AAH!!!! MY COMMUTATOR TURNED PURPLE!!!!

[Isky]

My commutator turned purple/blue. It was running fine yesterday..my brushes look like a hard blue/black. Did i brun my motor out of existance? It stills runs just like doodoo though...
- Isky

[tc3guy]

Well if it runs fine I geuss your brushes are OK. But usually you have to replace them because the motor is very slow when they are burnt blue like that. Ask somebody at your LHS they can tell you whether to replace them or not. You also better get your comm trued it should not look like that.

[This message has been edited by tc3guy (edited 03-28-2001).]

[XXXER]

Sounds like it was overgeared, if the brushes turn a different color, that is usually a bad thing, or maybe you just have some crappy brushes, what kind are they?

Definatley get your comm trued and new brushes.

[jrob440]

If the motor is getting that hot, it's definitely overgeared. Either get a lower gear ratio to allow the motor to spin at higher RPMs or get a higher turn motor with more torque.

Also, if you're using 7 cells, drop down to 6 instead.

[Aussie_Man]

Does burning your comms and making them go purple (**** that must have been hot) and blue, does it soften the copper on the comm or make it brittle like some other metals? Or can you just re-true it and be fine?

[Isky]

Thanks for your help guys...right now im running a 21/87 ratio in my T3. Its been running hot...VERY HOT...to the point where my fingerprint gets burned...well, i got the blue off my commutator by using an x-acto knife, and also cutting some material off my brushes. But, unfortunetly my shims broke. Im only using a 6-cell right now. I can not afford a new pinion gear, go figure.
- Isky

[Nairb]

Don't run it again until you can get a 19 or 18 tooth pinion. Don't try running your motor like this (after cutting the blue off with an exacto knife) either, you need to have it trued because I guarantee it's not round enough now. You should get new brushes, too. Come on, a measley $3? You can bum it off someone...

[FilthyPierre]

I agree with Nairb - get some smaller pinions and don't run the motor again until you've gotten the comm cut and some new brushes.

Except for the last occurence, my comm burns had been through too-high gearing. Last time however, I'd just put in a new pro armature (already trued) and a new set of Reedy brushes. Same pinion I always run. Ran 2 races no probs. Half way through the 3rd race, the car just stopped. Pulled the motor (eventually) and the comm was blue and one brush really black. I had it cut, put new brushes in and it's been running fine like that for at least 2 race meets (same pinion, 21T). The only thing I can put it down to is either the wrong type of brushes, or the one that got really black was a dud, or somehow got hung slightly and caused lots of sparking between it and the comm....

Don't use a knife on your comm. This will probably bring howls of protest from hard-liners, but I've found the best way to clean a comm is to use Brasso, yep good ol' Brasso. The main ingredient of brass is copper so it's perfect. Put a little on your comm after each race meet. Wait a few mins, polish it off. You'll see how much better it looks. Spray any residue off with motor spray. Clean your brush faces with a comm stick. I've found this prolongs the amount of time between cuts, and the motor never loses power.

[lil_general_lee]

Well, I bet that doesn't compare to how my friend over geared his motor. The car rolled about 50 FT, started to smoke so we ran over to end up seeing the endbell melt right off the motor can. After tearing it apart the comm was black ! I think he deserves the Micky Mouse award.

[JP]

Thats nothing http://www.rccaraction.com/ubb/biggrin.gif http://www.rccaraction.com/ubb/biggrin.gif http://www.rccaraction.com/ubb/biggrin.gif

Wait til you mix snow in with that, not only is the comm black, the WHOLE ARM is black, the magnets has black crust the endbell is helf melted, but you just ruined your new 14x2 D3.

[Isky]

Thanks for the help guys...there are two problems...one, I have no where to cut my comm, two...whats two...um, I dont know which brushes to buy...and I need some shims...bad, real bad...my car ran at like half speed. Accidently broke the shims on my motor. Anyone have some extra shims?
- Isky