ball bearing
The first known discovery of a device that used ball bearings was during the time of the Roman Empire. Used aboard Roman ships, the device was a rotating table with balls placed underneath for smooth motion. Leonardo intensely studied the use of bearings to reduce wear and tear on moving parts of machines. Leonardo invented the ball bearing as we know it today. His ball bearing uses balls, rollers and a lubricating oil to reduce friction between two moving objects. The image below depicts a series of rolling spheres with turning spindles placed between each sphere. As the spheres turn freely, the adjacent spindles rotate as well, but on their own axes. By reducing friction between the two adjacent mobile parts, motion is made easier for both parts. Today, this device is found in engines, kitchen appliances and other machines. In the Codex Atlanticus, there are drawings of many similar devices, including cage gears and ball bearing schemes. Photo from The Henry Ford Dearborn, Michigan, 2025.