Valken/Hakkotsu Thunder B Compatible Shell

thingiverse

Valken/Hakkotsu Thunder B Compatible Grenade Shell.As with anything dangerous, mess with this at your own risk. I wanted to manufacture my own shells rather than buy them - as I'm printing them for a cost of around $1.40/ea versus $1.83/ea ordered in bulk from Evike. Not a huge savings, but you can have a shell in 3hrs instead of 4-5 days.Print "Shell Neck Test" to make sure your printer is up to the task. It should be a solid thread fit and just fit past the center metal core. Adjust sizing on the test part if it doesn't fit, then use that multiplier on the real deal.Real Thunder B threads are 13tpi, 28.6mm nominal diameter. The printed object in CAD is ~29.03mm nominal, printing at 28.89mm, or thereabouts. The cut threads in the grenade head are pretty deep, so there's a fair bit of wiggle room.Printing should be done at 0.1mm layer height on a 0.4mm nozzle, 4 wall line count (4 inner, 4 outer), 12 top layers, 12 bottom layers. This should make the walls solid, as well as the critical parts of the neck and shoulder area at the top of the shell. No supports are needed, as all overhangs are 45-55 degrees.After slicing, inspect the layers above the threads on the neck and make sure that the walls are being printed 3 extrusion widths thick! If they aren't, adjust your extrusion diameter until they are. This is a critical strength area.DO NOT use hard filaments like PLA or PETG. These will fragment. Don't use TPU either, as it just makes a bottle rocket and blows the shell off. The stock shell is designed to rupture in a SAFE FASHION without fragmenting. That's why it's made out of HDPE!This design ONLY works properly with Polypropylene! In my testing so far, either the Z-Seam ruptures or the bottom blows out (usually off). This design is specifically designed to take advantage of Polypropylene's physical properties, and will not work in a safe fashion with any other filament. You must follow the printing instructions exactly or the behavior of the grenade shell can't be guaranteed.UPDATES BELOW:11/23/2023: Shell updated. Still blowing out too fast. Working on it.11/24/2023: Shell updated again. Wall thickness now 2.25mm, 5 extrusion widths at 0.4mm. Floor thickness 2.4mm. This version pops in ~2-2.5 seconds and tends to split in the middle.11/25/2023 Part 1: Shell update. Wall thickness increased 1 more layer to 2.45mm, now 6 extrusion widths. Added the Thunder Devil step rib trying to get the case to fail in that location rather than at random. Worked well, but blew off the canister like a rocket - neck section at the threads is too thin.11/25/2023 Part 2: Shell update. Thickened the OD of the neck as bottle rockets were happening again. Shooting for the max the sim head can accept. Also updated the threaded neck section test STL.