Lego© compatible Cannon XXL (8 m/s)

thingiverse

This Cannon shoots 9.5 mm steel balls with a velocity of about 8 m/s, which means around 0.1 Joule. That's enough to smash interlocked bricks of Lego castles, pure fun! The cannon can be cocked by pressing in a stick (left over from the Ball Point Pen?) or pulling the plunger, fires while pressing down the trigger board. SERIOUS WARNING: Make sure that EVERYBODY doesn't shoot at humans and animals don't shoot pointy or sharp projectiles don't shoot ANY projectiles (ex. candies...) into the MOUTH => choking Hazard. Treat the cocked cannon as LOADED! Your spouse will complain about the lost ammo when stepping onto it... I strongly recommend steel balls from 9 to 12 mm, plastic balls will be faster but reflect and potentially come back. The cannon can be completely embedded into a Lego structure like a ship or castle. Print Settings: Printer: da Vinci 1.0 Rafts: No Supports: Yes Resolution: 0.2 Infill: 30% Post-Printing: Please refer to the pictures. All parts probably need fine tuning. The Lego Clip Holes need to be reworked with a 4.8 mm drill! Some parts need to be glued together. I use Super Glue, but then you need to be fast and accurate. You need 5 springs from Ball Point Pens (4 mm diameter and about 25 mm long) and two 3 mm axes (nails?). The 'Cross Bar' needs to be about 1 mm thick, must stand upright when intersected. The 'Cross Bar' must be a tight fit into the 'Plunger Plate' and 'End Puller', but move freely in the 'Barrel End Cap'. (1) Glue the 'Plunger Plate' to the 'Cross Bar', pins oriented to the 'Cross Bar'. (2) Slide in the Barrel End Cap', sphere shape opposite from the 'Plunger Plate'. (3) Glue in the 'End Puller' in a way that the 'Cross Bar' doesn't stick out. (4) Smoothen the inner Barrel and the 'Plunger Plate' so it moves without resistance. (5) Put in 4 springs, first clip into the barrel to check alignment without gap and free movement. (6) Glue the 'Barrel End Cap' into the barrel, 'X' oriented, NOT '+'. (7) Put a spring between the barrel and the 'Cocking Board', put in the 3 mm axis. (8) Put the assembled barrel between the frame and put in the 3 mm axis Optionally fix one side of axis with silicone for later removal. (9) Fine tune the cross axis for the wheels that tightly fits into the Frame holes. How I Designed This First, I sketched the function and power, four Ball Pen Springs determined the cannon diameter. Second, I adjusted the dimensions to be Lego compatible. Last, I applied 'look alike' features.