Is this brush and guide clean enough?

2988 Views 6 Replies 3 Participants Last post by trops357, Sep 5, 2010

trops357

Discussion Starter · Sep 5, 2010

Hey, I wasnt sure just how free the brush was designed to move in the brush holder/guide. I shot a short video of the cleaned brush.
Let me know if you think it is moving free enough, or if I sanded too much, lol.
Got the motor appart, cleaned it up with degreaser , tarn-x, local carwash preasure wash. 800 wet sandpaper.

Thanks for taking time to look.

BTW: It has 75 bars on the communtator.

http://www.youtube.com/watch?v=nYhe6PPfyGU&feature=channel

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EVfun

· #2 · Sep 5, 2010

It is most likely good enough but I would try to do a little better. It seems a tiny bit stiff as a starting point though it seems to work pretty well with the spring.

I generally wipe out the inside of the holder (where the brush goes) with some scotchbright and make sure there is no corrosion lumps of bumps inside. Then I might give each side of the brush a single pass or 2 on a piece of fine sandpaper. I would do that dry because I want the leave some graphite dust for lubrication.

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major

· #3 · Sep 5, 2010

trops357 said:
Hey, I wasnt sure just how free the brush was designed to move in the brush holder/guide. I shot a short video of the cleaned brush.
Let me know if you think it is moving free enough, or if I sanded too much, lol.
Got the motor appart, cleaned it up with degreaser , tarn-x, local carwash preasure wash. 800 wet sandpaper.

Thanks for taking time to look.

BTW: It has 75 bars on the communtator.

http://www.youtube.com/watch?v=nYhe6PPfyGU&feature=channel

Yeah, it appears to be able to move smoothly all the way with the spring force. I'd use it. The brush face is the part which contacts the commutator. So be sure to shape it to the comm diameter upon installation. I'd wrap crocus cloth around the comm and "drum sand" all 4 brushes to the comm diameter. Then use a commercially available dressing stone while running the motor at 12 volts to finish the shaping process. Then run it for hours to seat the brushes and film the comm.

While you're going through this process, check often to see if each brush is free to move radially back and forth by pulling it up by the pigtails. If the pigtails can't withstand that much pull force, they would soon fail from a high current pulse anyway.

major

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trops357

Discussion Starter · #4 · Sep 5, 2010

EVfun said:
It is most likely good enough but I would try to do a little better. It seems a tiny bit stiff as a starting point though it seems to work pretty well with the spring.

I generally wipe out the inside of the holder (where the brush goes) with some scotchbright and make sure there is no corrosion lumps of bumps inside. Then I might give each side of the brush a single pass or 2 on a piece of fine sandpaper. I would do that dry because I want the leave some graphite dust for lubrication.

Ok, I will go over the holder better, I didnt use the sandpapper wet, I have just heard a lot of people refer to it as wet sandpapper.
Thanks for the info!!!

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trops357

Discussion Starter · #5 · Sep 5, 2010

major said:
Yeah, it appears to be able to move smoothly all the way with the spring force. I'd use it. The brush face is the part which contacts the commutator. So be sure to shape it to the comm diameter upon installation. I'd wrap crocus cloth around the comm and "drum sand" all 4 brushes to the comm diameter. Then use a commercially available dressing stone while running the motor at 12 volts to finish the shaping process. Then run it for hours to seat the brushes and film the comm.

While you're going through this process, check often to see if each brush is free to move radially back and forth by pulling it up by the pigtails. If the pigtails can't withstand that much pull force, they would soon fail from a high current pulse anyway.

major

Yeah, I thought it might be a good idea to dosomething like put sandpapper on the communtator,(rough side up,lol), and sand the brush into shape. My partner said the brush would take shape on its own.

I am not sure how to get crocus cloth or the dressing stone in the area to be shaped w/o the motor being apart?? I must not be visualizing it correct.

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major

· #6 · Sep 5, 2010

trops357 said:
Yeah, I thought it might be a good idea to dosomething like put sandpapper on the communtator,(rough side up,lol), and sand the brush into shape. My partner said the brush would take shape on its own.

I am not sure how to get crocus cloth or the dressing stone in the area to be shaped w/o the motor being apart?? I must not be visualizing it correct.

Hi trops,

Sandpaper should not be used. Sand is silicon. A grain of it inbetween the comm bars acts like a semiconductor. Crocus cloth and seating stones should be available from McMaster Carr or other full service hardware supply houses, maybe Grainger.

Cut the crocus cloth to the length of the comm for the width and long enough to wrap completely around the comm plus a little overlap. Use the blue painter's masking tape and fix one end to the comm. Then wrap it around the comm. Temporarily tape the other end to hold it in place while you assemble the motor and brushes. Reach in and pull off the top tape. Rotate the shaft in the direction to drag the crocus cloth under the brushes. Do it enough times to completely shape the brush face. Then reach in and pull the crocus cloth off and out. Blow out the motor with dry compressed air.

This leaves the brush face shaped to a slightly larger diameter than the comm due to the thickness of the cloth. The dressing stone finishes the shaping process.

Dressing or seating stones don't really seat brushes, they shape the brush. They are thin long shaped things which can be pressed against the comm while the motor is running by inserting them thru the brush access window. Do a search for DC motor brush seating (or dressing) stones and I think you will find out how to do it.

major

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trops357

Discussion Starter · #7 · Sep 5, 2010

major said:
Hi trops,

major

Thank you very much for the details!! Its a cool day outside, gonna be perfect for tinkering on the motor!!!

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