# Chasing an Armature Ground



## sonicj (Mar 17, 2010)

the "blob" is a putty used by the motor builder to balance the armature. 

imo, your commutator looks glazed over. ideally, you would want to have the commutator turned down on a lathe. this exposes a smooth, round, fresh copper surface for the brushes to ride on. just to get the thing going, you can take some 600grit aluminum oxide sand paper and lightly sand to reveal fresh copper. you can do the same with the brushes, just don't breathe the stuff. blow the comm out with a air compressor, inspect for shorts, assemble and re-test the motor.
-sj


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## sonicj (Mar 17, 2010)

this is about what yours will look like once cleaned. a scotch brite pad and some alcohol in a spray bottle helps break up the muck. once you have the commutator turned down on a lathe, that copper surface will look brand new.
-sj


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## albano (Jan 12, 2009)

green caveman said:


> Following Major's advice in the forklift motor thread we connected a 120V bulb from the shaft to the commutator. The bulb lights somewhat and there's about 50V across the motor connections.
> 
> We cleaned the motor at the car wash in the hope that brush dust was the problem. Either that wasn't the problem or a car wash is not a good way to clean an armature.
> 
> The armature smokes. It smokes from around the area of the blob in the photo. The blob looks as though someone has pushed modeling clay, plasticine, plumbers putty or similar into that spot. Any idea what it might be? Is it possible that this blob is a former repair that has now failed and that there's some hope we might be able to fix the motor by cleaning this out and re-repairing?


 ...........


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## green caveman (Oct 2, 2009)

sonicj said:


> this is about what yours will look like once cleaned. a scotch brite pad and some alcohol in a spray bottle helps break up the muck. once you have the commutator turned down on a lathe, that copper surface will look brand new.
> -sj


We were going to have the commutator turned, but that's when the ground fault was discovered. (Ground meaning the shaft)

Are you suggesting that further cleaning, (and turning?) might resolve the fault? Doesn't seem a great deal of purpose in turning if the motor if we can't figure out what's wrong.


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## albano (Jan 12, 2009)

green caveman said:


> following major's advice in the forklift motor thread we connected a 120v bulb from the shaft to the commutator. The bulb lights somewhat and there's about 50v across the motor connections.
> 
> We cleaned the motor at the car wash in the hope that brush dust was the problem. Either that wasn't the problem or a car wash is not a good way to clean an armature.
> 
> The armature smokes. It smokes from around the area of the blob in the photo. The blob looks as though someone has pushed modeling clay, plasticine, plumbers putty or similar into that spot. Any idea what it might be? Is it possible that this blob is a former repair that has now failed and that there's some hope we might be able to fix the motor by cleaning this out and re-repairing?


 . .


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## green caveman (Oct 2, 2009)

Further question. Is there anything more practical dismantling of the amature? Can the shaft be removed, and how easily?


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## sonicj (Mar 17, 2010)

ok, so you've confirmed the that the coils are shorting to the armature. hmm...

cleaning out any muck that might be shorting the commutator segments and resurfacing the commutator face might correct some other underlying issue/s, but it won't fix a shorted coil.

most are serviceable. is it easy? probably not unless you are setup with the proper equipment & supplies. heres a good photo tutorial on the process: Flat Wire DC Motor Armatures Rewound
-sj


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## green caveman (Oct 2, 2009)

sonicj said:


> heres a good photo tutorial on the process: Flat Wire DC Motor Armatures Rewound


That's an interesting link. Probably tells me there nothing simple I'm going to be able to do to fix the armature. On the other hand, if I get it rewound then I don't have to worry about turning it!


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