Which component transforms the reciprocating action of the piston to the rotating action of the crankshaft?

The connecting rod plays a crucial role in the engine's operation by converting the linear (reciprocating) motion of the piston into the rotational motion necessary for the crankshaft's operation. When the piston moves down due to the combustion of fuel and air, the connecting rod, which is attached at one end to the piston and at the other end to the crankshaft, pivots about the crankshaft. This pivoting action is what allows the reciprocal movement of the piston to be transformed into a circular motion, which is essential for the crankshaft to turn and ultimately powers the vehicle.

The crankshaft itself, while it is a vital part of this process, does not transform the motion but rather is the component that receives the rotational force generated by the connecting rod. The wrist pin is simply a fastening element that allows the connecting rod to pivot on the piston and doesn't contribute to the conversion of motion. Therefore, the connecting rod is the key component in transforming the reciprocating action to the rotating action of the crankshaft.