Four rotor helicopter report #1

After about half a year spare time work, we finished the helicopter platform and tested it’s capabilities. Here is a picture of the helicopter on stakes to prevent it from tipping over. The platform has a diameter (measured rom the end of the carbon sticks) of 64.5 cm.


The motors are Robbe Roxxy BL 2827-34 outrunner driven by Robbe BL-Control 818 regulators.

Motor topregulator

The motors are mounted on alloy elbow fittings screwed on plastic sockets which in turn are glued on carbon fiber sticks. These sticks are then clamped onto the base.

base from the bottom

The power source is a Kokam 3200/3S HD 20C 11.1V Lithium Polymer accumulator. We have tried to launch the helicopter once using the stakes and a leash to prevent it from acending more then 15cm above ground. Although steering it is very hard we confirmed that our construction works as intended. A problem is that we cannot mix all channels in a way which increases one channel, simultaneously decreases the speed of the opposite motor and increases the speed of the two remaining rotors to compensate for the torque about the vertical axis. However, as soon as our motor controller curcuit board is finished we can easily solve that problem.

Here is a part list of everything (neglecting small parts and tools) we used to build the platform:

  • 4 concave carbon fiber sticks, 1cm diameter (~ 6€/piece)
  • 20 cm x 20 cm x 5 mm plactic plate (unknown)
  • 8 metal clamps fitting the carbon sticks (unknown)
  • 8 1cm M4 screws and nuts (~ 3€)
  • 8 2cm M4 screws, nuts and M5 wingnuts to clamp the stakes (~ 4.5€)
  • 4 alloy sticks to be used as stakes for the platform (~ 3.5€/piece)
  • 4 plastic sockets fitting exactly on the fiber sticks and allowing the elbow fittings to be screwed on (unknown)
  • 4 elbow fittings (3 mm, self made) with holes for the motor fixing (make sure that the fittings are not bent, but casted-in). (unknown)
  • 4 Robbe BL-Control 818 regulators (~ 40€/piece)
  • 4 Robbe Roxxy BL 2827-34 motors (~ 30€/piece)
  • 1 R/C receiver with at least four channels (unknown)
  • 1 R/C remote control with a mixer (unknown)
  • 2 Graupner air screws 25cm diameter, 15 cm pitch with clock wise rotation (~ 4€/piece)
  • 2 Graupner air screws 25cm diameter, 15 cm pitch with counter clockwise rotation (order nr: 1317/25/15L) (~ 4€/piece)
  • 1 Kokam 3200/3S HD 20C 11.1V accumulator (~ 110€)

That’s in sum about 460€ (added 19€ for the pieces we got for free).

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