While making this Instructable, make sure to have plenty of ventilation, preferably working outside. Also, wear gloves if you are worried of getting PVC cement on your hands.
Air cannons are capable of shooting projectiles at very high velocities. THEY ARE NOT TOYS!!! Never fire an air cannon at any person, or living thing as this could possibly injure or kill someone. When firing, make sure you are in an open field, or a place where the projectile has absolutely no chance of hitting someone, or someone's property that isn't your own. If you are under 16, then make sure to have an adult nearby when firing. Make sure to use common sense when firing, and don't do bad things with it. I nor Instructables take any responsibility for anything you do with this cannon.
Step 1: Materials
PVC parts (make sure all PVC parts are PRESSURE RATED )
1. 1 - 4' length 2" diameter PVC pipe (~$4.16)
2. 1 - 3' length 2" diameter PVC pipe (~$3.12)
3. 2 - 2' length 1" diameter PVC pipe (~$2.16)
4. 2 - 2" x 1" PVC bushing (~$1.35 each)
5. 2 - 3/4" PVC coupling (~$0.20 each)
6. 2 - 1" PVC elbow (~$0.51 each)
7. 2 - 1" PVC threaded adapter (screws into sprinkler valve) (~$0.74 each)
8. 1 - 1" FNPT threaded in-line sprinkler valve 24 volt >100PSI rating (I used this one: http://www.lowes.com/pd_50552-74985-57101P_0__?productId=1186963&Ntt=orbit+inline) (~$11.53)
9. PVC cement can (such as Christy's Red Hot Blue Glue) (~$4.37)
10. PVC purple primer can (~$4.00)
11. 3 - 9 volt batteries (~$1.00 each, but usually can be found around your house)
12. A new or broken bike tube (all you will need is the bike pump input) (~$2.00)
Drill and 1/4 drill bit
Total cost, if you don't have any of these parts, and excluding tools, adds up to ~$40, but if you already have pvc primer, pvc cement, batteries, bike tube, and/or any other parts, then it should be a bit cheaper
Step 2: Beginning the Air Tank
Note: Make sure not to get the PVC cement on your hands! (wear gloves if necessary)
Step 3: Start the Joints to the Valve
Step 4: Attach the 3/4 Coupling to the Bushing
Step 5: Attaching the Elbows
Step 6: Attach the 1" Connector
Step 7: Attaching the Threaded Adapter
Step 8: Connect Both Joints to the Sprinkler Valve
Step 9: Adding in the Bike Pump Connector
Step 10: Connect One Joint to the Barrel
Step 11: Connecting the Other Joint to the Air Tank
Step 12: Fire at Will!
How to launch
1. Put your projectile into the barrel, and make sure it hits the bottom. The projectile has to fill the diameter of the barrel, or it won't launch. If it doesn't, add something that will act as wadding, such as newspaper.
2. Pump up the cannon to either 10-30 PSI for short distance shooting, 40-60 PSI for medium distance shooting, and 70-100 for long distance. Don't go above 100 PSI, as the valve probably can't take any higher value, and the smaller PVC parts might explode.
3. Aim your cannon in a safe direction, away from houses and people
4. Launch by attaching the 3 9v batteries to the sprinkler valve wires
5. Enjoy :)
The video below demonstrates the power of the cannon at only 50 PSI. The projectile is an orange, and it manages to hit with quite a punch!
In another video, I shot another orange at the slide, and it managed to leave a crack in the plastic. I haven't tested the cannon at 100 PSI yet, but I'm pretty sure it wouldn't be good news for the orange, or the slide.