Leonardo da Vinci depicted a ball bearing in an early study of friction reduction.
His notebooks from the late fifteenth century include designs using balls between moving surfaces. The balls were intended to reduce sliding friction by replacing it with rolling contact, a principle central to modern bearings.
Leonardo’s arrangement also shows that he understood a practical problem: loose balls can bunch together and interfere with one another. His sketches explored ways to keep the rolling elements separated, anticipating the importance of cages in later bearing designs.
Leonardo did not create the complete modern ball-bearing industry. Precision manufacture, hardened materials, standardized dimensions, and reliable lubrication developed much later. His drawings are significant because they record an early mechanical analysis of rolling friction and the need to control the motion of bearing elements.