2. from: Floating Arm Trebuchet, the most effecient catapult! http://www.youtube.com/watch?v=-qDvMwa71Fg&feature=related

19. We are three guys from Sweden who made a Floating Arm Trebuchet as a school project. This is the most effecient catapult design known today. We managed to throw a 0.5 kg (1,1 lb) projektile 110 meters (361 ft), this gave us an effeicency of 41 %. Our counter weights were made out of concrete and had a mass of 40 kg (88 lb). The trebuchet is 2 meters (6,5 ft) high. does th beam have to be 1:2 (te ratio between the lng arm and short arm?) and and the degree at first whenyou pull the counterweights up should there be a certain angle? im telling you again to try to come up with your own design, there is no rules that say that a specific ratio needs to be 1:2. The angle between the ground and the arm is 45 degrees in loaded mode, nothing says thats the "right" angle tho, we just made it as simple as possible and it turned out really well.. Cool! I built a standard type 6 foot treb that launched 2lb rocks about 200 feet, using 230lb of counterweight. I heard that if you add wheels to a normal trebuchet, it is almost as efficient as the one you have here. Cool, have fun launching things!

20. Estimate the inside diameter by subtracting 1/4-inch from the outside diameter, if your pipe is standard Schedule 40 galvanized pipe. If you suspect your pipe is Schedule 80 extra strong pipe, subtract 3/8 inch. Schedule 120 double extra strong pipe is significantly heavier and if you suspect you have it, subtract 11/32 inch. http://www.ehow.com/how_6390397_measure-diameter- galvanized-pipe.html

24. 4.5” diameter wheels w/ ¾” steel axel. Counter weight on 1” to 1 ¼” diameter axel. Could use galvanized pipe (1” I.D.).