Leonardo da Vinci designed screw-jack mechanisms to raise or move heavy loads through the mechanical advantage of a threaded screw.
A screw jack converts rotational motion into controlled linear lifting. Turning the screw advances a threaded component and raises the load gradually, allowing substantial force to be applied with relatively modest effort. Leonardo’s notebooks contain detailed studies of screws, gears, hoists, and other lifting mechanisms.
The principle was not invented by Leonardo; screw-based lifting devices were known before his time. His contribution was to analyze and refine mechanical arrangements with exceptional detail, documenting how parts could work together in machines for construction and engineering.
A screw jack differs from a pulley crane, which lifts by tension in ropes or chains. It also differs from the spring-powered cart commonly associated with Leonardo. The jack is a stationary or supported lifting mechanism, driven by turning rather than by stored spring energy.