One fixed rotor or two moving?

One fixed rotor or two moving?

Postby hammertime1 on Tue Feb 21, 2012 4:42 pm

My partner and I on Helicopters were wondering what is most efficient: 1 fixed rotor or 2 moving. Will the power of 2 moving rotors be to hard to control or will it provide a longer flight time?
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Re: One fixed rotor or two moving?

Postby chalker7 on Tue Feb 21, 2012 11:47 pm

hammertime1 wrote:My partner and I on Helicopters were wondering what is most efficient: 1 fixed rotor or 2 moving. Will the power of 2 moving rotors be to hard to control or will it provide a longer flight time?

They are (theoretically) exactly the same. The second "fixed" rotor on a helicopter with that design is actually rotating with the entire motorstick around the motor hook for the "free" rotor (this is due to Newton's Third Law.)
However, that being said, two "free" rotors is probably slightly more efficient. This is because it is easier to get the axes of rotation perfectly aligned, which improves efficiency and reduces the wobble teams often see. You can also pack a dual free rotor design into a smaller space since you can remove both rotors easily (essentially fitting the whole helicopter into a tube.) The major difficulty in a dual "free" rotor assembly is the added complexity of construction and significant added difficulties in attaching wound motors if you are winding off of the helicopter (for example, on a torque meter.)
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