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4 rotors

  1. Mar 10, 2008 #1

    wolram

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    How would one control a craft with 4 rotors in a square pattern, i imagine it would be best to have one power source and vary the rotor pitch, may be with a gyro controlling out of limit dynamics, apart from the military has any one had one of these in controlled flight?
     
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  3. Mar 10, 2008 #2

    RonL

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    Using counter rotation, any blade will be rotating opposite to the one on either side of it.
     
  4. Mar 10, 2008 #3

    mgb_phys

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    Control would probably be same as something like a 2 rotor Chinook
    It's big advantage would be that you could hang any number of loads anywhere within the area of the for rotors.
     
  5. Mar 10, 2008 #4

    FredGarvin

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    Having two rotors, even with the rather simple idea of having counter rotating and differential collective pitch, there is a HUGE amount of mixing and control system "behind the scenes" corrections. With 2 or 4 rotors, you'd have to have linkages to get all 4 moving at the same time, in the same direction as well as independent pivoting.

    Honestly, I would think the "easiest" (if such a thing exists with control systems) would be to have actuators on each swashplate that are electrically controlled, i.e. no mechanical linkages, except to the swashplate.
     
  6. Mar 10, 2008 #5
    quadrotor

    with a quadrotor, having the four rotors- a pair turning clockwise and the others counter, the yaw is stabilized. you could adjust pitch or roll by speeding up one and decreasing the other rotor in a pair. you could actual have fixed rotors, no swashplates
     
    Last edited: Mar 10, 2008
  7. Mar 11, 2008 #6

    FredGarvin

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    How would you handle forward flight? In your scenario, the only thing that would happen is the pitching action would happen. To obtain a forward airspeed without descending is to somehow vary pitch in the blades so you don't keep doing cartwheels.
     
  8. Mar 11, 2008 #7

    RonL

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    Going back to the Hiller flying platform, the motion in any direction was the results of luvers under the frame, in the propwash.
    I like Wolram's idea of square, but see it as a slow speed lift system. I think current helicopter design for serious flying is about as good as it will get.
     
  9. Mar 11, 2008 #8

    wolram

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    So if i wanted to make a model would it be best to have four motors with speed controllers
    and may be a gryo linked in some how, this is an idea for a camera platform.
     
  10. Mar 11, 2008 #9

    RonL

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    Sounds like a good project, and i feel electric is the way to go, and there are so many choices for electric power, and battery manufacturers. Everything depends on all-up weight, and duration of flight time. I'll give one link to start with in case you don't have a bunch already,

    http://www.astroflight.com/e/env/index.html?sid=0001eK215LFVztESN8549Z6&link=/index.html

    I bought Bob's book "Electric Motor Handbook", he has a section that gives small to large, model airplane propellers "dia/pitch, speed, and watts absorbed". Let me know if you don't find that info on his site, or some other one.

    I did have a link in the past, of a fellow in Fl. that was using a RC helicopter to do camera work, for different companies, a lot of building contractors from out of state would hire him to do arial shots and send them to their websites, for dailey or weekly updates on progress.
    Always a way to make money, doing something you like, if your creative.:approve:
     
  11. Mar 11, 2008 #10

    wolram

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    Great site RonL, speed controllers are so small now, but would you know how to keep four rotors in in controlled flight?
     
  12. Mar 11, 2008 #11

    FredGarvin

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    Either that or adding an axial prop for thrust purposes only. It could be quite a bit smaller than the others.
     
  13. Mar 11, 2008 #12
    four rotors

    Hi Fred,

    They actually make a RC four rotor aircraft called a dragonfly. It flies by controling the rotor speeds, I know it uses three gyros and some magic circuit board. you can check it out at http://www.rctoys.com/

    Wolram
    They make one with a camera/video
     
  14. Mar 11, 2008 #13

    wolram

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    Wow , this exactly what i need

    http://www.rctoys.com/rc-products/DF-VTI.html

    Many thanks.
     
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