Two weeks ago I came across instructions for a T-shirt Cannon in Popular Mechanics and decided to build it. Of course along the way I thought of suitable enhancements. Instead of using a bike pump to charge it I wanted to attach a tire pump and a power source so that I could pillage cord free!

WARNING: This should go without saying but this can be dangerous! Do Not Shoot at people or pets. When testing for the first time do not start with a high pressure, start with a low amount and slowly increase!!!

I will add many more pictures very soon, I dont have access to my digital camera atm.

Step 1: Gather Materials

There are three distinct sections so I will group the materials in those parts.
First: The Cannon itself
1x - 2 Ft of 4 Inch PVC Pipe
1x - 4 Inch diameter PVC End Cap
1x - 4 Inch to 1 Inch diameter adapater ( I substituted a 4 Inch to 2 Inch adapter and a 2 Inch to 1 Inch adapter)
1x - 2 Ft of 1 Inch PVC Pipe
2x - 1 Inch Male threaded adapter (to screw into the sprinkler valve)
1x - 1 Inch diameter Automatic Sprinlker Valve
1x - 1 Inch to 2 Inch adapter
1x - 3 Ft of 2 Inch diameter PVC Pipe

1x - Presta style Bicycle inner tube
1x - Presta to Schrader valve adapter ( I found mine at a local bicycle shop )

Second: The Air Pump and Electrical System
1x - Portable 12v Tire Pump
1x - Battery operated Electrical Drill ( This is only used for the batteries )
1x - Main power switch
1x - Normally off push button
1x - Electronic parts enclosure
1x - Nerf Gun ( I used this for the handle, Optional)
1x - Normally Off push button trigger switch

Third: Misc
2x - Clear Silicone Sealant
1x - Gorilla Glue Epoxy
1x - PVC Glue and Primer
1x - Package of Large Zip Ties
1x - Package of Medium Zip Ties

Step 2: Assemble the Cannon

Wait till you are completely finished with construction before you cap the Pressure Tank!

I started at the back and moved forward, so
1) Take your 2 Foot section of 4 inch diameter PVC Pipe and install your 4 Inch to 1 Inch adapter
2) Attach 3 Inches of 1 Inch diameter PVC Pipe Into the 1 Inch adapter
3) Attach the 1 Inch male threaded adapter to the 1 Inch PVC Pipe
4) Screw your Automatic Sprinkler Valve onto the 1 Inch male threaded adapter
5) Screw the other 1 Inch male threaded adapter into the other side of the Automatic Sprinkler Valve
6) Attach an aditional 3 Inches of 1 Inch PVC Pipe into the 1 Inch male threaded adapter
7) Attach a 1 Inch to 2 Inch adapter onto the 3 Inches of 1 Inch PVC Pipe
8) Finally, Attach 3 Feet of 2 Inch diameter PVC Pipe onto the 1 Inch to 2 Inch adapter

Be sure to use purple PVC primer and PVC pipe gule on all parts (except the threaded bits), the tank will be under pressure so I would prefer not to tempt fate.

Now we will install the Presta Valve into the Pressure Tank. The reason why I used a Presta Valve instead of a normal Schrader Valve is that Presta Valves are threaded the entire length of the valve. This means that we can screw it into the side of the tank to create a better seal then we would have otherwise.

1) Return to the open end of the Pressure Tank and drill a hole that is just smaller than the Presta Valve into the side of the Tank.
2) Cut the Presta Valve out of the Bicycle Inner Tube so that there is 1 Inch of extra material around the valve stem
3) Screw the Presta Valve into the side of the tank so the Valve sticks out the outside of the tank at least a full Inch

Seal the end of the Pressure tank

Step 3: Wire the Electronics

The Electronics on this are pretty simple.

First a bit on the power source. I found a Black and Decker battery powered drill set that had the drill, two batteries, and a wall charger on sale at walmart so I am using that. Its an 18 Volt battery pack. The Air Pump is expecting 12 Volts and the Automatic Sprinkler Valve is expecting 24 Volts AC. The pump just runs faster and noiser, there is some chance of it burning out sooner however it is just a cheap pump and it would be easy to replace. The Automatic Sprinkler Valve is something of a question, According to their website the Valves need AC power but it runs on 18 Volt DC power with no problems.

Automatic Sprinkler Valves are designed so that when there is no power the valve is closed. You wouldnt want the sprinklers to come one every time someone trips over the power cable...

According to the schematic above, the power wire (the red wire, or positive wire) runs through a main on/off switch to two different switches. One of the switches runs to the pump to turn it on so that it will turn on and start charging the air pressure. The other switch is our trigger, it will open the Automatic Sprinkler Valve so that the air can excape. The ground wires (the black wires, or negitave wires) are all just tied together.

Step 4: Make Everything Pretty

I put all of my electronics and the air pump into a plastic case. The pump makes a lot of noise from vibration, so I put down a layer of Silicone Sealant to act as a vibration dampener and used zip ties to secure the pump to the enclosure. The case I used was from a bluetooth headset that I bought a while back that I saved because I thought it might be useful for a project down the line ;)

The electronics enclosure was attached to the back side of the Automatic Sprinkler Valve using Silicone Sealant and Large Zip ties.

The grip was a bit more difficult to come up with. Finally I found a Nerf N-strike Maverick gun that had a really comfortable grip. Using a dremel I cut away everything but the handle. Then I spraypainted it black to match the rest of the gun.

Using Gorilla Glue Epoxy I put a small switch inside the handle that would open the Automatic Sprinkler Valve when the trigger was depressed.

Then, using more Silicone Sealant and Large Zip Ties I secured the Grip to the Pressure Tank.

Step 5: Making Darts

Rolling T-Shirts constantly so I could shoot them out seemed like a bit of a pain. So I created nerf-like darts.

They are simple to make. I used Foam Pipe Insulation for the main body, about a foot long. These are great because they are firm enough that they manage not to get damaged easily, but dont hurt much when you invariably get shot with one. I fill them with a plastic sack and cap it with Silicone Sealant and tape.

Step 6: First Test Fire and Thoughts for the Future

Heres my first attempt at firing

the T-Shirt Cannon

{Insert Video Here}

The dart I was using was only a first attempt at making a dart, it wasnt long enough and came apart before it could gather any force behind it. Also, 20 PSI is about half of what I normally fire it at now. I went with the cheapest air pump that walmart had avaliable, going with one of the mid range ones will significantly decrease the amount of time it takes to charge the Pressure Tank

Here is a video of one of my new darts at 40 PSI

Above 40 PSI this becomes rather dangerous, There is now a hole in the drywall in my living room from a dart going through the wall at 60 PSI...

I want to modify this in two ways, first I want to add a microcontroller with a pressure sensor so it automaticly pumps itself up to a predefined level. The other modification is a shotgun like reloading mechinism.

This is my second Instructable (and my last one was in 2007 :p ) Please feel free to comment. If anything is unclear or needs to be explaned differently please let me know. More information is always a good thing!