Leonardo da Vinci’s ball-bearing sketch addressed the reduction of friction.
The drawing shows balls positioned between moving surfaces so that sliding contact could be replaced by rolling contact. Rolling generally requires less resistance than dragging one solid surface directly across another, which is the central principle behind ball bearings.
Leonardo made the sketch around 1498 while studying mechanical motion. His design is often described as an early ball-bearing concept, but historians avoid claiming that he invented the modern bearing in a complete, manufacturable form. The drawing does not establish a continuous modern bearing assembly with all its later features.
Ball bearings are now used in machines ranging from bicycles to electric motors. Their performance depends on factors such as load, lubrication, material, alignment, and precision. Leonardo’s sketch is historically significant because it shows him isolating a basic mechanical problem and proposing rolling elements as a solution.