Instructables
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:
 
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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
hacksaw
file
boxcutter or X-Acto knife
super glue
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LucDaRocka14 years ago
could this shoot snowballs? i wanna whoop my uncles butt in a snowball fight.
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.
kind of late.... i broke his arm.... oops.....

Better than the nuts!!!!

tmandpea5 years ago
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?
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 _

But it would decrease the trejectory a lot! Similar to any gun!

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.
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
how much did the air compresser cost?
Around $30 online.
It might affect the accuracy some, but it shouldn't affect the range.
the barrel needs the same volume as the volume of air pumped into the barrel for max velocoty
wsandel3 months ago

Masher is right - PVC gets brittle with age. If you do use it, trash it "one season."

Masher0077 months ago

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
..

ALEXBUF3 years ago
Actually cant find PVC pipes and part in the UK. all i seem to find is copper :S
http://www.pisces-aqua.co.uk/ i made one with parts from here
Those are low quality pipes, i need Swagelok Tube Adapters and i bought from http://www.gekko-inc.com/store/574-tube-fittings-and-tube-adapters
well i have had it up to 8 bar and it fires a golf ball cleanly through a watermelon and at least 500m. i found that a wide valve is better which you can't really get with Swagelok (i have looked when i was researching), the diameter of my ball valve is 4mm smaller than that of the barrel so small enough for golf balls not to fall through but big enough for a large volume of air to travel through. it is expensive though, at £25 now (£45 when i bought it) it is a bit of an investment.
Dawson.J2 years ago
Fold back the air tank. i'v found it is much more practical.
Also if you want to shoot anything cut a paper dixy cup to the size of the barrel
and use as a shell
timmy1234s6 years ago
I kind of hate the 3" part of the PVC pipe. I had to call and go to like 5 different places and still couldn't find it. Will a 2" or 2 and a half inch pipe work? I dont care about the limitivity of the things I can shoot? Will it still work? Help
Tycho7 (author)  timmy1234s6 years ago
You can't find 3" PVC? Strange. Home Depot usually has boat-loads of the stuff. Either way, yes, you can use 2" PVC. You just have to get rid of the 3-2" reducers and replace the 3" end cap with a 2" version.
could i use a 2inch ball valve? home depot dosent have 1 1/4 
Yeah, but they're 20 bucks.
Thanks about saying that i can still make the cannon. But here in California, I cant find it. Its not at Lowes,Aces,Home Depot. All they have is DWV pipe that is 12 dollars. It is 3". Where do you live, as in state? Curious.
in virginia it's perfectly easy to find the pipe, anyway try looking in the plumbing section.
with 2 1/2 inch you can shoot tennis balls like mine!
or soda cans......
I would like to suggest that all high pressure air cannon instructables should include a warning such as:

"These air weapons can shoot things fast enough to cause severe injuries. Never use them to shoot things at people."
how much did this cost?
without the compressor this is under 20 dollars im guessing ive made one a bit different and it was cheap u just gotta find an old tire maybe a neighbor has a popped tire laying around or maybe u cud pop ur neighbors tire and steal it and u can use a bike pump sure its annoying but it works and is so worth it when u see the look in ur friends eyes haha
it is so awsome!
that isnt an amount
hammer395 years ago
No glue needed. When you pull a tire valve through the hole it seals because of its shape. Look at a car tire, You can see how it seals.
Its better to be safe than sorry though. That thing somehow slips (not likely) then there is no way to get that thing out without destroying your gun.
kef44444 years ago
could anyone tell my where the hell getting this damned pvc pipes from? i don`t find any internet site that sells em ... thx
H20 kef44444 years ago
maybe home depot?
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