This Instructable will teach you how to build an air cannon that can be triggered with a switch. This cannon is capable of shooting projectiles, such as oranges, or parts of a potato very far distances, and at very high velocities. At 60 PSI, this device is able to shoot a small orange at ~77 mph with a range of ~500 feet.
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
Here is a list of the materials you will need:
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
Prime both the outside of the 3' length 2" diameter pipe, and the inside of the 2" cap. Wait about 20 seconds for the primer to dry, then apply PVC cement around the place where you just primed. Then put the two pieces together.
Note: Make sure not to get the PVC cement on your hands! (wear gloves if necessary)
Step 3: Start the Joints to the Valve
Prime the outside of the 2" x 1" bushing, and the inside of the 2" coupling. After it dries, add cement to where you just primed, and connect the two. Repeat this for the other bushing, and 2" coupling.
Step 4: Attach the 3/4 Coupling to the Bushing
Prime the inside of the bushing on the piece from last step, and the outside of the 3/4" coupling. When it dries, put the 2 parts together. Repeat this for the other bushing, and 3/4" coupling.
Step 5: Attaching the Elbows
Prime the inside of one end of the elbow piece, and the outside of the 3/4" coupling. When it dries, apply cement, and attach the elbow piece to the 3/4" coupling. Repeat for the other piece, and 3/4" coupling.
Step 6: Attach the 1" Connector
Prime the inside of the elbow piece, and the outside of the 1" piece of PVC. When the primer dries, apply PVC cement to where the primer is, and attach the two pieces together. Repeat on the other elbow piece, and 1" PVC
Step 7: Attaching the Threaded Adapter
Prime the inside of the threaded adapter, and the outside of the 1" PVC pipe. When the primer dries, apply PVC cement, and connect the two. Repeat for the other 1" PVC pipe, and adapter. What you have now is the finished connector that will connect the air tank, and barrel to the sprinkler valve.
Step 8: Connect Both Joints to the Sprinkler Valve
Screw in the joints into the sprinkler valve (you may want to add some plumbers tape onto the adapters before doing this to ensure air can't leak out here) so that both joints are screwed in tightly, and are parallel to each other.
Step 9: Adding in the Bike Pump Connector
Cut the bike pump connector off from the pipe, leaving about a 1/2 inch left around the connector. Then, drill a 1/4" hole to start off with approximately 1 1/2" from the end of the air tank (opposite from where the end cap was glued on). Then, take the bike pump connector, and see if it fits through. If it doesn't, take your drill, and drill in the same spot, but moving it in a circular motion, expanding the hole a bit. Keep testing to see if the pump connector fits through snugly . If it does, then stop drilling, otherwise keep expanding the hole. When it fits, then apply epoxy to the rubber surrounding the connector. Push the stem of the bike connector into the hole, and push all rubber surrounding the stem so that it touches the PVC. When the epoxy dries, apply epoxy to the outside part of the PVC where the bike pump connector stem comes out of.
Step 10: Connect One Joint to the Barrel
Prime the inside of the 2" coupling, and the outside of the 4' length, 2" diameter PVC pipe. When it dries, apply PVC cement to the parts you primed, and connect the coupling, and pipe.
Step 11: Connecting the Other Joint to the Air Tank
Prime the inside of the other 2" coupling, and the outside of the 2" PVC air tank. When the primer dries, apply PVC cement to the place where the primer is (you might want to have a decent amount this time, considering this is one of the biggest parts under pressure), and connect the two parts.
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.