Leonardo da Vinci designed a crankshaft mechanism to convert rotary motion into repeated mechanical movement for machines such as looms or pumps.
A crankshaft uses offset crank sections to transform rotation into reciprocating motion, or to reverse that process. Leonardo’s mechanical studies include crank-and-rod arrangements that could coordinate repeated actions. Such mechanisms were valuable because one rotating power source could drive a sequence of up-and-down or back-and-forth movements.
A crankshaft is not the same as a flywheel. A flywheel stores rotational energy and smooths motion, while a crankshaft changes the direction or form of movement through its offset geometry. A pulley mainly transfers motion or changes force direction, and a water wheel is a source of power rather than the conversion mechanism itself.
Leonardo did not invent every component associated with later industrial machinery, and his notebooks contain many exploratory variations. His importance here lies in documenting and developing mechanical principles that later became central to engines, pumps, looms, and vehicles.