Leonardo da Vinci sketched a ball bearing for reducing friction between moving surfaces.
In his studies of mechanics, Leonardo drew systems in which small spherical elements moved between rings or tracks. The central idea is that rolling contact produces less friction than sliding contact. This principle allows a rotating component to move more easily while supporting a load.
Leonardo’s drawings are often cited in histories of bearing technology, but he did not invent every form of ball bearing in the modern industrial sense. Earlier cultures used rolling elements in various applications, and later engineers developed standardized bearings with precise races, cages, and materials. Leonardo’s importance lies in his detailed mechanical analysis and his recognition of the usefulness of constrained rolling balls.
The sketch is also sometimes described as an early cage bearing because it keeps balls separated. It should not be confused with a roller bearing, which uses cylindrical or tapered rollers instead of spheres.