Imagine an armored assault tank conceived by one of history’s greatest minds, only to discover that it could never move an inch: that is the paradox hidden in a drawing more than five centuries old. Leonardo da Vinci slipped a technical detail into it that continues to intrigue historians and engineers alike.
- Around 1487, Leonardo da Vinci drew for Ludovico Sforza, the Duke of Milan, an armored tank powered by eight men via a crank-and-gear system.
- The gears linking the front and rear wheels were arranged in reverse order, which would have entirely blocked the tank on the original plan.
- In 2009, a televised reconstruction corrected the gear order and made the vehicle roll, confirming the hypothesis that Leonardo intentionally sabotaged the design to protect his invention.
- A crank-powered tank that would never have rolled
- The gear detail that betrays Leonardo da Vinci
- Why some historians speak of deliberate sabotage
A crank-powered tank that could never have rolled
We are around 1487. Leonardo da Vinci is then working under the patronage of Ludovico Sforza, Duke of Milan, who hires him in particular to conceive war machines. It is within this context that he sketched with pen and brown ink a strange armored vehicle, shaped like a carapace, meant to sow terror on a battlefield.
The drawing is today housed in the British Museum, under inventory number 1860,0616.99. The sheet shows several studies of tank-like machines, including a horse-drawn version equipped with front fake rotors. A formidable sketch on paper, designed to sow panic among enemy ranks.
Leonardo had even contemplated using the force of horses to move the contraption. He ultimately abandoned this path, fearing that the animals might panic once confined in such a restricted and armored space. A fairly logical fear when one imagines the roar and the darkness inside such a hull.
The solution ultimately relied on human strength. According to the French reference sheet dedicated to this invention, eight men placed inside the tank were to operate a crank system connected by gears to the four wheels. An ingenious principle, at least on paper.
The gear detail that betrays Leonardo da Vinci
It is by studying the mechanism precisely that the problem becomes evident. On the plan, the gears linking the front wheels to the rear ones are arranged in reverse order. The concrete result: the front and rear wheels would rotate in opposite directions.
Imagine pushing a cart whose front wheels want to move forward while the rear ones seem to move backward. The vehicle would simply be stuck, regardless of the energy expended by the eight men operating the crank.
An article published by The Conversation in 2025 cites this case among Leonardo’s projects that do not function when reconstructed identically. The author notes precisely the tank’s gears, which would cause the front and rear wheels to turn in opposite directions.
The Henry Ford Museum in the United States leans in the same direction. Its analysis even adds a second obstacle: the machine would have been far too heavy to be moved by only eight men, even with a correctly arranged gear system.
Why some historians speak of deliberate sabotage
Faced with such a blatant error, it’s hard to believe it was merely a momentary lapse. Leonardo da Vinci was a technical draughtsman of formidable precision, capable of representing far more complex mechanisms without getting it wrong. That naturally invites scrutiny.
In the drawing kept at the British Museum, the arrangement of the gears indeed blocks the tank moved by the crank. Some historians see it as a deliberate error, intended as protection against the theft of the invention or its misuse by unscrupulous rivals.
This association is not trivial. Leonardo regularly practiced mirror writing in his notebooks, making his notes hard to decipher for an untrained eye. Embedding a technical flaw in a military plan would fit within the same logic of protecting his ideas.
Proof that the flaw was not insurmountable came much later. In the documentary The Machines of Leonardo da Vinci, aired in 2009, a team of engineers and craftsmen reconstructed the armored tank by simply correcting the order of the gears. The vehicle then rolled without difficulty.
This case perfectly illustrates Leonardo da Vinci’s personality, as brilliant a engineer as a wary strategist. For enthusiasts who want to delve deeper into this kind of mystery, the Leonardotheka platform, launched recently after ten years of work between the Museo Galileo in Florence, the Royal Collection Trust, the Biblioteca Ambrosiana, and the Biblioteca Leonardiana, now brings together a large portion of his writings and drawings for free consultation.
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