What do contra-rotating propellers do?
Use of contra-rotating propellers recovers energy lost due to the motion of the air in the slipstream of the forward propeller and allows for an increase in power without a corresponding increase in propeller diameter. It will also help counter the torque effects of a high power piston engine.
What is contra-rotating motor?
Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque.
Do Chinook rotors spin in opposite directions?
The size is not the only thing that sets the Chinook apart. The aft rotor blades, unlike forward blades, have a clockwise spin while all other blades rotate counter-clockwise. “There’s no other blade like it,” notes Roy Hollins, the director of Components Production at CCAD.
What is the other term for intermeshing rotor?
A helicopter with two rotors turning in opposite directions and mounted on two masts slightly inclined towards each other, so that the blades intermesh (without colliding), is called a synchropter.
Are contra-rotating propellers any good?
Contra-rotating propellers have been found to be between 6% and 16% more efficient than normal propellers. However they can be very noisy, with increases in noise in the axial (forward and aft) direction of up to 30 dB, and tangentially 10 dB. Most of this extra noise can be found in the higher frequencies.
Why did the Spitfire have a contra-rotating propeller?
In the Spitfire/Seafire and Shackleton’s case the primary reason for using contra-rotating propellers was to increase the propeller blade-area, and hence absorb greater engine power, within a propeller diameter limited by the height of the aircraft’s undercarriage. The Short Sturgeon used two Merlin 140s with contra-rotating propellers.
How does a contra-rotating propulsor work?
In the case of contra-rotating podded propulsors these tend to be hybrid designs which deploy a conventional propeller and stern bearing arrangement for the ship with a tractor azimuthing podded propulsor located immediately astern of the conventional propeller; Figure 2.9.
Why are propellers used on torpedoes and not on ships?
Contra-rotating propellers are used on torpedoes due to the natural torque compensation and are also used in some motor boats. The cost of boring out the outer shafts and problems of mounting the inner shaft bearings are not worth pursuing in case of normal ships .