Leonardo da Vinci studied and drew a ball-bearing design to reduce friction between moving parts.
His sketches from the late 15th century show balls arranged so that surfaces could move against one another with less rubbing. The principle is that rolling friction is generally lower than sliding friction, allowing a rotating shaft or component to move more efficiently.
Leonardo’s design is often described as an early ball bearing, but it was not the same as a modern sealed bearing. His drawings explored ways to keep the balls separated, because balls that touch and jam would reduce the benefit of the mechanism.
The idea later became central to machinery, clocks, bicycles, vehicles, and industrial equipment. Leonardo did not invent every form of bearing, and ancient cultures used simpler rolling devices before him. His importance lies in his detailed mechanical study and his attempt to solve friction and crowding problems systematically.