Vision 12x3 melted com!!!!!!!!

[kriss]

Hi all,
I have just ran my vision in a Yoke BC special with a 20 pinion. I was on a small tight track(30ft straight) It seemed to be good at the start but then it got slower an slower and then stopped. I took my motor apart and there was what looked like brush material melted to the comm. What do ant of you think has been the problem?

Chris

[Jason Potter]

are you running 3300's Chris?

we had a lot of problems last season with motors melting, and I am pretty sure in the end we came to the conclusion that the battery's give out far more than the motors can cope with.

[burgie]

it could also be a "bad" set of brushes...

[PDW]

There are a number of things:

Gear ratio - if you run the wrong gear ratio, the motor gets very hot - often enough to melt things.
Transmission - if the transmission is not running freely, the friction makes the motor work too hard, it gets very hot... (see above)
Motor faults - there could be something in the comm slots, a short in one of the stacks, a dodgy capacitor, some dirt/rubbish picked up from the track. All these make the motor get very hot... (see above, above!)
The motor was waaay overdue for a rebuild, and simply gave up the ghost!!

One thing it has nothing to do with is the cells. Motors will only draw the current they want, the cells cannot deliver excess. Cells from 20 years ago will still deliver enough current to melt a motor. If any of the above happen, the motor can draw high current for an extended period (as opposed to the very brief period of acceleration) and that is what makes them too hot.

Sounds like a bin job to me - forget the post-mortem and buy another motor. Rebuild the car completely before using it, to be sure that the car is not the problem. HTH :)

[MikeS]

Kriss, as most of the previous have said, the motor is now no use.
There are a multitude of things that could have caused it and they have all been mentioned already. One thing I would add, is that if your motor is THAT overgeared and running THAT hot, the brush shunts normally let go first (desoldering), then the armature winding tag joints......filling the inside of the endbell with silver particles.

My comment is about the current cells - they ARE the cause of a lot of motor problems these days, but indirectly! This is simply because these cells can deliver a large current over a much longer period, which means that if there is something wrong with the car or the gearing, there is a much higher chance that you will destroy a motor. The motors today are being presented with a much higher everage voltage over the 5min period than they ever were in the past.

With the previous generation of cells, and higher IR ESC's, the cells would lose their abiity to deliver such motor destroying levels of power long before the motors gave up. Motor problems have only become more common since the advent of low IR high capacity 3300 cells and their ability to sustain higher average voltage levels.

[MikeS]

Pete pm'd me ( thanks Pete) with some concern that some people reading my post might assume that I was stating that the cells were the problem, I don't actually think anyone would have read it in that way but to be on the safe side.........and for Pete ;)

I re-iterate that it is not the cells that are the direct cause of most motor problems, but other mechanical or gearing issues. My point was that the capacity of these modern cells to deliver such large levels of power just results in a motor problem that lesser able cells would not cause.

The moral is to ensure your motors are in good condition and fettle, correctly brushed and sprung (most motor problems I see are due to being under-sprung!), geared correctly for the conditions and your cars are free running, then you should have no problems.