Leonardo da Vinci designed a ball-bearing concept to reduce friction between moving parts.
In the late 15th century, Leonardo studied how machine components could move more efficiently. His sketches show balls placed between rings or surfaces so that rolling contact replaces much of the sliding friction found in ordinary joints. The principle is the same one used by modern ball bearings: hardened balls carry a load while allowing one part to rotate relative to another.
Leonardo’s drawings are important evidence in the history of bearing technology, but they were not necessarily a complete, manufacturable modern bearing. His notes show that he understood the practical problem of balls rubbing together and even explored separators to keep them apart. Industrial bearings later required better materials, precise machining, lubrication, and reliable manufacturing.
The idea is sometimes credited to Leonardo as if he invented every modern bearing. A more precise statement is that he produced an early documented design for a ball bearing. Ancient and medieval machines had already used rollers and other friction-reducing arrangements, so Leonardo’s work belongs to a long development rather than an isolated beginning.