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Old 12-03-2002, 11:03 AM   #1
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Default Brush wear Question?

Everyone;

When racing Stock 27T Motors.

How long do you let the brushes go before changing them?

Should I be changing when the serrations are gone (due to power). I don't want to get into RE-serrating my brushes.

How big of a power difference is it when the serrations wear off?
After about 10 runs the brushes look great except that the serrations are worn off. The motor seems to run fine and the com just needs a skim cut to clean up.

Thanks,
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Old 12-03-2002, 12:02 PM   #2
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The serrations are made for breaking in brushes faster.

Some guys cut the comms for 3-5 runs (it's more a skim, than a cut).

If a motor are well kept, it will both last longer AND run faster. But there are a limit, for how many times a commutator can be cut. And if money matters, how many times shall you cut comms and change brushes, before you can buy a new motor?

I'm a casual club level racer. I'm trying to get the most out of my car, for the quite limited budget I'm on. And here is what I do: I run my stock motors (P2K and Spitfire) for around 25 batteries. Then I cut the comm. If it's just befor a race, I change the brushes. If it's low end season with no races in sight, I re-use the brushes. I use the brushes for normally 2 comm cut (=50 batteries) and absolutely max. 3 comm cut, that is, maximum 75 batteries. Part of the story is, I use to have the current spare motor in a good shape, so I'm prepared for races.

So far my motors last for a long time, and for my needs, they perform very well. It's me as a driver that are the limitation, not the car....
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Old 12-03-2002, 12:13 PM   #3
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I would agree that you can get many runs on a brush, and the serrations are for breaking in.

After a few runs, I use a fine comm stick (with the cylindrical side) to clean up the face of the brushes to remove the dust and burnt area. You really can use brushes for a long time if the are NOT discolored from getting too hot. But when they get really short, remember that the spring pressure will be less, and they may begin to bounce.
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Old 12-03-2002, 01:01 PM   #4
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Maybe I should add, that my motors dont get that hot, that comms/brushes get discolored. I've geared properly and I use a heatsink.
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Old 12-03-2002, 01:31 PM   #5
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pops i usaly turn my motors after 3 or 4 runsand changebrushes also regardless condition of the brushes i've found out over the yearsthe motor runs the best when the com is cut down to the
.075 to.072 dia. but not much com left to cut after that i only do this on level3and level4 races not club races but comp. is getting tough at those races also. Ihave diffrent size serrators for the brushes as i cut the coms. attenion to detail is what wins races.
luck does'nt hurt also................B
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Old 12-03-2002, 01:47 PM   #6
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most motors do loose a little power and RPM when the serrations are gone, but you need to decide if that is really limiting your performance. For me it's not, just like Cole Trickle posted....
Quote:
It's me as a driver that are the limitation, not the car....
so if you can lay down a flawless run and need that little extra you might want to re-serrate or re-brush your motors more often.
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Old 12-03-2002, 02:09 PM   #7
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Default Brushes and MORE

Everyone;

Thanks for the quick replies. After 2 weekends of running (8-10 packs/runs) the serrations are gone but everything else looks perfect and I mean perfect. NO burning, discoloration, Com looks nice, but I will usually do a skim cut and a few minute break-in after.
I am ONLY running Stock Motors and have no immediate plans for running Mod in the future. (probally will race 1/8 On-Road)

I'm looking for MAX power and at what point in brush life does that occur.
I am a VERY competitive Sportsman Nitro driver and most always finish in the top 3 at the Club level races.
My Pro-3 is set-up fairly well but I need that extra edge to put me on top more often. (driver errors aside)

Thanks,
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Old 12-03-2002, 11:02 PM   #8
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Popsracer - "chim chim get off rto's back" hahahahaha RTO claims Trixie is on his back
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Old 12-04-2002, 12:27 AM   #9
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Minicooper;

RTO "Wishes" Trixie was on his back. The only thing on RTO's back, is the rest of us during a race. (for 1 lap anyways)

La Mirada is racing THIS Sunday Per: Charlie B.
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Old 12-04-2002, 07:32 AM   #10
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Default Re: Brushes and MORE

Quote:
Originally posted by popsracer
I'm looking for MAX power and at what point in brush life does that occur.
I am a VERY competitive Sportsman Nitro driver and most always finish in the top 3 at the Club level races.
My Pro-3 is set-up fairly well but I need that extra edge to put me on top more often. (driver errors aside)

Thanks,
You'll get max power when the serrations are gone...full face contact with max amp draw...the scarifice is you lose a little on RPM.

If the brushes aren't discoloured you can wear them to half their original length before you start losing some spring compression.

For those who run out their serrations and then junk their brushes.....can you send them to me!! The brush are just run in fine!!
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Old 12-04-2002, 08:06 AM   #11
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Default Re: Brush wear Question?

Quote:
Originally posted by popsracer
Should I be changing when the serrations are gone (due to power). I don't want to get into RE-serrating my brushes.
Why not? I've been re-serrating since about mid-summer, and I use about 1/2 the brushes that I used to.

I generally run them unill the serrations are gone, or almost gone, then re-serrate them. I usually re-serrate them about twice before i toss 'em. I usually buy brushes for the main, then run the same set for Practice and Qual the next week, tossing them before the main.

I've been using the Promatch serrator. I just mounted it up on top of an old Trinity X-star , and run it at 5v.

-Troy
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Old 12-04-2002, 09:50 AM   #12
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The most important thing is that the hoods are aligned and that the brushes are seated. This subject always seems to spark a big debate. If the brushes or comm are discolored that means one of two things. Either your overgeared or your springs are too light. I usually go 3 or 4 comm cuts before I replace brushes unless the brushes are discolored.
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Old 12-04-2002, 10:51 AM   #13
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Default The Big Brush Off

DTM & Psycho;

Thanks, that is what I was hoping I could do. My Brushes ALWAYS look perfect minus the serrations. I'm just new to electric racing and am always looking for that extra edge. (have a Dyno on the way)

TSR6;

I am responseable for getting 4-5 Cars ready for race day, so I'm hoping to avoid any unnesessary maintenance unless there is a noticable performance gain to be had. If I find out on my Dyno that there is a power gain. Then I will HAVE to get the serrator.

Newracer;

Flawless run? Never had one I think, but then neither does anyone else. The more you have over the other racers just makes it easier to catch up when you do make a mistake. It's just harder to do in Stock class than in Nitro.

Thanks to all for the replies,
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Old 12-05-2002, 01:15 PM   #14
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pops i know what u mean. stock racing all it takes is one little mistake and u go from first to worst but u can have the best of everything but u still have to drive it to the finish line
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Old 12-05-2002, 04:27 PM   #15
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Default Brush serrations and power

DTM;

See this is why I asked. Not having a Dyno yet, I am wondering what produces more overall power. Serrated brushes or Full contact brushes. I've heard theories that the serrations actually allow MORE current to the Com, while others like yourself claim that a FULL contact brush makes more power.
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