What is the name of Leonardo's design for a self-propelled cart?

Leonardo’s design for a self-propelled cart was called the self-propelled cart. Drawn in the late fifteenth century, it is often described as an ancestor of the modern automobile, although it was a spring-powered mechanical device rather than an engine-driven car.

The cart used two large, coiled springs concealed in drum-shaped housings. As the springs unwound, they powered the wheels. Leonardo added a balance wheel to help smooth the motion, much like the regulating components used in clocks. A steering and control system allowed the machine to follow a predetermined route, making it an early example of programmable mechanical movement.

The design is sometimes mistakenly labelled a car, tractor, or bicycle. Those names describe later vehicle categories, not Leonardo’s own title. Because the original machine was never built in his lifetime, modern replicas—including one associated with the Clos Lucé museum in France—help demonstrate how the mechanism may have worked.