Gyropter

Background

A unique radio-controlled rotorcraft consisting of a 3-bladed rotor, each rotor equipped with a pusher prop and an aileron, with the ailerons actuated by a swashplate-analogous mechanism at the center, mounted on a gyro-stabilized turntable.

Video

Diameter: 40”
Empty Weight: 500g
Battery: 3S850 (+80g)
Motor: 4x 1404 3800kv

Theory of Operation

At the center is a turntable mounted on two ball bearings, spun by a brushless motor using a #64 rubber band. Power is delivered via a slip ring module. Aboard the turntable are two key components: the flight controller, and the three servos holding the swash ring.

Like a helicopter tail rotor, the flight controller stabilizes its own yaw axis with the turntable drive motor. Like a helicopter swash plate, The pitch, roll, and collective inputs are mixed into the three servos, and the throttle controls the three pusher prop motors in unison.

Each wing root is equipped with a lever that slides on the swash ring and pulls on a kevlar string extending out the wing to an aileron at the wingtip. Performance of the control system requires minimal inertia, friction, and backlash in the linkages, and it was designed with that in mind; but care must also be taken during construction.

The slip ring is rated for 300 rpm, but analysis of video from first flight tests showed it reaching speeds of 450 rpm. This equates to the wingtip traveling at 53 mph and experiencing 113g of radial acceleration. The structural failure point of this design is not known.

For balanced flight, the following adjustments are expected to be required: that the swashplate is exactly flat when the right stick is neutral; that its height is suitable for zero collective; that the center of gravity is exactly in the center; and that all three wings have the same relationship between slider position and aileron position.

The flight controller must have two motor outputs and three servo outputs, in addition to any required for user accessories. A dedicated servo BEC in the FC is preferred for the three swash servos – to reduce current in the slip ring, power should be stepped down from 12v (3S) to 5v within the stabilized section. The author used a Matek F411Wing.

The slip ring connects wiring in the spinning section to the stabilized section. The hub provides room for a 12mm diameter capsule; many different types of module are available in that form factor. The minimum number of slip ring channels is four: power and ground supplied to the flight controller, and two ESC control signals. (The single throttle is split to all three ESC inputs.) More channels are desirable for current sensing and ESC feedback, and for any accessories that might be added to the spinning section such as RGB LEDs, sonar altimeters, etc. If extra channels are available, power and ground should be doubled or tripled up.

The recommended ESC is any 20mm 4-in-1, and there is a footprint for the same. The author used a Diatone Mamba F30 Mini.

As an alternative, four single ESCs could be used. In that case one would be placed in the hub to control the yaw motor, and the other three would be placed in wings between the root and the motor. Instead of three motor phases, the wing connector would carry power/ground/signal.

If the vehicle is to be flown LOS, clear orientation indicators are necessary, as the vehicle is symmetric. The 3d print was designed to fit a strip of 12 WS2812 programmable RGB LEDs but the author ended up using a few simple red and green 5mm LEDs.

Other

During development a one wing version similar to a Charybdis was considered. However this design is not a great idea. A monowing like this should minimize its central weight, and the gyrostabilized control assembly is contrary to that goal.

This guy didn't seem to know that.