This project was started in , electronics and control loops. Because I always need a cool project to learn new things, it was clear that something that can fly had to be built.
The project started as a "tricopter-only" project, but as I wanted to build smaller vehicles with more payload capacity, I decided to make some quadrotor, hexacopter and Y6 hexacopter firmwares too. My main interest is to build very small MAVs that fly as good as larger ones (or even better) and that can be controlled by wireless video link. I also experimented with autonomous flight in GPS-denied areas (video), and with GPS assisted autonomous hover (video).
-- William

Contact: Shrediquette @ g m x . d e --- All content published under CC Attribution-Noncommercial-Share Alike 3.0 Germany

GEMïNï motors arrived

Yesterday the motors arrived from hobbyking (Turnigy C1822-2100KV). As usual with small motors, the shafts were all way too short to attach a propeller. Three-bladed props do not really work nicely with the provided prop-saver... Hence the original shafts had to be removed. It was pretty hard to exchange all motor shafts, as they have a very tight fit with the bell, and they are additionally glued with cyano. Some "nail polisher remover" and some heat helped a lot to remove them. The quality of the motors is really good.

I did some tests and compared them with the Robby Roxxy 1815-25 that I use in a similar copter (the BOLT). Both motors have the same size and the same weight, Surprisingly, the turnigy motors have the exact same performance as the much more expensive Roxxy motors. The increased KV number leads to an increase in the peak RPM and thrust.
The endurance with these motors will be around 8 minutes (the aerodynamic efficiency of the GEMiNi will be higher than that of the BOLT, because coaxial motors have somewhat higher losses - a factor of 0.75 to 0.8 is a good approximation).

The only thing that is really different between the motors is the price per motor:
9 € Turnigy (incl. taxes...)
27 € Roxxy


  1. Hello William Tx.
    Please tell me how to behave in the engine, which censures exactly which trees to take to replace (you can link)?
    Thanks in advance.
    Regards Sergey.

    1. Dear Sergey, sorry, I don't understand a word... I guess you used the Google translator...?

  2. Yes, Google translator, I don't speak German, do not speak English, so I use a translator.

    I was asking you about engines Turnigy C1822-2100KV , how they behave, there is a claim.
    What shafts you purchased for replacement, please give the link.
    Sincerely, Sergei.

  3. I made the shafts myself from 2mm steel. Very easy...