Scary Wobble During Quick Movements. Cause?

Posted by Christopher Gehrich on May 8, 2015 at 8:46pm

I was flying my hex yesterday and everything was going well.

Pixhawk, Tarot680, 800KV high watt motors, SK40A ESCs, (2x parallel) 4S 5200mah 25C LiPo

Then as I did my fifth and final power-climb I heard something weird, like prop chopping through rough air. Panic washed over like many of us have had such sensations, but I slowly descended and landed without incident.

Now the hex hovers fine as before, but if I punch throttle the left side dips first and the hex oscillates 3 to 4 times. I immediately back off of the stick. Left side will also dip when I yaw left (this maybe important for diagnosing which motor has issues). I did an ESC recalibration to be sure, didn't solve the problem. I think one of the ESCs may have been damaged somehow. There is no "magic smoke smell" or scorch marks and all connections are still secure.


Here is my log for some gentle flying with a few attempts to cause the wobble (not sure what time).

2015-05-08%2023-02-50.log

Any idea what my issue may be? Any tips on how to diagnose it?

Thanks.

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Replies

  • Christopher Gehrich May 10, 2015 at 1:55pm

    Thanks a lot for identifying the issue for me! That will be a big help.

  • John Edgerton May 9, 2015 at 5:23am
    Is there any chance that one or more props is installed upside down? I saw similar symptoms once when I installed one of my props incorrectly.
  • Andy Roberts May 8, 2015 at 10:08pm

    I had a similar problem with my Y6 using the APM. Erratic, it would be OK for many flights then it would dip hard on the left and recover. Caused one hard landing and broken undercarriage. Preceded by a loud ticking sound so I always knew when something was going to happen. Managed to see which motor was affected and replaced the ESC. Fine ever since. Induce the problem and see if you can spot the problem motor. Getting a friend to video it may help.

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