Leonardo da Vinci depicted a ball bearing using freely rotating balls between surfaces.
In studies associated with his mechanical work, Leonardo explored how rolling elements could reduce friction between moving parts. A ball-bearing arrangement places hard balls between an inner and outer surface, allowing one part to rotate while the balls roll instead of sliding. This principle is fundamental to many modern machines.
Leonardo’s design is often credited as an early ball-bearing concept, but he did not invent the complete standardized bearing industry. Renaissance engineers had not yet developed the precision manufacturing, hardened steel, seals, and lubricants needed for reliable mass-produced bearings.
The idea also differs from a gear. Gears transmit motion through toothed wheels, while bearings support rotating loads and reduce resistance. Leonardo’s drawing is significant because it shows an early understanding of rolling friction and the value of separating moving surfaces with round elements.