Which Leonardo da Vinci device is regarded as an early ball-bearing design?

Leonardo da Vinci’s ball-bearing design is regarded as an early concept for reducing friction between moving surfaces.

In drawings made during the late fifteenth century, Leonardo explored balls placed between rings or tracks. The balls were intended to roll instead of allowing two surfaces to slide directly against one another. That principle is the basis of ball bearings used in machinery today.

Leonardo’s design also addressed a problem he noticed in practice: rolling elements can bunch together and create friction if they touch one another. His sketches show attempts to separate the balls so they remain in useful positions. The drawings are evidence of an important mechanical insight, not proof that a modern standardized bearing was manufactured.

Modern ball bearings use carefully shaped races, cages, lubrication, and precisely made balls. Leonardo’s concept predates those industrial refinements by centuries, so it is best described as an early design or conceptual precursor rather than a complete modern bearing.