Leonardo da Vinci designed a ball bearing to transfer rotation between shafts using small rolling balls.
Leonardo’s notebooks contain a design in which balls move between rings, reducing the rubbing contact between rotating parts. The purpose was to limit friction and prevent the balls from bunching together. His sketch is commonly cited as an early ball-bearing concept and is dated to the late fifteenth century.
The principle is straightforward: rolling contact generally produces less friction than sliding contact. Leonardo’s design shows that he recognized this mechanical advantage, even though Renaissance materials and manufacturing could not produce the precision associated with modern bearings. His proposed separator arrangement is especially important because freely moving balls would otherwise interfere with one another.
Leonardo was not the first person to use rolling elements in every possible mechanical sense, and later engineers developed bearings for clocks, vehicles, and industrial machinery. The drawing is best understood as an early documented design, not the direct ancestor of every modern bearing. Ball bearings became widespread only after precision manufacturing improved centuries later.