What machine did Leonardo da Vinci design to produce continuous motion from a coiled spring?

Leonardo da Vinci designed a spring-powered cart to produce continuous motion from coiled springs.

The device is usually called Leonardo’s self-propelled cart. Leonardo’s drawings from around 1478–1480 show a small wheeled vehicle driven by mechanisms hidden beneath its body. Coiled springs supplied the stored energy, while a programmable system of cams controlled the distance and direction of travel.

The cart may have been intended as a theatrical or ceremonial machine rather than as transportation. It could move without someone visibly pushing it, which would have made it effective in court spectacles. The design is therefore an early example of a programmable mechanical automaton.

It was not powered by steam, electricity, or an internal-combustion engine. A modern reconstruction displayed in 2006 showed that the surviving drawings can support a working interpretation, although reconstructors had to resolve ambiguities in the original plans. The machine’s spring power also limited its range.