Do you want to launch a softball 50-60 feet without having to get down and dirty cutting wood, metal, and using power tools? Here’s an easy way to build a fairly sizeable trebuchet out of cardboard and a few other basic materials.
For this project, the components are glued together and assembled with bolts for the axles. A few small pieces of PVC are used to create axle bearings–this could be improved by using skateboard ball bearings instead (side note: it’s crazy that you can now get a single skate bearing for 99 cents). Also, a commenter makes a great point that adding wheels will allow the trebuchet to rock as the counterweight falls, which allows the counterweight to follow a much more efficient linear path and increases the capabilities of the machine.
Glued corrugated cardboard develops a decent amount of strength while remaining fairly lightweight. And as anyone that watched Punkin Chunkin knows, lower weight means faster speeds. Keeping the throwing arm as light as possible is key for massive launches.
Follow all the steps on the Instructable here: Cardboard Trebuchet. Also, I lied about the power tools part. You may need a drill to create the opening for your axle. No big deal.
And if you want something a little more desktop sized (plus kill some time at work), check out the Paper Trebuchet instructable too.