Catapult - Science-Project-a-pult

My son and I designed this catapult (patterned after an onager or mangonel) for his 6th grade science project. It is designed to go together without any glue, and only requires a length of 1/4" rod for the main axle, and two 1/8" pins for the bucket.

The bucket can be positioned along the length of the arm to explore how the length of the arm changes throwing mechanics. The bucket could also theoretically be turned one of two ways to see how the different inner profiles affect the release trajectory. Different numbers of rubber bands can be added, but my son and I found that more than one rubber band started getting into "don't tell Mom" territory.

You will need to print two frames, two spacers (go on either side of the arm when the axle is slid into place), two secondary braces (they go under the ends of the main frame), and one of everything else. I used ABS with a relatively low infill but thick shells, since I wanted to preserve some elasticity. We discovered that thick