Quadcopter with down facing motors/props


I'd like to try a quadcopter with motors facing down. This setup could possibly provide better stability in the wind (hypothetical), I'm only guessing here. Since nothing will obstruct the prop wash, this could help. Now I'm not sure if I can use normal quad APM firmware for this (with motors facing up).. What do you think ?


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  • How do you change the motor direction in APM Planner 2? I do not see any options for that.


    DG said:

    Nothing changes for the firmware, but performing Auto Tune is a good idea.

    Mounted the same why. The props are flipped (print always faces upward) but stay on the same motor,  and the motor rotations are reversed.  Very simple.

    It can be a brain teaser, but with the motors facing normal up and spinning clockwise while viewed from above, when flipped over the props are spinning ccw when viewed from above. Therefore the motor rotation must be reversed from whatever direction they were spinning before flipping.  I've done it at least 17 times so have retained in memory :)

  • Hey Paul! don't sweat the old post. Yes I think that's been done' but assuming you have a square frame I don't think its worth it. Plus the props up above will cause more turbulent flow over the props underneath - causing reduced efficiency, more vibration and potentially bad attitude control.

    It might be more worth it in something like a hex where the props are only close to their nextdoor neighbors, and very far from the opposing prop 

  • I know this post is old, but I have an idea and I wonder if it has been done. I want to put 2 motors facing down and 2 opposing motors facing up. I will have nothing above or below so I am hoping in theory to be able to put larger props on a smaller frame.

  • I've built three lawnmowers (Down Facing Motors) and have had good success. I like downward as I pull the retaining clips on the motor shafts allowing me to be able to pull the tops of the motors off with the propellers still attached. Great for easy transport, and removing metallic grit I sometimes pickup while stiring up dust in driveways. One downfall. Had a failure once, with the props drag being lower then center of gravity, the quad turned upside down as it fell. (Crushed all of the good stuff...)

  • This discussion cemented my building a Danaus upside down:


    Full details at:


  • Hey if you hadn't thought of it already, having upside down motors actually gives you a tiny bit more safety in that, if you lose the C-clip that holds the motor shaft in, the prop will not pull the shaft out. In fact, I believe you can fly without them. 

    Also you will have potentially a bit less airflow over the motor, beware of that. 

    • I pull the C-clips on my downward facing motors. This way I can just pull off the tops of the motors and props with them for transport. Also allows for cleaning of iron grit that the magnets can pick up.

    • There is no weight on the c clip, the shaft is held in place by magnets.

  • I use it in my quadcopter long time and I have no problems , in fact I think it is more stable than other configurations
    • What's the specs on that quad?  And what is the gimbal?

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