Renaissance engineer and artist Leonardo da Vinci is well known as the intellectual father of the modern tank, submarine, and helicopter. He reputedly introduced a deliberate design flaw into his tank’s locomotion system because he never wanted anybody to actually build this terrible weapon.

The specific flaw was that the cranks that turned the wheels revolved in opposite directions, so the men would either work against each other, or else cause the tank to revolve like a top. If this was da Vinci’s intention it was unlikely to have deceived a skilled mechanic of his era for very long. A motion efficiency perspective suggests, meanwhile, that da Vinci might have actually intended the “tank” to rotate in place.

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