The Trebucet of Doom

Golf-ball throwing trebuchet built for grade 11 Physics project

Lots of Monte Carlo and general fun simulations from The Algorithmic Beauty of the Trebuchet

The trebuchet was built from sections of aluminium sheet - the components had to fit in a shoebox 30cm x 20cm x 16cm. Elements under compression were bent to a shallow "L" section for stiffness. The axle is screwed rod with sleeve bearings made from brass tube. The release finger is basically another sleeve bearing designed to come apart. The sling is nylon cord with a naugahyde cup.

What I think got built (for wintreb and monte carlo):

l1 13cm    0.426ft
l2 51.5cm  1.69ft
l3         2.1ft (adjustable)
l4 29cm    0.95ft
l5 50.5cm  1.656ft
m1         11.4lb (3 small SCUBA weights)
m2         0.1lb  (golf ball)
mb         0.5lb

GIF animation of treb in action Simulated free-sling treb

Photos:

video of the trebuchet in action:

3.avi
4.avi
(also 1.avi,2,5-8 etc. All pretty similar, with slightly different sling lengths - AVI from xawtv video capture from 8mm camcorder, no sound)
000_0550.MOV (served from TRIUMF on BCnet)
(also 0552, 0553, 0556, 0557, 0558, 0560: Quicktime from digital camera)

The range of the trebuchet is a complex function of the beam dimensions, counterweight arm length and sling length. Maximum range is acheived when the projectile is released at an angle of 45 degrees. Maximum efficiency is acheived when all the potential energy in the falling counterweight is transformed into kinetic energy in the projectile. For this to happen, the counterweight must come to a halt at release (otherwise it would still have some kinetic energy). With optimal sling length, the sling pulls back on the throwing arm, slowing it and transferring energy to the projectile.