Leonardo da Vinci sketched a ball bearing using a rolling ball between two rings.
His studies of friction and mechanical motion included a design in which balls could roll between circular races. The arrangement was intended to reduce rubbing friction by replacing sliding contact with rolling contact.
The sketch appears in Leonardo’s Codex Madrid I, dating from the late fifteenth century. It is often credited as an early ball-bearing design, although Leonardo was not the first person to imagine rolling elements, and his drawing did not become a modern standardized bearing.
Modern ball bearings use carefully shaped races, multiple balls, cages, lubrication, and precise materials. Leonardo’s arrangement also had a practical weakness: without a cage, the balls could bunch together. Even so, the drawing demonstrates his systematic interest in friction, an issue central to machines ranging from clocks to vehicles.