pnuematic pocket football cannon

This instructable is an air cannon that fires nerf pocket footballs at 145psi up to 450 yards. For is simplicity i think this is one of the best high powered air cannons on instuctables. If your wondering why i didn't usea sprinkler valve its because it doesnt release the volume of air a ball valve does and i didn't feel like spending $60 on a 2 inch sprinkler valve. All the pipe i used was pressure rated to 250 psi and up. The valve being the acception it was rated to 165 psi. I am making a pnuematic ram to turn the ball valve very quickly.

Step 1 Collect what you need

To start buy the following as seen in the image below.

Comments

[ballistic builder]

I have built one of these a while back, it is awesome

do you mind if I use the concept for an instructable to make a nerf gun the same way? (i will link it to this instructable)

[dorro]

what type of tire vale did you use and where did you get it from? also what sealant did you use on the valve to keep it air tight?

[Audio Alchemy]

I used a tank valve. It is supposed to go on a portable air tank. Drill a 3/8 hole where you want to and wrap the threads with teflon tape. I got mine at the auto parts store but major DIY home improvement stores should have them in the pneumatic tool section.

[Audio Alchemy]

I have built this cannon.  The only thing different is that I used a brass ball valve with a large handle that lets me "throw" the valve open very quickly.  I also have made interchangeable barrels.  For golf balls I used 1.5 inch SDR 21 Sch. 40 PVC.  For foam "mini footballs"  I used 3 inch Sch. 40 PVC.  I also have a 2 inch barrel for the "nerf" pocket football but I have never used it for fear of losing the only one I have.  This cannon is VERY powerful!!!  At only 100 psi I can puncture my METAL wheel barrel with a golf ball  from about 30 or 35 feet.  The only cons (which are very insignificant) is that the darn thing is rather heavy and it takes a while to pressurize up. 

[hackmattr]

Bell reducers are not pressure rated so I would not use them in building an air cannon.

[frankinator]

there are pressure rated bell reducers, however i was naive and younger when i built this gun and didn't know the dangers of using no pressure rated fittings. the reason people suggest not using them is because of their reduced socket depth(area where pipe can solvent weld to fitting) not because of how thick they are, if you traffic spudfiles a test was done a while back that proved that bell reducers could take as much shock and pressure as "pressure rated" fittings of the same size

i will be making an instructable on a medium size piston gun next, it will be in 2" so people will be less likely to get non pressure rated "pipe" where the real danger lies

[polabearboi]

can you use a bike pump?? if not what should i use? please help

[The Porsche Fan]

a compressor works fine if you have one, bikepumps are pretty slow

[frankinator]

i have a 60 gallon compressor i am making a instructable of a piston driven one next so stay tuned

[polabearboi]

would it be a bad idea to drill a hole in the air reservoir and stick a pressure gauge in it?? really sweet gun btw. roughly how much for all the materials??

[The Porsche Fan]

it would probably compromise the pressure rating (blow up?) you could make a metal valve extension, but most compressors, or bike pumps already have a gauge on them

[i wanna do that]

wow really good cannon, but how much and where did u get such a high pressured rating pvc piping from?

[The Porsche Fan]

you could try home depot

[frankinator]

sorry I haven't been on Instructables in a while I got it from a local place called Wilson's plumbing supply I have moved on since I made this cannon my new ones are much more powerful and advanced

[ballistic builder]

awsome, works great

[polabearboi]

any other things u recommend firing?

[polabearboi]

hey! i finally got all the materials (and consent form my parents) and just built it last night evry body was thinking like 2 ft. and it wasnt gonna work but we were all amazed at how far it went it is an awesome gun!!

[wunmanband]

what powers it?

[illdoyourdrugs]

Pnuematic Equals AIR

[polabearboi]

where should I look to find all these materials????? how much will it all cost? please help

[chibiwind]

On step 1 it says 3 inch end cap with tire valve do u have to put the tire valve in it or can you buy it like that...?

[frankinator]

make sure to ask for valve stems at your local auto shop or hardware store

[frankinator]

you have to drill a 1/2 inch hole and pull it through with a pair of pliers

[joedynamite]

what kind of compressor or pump do u use to get that pressure!!! cause i am looking for one and i dont know where to go and where to look.

[frankinator]

i used a pump i scavenged from an old refridgerator it can goe up tp 350psi i modded it if you want info about stuff like that just go to spudfiles

[Derin]

u need one rated for 10 bars

[polabearboi]

did u get 450 yds w/ or w/o the mods?

[joedynamite]

idk what tat means but i just had my b day and my dad got me all the stuff i need he got me a compressor with a 5 gallon tank at the bottom i guess that will work but i could die because theirs no gage on the compressor or the cannon. so i kindof have to go wit the gut fellin

[frankinator]

i've calculated the volumes of the barrel and the chamber and it is 452.16:150.72 a perfect 3:1 ratio

[PerfectlySquare]

Using 3.1415 (four places seems more than enough) as the value of Pi: A 4' L x 3" D cylinder has a volume of 1357.1258, and a 4' L x 2" D has a volume of 603.168, making your ratio 2.25:1, and not 3:1. :) I am going to the Depot today for the parts,so I will let you know how mine turns out. I'm going to build mine from ABS so it can handle much higher pressures safely! I'm already fantasizing about getting it up over 200 psi...

[frankinator]

i've also counted the 180 degree turn and the 18 inches of 2 inch pvc behind the ball valve and the 6 inches in front of the 180 degree turn if you count those in it is 452.16 inches cubed to 150.72 inches cubed and it comes out at a 3:1 ratio

[PerfectlySquare]

Ah...well, you didn't say that! :P

Just picked up all my parts and was dry fitting it all, when I tried out the ball valve and it would barely turn. I tried greasing it, but it made things worse, so now I get to make a trip to the Depot tomorrow and get a better ball valve. I also switched to Schedule 40 PVC since I was told by the guy at the plumbing wholesaler that it's the most durable stuff thats readily available.

Got a question for you though...I got a Schrader valve for the chamber, but it's shaped like this. I dont think it will fit right given that the thickness of the wall of the pipe is bigger than the gap between the round knub on the end and the tiny lip that seals it .

Do you have any tips for getting a safe connection to the chamber from this type of valve, or is there another type of Schrader you recommend? I went to Home Depot, the auto parts store, a bike shop, and the tire store. The auto parts store had bits and pieces, but I wasn't sure which I'd need so I tried to find something already put together. The bike guy gave me an old tube with a valve and the tire guy gave me what you see in the picture. I could go either way, I just want to make sure I do it safely.

Thanks in advance for your help!

[mking2012]

You can duct tape a thin PVC pipe as a firing lever. I tried it on a launcher that I built and it made a huge difference.

[frankinator]

use the ones you got from the tire guy they are the same type i used just drill a half inch hole in the end cap and pull it through with a pair of plyers the small ring above the bottom will create an air tight seal make sure to use the primer befor you glue your pvc and it will seal correctly

[PerfectlySquare]

Do you ever have a problem with the valve falling inside the chamber if it's pressed on from outside? That was my main concern, but since it's what I got and FREE, it's going to be the valve. I made one goof while welding the pieces together...I moved the parts out of "mockup" positioning due to workspace limitations, and as a result ended up switching the 6" and 18" pieces around. DOH! Welds are permanent! :P I just trimmed the 18" section a few inches so that when I'm finished the two sides (chamber and barrel) will be equal in overall length. I'm sure it tweaks my power a bit having a longer section between the chamber and the barrel, but since there's really nothing I can do, I'll just have to see how it comes out in the end. At least it will have some symmetry, which will look cool. I also ended up going with a 1" ball valve instead of a 2", since none of the 2" valves I found turned fast enough to release the pressure efficiently. I used 2 (2" to 1") adapters with two 1" threaded nipples to connect the valve. I am thinking since it's going to be smaller this will ramp up the pressure a little bit, and hopefully will help compensate from the screwup I made, but we'll see. At least it turns quickly, and without hurting my wrist! I should be fully complete this Sat, so I will try and get some pics/stats up after I get it out in the field. Thanks for the tips, I can't wait to hear what you think!

[frankinator]

yeah thats the reason i'm switching to a copper ball valve their much easier to turn than pvc i sprayed some wd40 on my valve before i installed it it helped it turn for a while i'm making a new cannon my uncles a plumber and he can get me a 6 inch spring loaded butterfly valve and i'm going to be using galvnized for the chamber it's going to launch soft balls

[blugyblug]

Nice gun!! Execpt that chamber is waaay to big. If your chamber is too big it might actually make it less powerful. The chamber should be about 2 times the volume of your barrel

[frankinator]

I know its to big for this barrel but it was the only scrap piece of pvc I had laying around at the time I have replaced the valve and the barrel since then and now I use a copper ball valve with a pneumatic ram mod and a 15' long by 1" barrel I shot it through my chrono and got about 950 fps at 100psi and my new barrels are all about 2/1.

[frankinator]

I've replaced the pvc ball valve with a copper one I'm working on a pneumatic ram to turn the valve but it's not to hard to turn so I might use a spring I will be loading up pictures of it with the new valve shortly.

[ry25920]

You need to lower the PSI or your going to kill yourself. sch 40 PVC will rupture at 170psi and your pushing your luck.