Dual-rotor also known as coaxial rotors helicopters consist of a pair of rotor rotating in opposition directions. One rotor is positioned above the other. Coaxial helicopters are popular because of its clear stability while in flight making it easier to learn. It is also considered to be a favorite indoor activity comparable to the single rotor model. Its maneuverability makes it ideal and safe even within one's home.
Underlying Theory: When a helicopter is not in motion its angular momentum is zero. Once the engine is started, it produces a significant amount of angular momentum that can cause the body of the helicopter to spin around in opposition direction of the rotors. To maintain flight stability, coaxial rotors are used by turning each rotor in opposition directions. This allows the fuselage to sustain a zero angular momentum.
How does it work ?: Coaxial helicopters do not needarily need a tail rotor. The torque created by the 2 rotors spinning in opposite directions cancels each other. This results to a more stable flight and hovering capabilities. Hovering is one of the main elements in flying a helicopter. When the pilot slows down or speeds up one of the 2 rotors, he can control the hover or direction of the helicopter.
Why go for a dual-rotor helicopter ?: Coaxial designs are remarkable because of its ability to maximize each available engine power. A tail rotor typically throws away some of the power would have been used in lifting and thrusting. It also observed that most dual-rotor R / C helicopters have less noise. Conventional R / C helicopters generate a loud "blowing" noise because of the interaction involving the flow of air between main and tail rotors. More and more coaxial helicopters available in the market these days consume less space making it a more compact model.
Things to consider: The speed of the rotors should be appropriately controlled and maintained. The stability of a coaxial R / C helicopter greatly depends on the 2 rotors' synchronization such that any deviation may result in damaging effects. Another downside is the possibility of the rotors getting into each other especially during extreme flight maneuvers.
Recently, several R / C helicopters began adopting a simplified coaxial design. This new model consists of a coaxial unbending rotor system with fixed-pitch blades and a swashplate. One thing is clear, dual-rotor R / C helicopters are sure to make a wave in the next couple of years.
There is a website that has great information on RC Helicopters, the website is called: RC Helicopters World, and can be found at this url:
By Robert W. Benjamin
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