What type of catapult did Leonardo da Vinci design using a large spring?

Leonardo da Vinci designed a spring-powered catapult that stored energy in a large mechanical spring.

The weapon was part of his late-15th-century studies of siege machinery. Instead of relying only on a bent wooden arm or twisted ropes, the design used a spring mechanism to accumulate and release energy. A locking and releasing arrangement would allow the arm to launch a projectile when triggered.

This design is often confused with a trebuchet. A trebuchet uses a counterweight or, in earlier forms, traction to swing its throwing arm. A spring-powered catapult stores energy elastically, making its operating principle different even though both weapons launch projectiles from a pivoted arm.

Leonardo’s military notebooks contain many proposed improvements to familiar weapons. The spring catapult demonstrates his interest in repeatable force, mechanical advantage, and controlled release. As with several of his siege designs, the surviving drawings document an inventive proposal rather than confirmed mass production or battlefield deployment.