Here’s the model that started it all, with some new upgrades! This catapult uses one or more elastic bands to launch a U.S. penny if you print it at 1:1 scale. You probably won’t get enough torque to be impressive with fewer than 3 bands.
Construction is snap-together!
Feed an elastic band through each of the bores on the side braces. Tie it through the bore on each winding key. Slip the end of the throwing arm through the rubber bands. Repeat with as many rubber bands as will fit through the holes. Needlenose pliers will help here.
Twist each key 10 times and then lock it in place by inserting the locking tenons into the square holes on the side braces. The more twists, the more launching power you’ll have. Careful, pennies can sting, especially if you take an Abe to the forehead.
Flagrant stagecraft alert: the clever-eyed among you will note the use of a twist tie to keep the throwing arm cocked for the photo.