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Old 09-18-2004, 10:32 PM   #16
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Quote:
Originally posted by fatdoggy
kh15 - Sounds like your getting screwed, you should be getting quite a bit more then 40 runs out of an arm provided your not abusing it. You can take the comm down to .270.
yea i think so to i have only had it cut 2 times and i do not abuse my motor and my comm is allready down to .276 hmmmm i think my lhs is gonna get a call from me tommrow thats not cool
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Old 09-21-2004, 09:54 PM   #17
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yea i cut the eyelets of the end of the brushes and soldered them on, i put lighter springs on and its back to normal once the brushes were nicely broken it!
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Old 09-21-2004, 11:06 PM   #18
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You don't need serrations to make the motor fast....most people misunderstand how they work in the first place.

If you are that concerned about having serrations, then buy a serrator so you can add them back with ease. Trinity, Integy, and Fussy Brush all make good units....

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Old 09-22-2004, 01:08 AM   #19
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how do you make the motor fast without serrations?
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Old 09-22-2004, 11:24 AM   #20
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I've been wanting to know that question for a long time.
Chris
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Old 09-23-2004, 06:03 AM   #21
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Default how do you make the motor fast without serrations?

BUMP
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Old 09-23-2004, 08:17 AM   #22
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Electrical efficiency is what you are after, serrations are really only there to help the brush break in and have a full contact patch with the comm. If your motor is faster before the serrations go away that indicates that the brush should be slotted, cut or some other mechanical variation such as a change in spring tension is appropriate.

If you don't have a serrator or serrated brushes the old trick of water dipping can help break in the brush without excess commutator wear. Take your motor with brushes and springs installed, chuck the shaft in a dremel, turn on the dremel while holding the motor can and dip the end bell into a cup of tap water.

Check the brushes after about 30 seconds of dipping and repeat if not fully seated. When seated, take the brushes out and spray the motor out with motor spray, lube and you're ready to run.

Dyno readings are meaningless until you are working with fully seated brushes. That's why "pro" motors with a dyno label are frequently dissapointing.
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Old 09-23-2004, 08:59 AM   #23
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Well, there are simply too many variables to attempt to answer that question...

A simple test though, find a motor, like a Reedy KR where the 766 is the brush to use.....which is unserrated. Serrate it and put it in the motor.....I can pretty much guarantee the motor will be slower than the non-serrated setup. The 766 just does not like to be serrated, thats why its not sold that way.

It really depends on the motor/spring/brush combo to determined if a motor likes serrations or not. Sometimes they love them, sometimes they don't. Its a lot of trial and error.....

And sometimes just a simple hole or slot in the brush will make a faster motor than a serration will....but likewise, sometimes none of the above will make a faster motor.

At Paved nationals, Peter Robinson's stock motor that I tuned used the same brushes in round 3 and 4, along with all 3 a mains. The thing just kept getting faster and faster each run with those old brushes....and after the 1st a main, they were gone....all I did was put a light skim cut on the comm and clean the motor and the brushes....

While I never like to send people away from this forum, I do reccomend you check out www.rccars.com and look at big jims motor forum.....tons of info. Jim can be unique at times, but its easily worth the information.

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Old 09-23-2004, 08:39 PM   #24
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Thanks EddieO
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Old 09-23-2004, 09:14 PM   #25
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Side note... you can actually cut a comm down to .262 and it will last 1-2 runs - then it blows up...lol... Been there, done that, won the Nats a long time ago with my fav 13x3 that was on it's last leg....lol....
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Old 09-23-2004, 09:22 PM   #26
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Eddie,

What about a monster stock. It seems to me that the serrations with purple and red springs are the only way to go when the brushes are 4505's. What you think or experienced?
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Old 09-23-2004, 10:10 PM   #27
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I am not a big fan of the 4505....the cross cut serrations are a pain to break in and to tell if they are aligned correctly.

Just get the 4503, its the exact same compound, but with regular serrations. And yes, the 4505/4503 is one of the compounds that seem to work better with serrations.

For touring car, I typically will use the 4499 or putnam green in the monster....while in offroad, I use the 4500, 4503 or sometimes putnam green.

And purple/red or red/red are usually the spring combos I tend to use.

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Old 09-23-2004, 10:56 PM   #28
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What if the brush has no serrations? Which brush works without serrations well?
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Old 09-23-2004, 11:19 PM   #29
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766, 729, and I prefer the 4383 without serrations.....and the 767 along with the putnam green sometimes work well when the serrations are gone....but it depends on the motor and other variables.

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