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Guest

Tue Dec 08, 2015 11:29 pm   



I notice, with these new toy drones, they all use quad
rotor design. Why?

I never studied aerodynamics, but I'm willing to learn -

--
Rich

Ian Malcolm
Guest

Tue Dec 15, 2015 11:46 pm   



rdelaney2001_at_gmail.com wrote in news:a09f1b3d-f43f-4d76-810c-
e83901ac302e_at_googlegroups.com:

Quote:
I notice, with these new toy drones, they all use quad
rotor design. Why?

I never studied aerodynamics, but I'm willing to learn -


No deep knowlage of aerodynamics is required. Its simply a matter of
torque balance.

The rotor downdraft has considerable swirl and there is naturally a
reaction torque on the motor. To prevent the craft spinning about a
vertical axis, you need either a tail rotor (e.g. conventional
helicopter) or a contra-rotating rotor to balance the torque.

Two rotors are sufficient, but then you need to either gimbal the rotors
for directional control and forward thrust or implement a swashplate to
provide dynamic cyclic blade pitch control (Chinook helicopter), with
considerable mechanical complexity for either.

Any even number of fixed axis fixed blade rotors can give you torque
balance, and if each group of rotors of the same rotation direction is
distributed symmetrically, the craft can be tilted in any direction
without net torque, or power can be shifted from clockwise to
counterclockwise rotor groups or visa versa to provide torque to rotate
the whole craft about its vertical axis, while maintaining lift.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

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