Leonardo da Vinci studied a ball bearing concept to reduce friction between moving parts.
His sketches show balls placed within a bearing assembly so that surfaces could roll against one another instead of sliding directly. Rolling contact generally produces less friction than sliding contact, making the arrangement useful for machinery with rotating components.
Leonardo investigated the idea while studying mechanics and machine construction. The drawings are important because they show an early understanding of how separated rolling elements could prevent friction from causing parts to rub together. His design resembles the principle used in modern ball bearings, although it was not a standardized industrial product.
The concept is sometimes credited as a complete invention of the modern bearing, but later engineers developed the manufacturing methods and precise races needed for reliable mass-produced bearings. Leonardo’s contribution was an early documented mechanical design using rolling balls.