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  • Hi,

    This is a similar solution to my PhD research. I came up with this idea in 2013.

    You can find my prototypes here:



    The paper: http://limo.libis.be/Lirias:Lirias:lirias123456789/455713

    My design is focused on fitting inside the narrow corridors of fruit orchards for fruit inspection. 

    I focus on endurance and less on high-lift and therefore I use single large props and not co-axial ones.

    Best regards,


  • Thank you, each argumented criticism is very valuable and useful.
    I'm not sure about the quality of navigator engine with 20-inch rotor (II think that is always better to have somewhat stronger engine on the rotor-to have some power to spare), 
    and it is acceptable that 4 stronger EM with corresponding rotors provide the same, or even better lift.
    In any case, from the drone I gave up, because the price is too high, and the effect of invested effort and money is uncertain.
    Of course I will try with another idea to come to a satisfactory solution.
    At the same time it is much clearer (to me), why Kamov always uses widely spaced contra-rotating rotors on their helicopters.
  • Hi,

    Twenty percent is considered about normal loss for a coaxial configuration.

    However, it can be a bit less and the ducted configuration can also help a little.

    That said, why bother, your setup would be more efficient and work just as well using single motors as the primary lift motors rotating in opposite directions and would be more efficient.

    Of course the most efficient mode would be to simply make your 2 coaxial units into 4 equally spaced  lift units and lose the 4 control units, of course that would be a quadcopter.

    Your Octo Thing would definitely fly as you show it, however, the anemic (comparatively) little control units would provide very compromised control, speed and response.

    And the combination of redundant control / flight motors and coaxial props would reduce carrying capacity and battery life appreciably.

    Honestly simply making a quadcopter that used only your 4 lift motor / prop units would be considerably superior in every way I can think of.

    Best regards,


  • But I am not sure completely in the lateral sponsons, if I remember well after the project Hummingbird NACA published a manifesto why is not good to insert rotors in the wing (I didn't see that material so I dont know why is this not good)

  • To be honest your figure (20%) is very high, do you have some internet address, or it is from the book? Also lost in one way, you benefit in the other (puting rotors in the well gives me a higher thrust)

  • You can see it better in Autodesk fusion 360 gallery, it is just proposal

  • Since I'm thinking about it..
    My only concern is that coaxial motors lose 20ish percent efficiency, I think.. 
    So the only real benefit of that setup vs 6 or 8 spread out motors might be size..
    but then, size can be a very serious design parameter, so I can see the benefit. 

  • I think it's a great idea. (I hope you code, so you can add it as a frame style.. or a programmer sees it and tries it)

  • Not yet, but I think it is quietly logical solution to enhance maximum power for the given motors (static thrust calculator gives figure of much more than 30 kg for tiger EM and 26 inch rotors and 4 navigator EM with 20 inch rotors)

  • This looks like a model, right? 
    It's really interesting, with the middle motors providing lift, and the smaller outer ones providing control..  Have you flown anything with that configuration?

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