V Octo Copter

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

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

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

  • 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.

  • 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).
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