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Ticking/surging motors when given constant pwm signal
#1
I just installed some EMAX RS2205 2300KV motors to replace some stock Spedix brand motors of the same size and kv.

I powered them up under the betaflight motor tab to make sure they were all running the correct directions, and they sounded strange.  They sound like they are constantly ticking or clicking.  At first I thought maybe it was a bad bearing, so I tried each motor individually, and they all seemed to make the same noise.  I figure the chance of a bad bearing on all of them is pretty low.

I put a finger on them while they were spinning, and they seem to be "surging" or pulsing with the ticks.  The motors do seem to stop "ticking" when you get above ~1500 though.  I never remembered this with the old motors.  I took this quick video this morning on my way out the door:



What's going on here?  Something with esc timing?  Is it even a problem?

I'm running multishot - don't remember all of the settings in the esc off hand, but I can check later if it matters.  I'm thinking about trying oneshot, see if that has anything to do with it, then try to mess with the esc timing.

Any advice is helpful.
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#2
First thing I'd do is make sure the mounting screws are not making contact with the windings of the motors.
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#3
Just found this issue on github, and this associated video:

https://github.com/betaflight/betaflight/issues/1537



It sounds like it could be associated with looptimes and the oneshot refresh speed interfering somehow. The suggestion is to decouple the PID loop and motor PWM speed. Now I gotta go find that option in Betaflight.

Interesting to note that his motors also twitch when disarmed (see the last two seconds of the video above). I recently had to lower my disarmed pwm value to 850 to get rid of the twitching. I'm betting that the clicking when the motor is at speed is the embodiment of the same signal interruption.

ETA:
Of course, Joshua Bardwell has a great video explaining what the decouple option does, so I'll try that out later:

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