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Description of the Picoflyer, smallest RC helicopter ever presented

The 60 mm rotor diameter, 3.3 grams Picoflyer is the smallest size electric powered
contra-rotating coaxial-rotor RC helicopter ever built. It is battery powered and it
uses the Proxflyer concept to give it inherent stability. It is built to test how
small helicopters using the passively stable rotor concept could be.


Key specifications, components and materials used to build the small Picoflyer:

Rotor:


Airframe:


Main motors:
Gears:
Tail motor:
Battery:
Control:




Weight:
Flight time:
    60 mm diameter (2 contra rotating 4-bladed rotors)
    Carbon rod 0.3 mm and 0.5 mm from WES-Technik
    Aramid 30 g/m2 fabric from CST, foam tape hinges
    72 mm long, 0.08 mm carbon plate, 0.3 mm rod,
    1.5 x 0.2 mm tube, brass bearings 0.7 mm from Didel

    4 x 8 mm, 11 ohm from Didel (2x)
    Plastic gears, module 0.2 from Didel (6.7 : 1)
    2.8 x 6 mm, 25 ohm from Shicoh, 0.16 grams
    1 x 3.7 V, 30 mAh Didel cell, 0.86 grams
    3 channels custom Plantraco 900 MHz radio control
    Atmel ATtiny26L with 3 x ESC
    Yaw control by differential speed of rotors
    Tail motor used for forward horizontal flight

    3.3 grams (incl. battery and control)
    Up to 1 minute, (0.5 minute continues)


Because of the new Proxflyer concept, this helicopter is much simpler and has
much fewer parts than other model helicopters. The helicopter is passively stable
in hover and during forward flight and has no need for cyclic control. It is controlled
vertically, in yaw (rotation) and forward speed. It is operated via an 900 MHz radio link,
however, due to its small size and no aid from electronic sensors it is rather difficult to
control precisely in the air.

STABILITY: Most other "stable" model helicopters, including some toy helicopters from
i.e. Asia, achieve some kind of stability by utilizing centrifugal forces and gyroscopic
effects to keep the rotor and helicopter horizontal at all times, thus preventing it from
entering into oscillations or becoming unstable. The Proxflyer, however, uses a different
approach (patented). In stead of trying to keep the rotors in a horizontal plane, they
are arranged in an innovative way so that they do the complete opposite. Triggered by the
smallest horizontal movement, the rotors tilt up, creating a horizontal force stopping the
motion almost before it starts. The helicopter is kept at the exact same position relative
to the surrounding air. The Proxflyer concept gives the helicopter incredible stability,
but limits the maximum horizontal speed. The concept, without relying on centrifugal
forces alone, give the rotors good and quick stability with respect to the rotor shaft as
well, and it will therefore let the helicopter move in the same direction as it is
tilted by the small horizontal tail propeller.


Key benefits of the helicopter:

  • Absolutely stable without the use of any gyros or autopilots

  • There are no servos, actuators, rods, links, gears or other moving part

  • The whole helicopter is operated and controlled by 3 electric motors

  • Forward flight is achieved by tilting the helicopter with the tail propeller

  • The rotor blades are encircled by a ring that supports and protects them

  • It is very efficient, all the power is used to generate lift

  • It is silent, the mechanical drives and the rotors generate very little noise

  • There are no vibrations

  • It is safe



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