The Witch Gets a Broom...

3690980367?profile=originalA fundamental characteristic of multicopters is that they change flight direction and speed, and also hold position against a wind, by tilting the entire aircraft. If the multicopter is being used as a camera platform, the camera mount must compensate for this on the fly with all the attendant mechanical and electronic complication of that, even if the flight stabilization system is ultra-smooth and quick. I've been kicking this problem around for a while with my friend Gary McRay (a very active contributor here on DIYD). One idea that arose was to provide separate horizontal propulsion for the multicopter in the form of one or more propellers acting on the horizontal axis, as in a conventional aircraft. Thus the regular rotors would do nothing but provide lift and basic stabilization while the horizontal prop(s) handle travel, leaving the platform level in the process.

To give this concept a very preliminary and crude test, I've plundered the stick-fuselage, motor, prop, esc and battery from a Slo-Stik airplane and mounted them on my APM2 controlled Flame wheel F550 hexacopter (named  the Witch - "Hexe" being German for witch...).  See attached really bad cellphone photo, proper ones will follow in an update. So, the Witch has a broom to ride around!

Mounting is via zip ties through existing holes and some double-sided foam tape to keep the stick from sliding around on the Witch's upper deck.

Throttle control of the new prop is achieved by assigning a rotary knob on my Tx (a JR 12X) to an unused channel (Aux 5 in this case).

Now we're waiting for a break in the weather here on the Northern California coast. A flight report will follow. 

Conventional props pushing or pulling rotorcraft are nothing new of course, beginning perhaps with autogyros in the 1930s. Currently Sikorsky and maybe others have prototype hybrids in the air. We don't know if anyone else has played with this concept in our sandbox here, but we're having fun!



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  • Made the first flight of the Witch-with-broom this morning between rain showers. The expectation was that the hex would rocket off horizontally with not much of a push, and that the mounted motor was probably way more powerful than it needed to be. But in the event it didn't move the Witch along at much more than brisk walking speed, even cranked up!  On reflection, what may be happening is that the horizontal thrust of the pusher, being well above the Witch's center of gravity, is trying to induce forward tilt, for which the stabilization system is compensating by "leaning" backward. So if that's correct, it's fighting itself. Next step is to move the broom from the top of the top deck to the bottom of the bottom deck, which will be much closer to the CG (due to location of landing gear, GoPro & mount, and batteries). That should tell us if this theory is correct. In any case, this is sure interesting!  Will try to post a video later on.

    Slightly off-topic: in my original post I misspelled my friend and flying co-conspirator's name - it's Gary McCray.  

  • Here are a couple pictures of mine which I am currently referring to as a QuadroPlane.

    Working name only, hope for better.



  • As Oliver knows I am trying the same thing but in tractor mode on my Flamewheel 450 and with a much smaller horizontal drive motor.

    Basically if this works out I am going to put together a quadcopter with four horizontal thrust motors and reassign directional control to them.

    Initially the APM will be used for stabilization, altitude and yaw control and the separate horizontal motor controller will provide positional control.

    Eventually it might be integrated into or with the APM for fully automatic control.

    The side thrust motors are considerably smaller and lighter than the primary vertical motors so weight gain is minimal.

    The hope is to achieve much higher air-frame stability by eliminating as much roll and pitch as possible as well as reducing or eliminating undesirable vertical excursions even under windy or gusty conditions.

    It should at least be interesting to watch in flight whether it is ultimately successful or not.

    Any thoughts for a name, nobodies ever done anything quite like this and it needs a good name?

  • Brilliant,   I am replying just to subscribe to this post.  Oh and I assigned it to the Aircraft platforms section.  Keep us informed and by us I mean me.  

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