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new motors and their comms

new motors and their comms

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Old 08-27-2004, 12:50 PM
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I recently got a new Reedy 19 quad and ran it twice out of the box..
I wasnt very impressed at all even though I had it way undergeared.. 23 - 72 in a tc3.

I then decided to skim the comm try different springs and brushes..
I used a sharpy on the comm and proceeded to cut it, and thats when I found the comm to be very far off from round.
it took at least three passes to get it close. I know it wasnt because of being ran a couple times because after the first couple passes there was still marker in "blotches", not just where the brushes contact.

my question is, is it normal for a new motor to have a comm that is so far from being round?

after the cut, going to 4499 brushes, and trinity purple springs on + and - then changing the gearing to 30 - 72, it is a whole different motor... tons of torque and speed.
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Old 08-27-2004, 12:57 PM
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Unfortunately it happens. Unless you're paying top dollar for a hand wound mod or a "Pro" version of some other motor you probably need to lightly skim the comm before you run it.
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Old 08-27-2004, 01:10 PM
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Actually, this is probably no common than you would think. Either that or I get a lot of bad motor's. Everything from my hand wound Reedy's, Trinity's and Fantoms. They only time I have never incountered what you are describling is if I have purchased a motor from a smaller tuner: Putnam, Team 1, Paradigm...etc.
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Old 08-27-2004, 02:57 PM
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looks like I will be cutting the comm on new motors before any runs from now on.

Thats a bummer for people that dont have a lathe..
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Old 08-27-2004, 05:48 PM
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a undergeared quad19t it will suck. no matter what you do to it. you can take a new motor (uncut) over gear the crap out of it and it will fly.
but cutting new motors is always a good idea unless you buy the "pro" version thats already been cut. (thats why they cost more)
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Old 08-27-2004, 05:56 PM
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You are WAY undergearing that Reedy....In order to get any performance out of it you gottta gear to the moon...Try a 6.9 Final drive
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Old 08-27-2004, 06:06 PM
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6.9 is still undergeared, most people are running them in the 5.7-6.2 range now.
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Old 08-27-2004, 06:10 PM
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did you read the whole post?..... or am I missing somthing?
6.00 at 30 - 72 seems good.
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Old 08-27-2004, 06:20 PM
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Not that I trust a trued comm from any company (because they can all be way off)......but because of what you said about the comm being un-true even in areas other than where the brushes make contact........for the heck of it (just to rule it out) check that your lathe is cutting pretty close to round with a micrometer or even a set of digital calipers.....and if your interested in maximum motor life, try to stick with 766's ,767's or brushes with similar compounds ,4499's are much harder on the comm on a reedy 19turn quad mag....and in my experience offer no power advantage..................Joe
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Old 08-27-2004, 06:21 PM
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oh yea ,I almost forgot...... your way under gearing it
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Old 08-27-2004, 06:26 PM
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Originally posted by onnetz
did you read the whole post?..... or am I missing somthing?
6.00 at 30 - 72 seems good.
I think these guys are pointing at your gearing because if you way under gear a motor it will tear up the comm almost as much as overgearing it.
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Old 08-27-2004, 06:32 PM
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Hey Joe,
yeah a micrometer is on my list of things to get..
but I still dont think it was the lathe, unless the bit is moving forward and backwards..
it was like the front half of the comm was getting cut, but not the back half.. if that makes any sense...

by the way, am I undergearing it? ..

almost forgot.. I have been only using 767's but I had read that some motors work well with the 4499's so I thought I would try them out...
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Old 08-27-2004, 06:34 PM
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The part next to the stacks isn't getting cut as much as the top part?
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Old 08-27-2004, 06:40 PM
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Originally posted by Jack Smash
The part next to the stacks isn't getting cut as much as the top part?
and that would mean the lathe is out of whack right?

what I mean is that if you stand up the armature vertically, the part of the comm your looking at was getting cut, but not the part of the comm you cant see..
thats why I said I dont see how it could be the lathe.
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Old 08-27-2004, 06:49 PM
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Lathes will cut out of round if its messed up pretty bad. Not quite sure causes that but I have seen lathes that do cut out of round.
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