Wednesday, August 3, 2016

FK130PH-2460 Motor Failure

A quick tech observation post: This -2460 was one of the pair driving the flywheels in our scout's pistol Stryfe during NvZ'16. It had previously given reliable service through several games. Coming into the final mission briefing, the user discovered a malfunction with a dart left between the flywheels, cleared it, and then found the dead motor. The Vulture in my backpack was promptly issued.

On gun teardown the offending motor was found to turn freely and smell of burnt magnet wire. The motor was then removed and disassembled and the cause was found to be a winding burnout as expected. You can see melted varnish on 2 poles.

Commutator, brushes, and winding terminations were all intact and the windings had not structurally failed.

The battery at the time of failure was a 2S 1600mAh Monolith.

User was questioned as to what immediately preceded failure and noted that he had been running to a safezone and then noticed that his flywheels were locked up. I could not get a clear idea of how long the motor may have been stalled. It is possible that this is simply a sustained stall failure from a malfunction followed by accidental activation while running, but also possible that the only stall occurred when the problem was discovered and the failure had been ongoing up to that point.

Based on what happened here, the bright (clear varnish) color of the undamaged wire, and the failure mode (melting at what must be a low temperature from the lack of carbonization, compare to the appearance of other high quality motors' burnouts, example being the Mabuchi -3240) I have my suspicions that these cheap motors are wound with wire of insufficient insulation temperature class and are vulnerable to thermal damage from momentary stalls and/or sustained hard use.

I am planning to preemptively take these out of the remaining Tacmod in the squad that is equipped with them as soon as the chance presents itself to do so. Suspicions like that are not worth playing with.

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