Trebuchets have always been a fascination of mine. Years ago I saw a NOVA documentary where two teams built authentic replica medieval trebuchets, and launched 300 lb projectiles over 200 yards. The impressive power created by these simple counterweight contraptions inspired me to investigate the physics and engineering principles that made them possible. The trebuchet shown on the right is one that I build as a teenager, and demonstrated at various science club events at Portland Community College. Later on, the campus president would ask me to bring the trebuchet back to display as an example of student activities during the faculty inservice meeting.
Below are more photos of the trebuchet at various stages of development and redesign. The original design used a swinging wooden bucket filled with sand as the counterweight. Later on, I replaced the bucket with an 840 lb concrete collar and upgraded the timber used for the throwing arm. I’ve also experimented with different pulley mechanisms for retracting the throwing arm, eventually settling on a type of large wooden ratchet.