I wanted to show my son the process of designing, printing and assembling so I chose to make a catapult. This is a very simple design, and quite robust. Good use of a rainy afternoon.Print the following: 1 x Arm 2 x Side 3 X CrossbeamYou may have to whittle the crossbeam end to make them fit, but that's fine, you want a really snug fit.Fit the crossbeams to one side and then add the second side, use a hammer to persuade them to fit.Use a length of filament to thread through one side, the arm and the other side. Use a rubber band to power it.I will probably update this soon, the axle and fixing points need to be better.