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Toy Helicopter

toy helicopter in front of SE Linux mug
I have just bought myself a toy helicopter. I had been tempted to buy one for a while and when I saw them on sale for $30 I couldn’t resist.

My helicopter is model FJ-702 from Flyor, it is controlled by infra-red and is designed for indoor use only. It seems that the trick to flying one is to control the rate of ascent and descent. If the helicopter rises too fast then it may bounce off the ceiling which results in it swaying uncontrollably and crash-landing. If it is allowed to descend too fast then it becomes impossible to slow the rate of descent, I suspect that this is the settling with power [2] problem that is documented in Wikipedia. The helicopter is very fragile, I broke one of the skids and part of the tail assembly before I learned how to control it properly. Probably the main thing to look for when buying a model helicopter is a solid design – some time after buying (and breaking) my helicopter I visited the shop which sold it and heard the owner advising other customers to buy the $45 model which is apparently more solid.

It seems that an ideal design would be a frame made of spring-steel (not to make it springy but to avoid it breaking when it hits). I recommend flying in a room with a carpeted floor, bouncing off a solid surface such as a wood floor will break a helicopter.

Controlling a helicopter is really difficult. The models that I have tried and seen demonstrated all have serious problems with unwanted rotation. My helicopter and the others I have seen have coaxial rotors to avoid rotation without a tail rotor. According to the Wikipedia page a lot of energy is used by a tail rotor [1], as there has been obvious difficulty in designing the helicopter with adequate power (in terms of the light and weak frame and the short battery life) it seems that they didn’t use the tail rotor design to save energy. It’s a pity that instead the designers couldn’t have skipped the flashing LEDs etc.

One strange thing is that one pair of blades can have their angle changed (which appears to be similar to the “semirigid” design shown on the wikipedia page). I’m not sure how increasing the angle of one blade while simultaneously decreasing the angle of it’s pair will do any good. I expect that this has something to do with the fact that the helicopter will rotate at different rates when under different amounts of vertical thrust. This incidentally makes it almost impossible to maneuver the craft. It has a tail rotor on a vertical axis to control forward and reverse movements, but the extreme difficulty in keeping it facing in one direction makes this almost useless.

I wonder what the minimum size at which a gyro-stabiliser becomes practical. But as Wikipedia doesn’t document the existence of an autopilot for full size helicopters the chance of getting one for a toy is small.

In summary, while I have had $30 of fun, I think that a more solid helicopter would be a better investment.

5 comments to Toy Helicopter

  • tomás zerrolo

    So you are longing for a gyro stabilised one? Then maybe this is for you:

    Disclaimer: I haven’t tried it (and I guess I won’t out of fear that it could eat up all what is left of my productive time and sanity :)

  • Martin

    A helicopter wastes a lot of energy (I heard about 30%) to compensate its own torque. If it uses a second main rotor rotateing in the opposite direction or if it uses a tail rotor doesn’t matter in terms of energy.

    The thing is that a coax heli is much easier to fly, it has only 2 axes instead of 3.

  • etbe

    Tomas: Somehow the link was missed from your comment. Could you please re-send it?

    Martin: The Wikipedia Helicopter page states that having a second rotor in the opposite direction allows the helicopter to generate more lift. If you believe that this is incorrect then please find a suitable reference and correct Wikipedia.

  • tomás zerolo

    Sorry for forgetting the link. Coffe input buffer overflow, I guess. Here it is:

    [http://events.ccc.de/congress/2008/wiki/Build_a_Quadrocopter]

    Enjoy :-)

  • rdb

    Not a Helicopter but the FlyTech Bladestar looks interesting though I haven’t seen it in AU.
    Sounds like an Autogiro.

    http://spectrum.ieee.org/nov08/6916/3
    http://www.bladestaronline.com/