The reduction gearbox reduces the revolutions per minute (rpm) of an engine. This allows the drive shaft connected to it to turn at a speed better suited to its functions. A reduction gearbox for ships is of substantial size to match that of the engine.
The reduction gearbox is used with engines turning at high revolutions per minute (rpm), such as gas turbines and certain diesels and electric motors.
Reduction gearboxes link the engine to the propeller shaft. They consist of a series of gears and toothed wheels of different sizes, which enable the engine's rpm to be reduced to the range of appropriate working speeds of the shaft.
Choice of gearbox will depend on the characteristics of the engine to which it will be linked. These include the engine's power and rpm, the torque and speed to be transmitted by the gearbox and the number of input and output shafts of the gearbox.
