The video above from Sabins Civil Engineering promises to reveal “the MAGIC behind Da Vinci’s Self Supporting Bridge.” That sounds like a typical example of YouTube hyperbole, though on first glance, it isn’t at all obvious how the fragile-looking structure can stay up, much less support the weight of a crossing army. Not only does the design use no permanent joints, says the narrator, “the more weight on the bridge, the stronger it becomes.” The key is the distinctive manner in which the pieces interlock, and how it directs force to create a “friction lock” that ensures stability.
Remove just one piece of the bridge, however, and it all comes crashing down, which is more feature than bug: designed to facilitate troop movements, the structure could be dismantled to prevent use by the enemy even more easily than it was put up in the first place.
Just one of the various tools of war Leonardo came up with, this bridge was conceived under the patronage of the famous statesman Cesare Borgia (a chief inspiration for Niccolò Machiavelli’s The Prince), who employed him as an architect and military engineer in the early fifteen-hundreds.
Though Leonardo’s bridge designs have proven influential in the half-millennium since his death — think of him next time you cross the Galata Bridge in Istanbul — no evidence remains that he ever built one in his lifetime. But unlike most of his inventions, realized or theoretical, you can build it yourself today without much difficulty. The video presents an example large enough to walk across, which may make it feel rather less stable than it actually is. Luckily for students looking to understand the self-supporting bridge in a hands-on manner, the same engineering principles apply just as well on the more manageable scale of popsicle sticks — a modern building material at which Leonardo himself would surely have marveled.
Related content:
The Ingenious Inventions of Leonardo da Vinci Recreated with 3D Animation
Leonardo da Vinci Draws Designs of Future War Machines: Tanks, Machine Guns & More
Built to Last: How Ancient Roman Bridges Can Still Withstand the Weight of Modern Cars & Trucks
Based in Seoul, Colin Marshall writes and broadcasts on cities, language, and culture. His projects include the Substack newsletter Books on Cities and the book The Stateless City: a Walk through 21st-Century Los Angeles. Follow him on the social network formerly known as Twitter at @colinmarshall.
