Leonardo da Vinci designed gear trains to multiply rotational speed using toothed wheels.
Leonardo’s notebooks contain many studies of gears arranged in linked sequences. By changing the relative sizes and numbers of teeth, one gear could turn faster than another. This allowed a machine to trade torque for speed or speed for torque, depending on the arrangement.
Gear trains were not invented by Leonardo; toothed gearing was already known in ancient and medieval technology. His importance lies in the variety and detail of his mechanical studies. He examined transmissions, screws, pulleys, and other components as parts of larger machines, often drawing them from several angles.
A gear train does not create energy. A speed increase normally comes with a reduction in turning force, while friction causes some energy loss. Leonardo’s gear studies supported designs for vehicles, weapons, lifting equipment, and clocks. They also helped make mechanical relationships visible through precise diagrams rather than verbal descriptions alone.