The parts of a simple wedge catapult - base,catapult and trigger. The catapult is driven by an elastic wrapped around the wedge. This is a just an exercise I used to figure out how to use the shapesmith.net design tool. No idea what size this will print at. You need to make a couple of pivot dowels to fit the two holes, so if you can scale your prints, try to get the big pivot sized to a standard size of steel or aluminum rod.

My first 3D design. I don't have my printer fully built yet, so I don't know if it will print well or not.