What powered Leonardo da Vinci’s proposed tank?

Human muscle powered Leonardo da Vinci’s proposed tank.

Leonardo’s fighting vehicle was a covered, conical armored machine fitted with guns. Inside, men would turn cranks connected to the wheels, supplying the force needed to move the vehicle. The design therefore depended on human operators rather than an engine, fuel, or animal team.

The vehicle is often called Leonardo’s tank because its armored shape and weapons resemble a modern tank in broad outline. It was not a tank in the modern mechanical sense. It had no internal-combustion engine, tracks, turret, or electric systems, and the surviving drawing presents a concept rather than a completed vehicle.

A famous drawing contains a likely gearing problem that would make the vehicle move backward if built exactly as shown. Some historians think this may have been an intentional error to keep the design secret, while others regard it as a drafting mistake. Either way, the planned power source was human effort.