Cause of motor stall?

So this is really getting on my proverbial mammary glands.

I’m having issues with my 7inch LR quad whereby motor number1 (rear right) randomly stalls. I’ve ruled out desync as it can stall in idle, in a hover, pretty much at any throttle level.

I’ve tried to recreate the stall on the bench, subjecting the quad to excessive vibration, constant throttle changes, applying excessive load to the motor, monitored the temperature of the power FET’s, resoldered the wires, changed the wiring loom between the 4in1 ESC and the flight controller, and no matter what I do the quad behaves like a champ on the bench.

But when I put it in the air the motor still randomly stalls. It can stall when armed, it can stall on throttle up, I can leave it in a hover and at some random moment it will stall. When it stalls and the quad hits the ground I’ve checked the temperature of the motors and ESC’s and they’re all well within acceptable heat ranges.

So other than the suspension of natural law, what are other’s thought’s on the matter?

It’s got to be a fault in the ESC or motor. Or I suppose the wiring from FC to ESC.

Though you’ve simulated vibration on the bench I can’t see what else it could be… I suppose the frequency of vibration might matter?

So my next step would be to swap motors around and see if the same motor still fails. That would then mean at least you’d know if it’s ESC/FC or motor related…


These kind of intermittent faults are always the hardest to find :unamused: I would change the motor to a different position like Yith said as a starter. Atleast that would rule the motor itself out

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I know nothing of these machines but I’ve been fixing mending for a living for 30 years, my money is on the motor.

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Time to remove the motor, put it on my motor testing rig, and thrash it to within an inch of its life. The only point of failure I can think of will be where one of the three wires terminate on the three windings.

For the time being the quad has been put into the queue along with other repairs outstanding.

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There isn’t something inside the motor bell snagging every now and then causing the motor to stall? Probably a long shot but might be worth checking if you haven’t already?

Not that I could find. I’ve spun the motor in both directions at various speeds from idle to full throttle, monitored for unwanted vibrations.

The one thing I haven’t done, as I totally forgot, is to check the black box data. So before I start breaking the quad down to a molecular level I’ll dig out a micro-SD card and test fly the quad to the point of failure. Sod’s law I bet I can’t get it to fail now.

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Definitely worth a look but like you say, as soon as you put an sd card in, chances are it will probably sort itself out :laughing:

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