Fried motor

[lti]

I have never seen this happen to a motor before. What could have caused the failure?

[joshnz]

Re: Fried motor

WOW looks like someone connected to high voltage.
Or the communicator got very dirty = heat.
another thing if it is a 3v motor someone may have connected to 12v high current source.
What did it come from?

[lti]

Re: Fried motor

It came from a low-quality electric toothbrush that was powered from a 2.4V NiCd battery. The inside of the toothbrush body and the outside of the motor were coated in a gray film.

[joshnz]

Re: Fried motor

That is crazy.
After looking at it more it looks like they greased the communicator.

[370forlife]

Re: Fried motor

Just a bog standard 180 motor. Looks like the commutators probably arced a lot through that grease covering the contacts and it burned them up.

[kaboom]

Re: Fried motor

That is crazy.
After looking at it more it looks like they greased the communicator.

Sure does! Almost looks like that chinese 'slop' grease that, when used in cheap fans, guarantees an early death.

Years ago, I got a bit too "enthused" about oiling one of my radio shack 'toy' motors.

Its commutator looked just like this one.

[b700029]

Re: Fried motor

It looks like it's just grease to me, burnt grease. The motor doesn't work anymore?

[lti]

Re: Fried motor

No, it doesn't work. I can't get it to spin for more than half of a revolution.

One of the brushes is shorter than the other three (this motor uses two brushes per terminal) and has been bent so it could still make contact. That shows how cheap the motor was.

[lti]

Re: Fried motor

I cleaned the grease off the commutator and brushes today and discovered that the shorter brush had actually worn down so far that the end broke off. The other brush on that side of the motor has a hole worn in it. Strangely, the other two brushes look fine.

Also, I put the back cover on it, spun the shaft a few times, heard a loud snap, and it works now.

[lti]

Re: Fried motor

Here ar some pictures of the motor with the grease removed. You can see the worn brushes. You can also see that the commutator is worn, especially at the edges of the bars.

It appears that the motor driver circuit puts a lot of stress on the motor. There is another version of this toothbrush that runs from two AA batteries, and the motor doesn't wear out in that version. Why would that happen?

When I first took this motor apart, I thought that the black grease splattered inside the housing was actually the remains of the commutator.

[momaka]

Re: Fried motor

Many of these cheaper, small motors have cheap non-graphite (usually copper) brushes that wear out fairly quickly, especially if the motor is subjected to dust, dirt, or sudden high start-up voltages. The grease is actually there to slow down the wear of the brushes, but they do wear down eventually. The graphite brushes, on the other hand, will last much longer. Motors with graphite brushes also won't have any grease on their commutator - so don't put any if you take one apart. They also have a bit more resistance when you try to turn them by hand.

I'm not really sure if anyone even makes these 180-sized motors with graphite brushes. Some of the 260 and 280 -sized are for sure. From what I've seen: Mabuchi offers both, Sun Motor are mostly graphite, Super Jack are mostly non-graphite (copper). Of course, this is only for the small sized motors. 360 -sized ones and above all have graphite brushes since they draw a lot more current, resulting in much more arcing between the brushes and the commutator. If copper brushes were used, they would wear down too quickly.

[lti]

Re: Fried motor

This motor does use copper brushes and so much grease that it sprays out of the ventilation holes in the motor's case when it spins.

This motor is marked "Action Motor," and it was probably the cheapest motor the manufacturer could find. However, it runs smoother than the size 180 "Hing Lung" motor in my parts collection.

[Agent24]

Re: Fried motor

High quality! Made in China! You buy!


End of story.