Black comms

[slotwookie]

What causes the comm to become black. Does this impact the performace of the arm. My arms get black but even my backup car is alway the fastest in its class.

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Wookie,

That black finish is composed mostly of various metal oxides and carbon from decomposition of the brush and commutator. This process is accellerated at higher temperatures, and so the amount of black deposits is a good indicator of how hard you are pushing the motor. Cool running motors usually stay shiny over the majority of the brush track on the comm.

You probably are losing some power by the time the black deposits are readily visible. Try gearing a bit lower in most cases. I'm happy for you still dominating the local field, but be aware that someone is always just a lucky discovery away from catching you!