Leonardo da Vinci sketched a ball-bearing design that used rollers to reduce friction between moving parts.
Around 1498, Leonardo drew a device in which balls moved between rings. The arrangement was intended to keep the balls separated and allow a shaft or ring to turn with less rubbing contact. This is the basic idea behind a bearing: supporting motion while reducing friction.
The design was part of Leonardo’s mechanical studies rather than a documented mass-produced invention. Modern ball bearings use carefully manufactured balls, races, cages, and lubricants, making them far more precise than a Renaissance sketch. Leonardo’s drawing is important because it demonstrates an early understanding of rolling contact as a solution to friction.
A ball bearing is not the same as a pulley. A pulley changes the direction or mechanical advantage of a force, while a bearing supports rotation and reduces resistance.