Leonardo da Vinci designed a chain drive to transmit continuous motion between rotating shafts. A chain drive uses linked elements that engage with toothed wheels, allowing force and movement to pass from one shaft to another.
Leonardo's mechanical studies include sketches of chains made from connected links. Such a mechanism could transfer power over a distance while maintaining a positive connection between the driving and driven parts. This made it useful for machines requiring coordinated rotation and controlled movement.
Leonardo's chain should not be confused with a simple belt drive. Belts transmit motion through friction and can slip, while a chain engages with sprockets or shaped wheels. Historians often credit Leonardo with an early chain-drive concept, but modern roller chains and bicycle chains developed much later and use more refined manufacturing methods.