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Major pitch drift in quad

Posted by Chris on June 2, 2012 at 7:06pm

I just finished building up my first quadcopter (X):

  • RCTimer 2836-11 750kv Motors
  • RCTimer 40a ESCs
  • 12x4.5 props
  • Flamewheel 450 frame
  • Zippy 2650mah battery
  • Xbee for telemetry
  • Flysky 9x transmitter/receiver (er9x firmware)
  • APMv2 (Arducopter 2.5.5 Quad firmware

I have been having major drift issues to the back (pitch).  I've done everything as far as leveling out the quad, balancing props, throttle calibration of ESCs, checking the center of gravity, and putting styrofoam under the board to prevent vibrations and move it further away from the larger DC wires.  I can somewhat trim it out on the transmitter, but I really prefer to not do that at all.

I thought maybe if I adjusted the Rate Roll P value it would help out, but I noticed the lower I set it the worse the drift or lean becomes.  If I set the P value down much from the default value the copter will nearly flip backwards on take off.  If I set it very high 2+ it seems much better, but I still have to fight the drift on the transmitter.  

Does the APM board need to be absolutely level with the air frame? I sort of figured that when you level it in mission planner it would offset any inaccuracies of the board as it is mounted in the air frame.

I've tried to figure this out on my own for the past month, but I think it is now time to go to the community for help.  Does anyone have ideas?

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Tags: apm, drift, flamewheel
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Replies

  • Jerry Normandin June 4, 2012 at 11:35am

    Also after you run the test that John Church suggested, maybe it wouldn't hurt to re-calibrate the ESCs.

    I wasn't aware that large props on lower rev motors was ok.  Maybe you want to check to see if the props are balanced too.

    There's a lot of info on the net on how to balance props.  

  • Moderator
    John Church June 4, 2012 at 11:26am

    Hi,

    APM does not need to be absolutely level in the airframe. This is what our Level routine takes care of. You are right to use large props with low KV motors.

    Can you spool up your motors to just before take-off and look at the HUD in MP? See if you have drift being displayed there. After that, take your props off and try the same thing. Note any drift.

  • Jerry Normandin June 4, 2012 at 10:50am

    I've just started building drones so If there is someone else that can confirm what I know so far that would be cool.

    You've got large props for your slow motors..  Either reduce the size of the props, or get motors with a higher kv .

    Sure the motor has torque, but I bet it's not fast enough.   My 30a motors are rated at 1400kv.

    A 2650ma battery is pretty heavy. and you are loaded with equipment. 

    Try to fly with a lighter load. For laughs try a lighter battery.. like a 850mah, remove the xbee and flysky.

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