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Old 04-21-2004, 07:47 AM   #1
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Default Brush issue, anyone help?

I just rebuilt my Reedy Quad mag 19 turn motor.

When breaking in the brushes, I noticed some burn on the trailing edge of what I believe is the negative side ( trying to remember ) and I had a weird burn line on the positive side brush that ran across the brush, about 3/4 of the way up the brush.

What is even stranger is that the texture of the brush on the negative side and the positive side below the burn line was alittle rough, but above the burn line was perfectly smooth.


Any ideas why I am getting this?
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Old 04-21-2004, 07:51 AM   #2
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one other thing, the brushes are 767s, they appear to be the ones that for some reason the shunt wire is stiff instead of very soft. I was told these would work but you have to watch them more.

When reseating the brushes I noticed that you could hear the motor bog down basically. it would sound great at first, then just slow down like it was caught on something then rev back up. Very strange...
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Old 04-21-2004, 10:29 AM   #3
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anyone with any info?
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Old 04-21-2004, 11:25 AM   #4
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i had a problem very similar sounding to this with my 27T this sunday. it turned out to be my brush hoods were way out of alignment. are your ok?
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Old 04-21-2004, 11:51 AM   #5
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Possibly your comm is not true, as in its tapered... Or, just a bad set of brushes.
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Old 04-21-2004, 12:08 PM   #6
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Sounds like a 'hung' brush....... this will produce a lot of arcing and might do what you are seeing. Make sure you "snap" the brushes once they are on the motor with the springs. Also make sure your comm is free of all debris after cutting it.

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Old 04-21-2004, 12:37 PM   #7
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Bogging down - I get this during run-in sometimes(can be caused by a brush being out of alignment). Actually I know my brushes are properly run in when I don't hear the bogging any more. Generally 6 minute or a little more, re-cut 30-60 seconds and it's read to rip.

The burns on the trailing or leading edge of the brushe is due to brushes that arn't aligned.(aligning the hoods so the brush contacts square to the comm) The up down wear is due to I think a bent hood, if you not getting even wear vertically this will happen. If you hoods are perfectly aligned you won't see any burn marks on the brushes. No tool can align the brushes correctly, you HAVE to cut a brush(8mm or longer) square and use that and make sure they are wearing perfectly in the center.
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Old 04-21-2004, 01:20 PM   #8
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Ok, so it is possible that my hoods are bent and that is why my wear on one side is off. I think that would make more sense than the comm out of round. I should see it on both sides then.

Damn. Don't have an alignment bar.
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Old 04-21-2004, 01:27 PM   #9
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what springs are u running??? brush hop can be caused by to soft of springs....
how old are the brushes.... a while back there was a suposed bad batch of 767's if they were old stock that might be it...
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Old 04-21-2004, 09:02 PM   #10
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my 767s are the ones with the hard shunts so I believe this is the batch in question.

I am going to try another set of brushes instead that don't have the shunt issue.

You can see the wear however is not fully even up and down. Will look more into this.
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Old 04-21-2004, 09:24 PM   #11
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I've got a monster that I have prepped ready to run and it has some hard shunt 767's in it. I havn't run it yet but the wear on the brushs after break-in is perfect, no burn marks at all. All looks in order to me. They do look like there a little hard on the comm though.
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Old 04-22-2004, 07:59 AM   #12
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I ran the motor last night. I actually got into the A-main and was on pace with the LHS owner, the Factory Team X-Ray driver was spanking us of course but the vehicle felt close to dialed, alittle more work and it should be.

The motor brushes do have a angle to them, I am going to tear the motor apart and re-measure the comm to make sure it is level with my caliper, don't know how close it will tell but I will see. The brushes however look better as far as the wear.

Looking at some other guys brushes theirs do the slant thing as well, maybe not as hard but its there so I don't feel too bad.

I think I just need to rebuild the motor with new brushes , rebreak in the motor at 0 degree timing to cut down on arcing ( finally made the motor timing adjustable, wow, what a difference ) and see how it goes tommorrow when I head up for practice.
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