PVC Air Cannon




About a month ago, my friends and I had too much time on our hands. And, as most devious college students are wont to do, we decided to make something that went BOOM! And so, we came up with plans for what we now call the Thompson's Nightmare Class Air Cannon. Our version has been known to launch water balloons over 250 feet!

This also happens to be my first instructable. I hope you enjoy!

Here's how to make one:

Step 1: The Parts

For the cannon, you will need a bike, an air pump, and PVC (hence the PVC air cannon). Here's a full list of parts:

6 feet of 3" diameter PVC pipe
1 1 1/4" PVC ball valve.
1 3" PVC end cap
2 3-2" PVC reducers
2 2 - 1 1/4 PVC threaded reducers (the 1 1/4" end needs to be threaded to fit the ball valve)
1 Husky 12V inflater with light

All the above can be bought at Home Depot for about $40.

You'll also need an old bike tire.

Tools for this project:

PVC glue
electric drill
boxcutter or X-Acto knife
super glue

Step 2: Cut the PVC

Simple enough. You will need one length of 3" diameter about 4 feet long for the barrel, and one about 1.5 feet long for the air tank. File the edges down once you're done to make gluing easier.

Step 3: Modify the End Cap

This is the trickiest step in the whole build. First, you need to cut out the valve part of the old bike tire. Try to make it square, but its no big deal if its not. Make sure to leave a lot of the surrounding rubber though.

Next, drill a hole about the size of the stem of the valve into the center of the end cap. A 5/16" bit worked well for me, but check for yourself before you drill. The important thing is that there's a really snug fit when the stem goes through the end cap. Remember, there's going to be 100+ psi of pressure there.

Once you have a nice snug hole for the valve to go into, put some super glue on the rubber surrounding the valve, and stick the valve into the end cap. Smooth out the rubber so there is a tight and smooth seal against the PVC.

Step 4: Prime It and Glue It

Another simple step. First, use some purple primer on any surface that you're going to glue. This cleans it up and readies it to be glued.

Once the primer has dried, glue one 2-1 1/4" into one 3-2" reducer. Then do the same to the other reducers. Glue one reducer assembly to the 4 foot barrel, and the other to the 1.5 foot air tank. Finally, glue the end cap to the other end of the air tank.

Watch out for the PVC glue. It stinks to high hell and can really mess you up. And don't smoke while gluing either.

Step 5: Put It Together

Screw the barrel and the air tank into the ball valve. Congratulations! You've made your own air cannon!

Step 6: Load It Up and Launch It!

The air compressor can charge the cannon up to 150 psi (which is the most you should charge it to anyways. Ball valves are rated for 150 psi). Simply plug the charger into your car, set it to the target pressure, attach the pump to the valve on the air cannon, and let it charge.

Once you've got it fully charged, load the cannon up with whatever you please. I think water balloons are a lot of fun; just make sure you put a soda can or something in the bottom so the air pressure doesn't pop the balloons. Aim and fire! You can literally launch anything you can fit in the barrel.

You can slap a really cool paint job on it, too. We used a plastic primer and some simple spray paints to do a camo design. Then I did some air brush work to christen it Thompson's Nightmare after our favorite attorney from Florida.

Just keep in mind one thing: anything you launch out of the cannon is coming out at 90+ mph. Don't be stupid. Have fun!



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    135 Discussions


    10 years ago on Introduction

    hey im kindof smaller than you (13 years old) and I wanted to make one. Im pretty smart so I can follow instructions...but do you think that if i made the length of the barrel shorter, that is would decrease the fire distance?

    10 replies

    Reply 2 years ago

    the us air force did a study with sevral barel lengths and propellants in a combustion patato cannon, the farrther from the end of the barrel the better range and muzzel velocity. So biger=beter


    Reply 9 years ago on Introduction

    no it would actually increase it. I;m 14 (but not small) and i know a lot about stuff.
    making the length smaller would allow for more air compression. correct me if i'm wrong, but if you use the same amount of air (without putting too much in there) the air will decompress at a much higher rate. This will cause either a mass explosion or a really good cannon.

    also for extra small ones, you could try using a valve and foot pump Instead of a compresser. (jump on the pump like theres no tomorrow because you;re small and need a lot of air in there) good luck _

    An Villainschetleft

    Reply 9 years ago on Introduction

    actually, with chombustion it fires longer with a longer barrel because the expanding gases have a longer time frame to act on the projectile. (Not sure about pneumatic/hydraulic.)

    it would act the same because these gases are expanding too, but in reference to length; shorter length wont make higher pressure, what they said length and equalizing pressure is correct, so a longer barrel with a smaller bore means more power

    To a point, eventually you will reach a point where the pressure of the tank and barrel is equivalent to the pressure of the air outside the tank and barrel. At this point the projectile (if a gas-seal is formed) will either stop dead or fluctuate in the barrel due to inertia. However this would require either an extremely small air-tank or an exceptionally long barrel.


    Reply 9 years ago on Introduction

    sorry, but your science is a bit off. the projectile will accelerate only as long as it is being acted on by the air in the barrel.  wkojako is somewhat correct: the ideal situation is one where the pressure equalizes at the same moment the projectile leaves the barrel. you would have to calculate exactly what size that would be based on the intended pressure in the tank and the size of that tank. and since this is not a perfect system (there will be leaks and friction) making the barrel a little smaller than the theoretical perfect size would be ideal


    2 years ago

    How far would this shot a tennis ball? I'm hoping to dislodge an object out of a tree.


    2 years ago

    Can a bike pump do?


    3 years ago

    i am 16 and i have built 2 to 3 cannons i want to decrease the diameter of barrel to 1.5 inch and keep the air chamber same and operate it at 75 psi using bicycle pump keeping the dimensions same comments on working please


    3 years ago

    Looking to build a air cannon primarily for a dispkay. Interested in the "boom" or sound. How loud do these cannons sound? And is there a way to modify them to make them louder?


    4 years ago

    Use abs instead of pvc when abs fails it just splits open and doesn't shrapnel like pvc

    DON'T EVER use anything like this to shoot at people. As it says on the last page, stuff comes out at 90 mph. That means it will injure or kill people. This might easily be classified as a deadly weapon.