Coax dodeca-copter on Arducopter 2.x

Hi guys, I've been grounded for a while (due to a motor that I was too lazy to fix) but I'm back now, and I have questions.

I'd like to eventually make my current hexa-copter, into a coaxial 12 rotor machine; a dodeca-copter. I was wondering if anyone else had done this, and how it's done.

My current frame is a Tarot FY690s, modified with longer arms to be 800mm from the hub of one motor to the one directly across from it.

Currently mounted on each of it's 6 motor mounts is one of these (http://www.ebay.com/itm/Mystery-5010-750KV-Quadcopter-brushles-motor-for-multi-axis-aircraft-/271517507633)

Not necessarily that brand but  5010-750kv motor of that design.Each motor swings a 13"-5.5 prop

Each motor is controlled by a Hobbywing Platinum Pro 30 Amp opto ESC.

This is all controlled by a "Arducopter" flight controller Running 2.5 firmware (I think, it's whatever the latest 2.x firmware is, updated it yesterday 9/6/18)

My question is basically- is it possible to use a 'Y'-splitter on each servo channel to the motors and control 2 ESCs and their respective motors per channel?

Basically signals from each of the 6 output channels would go to 2 ESCs and motors on the same arm counter-rotating one another.

Is it really that simple or will there be other limitations, such as the Flight controller being unable to control 12 motors. Will each motor pair be able to share a contacts on the power distribution board or will I need a Power distribution board that can give 12 separate motors, 12 separate spots to draw power from?

Are there any Flight controllers that /can handle 12 motors without modification?

How do Coax-copter control their Yaw? If you slow the counter-rotating motor on one side and speed up the ones directly opposite of them, won't that just cause a roll as opposed to a yaw? Since the motors are counter-acted by one another?

It seems to me that each channel would need to control the upper motor on one side and the lower motor on the side directly opposite, to achieve yaw, but that would cause other problems, such as unwanted yaw when trying to control pitch, I think.

To overcome this, would i need to run it as an Octo-copter and have outputs 7 and 8 control pitch and yaw, or upgrade to another Flight controller?

...

After some further research it appears that simply setting up the Flight controller to fly a coaxial 6 rotor would solved all the previous yaw and pitch issues I was mulling over, it'd simply be a Y-6 only doubled and inverted in every way.

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Replies

  • I agree is old discussion, but need your advice. Indeed 2 coaxial motors spinning on same direction (on the same arm) does not have gain, not a good lift. Counter rotating provides a better lift.
    But I am thinking to next setup: on my hexacopter, I want to add only 4 motors on position 3, 4, 5, 6, which will be controlled by a Y split. And not duplicate motor 1 and 2. In total 10 motors, not 12. This way the yaw will controlled by motors 1 and 2 (left/right), see setup from link. What is your opinion?

    https://ardupilot.org/copter/_images/motororder-hexa-x-2d.png
  • See also this: https://discuss.ardupilot.org/t/dodeca-hexa-esc-wiriing-and-propell...

    Dodecas are not supported yet with Arducopter on mainstream release, but it is available on  3.6 dev (master).

    Dodeca-Hexa ESC Wiriing and Propeller Direction
    Hi All A new frame class dodeca hexa is added recently in Copter Firmware. But there are no details about how to connect ESCs to Pixhawk and there…
  • Marc beat me to an answer and i agree completely.

    I am certainly not an expert in this field and therefore could not possibly give a reasoned argument why contra rotation is better but you are correct in understanding that it must be better. Of course it is otherwise this would not be the norm.

    However, you wanted an answer to your question about Y splitters and the option i gave is an easy solution for you and confirmation that splitters will work perfectly well in your scenario.

    Whether it flies well is up to your choices.

    Good luck

  • ContraRotation on a flat Hexa or Octa is for Yaw control.

    Developpers choose to have contrarotatings motors on Y6 then Octo-Quad X config for thrust distribution staying even during Yaw.

    As 12 motors control card are not common on the market, your configuration should be a double Hexa flat with each motor group rotating in the same direction. So you can use the Hexacopter settings without modification and have good yaw control. With contrarotating pairs you cannot have Yaw control.

    Marc 

    Darius said:

    I mean I understand where you're coming from, having the motors turn the same way for each pair would be the simplest way to achieve results. But normally they contra-rotate for a reason, right?

  • I mean I understand where you're coming from, having the motors turn the same way for each pair would be the simplest way to achieve results. But normally they contra-rotate for a reason, right?

  • If it's that simple then why doesn't everyone just have the motor-pair for each arm rotating in the same direction on any coaxial setup 6, 8, 12, 16 or what have you? What's the point at all for contra-rotation?

  • Why counter rotate the pair on each arm ? My X8 does this but the flight controller knows what an X8 is.

    I do not believe any flight controller can operate 12 independant motors.

    But you dont have to, use the Y slpitter as you mentioned and run it , from a logic point of view, as a hex. For this the motor pair on each arm would have to be doing the same thing. By that i mean spinning in the same direction,simples.

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