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Radio Contolled Helicopters Concept

  1. Apr 20, 2008 #1
    Radio Contolled Helicopters Concept!!

    Hi guys does anybody know concepts behind the Fixed pitch Radio heli principle

    Thnx a lot in advance
  2. jcsd
  3. Apr 20, 2008 #2
    As I understand it, with a Fixed Pitch the angle of the main blades remains constant and the flyer controls altitude by using the speed of the main motor, simply creating more or less lift by choosing the attitude of the helicopter (which determines how much of the lift propels the helicopter forward, and how much upward) and the speed of rotation (which provides the lift).

  4. Apr 20, 2008 #3
    Hi thanx for ur reply!

    You are correct on that but I am not able to understand how would the speed of DC motor vary with help of a Transmitter?
    Can you give an idea how would the thrust be produced and how would an helicopter move left or right by speed variation??
    Thnx a lot
  5. Apr 20, 2008 #4
    I believe that the transmitter controls what's essentially an amplifier (either via op-amp or transistor), controlling the size of the voltage sent to the motor. So I believe fixed pitch helicopters can't actually roll unless they have extra ailerons; without ailerons, the torque control is used to slip (that is, yaw) the helicopter left and right.
  6. Apr 20, 2008 #5
    thanx a ton .. it answered my question perfectly!
  7. Apr 20, 2008 #6
    I just wanted to add a bit to this...

    Fixed pitch helicopters will have no collective (rotors rotating equally on each side to provide more/less lift) or cyclic (rotors rotating unequally on each side to provide tilt in any direction, be it forward, backward, or left and right). The tail rotor balances the torque from the main rotors and changing the tail rotor speed gives the helicopter yaw (like aresnick said).

    Now, I have a small remote controlled helicopter that has no control for collective or cyclic control. All of the control is done by speeding up the main rotors (which means I also have to increase the tail rotor speed so that it faces in the same direction). What's neat about the helicopters I have is that they aren't fixed pitch, I just can't actively change the pitch. There are 2 main blades and 2 paddles. The paddles are short and stubby and are offset by the main rotors by about 30 degrees or so. They have weights on them. What happens, is that if the helicopter tilts in any direction, the weight of the paddles resist this, and this resistance is mechanically linked to the main rotors. The paddles, in effect, cause the main rotors to tilt in a way that forces the helicopter to right itself. This is because a pure fixed-pitch helicopter will be very unstable with only 2 blades, but by adding a passive mechanical control, it can be stable.

    Also, because of the paddles, I can add weight to the nose of the helicopter which will make the helicopter fly forward. It's a really simple design, and you can buy the things for about $20 or less now.
  8. Apr 20, 2008 #7
    Thanx for that info !!! Really appreciated!!
    so its flybar which causes tilting of rotor mast and ultimately the movement forward!!
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