Video Fast Helicopters - Theoretical Top End Speed

Discussion in 'The Chat Room' started by smakmeharder, Jun 1, 2016.

By smakmeharder on Jun 1, 2016 at 7:04 PM
  1. smakmeharder

    smakmeharder Administrator

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    Well I don't know if this helicopter is still the fastest RC speed heli but it clocked at 277 Kph and that was in 2013. Interestingly does anyone know what the limiting factor of helicopter speed is? Is it the fact that once the blade speed hits mach1 the blades become unstable because of the vibrations? Anyway this video is a classic. Enjoy.




     

Comments

Discussion in 'The Chat Room' started by smakmeharder, Jun 1, 2016.

    1. Min

      Min Well-Known Member

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      The speed is limited by rpm of the rotor head. As you go faster in a heli the blade moving into the direction of motion will experience a higher airspeed compared to a hover and the one moving away from the direction of motion will experience a lower airspeed compared to a hover. As you go faster the blade moving away will eventually have so little airspeed that it is essentially stalled. This then causes the helicopter to pitch nose up due to gyroscopic precession and slow down. This phenomenon is called retreating blade stall and you can reduce this by turning up the headspeed.
       
    2. ChopsyWA

      ChopsyWA Well-Known Member

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    3. HungryHungryHippos

      HungryHungryHippos Well-Known Member

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      If you are after a pure limiting factor, I would say the power plant.

      To simplify it, even at the risk of being inaccurate,

      When you get lift, which is what the rotor blade makes, you also get drag.

      The faster the blade moves, the more drag you get, as well as having less thrust available.

      The more drag you get, the more power the engine needs to make to over come it.
       
    4. Beaver

      Beaver Well-Known Member

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      Interesting sound.
      (Eeeeeeeeeeeeeeesrrrrrrrrroooooooowwww-WHACK!!!)
       
    5. smakmeharder

      smakmeharder Administrator

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      But does the sound barrier limit how fast you can spin the rotor head? If you can spin 700 size heli to 3,400 rpm to offset the stall on the lagging blade in order to travel at a faster speed, then as leading blade travels faster would the blade tip be approaching the speed of sound (1234 km/h) What then? Can the rotor tip break this limit without issues?
       
    6. smakmeharder

      smakmeharder Administrator

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      The jet stream sound of that heli was really frekin nice... so officially the world speed record is 311 Kph
       

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