Leonardo da Vinci studied a ball bearing to reduce friction between moving surfaces.
A ball bearing uses small spherical elements between rings or surfaces so that rolling replaces much of the sliding friction. Leonardo’s notebooks include sketches of bearing arrangements, including balls placed between components to prevent direct rubbing. The idea was useful for machines that needed smoother rotation and less wear.
Leonardo’s bearing studies are often presented as evidence of his advanced mechanical thinking. He recognized an important practical problem: if individual balls touch one another, friction and jamming can reduce the benefit. Some of his drawings therefore explore ways to keep the balls separated, a concern that also appears in later bearing design.
Leonardo did not create the modern standardized bearing industry. His sketches are conceptual and belong to a much longer history of rolling-element devices. A gear transmits rotary motion, while a flywheel stores rotational energy; neither is the specific friction-reducing component shown here.