Where is a reduction gear fitted in an engine setup?

A reduction gear is fitted between the crankshaft and the propeller in an engine setup to efficiently adjust the rotational speed and torque delivered to the propeller. In particular, this configuration allows for a higher engine speed, which is necessary for optimal performance, while simultaneously providing the lower propeller speed required for effective thrust.

The crankshaft typically rotates at a much higher rate than the propeller needs to operate. By incorporating a reduction gear, the engine’s high-speed rotation can be reduced to a level that's suitable for the propeller, maximizing overall efficiency and performance. This mechanism is particularly crucial in applications like aviation engines, where the balance between engine output and propeller efficiency directly affects the aircraft's performance.

The other placements mentioned do not align with typical design and operational needs. For instance, placing a reduction gear between the camshaft and the propeller would not make sense as these components are not involved in the same functional pathway. Similarly, fitting it between pushrods and valves or between the connecting rod and crankshaft would not effectively achieve the intended result of controlling propeller speed in relation to engine output.