Printed with 5 shells out of four different materials:
Photos were taken after five test shots on each catapult. PLA seems to suffer the most plastic deformation in the torsion bar.
ABS and PETG deform about the same amount however ABS is stiffer and because of that shoots better.
- Make sure there are enough shells or the neck will break even with high infill %.
- Using a thin support enforcer to stabilize the back of the "spoon" near the neck will do wonders to the quality of the print.
- Cooling is tricky to get right with ABS. Too little and the arm looks bad, too much and it will break near the neck because of poor layer adhesion.
- Test layer adhesion by setting the catapult on a flat table and press the "spoon" all the way down until the back of it touches the table. When printed correctly, the arm will have enough flex to allow this without snapping.