Leonardo da Vinci intended eight people to power his armored vehicle. They would turn internal hand cranks connected to gears that drove the vehicle’s wheels.
Leonardo sketched the fighting vehicle in the 1480s as a conical, covered machine fitted with guns around its perimeter. The sloped shell was meant to protect the crew and deflect incoming weapons. The concept is frequently called Leonardo’s tank because its enclosed shape resembles a modern armored vehicle.
The design has an important engineering problem: the gear arrangement shown in the drawing would make the vehicle move backward rather than forward. Some historians think this may have been a deliberate error to prevent others from easily copying a military invention, while others regard it as a design flaw. Leonardo’s vehicle was never built for Renaissance warfare.