After rough landing, weird motor/esc

Hi all,


I had a rough landing in wet grass (would call it a crash but no visible damage), and when I got to the quad the ESCs were beeping. Shortly after I was able to take off, but no yaw control and  then it flipped (first time ever, normally its dead on). Since then I can't even take off.


I've been working it on the bench, and I can start up, and control all the motors no problem without props. Holding it on the ground with props on, I push the stick to each corner to test that each motor lifts as expected. Some motors are nice and steady and will produce steady lift, while several will lift and then slow down, then lift again etc. If I let go at low rpm and try to steer, the quad will go forward, regardless of stick input.


I've checked the sensors, and each responds as expected (I graphed the output, and checked accel and gyro responses, which were normal).


Any thoughts on what could be wrong? I have 4 esc/motors spares, but I am hesitant to just replace it all without knowing what might be the issue. Any suggestions would be great.




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  • Hi all,


    Thanks for the inputs. I replaced one motor, but I'm not sure it behaved any differently. I again re-calibrated the ESCs and the jitter/unbalance is mostly gone. I just tested it in the garage (bad weather sigh. Snow soon). It hovers fine, slight drift, and can again rotate left/right. I've put it back together, and will take it out tomorrow for a full test. I'm hoping its all good again. I crashed on my maided FPV flights, and would really like to try again :)


    Thanks again,


  • Probably a loose axle. Take hold of the prop with one hand and the bell of the motor with the other and see if the axle can be rotated in relation to the "bell" of the motor. If so, tighten it and you will be alright. The set screw often looses its grip in a crash or even in a lesser encounter with any part of the solid environment.

    A very slight slip is enough for the prop to loose power.


    Checking for this has become part of my preflight inspection.

  • Hi,

    Thanks for the suggestions, i've tried redoing the setup, but no luck. I did try just hooking up 4 servos, as each individual pair of esc/motor seems to be working.


    The servos don't respond as I would expect, some twitching, and two do not move (even if they are the only ones). Is there a suggested way of checking the PWM outputs, short of an osciliscope?




  • 3D Robotics

    I would connect the suspect motor and esc into a spare receiver, and then the suspect motor with a working esc, and the suspect esc with a working motor. Isolate the issue to one of the above and replace. I suffered a similair issue where my quad tipped over upon landing, suddenly stopping the motor. The motor was fine, but somehow the timing of the esc got messed up and it wouldnt provide uniform thrust regardless of what motor i connected it to. although only 10 bucks to replace, it was a pretty annoying situation. 

  • 3D Robotics

    I'd do a full setup again and see if that clears it up.

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