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Tech index -> Custom Work -> Icebreaker T-shirt cannon

A project of mine for a projectile launcher able to fire t-shirts or any other suitable object acrosss a great distance. It's designed with a barrel nearly 4 inches in diameter but I could make a smaller sleeve/insert to reduce the diameter if needed.

Like most of my projects I envisioned several different ways of containing the assembly. Ideally I wanted to use a solenoid to control the firing, despite this adding complexity to the design. This isn't meant to be marketed but rather a personal project so the high cost of using electronics was irrevelant.

The proposed design:

Here's an exploded diagram showing all the components:

Here's the finished assembly:

Fabrication:
This entire project was actually produced at the request of the local college (where I work). It was ultimately made as part of a larger CNC machining demo. Part of that included documenting the fabrication, collecting the related instructional information I made for it (diagrams, renders, etc) plus the machine's G-code was manually written so students could understand it easier. Here are some cool pictures I took during the machining:


Here's a video...

CAD Files:
You can view all the associated CAD files for the machined parts by downloading this .ZIP file:
Ice_cad_files.zip
Inside are both Inventor 2009 solid models, and AutoCAD DWG prints I made for each component's lathe and mill operations (separately).
Feel free to use the files for anything you see fit. However, do note that the exact dimensions may have been altered slightly for the actual functional parts after I experimented with them. If you plan on making your own, be prepared for experimentation too!

CNC Machining Programs:
Here are the original programs I made for each of the machined components:
Ice_cnc.zip
Contained there are a collection of numerical control programs (.TXT format) and some associated pictures used to show some setup information of the material stock and whatnot. I don't have clear-cut instructions available here on the website since I don't expect anyone to literally walk up to a machine and produce any of these parts; rather I'm trying to show some of the code and work that was involved. Use at your own risk!

Operation:
The internals of the firing valve are based on that of an Airstar Nova or Legion Shocker. The core of the system is an unbalanced poppet valve which is actuated during firing. The firing valve shuts off its own air supply which makes the dump chamber's firing volume pre-determined.

A fluids schematic I produced to show people how it works, relating to pneumatics and hydraulics of course...

The device is fully electropneumatic and intended to be controlled by an on-board circuit just like a paintball marker. The only difference is my board is intended to be fired in either of two modes:
1. Timed mode (default): The launcher will fire the solenoid valve for 100 milliseconds then automatically close it, wait for the user to let off the trigger switch, then reset for another shot.
2. Manual mode: The launcher will open the solenoid valve as long as the trigger is held down, which can be timed as long as 1/4 second (250-ms). After this time the valve will shut off automatically and reset for the next shot. This is not the default mode since the device should be able to operate in regular timed mode unless there's a problem with the firing assembly. In this case the operator can select the manual mode, allowing him/her manual control over the solenoid dwell. This is not ideal for everybody though, since people unfamiliar with the device might make it short-stroke.

I built the firing circuit and programmed it myself using my loathesome knowledge of Assembly code. Here's a schematic of the board:

Here's the firing program. I have two versions uploaded, one is the standard code whereas the other is the code with added comments for each line.
Firing program, version 3A; Firing program, version 3A, with comments

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