Introduction: Build a Paintball Mine

About: We spend our youth trying desperately to fit in, and then the rest of our adult life doing whatever we can to stand out in the crowd.
My friends and I enjoy playing paintball out in the Arizona desert on occasion. It’s great fun, but sometimes pelting someone with a couple hundred paintballs traveling at 300 feet per second just isn’t enough. Sometimes you just need something extra…. So I built the paintball mine that you will see in this instructable!

Step 1: Concept

This paintball mine is based (i.e. ripped-off) from a patent I found online. (US # 6,688,234 B2) Browsing patents online is a great way to come up with cool ideas for your own projects! The mine is a small canister that you bury in the ground, filled with liquid paint. A standard 12 gram CO2 cartridge is inserted upside down into the canister. A top with a plunger centered over the cartridge is screwed on. When someone steps on the plunger the cartridge is pierced, pressurizing the canister and expelling the paint. I feel the original patent has a simple, but serious design flaw. Look at Diagram #1 below.  When the CO2 is released it follows the path of least resistance, and blasts directly out of the holes, carrying some, but not all, of the paint with it. It also tends to create more of a thin “aerosol spray” with the paint. Diagram #2 shows my design, which adds tubes/nozzles in the holes with a small gap beneath them. When the CO2 is released, it cannot travel down to the tubes, so instead it pressurizes the canister, forcing almost all of the paint out before it can escape out through the tubes. This results in more of the paint being expelled in a thicker and more forceful stream. 

Step 2: Materials

(1)        3” ABS Cap
(1)        3” ABS Threaded Adpater
(1)        3” ABS Threaded Plug
(1)        ½” PVC Cap
(1)        ½” PVC Union
(1)        ½” schedule 40 PVC pipe (appx 6” long needed)
(1)        ¾” schedule 40 PVC pipe (appx 4” long needed)
(1)        5/32” x ½” Metal Screw
(1)        ¼” Pex tubing (appx. 20” long needed)
All of these items should be easily found at your local Home Improvement store. The Pex tubing can be found near the heating and cooling supplies, or near where they have the stuff you use to hook up a fridge to a waterline. The diameter of the screw isn’t really important, but the length is. I wouldn’t go too small with the screw though, you want it to hold up to some abuse.

Step 3: Tools

3/32 drill bit
3/8 drill bit
¾ drill bit
PVC Pipe cutters
Measurement Device
EMPTY 12gram CO2 cartridge
PVC Glue
ABS Cement
All Purpose Permanent Adhesive or Epoxy
Hacksaw & Miter box (Optional/Not shown)
Dremel with sanding wheel (Optional/Not shown)
Straight Edge (Optional/Not Shown)

Step 4: Base of Mine

Take the ABS Cap and locate the EXACT center of it. It is very important that you take the time to get this as close as possible. My method is to take a straight edge and strike a line through the middle of the cap. Rotate the cap about 45 degrees and repeat. Do this a few times and you will end up with a bunch of lines whose intersection is almost exactly the center of the cap. Drill a 3/32 hole through the center. Put the screw into the hole so that the tip of the screw penetrates the inside of the cap. Tighten the screw down, but be careful not to strip the cap. It’s also important to keep this screw as straight as possible.

Step 5: Cartridge Support

Cut a piece of  ¾” PVC to 2 ½” long. This will be our CO2 cartridge support. One end of this piece will have to be perfectly straight. If you are using the end off from a new pipe, it should be good. But in my case I was using an old leftover section. I grabbed my hacksaw and mitre box and made a nice straight cut on one end. You can use pvc cutters for this, but they generally tend not to make perfectly straight cuts. The pvc cutters will work fine for the other cuts we will be making. 
Next, drill three 3/8” holes at ½” from the good end of the PVC pipe. This is where the CO2 will escape from when the cartridge is pierced. It’s always helpful to drill pilot holes first.
Cover part of the inside of the ABS cap with PVC glue, circling the area around the screw. Put some glue on the “good end” of the PVC piece and center it DIRECTLY over the screw. It is critical this is located correctly. Once it looks good, drop the empty CO2 cartridge into the support and ensure it aligns correctly. It should fall so that the point of the screw rests in the hole of the cartridge. Adjust as necessary and set aside. The screw head underneath the cap may cause it to wobble, so I set the cap on top of a fat rubber band to keep it stable.

Step 6: Plunger

Cut a 4” piece of the ½” PVC. Cut 5/8” off from one end of the ½” union. Glue the 5/8” piece of the union on to the 4” piece of PVC, so that about ¼” of it sticks out past the end of the pipe. (in the photo I only have about 1/8” sticking out since I cut the union a little too small) This small piece is what cups the top of the CO2 cartridge.

Step 7: Mine Top

Drill a pilot hole in the exact center of the threaded plug.. Then drill a ¾” hole through the plug. Our plunger will be going through this hole, but unfortunately the ½” PVC has an outside diameter that’s a little bit more than ¾”  You will have to enlarge the hole just enough so that the plunger will slide through it freely, but not too loose that it wobbles. I used a dremel with a sanding wheel. You could also try a large rasp, or heavy grit sanding paper wrapped around a dowel. 

Step 8: Nozzles

We will next begin working on the paint nozzles that protrude from the top of the mine.
This area is open for a little experimentation. What works better, straight up or angled nozzles? Four nozzles or eight?   Larger nozzles? Try some different variations and let me know what you find! 
Remove the plunger and drill four 3/8” holes around the top of the threaded plug. (Pilot holes!) 
The ¼” Pex Tubing should fit snugly in these holes. Cut four 4½” long pieces of the tubing. Put a mark at 1¼” from one end of the tubes. Using the all purpose permanent adhesive or epoxy, glue the nozzles to the plug with 1 ¼” projecting out of the top. This should allow a small gap beneath the tubes when the plug is screwed onto the mine. Make sure you have plenty of glue around the tube on the inside of the plug. You don’t want these shooting out unexpectedly!!

Step 9: Complete the Mine Base

Using the ABS Cement glue the 3” ABS adapter into the 3” ABS cap. Coat both the cap and adapter uniformly. Then quickly twist and press the two pieces together. The adapter should fit all the way into the cap.

Step 10: Complete the Top of Mine.

Place the CO2 cartridge back inside of mine. Place plunger in cap and screw cap on. DO NOT over tighten!   Mark the plunger at 7/8” to 1” above top of cap. Cut the top of plunger off at the mark and then glue on the ½” cap.  

Step 11: Final Notes

You’re done! Let all the glue and cement set up for 24 hours and the mine is complete!
There are a couple options for the paint. I boiled down some paintballs and used that. It worked great, except boiling them down was a lot more work than I expected. I had to fish out all the gelatin shells that wouldn’t dissolve. You can also use watered down, non-toxic washable kids paint. Or, you could always go and purchase a gallon of paint -mine paint, but where’s the fun in that!?

Also, PLEASE use this with common sense and safety.  This is a fun thing to play with, but it can be dangerous if not used properly and while wearing the proper gear.  I'm not responsible if you act like an idiot and lose an eye, so BE CAREFUL!
Be sure to check out the video below. It was the first field test I did on my prototype two years ago. It actually worked a little better than I expected.