Leonardo da Vinci designed a screw jack to lift heavy loads with a screw and crank.
A screw jack converts rotation into controlled linear lifting. Turning the crank moves a threaded component upward or downward, allowing a relatively small force applied over many turns to raise a much heavier load. Leonardo’s mechanical drawings explored this principle as part of his broader study of machines.
The screw jack demonstrates the mechanical advantage of a screw. Its threads trade speed for force: the load rises slowly, but the operator gains lifting power and precise control. This makes the device suitable for positioning or raising heavy objects rather than moving them quickly.
Leonardo did not invent the screw principle itself. Ancient engineers already used screws, and later jacks were manufactured in many forms. His notebooks are valuable because they show a systematic Renaissance investigation of threads, gearing, friction, and force. A screw jack should not be confused with a pulley, which lifts through tension in a rope rather than through a threaded rotating shaft.