What mechanical power source did Leonardo da Vinci design using coiled springs?

Leonardo da Vinci designed a spring motor using coiled springs as a mechanical power source.

In Leonardo’s engineering studies, wound springs could store energy and release it gradually to drive gears or other mechanisms. This made them useful for portable machines and automata, where a device needed power without a constantly turning hand crank or an external waterwheel.

The spring motor is especially associated with Leonardo’s mechanical inventions and reconstructions of his automata. A spring does not create energy; it stores energy supplied when the spring is wound. As it unwinds, its torque can be transmitted through gears, although the force changes as the spring relaxes.

Leonardo’s spring-powered concepts should not be described as steam engines or electric motors. They belong to the tradition of clockwork and mechanical automata. The designs demonstrate Leonardo’s understanding of stored mechanical energy, but surviving evidence does not establish that every spring-powered machine in his notebooks was built exactly as drawn.