set screw, and came off without too much trouble, despite having set out in the rain for a number of years. There was no evidence on the shaft of having ever slipped over the years (mind you, this was a 1/8HP motor, albeit a fairly large 1/8HP motor).Jon
It depends on whether the securing bolt/machine screw comes in from the side or whether the fan is held on by a nut on the end of the motor shaft itself. You don't say which you mean so the premise is faulty, as in FAWLTY TOWERS.
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