What did I make?
Well, I made a HPPL(High Preesure Projectile Launcher) all that is required to operate it is a bike pump a steady hand and some safety instructions. Pump up the barrel to about 20-40 psi, aim, and fire. With easy-to-obtain materials and a little hard work you to can fire anything that can fit in the barrel.

How did I make it?
I started off by drawing up a blue print on several sheets of graph paper and got to work. I consulted with my neighbor about the plausibleness of the build, since i know close to nothing the mathamatics required to build it. $50 later I had my parts and glues and was ready to build, when I discoverd the contest and took many photos in the process of building it.

Where did I make it?
At my house and my neighbor's house(He's a mechanic so he has every tool known to man)

What did I learn?
I learned that pressurizing and containing air is very hard from my viewpiont. The biggest challenge was finding a way to release all air at once. Some surprizes was the outstanding amount of teaking that had to be done in order to accomplish a working machine. If i had to do it again I would glue to gether all the parts with JB weld the first time and let it dry.

Step 1: Obtain the Materials

The supplies you will need are as follows.
1) 4in PVC end cap
2) 1 ft of 4in PVC pipe
3) 4'' to 2'' PVC connector
4) 2'' to 1'' PVC connector
5) 6'' of 1'' PVC pipe
6) 1 ft of 1'' PVC pipe
7) 2 1'' screw in connectors
8) 1'' Brass case steel ball quarter turn valve
9) Screw in Presta Valve(bike valve)
10) Screw in psi gauge
11) 6'' of 3/4'' PVC pipe
12) A tube of E6000
13) JB weld two part epoxy
14) PVC wet glue

Step 2: Cap to Valve

Take a 1'' wood drill bit and cut a 1'' hole in the center of the 4'' end cap.
To insert the 3/4'' PVC pipe into the hole you may need to dremmel the primeter of the hole to fit.
E6000 the pipe into place flush on the inside, sticking out on the outside.

Step 3: PSI Gauge to 4 In. Pipe

Many gauges have different screw widths to start small and slowly grow until you hit a sweet spot and E6000 into place.

Step 4: PVC to Ball Valve

Coat the threads of the PVC connectors with E6000 and screw into ball valve.

Step 5: 1'' to 1''-2'' to 2''-4''

Apply PVC glue generously to one end of the 1'' pipe and glue to the 1''- 2'' connector.
When the glue sets glue the that connector to the 2''- 4'' connector.

Step 6: Seal the Pipe

Saw off the extra pipe that is glued to the end cap as close to the glue as you can.
Now glue the end cap piece to the 4in pipe.
And glue the 4''-2'' assembly to the other end of the 4in pipe.

Step 7: Attach the Valve

Once the valve assembly has dried glue it the the 6 inches of 1'' so that the valve swings open toward the 4in pipe.

Step 8: Give It a Barrel

For my barrel I used a foot of 1 inch ,but the longer the more accurate, so experiment.

Step 9: Valve Stem Assembly

I have layed out the pieces in which you must glue.
E6000 the brass valve stem into the larger silver adapter.
DO NOT glue the cap on the valve stem!
Glue the whole assembly into the 3/4'' PVC pipe that is glued into the 4in end cap with JB weld.

Step 10: Finish It Up

Now pump it up and check for leaks.
If you find leaks cover completely with JB weld.
Trust me, do not use tape to fix leaks, use and let dry JB weld.
When you seal up the leaks pump up to 20-40 psi , load the barrel, and pull the valve!