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Small motors defect - what is the name of this defect?

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Prototyp_V1.0

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Hi.

I need some help to find the terminology for a rare kind of electrical motor fault/defect.
I've seen some toys where the small motor inside -when no load- began to make a scream-alike sound, strong vibration and a rapic decreased rpm.

In some cases, it help to apply oil to the bearings, but not always.

I just wonder - what is the main reason for this misbehavior, the bearings or is it the motor itself that isn't balanced?

Reason I ask is I have a citchen mixer that have this problem. I might have to do something with he motor, because it behaves like this.

Thanks
 

BradtheRad

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I've had devices do the same thing after extended use. It usually come and go. (Shavers, refrigerator fans.) I believe the inexpensive brass bearings get worn. The motor shaft wobbles within the enlarged hole, causing the screaming sound and decreased rpm.

A bit of oil quiets it for a while, if the area is accessible. I have never heard of an easy way to cure it.
 

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Terminology? how about "worn bearings"?

With a kitchen mixer I would be worried that food has gotten into the motor and the bearings got worn due to the food/liquid getting into them (food/liquid doesn't work well as lubricant, maybe social lubricant would work ;-)). This is actually one of the typical failure mechanisms of that TV blender "Magic Bullet" a bunch of reviews of that blender cite leaking of the bullet container into the blender causing first noise then complete failure of the motor.
 

Prototyp_V1.0

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No, the motor part is on top. That is also why I'm reluctant to use any oil - won't have it in the food.

I still cannot find any videos on youtube that cover the same type of failure. Those videos I heard the sound from, is more kind of "metal against metal" and not the high pitch "wobbling".
 

BradtheRad

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Over time it grows in volume and persistence. I picture that I could squeeze the bearing in a pliers, in the notion that the loose play is so small (a thousandth of an inch?) that I could take it up by applying pressure. But I'm sure that would not work. If the bearing could be compressed at all, then I think would bind the shaft, ruining the motor.
 

CataM

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I think post #5 is a good advice :smile:. I am curious as well.
 

Prototyp_V1.0

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I have a sound record now - pretty good quality too

Hi.

I've done a sound recording of that citchen machine. I did use some time because I needed to get in hand some mocrophones for this.
https://soundcloud.com/random-stereo-sounds/kjokkenmaskin

Actually - when I listen to this record it stroke me that on this particular machine, there could be something else than a bad motor.

The record is done by microphones mounted on the surface of the casing, so it's more clean than I hear with my ears a meter away.
 

Adrianosaunder

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A faulty relationship between the rotor and stator is also called an eccentricity.
 

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