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I have no engineering background at all, but when I bumped my small electric heater and it started whining and creating a burning smell, (since it's labor day with no stores open to buy a new one) I unplugged it and took it apart. Once I got down to the electric motor housing, I could spin the fan with a finger and hear the same whine, and noticed the axle (or whatever you call a rod that rotates a fan) attached to the fan was slightly crooked where it was housed within this piece.

Further inspection revealed that the brass-colored bearing (if that's the correct term) isn't securely seated within the star-shaped housing, but rather just held down by the thin tin flaps, and beyond that pressure moves freely, allowing it to seemingly cause the friction / disturbance creating the whine.

Is there a reason for the bearing to be held in place by this flimsy star chamber rather than a solid seating?

I tried to straighten it out and it appeared straight, but once I put it back together, the whine had only been reduced marginally, and the burning smell still occurred.

enter image description here

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Those thin flaps allow the bronze bearing inside to tilt about slightly and thereby come into alignment with the axis of the fan shaft, thereby minimizing noise and friction. If the bearing as a whole is out of lubricant, then the bronze bearing will stick and can't shift into alignment and the device will be noisy and may also have difficulty spinning up to speed when you first turn it on.

Closer inspection will reveal that surrounding the bronze sleeve is a felt wick which has been saturated with light machine oil (usually SAE #10) at the factory. The bronze sleeve contains tiny pores which conduct the oil from the wick into the sliding surface where the shaft goes through it. It is probably dry and out of lube. A few drops of "3-in-1" brand oil applied to the felt wick through the gaps in the tin flaps will restore the bearing to its happy place.

Note that the bearing on the other end of the motor will need lubrication as well.

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    $\begingroup$ My heater breaks, and I, knowing nothing more than how to use a screw driver, but with only a little screwdriver stub, use gorilla glue and electrical tape with the internals of a mechanical pen to create a screwdriver long enough to open the thing. Still can't figure out of how to fix it, so I ask internet strangers and learn it's just a matter of oil. Don't have any oil and its labor day, nothing's open. So I use a few drops of olive oil and I'm back in business. At least for the day. $\endgroup$ – J.Todd Sep 7 '20 at 18:39
  • $\begingroup$ good for you. take it easy today. -NN $\endgroup$ – niels nielsen Sep 7 '20 at 19:02
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Apparently the bronze bushing/plain bearing is self-centering in the cadmium plated steel holder. The bearing can move slightly to accommodate the position and angle of the motor shaft. Oil would likely help it.

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