What machine part did Leonardo da Vinci study using a rotating ball arrangement?

Leonardo da Vinci studied a ball-bearing arrangement in which rolling balls reduced friction between moving surfaces.

His sketches from the late fifteenth century show balls placed inside a bearing structure. The principle is straightforward: rolling contact generally creates less friction than sliding contact, allowing a shaft or other part to move more easily. Leonardo’s design is often described as an early ball-bearing concept.

The drawing did not create the complete standardized bearing systems used in modern machines. Later engineers developed cages, races, precision manufacturing, and durable materials that made ball bearings practical across industry.

Leonardo’s importance here is analytical as much as inventive. He recognized that loose balls could interfere with one another and explored ways to arrange them within a mechanism. This makes the sketch an early study of a machine component still used in motors, bicycles, tools, and spacecraft.