Man builds supersonic trebuchet in his backyard
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Generating a sonic boom is usually only the result of immense cosmic forces or highly advanced aircraft designs, but it is possible to create one in your backyard. Aerospace engineer and YouTuber Tom Stanton recently documented his quest to construct a mechanical trebuchet capable of launching an object so fast that it breaks the sound barrier. That means building a device capable of not only hurling an object at about 767 miles per hour, but withstanding the physics needed to make it happen.
“Accelerating a projectile to this speed using a purely mechanical launcher like a trebuchet has been a dream of mine for several years now,” Stanton says at the video’s outset, as if it’s a totally standard goal to pursue in your spare time.
A historical trebuchet was often very large, with its wooden beam easily measuring as much as 50 feet long. But despite their immense size, the siege weapon’s mechanisms have always been relatively straightforward. As Stanton explains, the entire construction essentially operates as a mechanized seesaw. The lengthy beam is yanked forward once its central weight is released, allowing it to whip a sling loaded with a heavy projectile like a massive stone towards the enemy.
Every standard trebuchet’s potential force has the same limitation, and that is gravity itself. Even history’s tallest trebuchets remained close enough to the ground that their weights wouldn’t fall any faster than 32.15 feet per second squared. This means any further increase in a volley’s speed needs to come from additional force multipliers like elastic bands or other tension sources.
While Stanton admires these alternative approaches, he remained dedicated to designing a trebuchet that reaches supersonic speed while still only relying on weight. Accomplishing this feat required a modified version of the weapon that removed the direct coupling between the weight itself and the arm beam, while also employing a rope setup on a 3:1 pulley system. This ratio let Stanton dramatically increase the rate at which the weight falls.
Of course, no experimental YouTube physics project would be complete without a maddening amount of trial-and-error. Beyond the initial alterations, Stanton ultimately landed on a design with a much shorter arm that tosses a sling measuring about double the standard length. Those dimensions let the sling complete multiple full revolutions to gain even more momentum as it unravels from the beam. Meanwhile, the falling pulley weight array was built strong enough to handle the immense physical forces at play. After much tweaking, the trebuchet’s whip-crack release finally announces Stanton’s success at the video’s 19:55 mark.
“I heard an echo over here and over here,” he says pointing to either side of him after the test run.
What’s more, the supersonic trebuchet didn’t break, even as the arm accelerated at 2,342 rpm. Upon release, the projectile traveled 6.36 feet in 5.6 milliseconds. Its final speed didn’t just break the sound barrier. It soared well over the 767 mph threshold at a staggering 776 mph.
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