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Old 10-03-2006, 05:09 PM   #1
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Default when is your motor comm to small?

When do you guys toss out your stock motors?

Looking for a size at wich most guys will just toss the sucker out. To be specific Monster horsepower and CO27 motors.

Post your comm sizes

thanks
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Old 10-03-2006, 05:20 PM   #2
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.273-.275" here
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Old 10-03-2006, 05:22 PM   #3
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.270"
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Old 10-03-2006, 05:29 PM   #4
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The lowest I take any of my comm's is .270. They tend to blow apart after that.
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Old 10-03-2006, 06:24 PM   #5
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i cut the comm at the smallest of .272". after that the motor is used for practice until the copper comm peels off like a ribbon.

-Zac
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Old 10-03-2006, 06:28 PM   #6
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Usually when i put it on the lathe to true it and the copper peels off it, usually followed by " Oh sheeeeeeeet, now ive got to buy another one!"
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Old 10-03-2006, 09:57 PM   #7
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About .270 here. Have run a couple at .268; but, not for a race.
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Old 10-03-2006, 10:26 PM   #8
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Usually when It Goes up in Smoke !! 3 minutes into a run ...
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Old 10-03-2006, 10:29 PM   #9
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never use smaller than 6.9 ~ 6.85 mm with current batt capacity,
below that, I am afraid thin copper layer may pop off from the comm insulation and damaging brush guide / endbell (never happen though)
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Old 10-03-2006, 11:30 PM   #10
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.270 for small comm .315 for big comm.....anything lower and you are playing with fire....

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Old 10-03-2006, 11:39 PM   #11
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Dammit Eddie you beat me.... I actually stop running mine at .270 mainly becouse once you get a small comm you lose Torque, but gain alot of RPM, which doesnt fit my particular style of racing.

Also as your comm gets small, keep in mind your brush tension should be a little stiffer from when your comm was bigger becouse now your brushes have to move in farther in the brush hood to make contact with the comm.

So basically if you were runnning green - and red + when your motor was new and now you measure it and are like crap I am at .270, you should go to red - and purple +, or you can put a slight bend in your current springs.

Best thing to do is get a fiddlestick to measure your springs tension...
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Old 10-03-2006, 11:44 PM   #12
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Quote:
.270 for small comm .315 for big comm.....
How do you determing small comm vs. big comm?
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Old 10-03-2006, 11:50 PM   #13
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ive gone as low as .265, and some sightly smaller.. ill run a motor till the comm explodes.. either on the lathe or in the car.. When a com gets smaller just take some off the face of the brush.. this reduces arcing..Small com tends to look super good on the dyno.. Usually flat on the track.. however if you do the brushes right, there wicked fast..

This is 4 cell tho..
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Old 10-04-2006, 01:47 AM   #14
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Quote:
Originally Posted by scottwk1
How do you determing small comm vs. big comm?
Big comm is Reedy KR and Reedy quad magnet spec 19-small comm is pretty much everything else.All stock motors are small comm.
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Old 10-04-2006, 04:36 AM   #15
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I heard that you shouldn't lathe more than 7.2mm for a stand up bruch motor, but that 7.2mm was just right for a lay down brushed motor.
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