Singing Fan

It's probably got some roughness, in the bearings. What kind of oil did you use? Should use ND-20. After complete cleaning, of course. Need to flush out the old oil with solvent.

Christopher A. Young Learn more about Jesus

However, just because it's a perfect fit for the small window in that shed, I decided to take it apart and make sure it was oiled. The bearings are all pretty tight. I oiled it's bearings well and reassembled it. I was surprised that it was much quieter for the first ten minutes. Then it went back to singing.

Just curious if anyone knows why it makes these sounds?

When a motor hums, it doesn't know the words.

What song does your fan sing?

Christopher A. Young Learn more about Jesus

However, just because it's a perfect fit for the small window in that shed, I decided to take it apart and make sure it was oiled. The bearings are all pretty tight. I oiled it's bearings well and reassembled it. I was surprised that it was much quieter for the first ten minutes. Then it went back to singing.

Just curious if anyone knows why it makes these sounds?

Does it have a run capacitor, I've seen situations where a defective run capacitor will make an AC motor make an odd sound. ^_^

TDD

Could the pitch be changing because of varying wind pressure against the window the fan is mounted in.

(I just love that nowadays I can end a sentence with a preposition and nobody cares that I do.)

Jeff

Maybe the bearings still does not have enough oil. Also, the bearings are mounted in spring-finger type of arrangement in many motors, if the bearings are too tight, the entire bearing may be rotating in the spring-finger mounts.

That was actually my first thoughts. However, we have had days of calm wind free weather. It does not seem to indicate that the wind (or lack of it) has any effect. For the heck of it, I placed another fan on the work bench in there and blew that fan toward the noisy one. There was little noticable change. However, I found that there is a certain amound of back and forth play in the motor. What I mean, is that the fan blade can be moved forward (away from the motor, or backward (toward it). This play is very small, but it exists. What causes this is beyond me, but I suspect that there may have been a fiber washer in there when it was new, and that wore out. This play is not visible when it's spinning, but I suspect that the in and out movement of the shaft is causing the different pitch. Putting a shim in it might be possible. I'll have to check what is available. Yet it seems to me that this type of motor always had a little play. After all, if they are too tight, they would drag and overheat. After all, this is a fractional HP motor. My guess would be 1/20 HP at most. No, there are no capacitors. Like I said, this is about the same as the old record player motors. Basically a laminated iron housing with coils and the rotating magnets in the middle connected to the shaft. (similar to this).

try more oil first, then chek to see if bearings are slipping in their housing

Ignore the play in the shaft.

All fans will have back and forth movement of the blade. I just checked 4 different fans:

A floor standing model, 2 dual blade window fans from different manufacturers and an rather old "industrial" style fan from back in the 60's.

Something like this:

Each and every one of them has a small amount of back and forth movement of the shaft.

You need to get one of these to accompany it:

Hi Fred, Our new house has a kitchen extractor fan fan that sounds exactly as you have described. I have mentioned this to my wife and some of my freinds who now think that I must be going a bit bonkers. The fact is that I can clearly recognise the changes in pitch and as you say it can be very soothing. Although the fan is very powerfull and noisy, the music cuts quietly through being reminiscent of perhaps a male voice choir singing distantly from the noisy valley below. Maybe this could be due to some sort of resonance and being tuned in. Meanwhile, I'll just carry on enjoying the music. Many thanks for your post :)