It’s true. Leonardo da Vinci sketched designs for helicopters, airplanes, and tanks, none of which would have worked. There are probably other examples of unworkable da Vinci designs. For all I know the Vitruvian man was an illustration of a failed attempt to invent the jumping-jack.
I’m certain he never actually thought the drawings for the airplane and the helicopter would work. They were most likely musings on what might be possible with a better power source. It’s not really fair to pick on him over that, but let’s look at his tank. My understanding is that he actually proposed building that one. It was made of wood powered by hand cranks.
Here’s a video of a full size working model.
As you can see, it would have been painfully slow, even on pavement. I bet it would speed right up when the enemy set it on fire, which they almost certainly would have done immediately because, again, it was made of wood.
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