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Counter-rotating propellers generally turn clockwise on the left engine and counterclockwise on the right. The advantage of such designs is that counter-rotating propellers balance the effects of torque and P-factor, meaning that such aircraft do not have a critical engine in the case of engine failure.
The reason for the clockwise standard for most screws and bolts is that supination of the arm, which is used by a right-handed person to tighten a screw clockwise, is generally stronger than pronation used to loosen. Sometimes the opposite (left-handed, counterclockwise, reverse) sense of threading is used for a special reason.
The torque on the aircraft from a pair of contra-rotating propellers effectively cancels out. Contra-rotating propellers have been found to be between 6% and 16% more efficient than normal propellers. [4] 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. [4]
The direction of vector rotation is counterclockwise if θ is positive (e.g. 90°), and clockwise if θ is negative (e.g. −90°) for ().Thus the clockwise rotation matrix is found as
The force rotating counterclockwise causes the blue circle to roll around the red circle clockwise. When it has rolled a distance πd, the circumference of the blue circle, point A again touches the red circle. Since the circumference of the red circle is π(d + δ), point A touches the red circle a distance πδ clockwise from the bottom.
A propeller that turns clockwise to produce forward thrust, when viewed from aft, is called right-handed. One that turns anticlockwise is said to be left-handed. Larger vessels often have twin screws to reduce heeling torque , counter-rotating propellers , the starboard screw is usually right-handed and the port left-handed, this is called ...
The figures illustrate a ball tossed from 12:00 o'clock toward the center of a counter-clockwise rotating carousel. In the first figure, the ball is seen by a stationary observer above the carousel, and the ball travels in a straight line slightly to the right of the center, because it had an initial tangential velocity given by the rotation ...
Torque forms part of the basic specification of an engine: the power output of an engine is expressed as its torque multiplied by the angular speed of the drive shaft. Internal-combustion engines produce useful torque only over a limited range of rotational speeds (typically from around 1,000–6,000 rpm for a small car).