Which engine component converts reciprocating motion into rotary motion?

The crankshaft is the component that converts reciprocating motion into rotary motion in an engine. When the engine's pistons move up and down in the cylinders due to combustion, their linear motion needs to be transferred into a form that can rotate the wheels of a vehicle. The connecting rod connects the piston to the crankshaft, and as the piston moves, the connecting rod pushes and pulls the crankshaft. This action causes the crankshaft to rotate.

The importance of the crankshaft in this process lies in its design, which includes offsets or "throws" that enable the conversion of the linear motion of the pistons into rotational motion. This rotation is what ultimately powers the vehicle, allowing it to move forward. The flywheel, while it also stores rotational energy, does not convert motion; it assists in maintaining a smooth rotational motion of the crankshaft. The connecting rod is essential for the connection but does not itself convert motion, and the piston itself provides the initial reciprocating motion but is not involved in the rotation directly. Thus, the crankshaft is the key component responsible for this transformation of motion in an engine.