Leonardo da Vinci studied the ball bearing as a friction-reducing machine component.
A ball bearing uses round balls between surfaces so that motion occurs mainly through rolling rather than sliding. Rolling resistance is generally lower than sliding friction, making the arrangement useful for rotating shafts and other moving parts.
Leonardo’s sketches show balls arranged within a bearing-like structure. A cage or separator can keep the balls from bunching together, allowing them to circulate more effectively between the inner and outer surfaces.
The drawing is often credited as an early ball-bearing concept, but Leonardo did not create the standardized industrial bearings used today. Later engineers improved materials, tolerances, lubrication, and manufacturing. The design demonstrates Leonardo’s habit of studying friction as a mechanical problem rather than treating it as an unavoidable obstacle.