New Zealand, Canterbury, Rolleston
Joined Oct 2011
If it is a new motor this shouldn't be the fault but after using one of these motors for a few flights, the "thrust washer", (a plastic tube over the motor shaft), melts and the windings rub against the front of the motor housing and wear through and short. There should be less than 1 mm of end float (in and out movement) of the motor shaft. Once it is more than that the motor will fail.
I suspect these motors are built for helicopters and in that case don't have the pull of the propeller to contend with. Other small planes (Champ etc.) use gears and again the motor doesn't need a thrust washer.
I have tried "pre-building' by replacing the plastic tube and putting a 2 mm length of hypodermic tubing over the shaft and a 1 mm copper wire washer in front of that but because of the tight fit it is easy to short through the winding insulation and it doesn't work. The copper washer is made by taking 1 mm wire and wrapping it round the motor shaft and cutting off. Also flattening it a bit with pliers. Even doing this in front of the plastic tube helps the motor life.
The real answer would seem to be changing the electronics and fitting a brushless motor. I'm in the precess of doing this.
See - http://www.rcgroups.com/forums/showthread.php?t=1502317
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