How to send your love 300 meters in three seconds: the Prairie Bench Trebuchet. (more pics and video below)
Siege engines, such as ballistas, catapults and trebuchets are medieval devices for throwing stuff. Originally developed somewhere in France? the trebuchet became famous during the reign of King Edward Longshanks when he employed the use of one to storm the walls at Sterling Castle. Since, trebuchets have mystified and terrified audiences with their immense power and rudimentary use of physics. We’ll be using this device to send tennis balls and water balloons, maybe a small pumpkin.
The trebuchet is really just an unbalanced see-saw with a counter weight on one end of a long boom or mast, and a sling on the other. The counter weight can be anything heavy enough to lift the long wooden mast and whip a sling holding the ammunition. When the sling moves overhead, centrifugal force causes one looped end of the sling to slip over an open prong at the tip of the mast. The latent energy to fling the ammo is held by raising the counter weight and then releasing it. Gravity does the rest. There are many strange terms and phrases used for trebuchets available online, however this post uses our own novice phrases.
The trick to designing a trebuchet involves three main variables: the size of the ammunition, the mass of the counter-weight, and the angle of the prong to release the sling. By adjusting these variables, consistent and powerful shots can be made quite easily. It’s also important that the entire frame is free to rock back and forth, allowing for a ‘whip action’ used in traditional hand slings.
Enter the Prairie Bench Trebuchet—sort of a wild west variation:
-V8 350 flywheel counterweight
-steel axle bearings with grease reservoirs
-100 kgs of latent energy (optional 400 kg spring upgrades)
– fold down portable
-adjustable chain stays
-adjustable launch center board by degrees
-wooden wheels and rocker
-easy load magnetic trigger set
-variable thrust dial including mayhem, havoc, and doom
-hand woven sling
-hand carved ‘loosing’ handle
-front and rear triggers
-hand crank draw winch
-barrow transport handles, optional
The trebuchet stands 7 feet tall with a three foot sling. Less than 30″ wide, our siege engine can easily fit through any castle door.
Our design uses a solid fir mast hand planed to a taper with steel flat bar reinforcing, laminated spruce pillars, fir frame, and chain stays. The trigger mechanism is used from the rear or the front using 1/4″ steel push rods and a safety lock. The sling is hand woven from sisal fiber.
In golf yell, “Fore!” With a cannon yell, “Fire!” With a trebuchet yell, “Loose!”