Simple Catapult

A small, simple catapult that uses a rubber band to fire superballs. A suitable project for teaching basic ballistics or just for fun.

You will need:
One (1) Rubber Band, preferably a thick gum band
Superballs (small rubber balls appr. 2cm in diameter)

You will need to print
One (1) cat_arm.stl
One (1) cat_spacer_rb.stl
Two (2) catapult_wall.stl
Three (3) cat_spacer1.stl

instructions1.pdf contains basic instructions for construction and use along with diagrams. Text instructions from that file are copied below. Sorry if they're insultingly simple. They were written for a friend with the mechanical skills of a drunken chipmunk.

Construction
1) Lay one Sidewall flat as shown above.
2) Insert the axel of arm into the matching hole in Sidewall (red dot), ensuring that the ammunition basket faces right when the arm is perpendicular to the base. Rotate arm
counter-clockwise until it is between red and blue dots.
3) Insert the retraction base into the matching hole in S