Leonardo da Vinci designed a catapult with a pair of giant rotating arms.
His sketches show a large wooden machine intended to store mechanical energy and release it to hurl a projectile. The paired arms and winding mechanism were meant to improve the force available from the device. Leonardo studied the geometry, springs, and leverage involved in siege weapons rather than simply copying a single ancient model.
Catapults had existed for centuries before Leonardo. Greek and Roman engineers developed several types, and medieval armies used related machines against fortifications. Leonardo’s contribution was his detailed analysis and redesign of mechanisms, including ways to control the release of stored energy.
This machine is different from a trebuchet, which uses a counterweight or traction system, and from the spring-powered stone launcher listed elsewhere among Leonardo’s designs. The broad term catapult is the precise answer for the rotating-arm weapon shown in his drawings.