Connecting rod

![Scheme of the Roman Hierapolis sawmill, the earliest known machine to combine a connecting rod with a crank.[3]](/uploads/202501/14/Römische_Sägemühle.svg0335.png)


In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts reciprocating motion into rotating motion.
Connecting rods may also convert rotating motion into reciprocating motion. Historically, before the development of engines, they were first used in this way.