How to Make a Coaxial Air Cannon

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Introduction: How to Make a Coaxial Air Cannon

This video shows how I make a compact 2" bore air cannon with a coaxial piston valve. To understand how these valves work examine the third animation in the following link:
http://www.spudfiles.com/forums/piston-valves-explained-visually-t8157.html
I also go into more detail of how these cannons function in a video I made many years ago, showing how to build a smaller version using these same principles:
http://youtu.be/9oARDyn4WwE

Warning: It is specifically against manufacturer recommendations to use PVC to contain pressurized air. This video is solely for education and entertainment purposes.

The parts used in this cannon are as follows:
(1) 3' length of 3" diameter pressure rated PVC pipe
(1) 3'2" length of 2" diameter pressure rated PVC pipe
(1) 1/2" PVC ball valve
(1) 1/2" x 2" long threaded PVC pipe nipple
(1) 1 1/2" to 1/2" threaded PVC reducer
(1) 3" to 1 1/2" PVC reducer
(1) 3" PVC coupling
(1) 3" female threaded adapter
(1) 3" male threaded adapter
(1) 3" to 2" PVC reducer
(4) 1" long self tapping screws
(1) brass air compressor tank valve
(2) 3" galvanized steel gas vent tee caps
(1) 3" rubber washer or sheet rubber
(1) 3" tank to bowl rubber gasket

Other supplies and tools needed:
PVC Primer & Cement
Epoxy
Super Glue
TFE Pipe Thread Paste
Coarse and fine Sandpaper
Bench Grinder or Metal Files
Drill & Bits
Bicycle Pump or Air Compressor

Thanks for watching!

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31 Comments

Hi. If the cannon is used for a fishing bait caster (say 500 gram bait) can you take a guess on what distance one can reach at 100 psi?

i made one with 1-1/2" Barrel, piston is 3" diameter x 1" thick hockey puck with aluminum tape wrap. End seal is a toilet flapper valve bolted to puck with 1/4" thru bolt and fender washers. Vent pipe is 3/4". Works great. Using hockey puck greatly simplifies the piston construction. The flapper valve provides a quick seal and release.

is it possible to use one of those electric instant air valves for this?

Danger: See link: This is not spam, but a warning. PVC will fail suddenly after a while. This was band member that hurt badly by a T-Shirt launcher explosion.

See the pictures and never use PVC to hold air, Please.

https://fundrazr.com/campaigns/1Zs3c
..

hey, i have some questions about this. I followed your design almost exactly everything except i had to use a coupling for the 3" female thread adapter because it required it to be attached which i thought would ad a small length to it so i made the barrel just a little longer to match the distance between the end of the barrel and the rear of the chamber in you design i don't know if maybe this is my flaw or that i used something else to make my piston. for the piston i used a 2" pvc end cap wrapped in duct tape to reach the desired diameter to fit in the 3" chamber then used the aluminum tape on the outside and then used a tire seal as a piece of sheet rubber to make the seal and when i pump um the cannon the seal presses against the barrel and holds air nicely and the piston seams to move freely when its not pressurized as in i can move the piston just by exhaling or inhaling into the rear of the cannon but when i pressurize it which i have tried with multiple different pressures from 30 all the way to 70 psi when i release pressure behind the piston all the air escapes out the back and none out the barrel I've thought maybe the piston is trapping all of the air behind it but this isn't the case because when i unscrew the muzzle and try to pressurize it, there is air coming from the chamber like i said maybe this could be because of the distance between the barrel end and the rear of the chamber but i have no clue i thought i would ask for your insight on this I'm a really big fan and have made a lot of your works including the static electricity generator that one is definitely one of my favorites thanks for reading this long message please get back to me as soon as its best convenient

There are three things you can change that will allow your piston to release better. Your problem is that air is not being released quickly enough behind the piston to create a pressure differential strong enough to pull it from the barrel before all the air in front leaks around it. To fix this you can:

1. Make the piston a closer fit so air cannot leak around it as fast.

2. Increase the size or the speed that your release valve opens. This could mean replacing it with a fast acting valve like a sprinkler valve.

3. Decrease the volume of air behind the piston so that there is less that has to be released by the valve before it will be pulled from the barrel. This can be done by using a larger bumper for the piston or doubling it up so as to take up as much volume as possible, or by increasing the length of the piston or the depth of the barrel so there is less space behind it. If the piston is increased in size you may need to remake it out of lighter materials because its weight will negatively effect the speed at which it opens, and it already is probably quite heavy with all that tape.

i forgot also to add my piston is only about 2 inches long

Hey! Great ible. I was just wondering the ballpark for how much this costs from scratch

I paid somewhere around 45 for everything including the bike pump

Have you considered combining the cannon with a pump like the "...High Volume Manual Vacuum Pump?" Like a Super Soaker, then you would not need to attach/detach a bicycle pump and it would make it a little more transportable.