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Contra-rotating propellers have benefits when providing thrust in marine applications. 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 ...
Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission. Although contra-rotating propellers are also known as counter-rotating propellers, [2] [3] the term is much more widely used when referring to airscrews on separate non-coaxial shafts turning in opposite ...
Propeller walk (also known as propeller effect, wheeling effect, paddle wheel effect, asymmetric thrust, asymmetric blade effect, transverse thrust, prop walk) is the term for a propeller's tendency to rotate about a vertical axis (also known as yaw motion). The rotation is in addition to the forward or backward acceleration.
A more serious problem with this type of propeller is a "frozen-on" spline bushing, which makes propeller removal impossible. In such cases the propeller must be heated in order to deliberately destroy the rubber insert. Once the propeller is removed, the splined tube can be cut away with a grinder and a new spline bushing is then required.
The propeller problem is the second setback for the Royal Navy in less than three weeks, following a collision by two warships in a harbor in Bahrain, causing damage to the vessels but no injuries.
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Replica of a propeller from the USS Monitor. Since the introduction of the marine propeller in the early 19th century, cavitation during operation has been a limiting factor in the efficiency of ships. Cavitation in marine propellers develops when the propeller operates at a high speed and reduces the efficiency of the propeller.
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.