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None whatsoever --- there are lots. They work well, although engines are heavy, so they have to be big. http://mydronelab.com/blog/gas-powered-quadcopter.html

None whatsoever --- there are lots. They work well, although engines are heavy, so they have to be big. http://mydronelab.com/blog/gas-powered-quadcopter.html http://mydronelab.com/blog/gas-powered-quadcopter.html I don't know whether they use direct coupling or motor-generators, though. Model aircraft engines have a long and time-honoured history. My father was into them as a child in the 1950s (before radio --- you controlled them by swinging them round your head on wire harnesses!), and still has some of the engines. Beautiful, beautiful engineering; about the size of my thumb, which ran on some ghastly cocktail of exotic oils and volatile spirits.

Retric 10y ago
Actually quad chopters don't scale very well. The reason they work so well as tiny drones is they are mechanically simple. No need to tilt the blades, just apply less power and almost instantly you get less lift on that side. However as you scale the drone it's blades need to get larger which causes more momentum which slows the response time. You can try and force the blades to slow down faster but the forces quickly get extreme, or change their tilt to generate less lift. But, if your going with tilting blades just use a helicopter design which is mechanically simpler than 4 tilting blades.
- RealityVoid 10y ago
  The swashplate mechanism is more complex than a tilting mechanism, be it 4x tilting mechanisms.
  - Retric 10y ago
    You can get into a lot of different trade-offs. EX: There are some options that don't involve a swashplate. (ZX-35041) considering it's 20$ it's probably junk. But, notice how the tail blade is pointing up. You could build a tilting quad copter with 4 engines, but that's significantly more complex. You can also use one engine and get power out to the 4 blades but that also get's complicated. Still the point still stands, Quadcopter's need to get more complicated as you scale them and things like vibration make everything worse.
    - RealityVoid 10y ago
      The example you posted has far more things in common with a multirotor than with a helicopter. What amazes me at those little things is how little side-to-side drift they have, considering that's all depending on the CG being well centered. A nice variable pitch quad: https://www.youtube.com/watch?v=Vy5Ky50eGJs https://www.youtube.com/watch?v=Vy5Ky50eGJs
      - Retric 10y ago
        That's a nice find with the variable pitch quad, though it looks like it has serious issues with vibration. Thrust vectoring is another option, as is using 3 blades at 90 degrees from each other. Autogyro's are another design which might work. However, in the end people have tried a lot of man sized flying designs and for vertical takeoff and hovering helicopters really are about as simple as it get's.
        RealityVoid 10y ago
        > though it looks like it has serious issues with vibration Yeap, nailed it, apparently, vibrations are its biggest issue.

Retric 10y ago

Actually quad chopters don't scale very well. The reason they work so well as tiny drones is they are mechanically simple. No need to tilt the blades, just apply less power and almost instantly you get less lift on that side. However as you scale the drone it's blades need to get larger which causes more momentum which slows the response time. You can try and force the blades to slow down faster but the forces quickly get extreme, or change their tilt to generate less lift. But, if your going with tilting blades just use a helicopter design which is mechanically simpler than 4 tilting blades.

RealityVoid 10y ago
The swashplate mechanism is more complex than a tilting mechanism, be it 4x tilting mechanisms.
- Retric 10y ago
  You can get into a lot of different trade-offs. EX: There are some options that don't involve a swashplate. (ZX-35041) considering it's 20$ it's probably junk. But, notice how the tail blade is pointing up. You could build a tilting quad copter with 4 engines, but that's significantly more complex. You can also use one engine and get power out to the 4 blades but that also get's complicated. Still the point still stands, Quadcopter's need to get more complicated as you scale them and things like vibration make everything worse.
  - RealityVoid 10y ago
    The example you posted has far more things in common with a multirotor than with a helicopter. What amazes me at those little things is how little side-to-side drift they have, considering that's all depending on the CG being well centered. A nice variable pitch quad: https://www.youtube.com/watch?v=Vy5Ky50eGJs https://www.youtube.com/watch?v=Vy5Ky50eGJs
    - Retric 10y ago
      That's a nice find with the variable pitch quad, though it looks like it has serious issues with vibration. Thrust vectoring is another option, as is using 3 blades at 90 degrees from each other. Autogyro's are another design which might work. However, in the end people have tried a lot of man sized flying designs and for vertical takeoff and hovering helicopters really are about as simple as it get's.
      - RealityVoid 10y ago
        > though it looks like it has serious issues with vibration Yeap, nailed it, apparently, vibrations are its biggest issue.