Leonardo da Vinci designed a ball bearing device that used rolling balls to reduce friction between moving surfaces.
His bearing concept appears in studies made during the late 15th century. It placed balls between rings so that one part could rotate relative to another with less sliding friction. The principle is the same basic idea used in many modern bearings.
Leonardo’s design included separators intended to keep the balls from touching one another, a feature important for smooth operation. Earlier rolling elements existed in other forms, so Leonardo should not automatically be credited with inventing every kind of bearing.
Modern ball bearings are manufactured with precise steel, ceramic, or other materials and are used in machines ranging from bicycles to turbines. Leonardo’s sketches are important because they show an early systematic treatment of the rolling-contact bearing.