Discussions

V Octo Copter

Posted by Bart on September 26, 2013 at 4:06pm

Hello all,

I have finally, finally finished building my octo, and had two test flights. Or rather, hops.

I have 10x45props with Motor AC2836-358, 880Kv from 3DRobotics. At the time, they were specified to provide 433grams of lift at 50% and 1095grams at 100%.

My frame, with 5000mah, 30C battery weights in at 3000grams. At 50%, I should have 3464grams of lift, in an ideal world.

However, while I start hopping at 50% throttle, even at full throttle I barely lift a foot off the ground.

I'm using custom motor mixing, to match my frame, as follows:

add_motor_raw(AP_MOTORS_MOT_1, -0.859746, 0.333333, -1.000000, 2);
add_motor_raw(AP_MOTORS_MOT_2, -0.859746, 1.000000, 0.867150, 1);
add_motor_raw(AP_MOTORS_MOT_3, -0.664349, -1.000000, -0.984903, 4);
add_motor_raw(AP_MOTORS_MOT_4, -0.664349, -0.333333, 0.882246, 3);
add_motor_raw(AP_MOTORS_MOT_5, 0.859746, 1.000000, -0.867150, 5);
add_motor_raw(AP_MOTORS_MOT_6, 0.664349, -1.000000, 0.984903, 8);
add_motor_raw(AP_MOTORS_MOT_7, 0.664349, -0.333333, -0.882246, 7);
add_motor_raw(AP_MOTORS_MOT_8, 0.859746, 0.333333, 1.000000, 6);

I realized (longer after staring the build), that a V shape is not optimal, but surely I am not losing this much power? I have calibrated the transmitter, ESCs.

Any thoughts or oversights that explain why I don't get the lift I am looking for?

Thanks,

Bart.

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Replies

  • Anthony October 27, 2013 at 10:22am

    You state that your using a 5000mah, 30C, but how many cells?

    At first glance it looks like you have an under-voltage situation??

  • Bart September 27, 2013 at 5:26pm

    More testing, I can get it up to 6' now, but as soon as I touch a roll pitch yaw stick, I plummet. All the pops were fine.

    Especially yaw, I end up with half the motors at 1200us output, and the other four at 1800. Have to see what could be causing that.

    I also tried adding a second battery pack, in case the pack couldn't source enough, but that didn't help.

    If anyone has any thoughts, let me know!

    Thanks.

  • Tissy September 27, 2013 at 3:47am
    Right propellers for right motors? Ie are the clockwise propellers on the clockwise motors?

    Even the most experienced builders sometimes get it wrong (me for example).
This reply was deleted.

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