Leonardo da Vinci designed a ball bearing to produce continuous rotary motion with balls between moving surfaces. His mechanism used rolling balls to reduce rubbing friction between parts that turned against one another.
The design appears in Leonardo’s studies of friction and mechanical motion from around 1498. It included balls arranged within a ring so they could move freely rather than become packed together. This arrangement addressed a practical problem: balls that touched each other too closely could slide or interfere instead of rolling efficiently.
Leonardo’s bearing was not the first use of rolling elements in history, and it did not lead directly to the standardized industrial bearings used today. Modern ball bearings generally use carefully manufactured rings, cages, and hardened steel or ceramic balls. Leonardo’s importance is that he clearly analyzed a compact rolling-bearing arrangement for machinery.