• Interchangeable Barrels!
• Multi-Sources for compressed air (CO2 or Bike Pump)
• Lots of safety features!  (Multiple ball valves, and a safety release valve)
  

Parts List:

To begin our build we will separate our build process into three different gun components:.

• High Pressure Air Chamber
• Barrel
• Quick Release Trigger Mechanism

Build Process

High Pressure Air Chamber

Make no mistake, this is the MOST DANGEROUS PART OF YOUR GUN (to you). Take your time, and make sure that EVERYTHING seems 100% right, if something seems "off" scrap it and build another one. The parts are cheap, your arms, legs, and everything in-between are not. Make sure you read through (and understand) this entire section BEFORE you start.

Now, before we start. Forget everything you were taught in 2nd grade about gluing. Gluing these parts is going to get messy, put down some news paper or drop cloths before you start. The general process of gluing PVC is such: Primer both components (ex. Outside diam of pipe, inside diam of fitting), apply PVC glue to both components (on top of primer), Insert FULLY and give 1/4 twist & hold for 30 seconds. Ok, read this next sentence like four or five times, it will save you headaches down the line:

USE TONS OF PRIMER, and 2x TONS of GLUE. (Seriously glob that glue on there, both sides. You want to make sure you have a good seal)

Start by using your hacksaw to cut a 10" length of 3" PVC Pipe, you may need to use a utility knife to clean the edges of any stray PVC. Primer & glue the 3" end cap on one side, and the 3" coupler on the other.

After a few minutes, Primer & Glue the 3" x 2" (non threaded) bushing into the 3" Coupler. Once give it a few minutes to cure.

As PVC is unforgiving when it explodes, it is VERY IMPORTANT that we don't over pressurize our air chamber, we can accomplish this by using a a safety valve. The 115 PSI Safety valve will open once the internal pressure hits 115PSI allowing excess pressure to escape.  This ensures that the air chamber doesn't become over pressurized and explode. Do not skip this part!!!

The Schrader valve is used to charge our air chamber with either an air compressor or a standard bike pump. Even though later we will discuss charging it via CO2, it is nice to have a secondary means. As you can see below, I chose to mount my Safety release valve on the rear of chamber, and the Schrader valve on the side. I would recommend mounting both on the side, as it is structurally stronger mounting into double layers of PVC. (One layer creates a potential stress point) Just make sure that neither would be pointing at you should they "blow off" and that both are easily accessible.

Decide (and mark) your desired locations for both the Schrader & Safety Valves. Before you actually drill and mount these parts, You might want to take a couple practice drills into one end of your UNUSED left over 3" PVC pipe, you have plenty.  Remember, practice makes perfect.

Using a 1/2" drill bit (in a drill press if possible) SLOWLY drill the hole for the Safety valve, ensuring you stay level while you drill. Switch to your 3/8" Drill bit and SLOWLY drill for the Schrader valve. Hand thread both in, then use a wrench slowly snug them down, making sure not to strip the self "tapped" PVC.

Drill a 3/8" hole directly in the middle of top of the 1" Plug & set aside.  Using your hacksaw to cut a 3" length of 2" PVC Pipe, you may need to use a utility knife to clean the edges of any stray PVC. Primer/Glue the 2" x 1" Bushing (non threaded) into the bottom of the 2" Tee, then the 3"x2" PVC pipe into one side of the 2" Tee, the 1" plug into the 2" x 1" (non threaded) bushing, and finally the 2" x 1" (threaded) into the remaining side on the Tee.

Hand thread a 1/4" Male coupling into the 3/8" hole you drilled into the 1" plug. Using a wrench slowly snug it down, making sure not to strip the self "tapped" PVC plug. Teflon tape the remaining side and connect a 1/4" ball valve. Using the 1/4" female coupler, connect the 300 PSI gauge to the ball valve, teflon taping both male couplings.

Finally Primer/Glue the 2" pipe sticking out of the 2" Tee into the 3" x 2" bushing in the other air chamber compartment. Make sure to lay it out and check for valve positioning before you glue.

Note the time you completed the Air Chamber and set aside. Do not pressurize this chamber for 24hrs.

Barrel

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Make no mistake, this is the MOST DANGEROUS PART OF YOUR GUN (to others :-D). Take your time, and make sure that EVERYTHING seems 100% right, if something seems "off" scrap it and build another one. These parts are cheap, your friend's doctor bills are not. Make sure you read through (and understand) this entire section BEFORE you start.

The great thing about this build is that it incorporates a 1" interchangeable Barrel. Even though we will be building a T-Shirt launcher, one could easily build a barrel for Tennis Balls, Golf Balls, or of course Potatoes.

Using your hacksaw, cut a 15-20" length of 3" PVC Pipe, making sure to clean the edges. Primer & Glue the 3" PVC Pipe into the 3" side of the 2" x 3" pipe expander. After a few minutes, Primer & Glue the 2" x 1" (threaded) bushing into the 2" side of the 2" x 3" pipe expander. Once give it a few minutes to cure.

Note the time you completed the Air Chamber and set aside. Do not launch anything out of this barrel for 24hrs.

*Note:  You can also build other barrels, as this system allows for interchangeable barrels.  You can have one for launching Tennis balls, Golf Balls, or the old favorite Potatoes.  I was interested in only launching T-Shirts, so I stuck with the 3" barrel, but don't let that stop you! 

Quick Release Trigger Mechanism

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We will need to make some simple modifications to the water sprinkler valve. Start by removing the black solenoid, it just twists off. Note the flow direction and lid placement, then unscrew all screws on the top of the sprinkler valve. Underneath there is a large spring, so as you remove that last screw, keep some pressure on the lid so you can slowly remove it. You need that spring, don't lose it.

Locate and mark the direct center of the lid. Make a 3/8" hole on this mark. I found securing the lid to a scrap board by re-using two of the lid screws held it in place well enough for me to drill slowly. It is IMPERATIVE that you remove any shavings and clean the lid well. From the top, hand thread a 1/4" brass coupler into the lid. Using a wrench slowly snug it down, making sure not to strip the self "tapped" lid.

Using some Epoxy putty, seal any holes that the solenoid originally covered. (Although this is not a high pressure point, it is important that you have a reliable seal, so epoxy of some sort should be used.) Once you are comfortable that the epoxy will not seep into the holes, Re-attach the lid making sure spring is still in place, and flow arrows match.

If you are not completely comfortable with this process, check youtube for "modifying sprinkler valve" and you will find plenty of videos walking you through the process. 

Wrap the blow-gun with teflon tape and connect to 1/4" Ball valve. Also wrap remaining side of the 1/4" brass coupling with teflon tape, and connect blow-gun assembly to valve assembly.

Final Assembly

Finally, connect the Air Chamber and valve assemblies using a 1" PVC close nipple. Then connect the Barrel to the valve assembly using the remaining 1" PVC close nipple. You T-Shirt cannon is complete! Before you go crazy with it you should pressure test it. (has it been 24 hrs yet")

Make sure BOTH BALL VALVES ARE CLOSED. VERIFY. The ball valves are closed if they are in a perpendicular position (all valves shown in pics above are in closed position) Now verify that the Safety valve is operating correctly by checking that the spring opens and closes correctly. (give the ring a couple tugs) Connect a 300 PSI gauge (optional) to the ball valve on the bottom of the Tee.

In order to test the system for leaks, we will pressurize the chamber and monitor it to see if it retains pressure. To do this, open the ball valve connecting the 300 PSI gauge so we can monitor the pressure in the chamber. Using a bike pump connected to Schrader valve, put about 40 PSI in there. Let it sit for about 10 minutes. Come back and verify that there is still 40 PSI in there. If not, re-pressurize your chamber and then use soapy water to find your leak. Depending on the location of the leak you can either use pvc glue, epoxy, or teflon tape to fix.

If everything seems ok, take it back up to 40 lbs and open the ball valve to the trigger. I will let you figure out what to do now!

Although the cannon has a safety at 115 PSI, you should never charge your gun over 85 PSI, trust me 85 is enough!

Taking it to the next level

Next Level Parts Needed

• (1x) Portable Compressed CO2 Regulator (Get it on Amazon)
• (1x) 20oz "Pure Energy" CO2 tank, (Optional) (I suggest using the "Buy Both" button on Amazon to save some $$)
• (1x) T10 Torx bit (reports of different screws, suggest Torx driver set)

Instead of pressurizing the air-chamber with a bike pump, I mean come on that gets old after awhile, wouldn't it be better to have some mult-shot action provided by a nice 20oz CO2 cartridge! There are some simple mods we need to do to the "Portable CO2 Regulator" before we can connect it to our cannon.

Start by disassembling the case surrounding the regulator. I had to use a torx #10 driver to remove my case. Once inside, using two wrenches (one to hold the fitting on the regulator and one on quick-connect) remove the quick-connect. After cleaning the threats and adding some teflon tape connect the 1/4" female brass coupler.

Once you are satisfied, put the case back together, and attach the brass coupler to the ball valve on the tee.

BEFORE YOU CONNECT YOUR CO2 Canister, READ THE INSTRUCTIONS on how to dial in the desired PSI. Go back and read it again.

After a simple paint job your t-shirt cannon is complete! Have fun!