Leonardo da Vinci’s invention using a chain to transmit motion between shafts was a chain drive.
His notebooks contain an early chain-drive concept in which linked elements transfer rotary movement from one shaft to another. The arrangement resembles the principle later used in bicycles, industrial machinery, and conveyor systems. Leonardo’s drawings show his interest in controlling motion with dependable mechanical connections.
A chain drive is distinct from a belt drive, which uses a flexible belt, and from a gear train, which transfers motion through meshing toothed wheels. Leonardo’s design should not be described as a modern roller chain: later engineers developed standardized links, rollers, sprockets, and manufacturing methods. The historical importance lies in the early mechanical principle.