Y6 drags tail on full power climb.

Posted by Euan Ramsay on September 20, 2014 at 9:07am

Beginning to wonder if I have a flaky rear motor...

Running a Y6 in A format, with 11" on the bottom and 10" on the top. Tmotor 2216's 900kv motors. running on 4S.

Flies very well, and is perfectly stable at 80kph, even touching 100kph in tailwinds. Vibes are good. Loiters very well.

However, if you gun 100% it from hover, it'll sit on its tail (ie nose up) quite badly, and struggles to get back level until I lift off.

CoG issue (I think it's ok), or a dodgy motor? Or....?

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Replies

  • Haygood September 20, 2014 at 11:23am

    ESC not calibrated or flaky?  Prop bent, damaged, or just not right? 

    • Haygood > Haygood September 20, 2014 at 12:28pm
      Yeah, B is just more convenient.
    • Euan Ramsay > Haygood September 20, 2014 at 11:24am

      Nah - all fine; first thing I checked.

    • Haygood > Euan Ramsay September 20, 2014 at 11:29am

      Then you are pretty much down to CG, or bad motor.  The problem there is the logs will show you it is one of these two problems, but not which one, I think. Regardless you can move CG forward and see if it flies better.  

    • Haygood > Haygood September 20, 2014 at 11:30am

      If the wiring were easier to reach I'd swap the top rear motor to the left and the bottom rear motor to the right.

    • Euan Ramsay > Haygood September 20, 2014 at 11:32am

      It's an option. If I'm taking it apart, maybe try the "B" config as well?

  • AndyC September 20, 2014 at 9:17am

    I think you might be right with it's a center of gravity issue - if the rear motors are having to produce more trust to compensate for an uneven weight distribution that'd seem to explain why its level normally but struggles to keep up why at full throttle.

    You could test this by enabling motor logging, flying in a stationary loiter for a few minutes, and then graphing the data to see whether the rear motors are running significantly higher than the forward four.

    • Euan Ramsay > AndyC September 20, 2014 at 11:27am

      Yeah, I'm having problem downloading logs in 3.2rc7 via mavlink, so no joy.

      I need to find a way to run some string round my motors and landing gear to get my CoG. Remind me - CoG in a Y6 is the same spot as CoT (centre of thrust)?

    • AndyC > Euan Ramsay September 20, 2014 at 12:22pm

      As I understand it (hopefully some one will correct if I'm wrong), CoT is equidistant between the three co-axial motor positions. For optimal climbing, CoG should be at (or very close to) the CoT, but this might not be the case depending on how you've mounted batteries/accessories etc..

      I think your sting idea should work fine as a rough indicator.

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