This what my third and final trebuchet, a counterweight powered catapult, looked like. I do not have photographs of it because it was dismantled several years ago, but the model is drawn to scale. The full scale swing arm (shown in red) is about ten feet long, and the sling (shown with the tennis ball attached) is about six feet long. All components are steel except for the swingarm, which is aluminum. One of the weights is shown removed from the trebuchet to show the hinged counterweight mechanism. The first version had a wood base with a three foot square footprint which consisted of thirty feet of 2x4's. The swing arm was steel and fiberglass with a rigidly attached counterweight. It worked well, but it was very heavy and bulky. The second version incorporated threaded steel pipe for the base with a three foot square footprint and aluminum for the sling side of the six foot long arm. Because it was aluminum, the whiplash generated by the release required the addition of a suspension cable reinforcement. This version only had a cable on the side that pulls on the arm upon release. The all of the dimensions were optimized with software developed at West Point. It also incorporated a rigidly attached counterweight. The rigid counterweight made it prone to fall over during the recoil of the arm. The threaded pipe made the trebuchet collapsible for easy transporting. The third and final version had a hinged counterweight, making the trebuchet more stable upon release and increasing the speed of the projectile. The arm was lengthened to ten feet, and reinforcing cables were placed on both sides of it. To release the projectile, one end of the sling was permanently fixed to the end of the arm, and the other was looped around a pin at the end of the arm. The release angle of when the sling came off of the pin could be adjusted easily by rotating the pin in the same direction as the arm.

Copyright ©2005-2010, Tom Brown
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