End-Around Pneumatic Cannon

While not particularly new or creative, here are my plans for a simple pneumatic (compressed-air powered) potato cannon. It can also be used for other projectiles, as long as they fit down one of the interchangeable barrels. It uses an electrically operated valve, originally made for in-ground irrigation systems.

This project is also documented on my website at: http://www.mbeckler.org/pneumatic_cannon/

Step 1: Safety Warning!

Safety Warning: Please be careful with this project. From what I've heard, PVC is not meant for holding compressed gasses. Gasses compress much easier than liquids, so be careful. The sprinkler valve used is designed for cold water, so be careful. The pressure gauge is designed for cold water applications, so be careful. Almost nothing in this project is used in its intended purpose, so please be extra careful. If you explode one of your PVC pipes, you will have essentially detonated a pipe bomb, and you are going to be in a world of hurt. You might want to take an old pair of jeans, cut off one leg, and wrap it around your pressure chamber. You can also use an old towel, or some metal screening. It probably wont help in the event of a pipe rupture, as one user has suggested. He also reminds us that some PVC is not actual PVC through the entire wall of the pipe. He says that 'cellular core' pipe, which is not rated for pressure, has a lightweight foam core, surrounded by thin layers of actual PVC. Please double check your pipe before purchasing, to ensure that you are not purchasing cellular foam core pipe. Another user has written that fiberglass mesh tape, used in construction for drywall joining, might be a stronger pressure chamber coating. Another user suggested taking coupling, sanding off the inner stops, and gluing them to the outside of your pressure chamber.

If you only remember one thing from all my safety warnings, remember this: PVC shrapnel will not show up on an X-Ray. The doctors will have an extremely hard time picking all the plastic shards out of your body if something goes wrong. You have been warned.

organicengines adds a helpful reminder to keep your PVC out of direct sunlight, because the light will degrade the plastic and make it brittle. Be careful!

Yes, this could be a dangerous project. I'm not a lawyer, but I'd like to say that I'm absolving myself of all responsibility for your actions. If you decided to build one of these cannons, by all means have fun, but please be safe. I'm not responsible for anything except for fun. If any of the Instructables administrators or moderators feel this project is too dangerous for this website, I will gladly remove it as soon as possible.

Another safety point: This is a cannon, which is a type of gun. Guns are meant to be dangerous, they would be pointless if they weren't. If you have no experience handling guns, please be very careful with this project, and do yourself a favor and take a firearms safety course. It will be a good experience even if you never shoot a gun again. If you have experience with guns, please be careful regardless. When I went through hunter's safety, they taught us three important rules of firearms safety:
1. Treat every gun as if it is loaded, so always point it in a safe direction. This means not at you, your dog, or anybody standing around. Point it up in the air, or down at the ground.
2. Always keep your finger off the trigger (valve switch) until ready to fire. Enough said.
3. Know your target and what's beyond. Plywood, fences, and garage walls are not strong enough to stop some of the things you can shoot with this cannon. I've put clean holes through both walls of an empty 55 gallon steel drum, so know what's behind your target. Try to not shoot this cannon in residential areas, or use really low pressures and soft projectiles. Soft projectiles include rolled-up, wet socks (more on this later), water, and loose snow.

That being said, this cannon can provide hours of entertainment, as well as a bit of education, in projectile physics and the ideal gas law.

Comments

[cnc routers]

I do find the pneumatic vale
http://www.air-matics.com/Pneumatic_valve/

[blackcat2]

Very similar to my ible but mine is a sniper instead of a cannon. It looks great and well attached.

Well done! :D

[freeza36]

I would love to see an ible of yours.

[TurboFusion]

What would happen if instead of a PVC pipe for a air tank, you used a copper pipe? I suppose the increased strength of the tank would lower the risk of rupturing and allow you to put more pressure into it.

[matthewbeckler]

I suppose you could use higher pressure and have less chance of a rupture. Also pieces of copper embedded in your body will show up on the x-ray so the doctors can pull out all the pieces, if the worst comes to worst. Honestly I think the pressure limitation comes from the valve primarily, so if you switched to a ball valve or other value instead of the electric diaphragm value, you could use higher pressures with the same PVC. Perhaps the best option would be an all-metal design with a piston valve (info here http://www.spudfiles.com/spud_wiki/index.php?title=Piston_valve) ?

[Football viking boy]

url for your website doesn't work

[matthewbeckler]

Thanks for the heads-up, I just fixed it!

[epierce]

Have you ever considered building a "P" trap tipe loop to contain the water before it is fired?

[matthewbeckler]

Huh, that's a good idea, I might have to try that sometime. Sort of like a mini reservoir for the water. I wonder if you could use something larger too...good idea!

[de0509]

hello bro. This is one idea i did for kinda safe projectiles, didnt document it anywhere but the idea is simple. I mashed newspaper and inserted into PVC pipes, then compress to squeeze the water out. make them real dry and then remove from mould and dry under the sun or other means for drying. Its ready now but i prefer to coat them with a clear cellophane tape for more durability. Can be substituted with foam things, but the density of paper makes the hardness and inertia feel just right. i dont know why, but it feels just right. And its cheap

[kayu]

how can i make littel one of it anyone no ?

[knuckel]

mine is like yours but HUGE

[kayu]

mine has an oxigen tank lol :)

[urtlesquirt]

never knew guns can kurt you.

[Dashadower]

Is the ideal gas law Pv=nRt?

[matthewbeckler]

You are correct!

[TDWay]

I could not help but notice the snow, just another word of caution, cold temperatures drastically slows down the curing time and the PVC Cement should never be applied or used below 32 degrees, always read the labels for working temperatures. I'm some what surprised that some of the last joints haven't failed.

[al_packer]

Wrapping the PVC with a couple of layers of 3M Filament tape (the stuff used for packaging) will reduce the danger of shrapnel

[Pizzapie500]

What if your solenoid runs on AC?

[jj.inc]

It should still work, just fine, I can imagine how it could anyway. Hook it to a 9v battery and see what it does. (It can't hurt it)

[Pizzapie500]

Dang it! The solenoid blew up! JK! Yeah it works, it makes that clicky noise.

[jj.inc]

Good, you actually got me there. Yea, do you have a sprinkler system that uses these which plugs into your outdoor AC, if so then that control box actually adapts the power to lower voltage DC. That may lead to the belief that it is an AC valve, or I don't know what I'm talking about.

[kve23]

some kinds of pvc are not for pressure but others are designed for pressure

[ghoru]

Coolest sound ever! lol cant wait to build one...or 2...ah hell go for 3 how big are paint balls... :D

[seltzer10]

paintballs come in different sizes but the best to easily fit is the .50" paintballs

[tomtortoise]

3/4 inch pvc barrel

[ghoru]

hmm... wonder how a 3 barrel separate trigger system would go....?

[paul1256]

dose the size of the air chamber matter

[imthatguy1125]

YOu used a dwv reduser, this means its not pressure rated a can explode 

[matthewbeckler]

Thank you for your comment. This is a very real and serious concern, and has been mentioned at least once in my writeup above. I have never had problems with my DWV reducer, but in future designs I will only use pressure-rated fittings as I mentioned in step 2. Thanks for your concern.

[imthatguy1125]

 ok sorry I just noticed it in the intro, also you may not want to shoot it in the snow because pvc becomes brittle, for more info you can check www.spudfiles.com

[lew0004]

I was wondering if you should make a picture of a End-Around Pneumatic Cannon except with a 3 barrl

[matthewbeckler]

Part of the design restrictions that come with using the U-shaped valve is that the barrel can't be too large, otherwise it would collide with the pressure chamber. The 1.5" barrel is probably the largest diameter that would work alright with this valve.

[lew0004]

what size wood a tennisball need.

[matthewbeckler]

Spudtech sells 2.5" Schedule 40 PVC that fits tennis balls. I have never purchased any pipe this size, but I've heard of people getting good results.

http://www.spudtech.com/detail.asp?id=38

[stuffman366]

try thiswww.spudgun.com/product.htm

[mettaurlover]

i'd use shooter marbles as ammo. lots of them. you ever seen what happens when a marble hits a wall at 300 FPS? it explodes. loudly.

[The 4th Doctor]

You should use some disposable cameras for your firing circuit i bet you could get a pretty good power increase if you try it tell me how it goes

[covey12]

why do you even use nine volts? it has so much less power than operating the valves when pneumatically modded. you should look up on spudfiles.com how to mod a sprinkler valve, it uses a blow gun as a filot so you have an actual trigger on the gun

[matthewbeckler]

4th Doctor, Thanks for the comment. I don't think that the current firing circuit of 3 - 9v batteries and a switch impacts the power of the cannon. I could certainly get a more powerful cannon by modifying the sprinkler valve, but I haven't done that yet.

[The 4th Doctor]

the 330volt pulse capacitor in disposable cameras should open the valve faster which should increase the power of the cannon, maybe a small pointless increase maybe a pretty decent increase or maybe something entirely unexpected too

[matthewbeckler]

Certainly, a quicker-opening valve would increase the amount and rate of airflow through the barrel, but I don't think the limitation is from the electronics or the solenoid, but rather the diaphram action of the sprinkler valve. In addition, the huge voltage spike would probably damage the solenoid coil, as they are really only designed for up to 30v operation. A quick google search can help you find videos and instructions about moding a sprinkler valve:

http://www.google.com/search?q=mod+a+sprinkler+valve

[The 4th Doctor]

ive used solenoids alike to the solenoids in sprinkeler valves the capaciters give a pulse that they put up with fine and give a quick strong pull which should open the valve faster it could be a pretty pitful or a pretty impressive increase it should help itleast somewhat and its simpler then modifying valve all you need is a disposable camera if anyone trys this post results

[qballcat]

urs looks cool :D check out mine plz

[diablo735]

Out of curiosity (this lack of curiosity may kill the cat. :P), anyways, I am not sure whether you should or must drill the hole for the tire valve stem where the pipe and end cap meet or it does not matter? Thanks for the reply(-ies) in advance.

[matthewbeckler]

I've never had a problem with putting the tire value stem in the middle of the the end cap, but some people suggest drilling the hole where the end cap overlaps with the pipe.

[imthatguy1125]

I would not use it in snow cold weather weakens pipe

[Dr. Explosion]

The valve you used makes the coolest noise! You should try modding it to be manual for more power, if you don't know what i'm talking about, search "mod a sprinkler valve" on youtube. I don't know if it would work on your type of valve though.

[DYLEGO]

actually, with 27volts it has more power than manually, also you press a button and it fires!

[Dr. Explosion]

oops, UberNoober already told you to do that but oh well

[UberNoober]

Wow, amazing. This is easily one of my favorite instructables ever. You really go in depth with the instructions, and even focused some on that *safety thing*... I am currently making a similar air cannon/spud gun/Pneumatic Thingy Of Doom, mine having a few minor differnces from yours. I'm using a Rain Bird 1" straight valve, and used two 90 degree elbows. I also modified said sprinkler valve with a blow gun valve to increase the speed and efficiency of the air cannon. YouTube "How to Mod a Sprinkler Valve For Pnuematic Cannons" (or something like that) to get what I mean.

[UberNoober]

Here is a diagram of what my cannon *should* come out like when complete, note the green square is the modded sprinkler valve.

[DYLEGO]

if you havent made it yet, a better and cheaper idea would be to put the sprinkler valve on the bottom layer and use smaller corner turns, like 1 or 3/4 inches, whatever sprinkler valve takes.

[cowscankill]

Can you help me? I bought a valve and modded it, but it had a hole in the center of the diaphram. When I pumped the gun, the air pressurized, but when I pressed the trigger, the air came out the blowgun trigger instead of the barrel. So I plugged the diaphram, and now the air comes out the barrel, but the trigger doesn't stop the air from coming out. Does your diaphram have a hole in it? Does it need to be there? I would like and answer ASAP. Thanks.

[blugyblug]

OMFG its the DWV POLICE. The elbows on your picture are DWV lol... just in case you were actually going to use DWV for the real gun.

[Mr.Bean]

about how much did this whole project cost?

[matthewbeckler]

I'd say less than $50 total. The fittings are about a dollar each, the pipes are a couple dollars each for 5ft sections. The big expense is the valve, which was $15-$20 I guess.

[DYLEGO]

you lucked out! mine cost like 93 dollars... Now i owe my parents like 100 all together!

[DYLEGO]

when you do the glueing, here is what you do. You put on the purple primer, then glue, stick them to gether and PUSH while twisting 90 degrees. if you dont twist, you get leaks, and thats where your leaks are coming from!

[matthewbeckler]

Thanks for the tip. I had read online about the magic twist when gluing PVC together, so I think the regular connections are just fine. I'm 90% sure the leak is either where I drilled through the end-cap to attach the schrader value for filling the tank, or where I attached the pressure gauge.

[mking2012]

That's a pretty good cannon. I've been wanting to make one with an electric valve.

Someone should make an instructable for this...

[apothocry of hypocrysy]

sick knife in the corner of the second picture step 1... I have the same one.

[rock climber]

This is definitely one of the best Instructables. Hey, do you use a pushbutton or some other thing to open the valve?

[matthewbeckler]

Check out step 7. Let me know if that doesn't explain it properly.

[matthewbeckler]

Oh yeah, I guess I wrote this instructable before finishing the firing circuit. Basically just use three 9v batteries in series (connect + to - between the three batteries, you should then have a "super battery" with one + and one - terminal still free), and put it in series with a switch to the two wires that go to the valve's solenoid. I'll make up a diagram and put it on the instructable. These kind of valves also have a manual override switch, for if you want to water the lawn even if the timer hasn't gone off. On my valve, it's a little black switch by the solenoid, and if you flip it, it opens the valve. I usually just use that, as it's a bit of a pain to have the batteries and switch attached to the cannon. Thanks for your comment!

[rock climber]

Thanx for the info. I think that is all I need.

[bob the builder #1]

don't use this above about sixty psi because of the dwv bell reducer.

[explosivemaker]

.....is the gage anything different from like a tire gage or is it the same thing......

[matthewbeckler]

The gauge is the one I found in the plumbing section of the home-improvement store. It's definitely the least air-tight connection, as I'm not sure it has the right kind of threads to interface with the PVC. Your best bet is to find any sort of gauge and get it connected to the pipes. As long as it's a gauge for air/CO2, it should be just fine.

[explosivemaker]

......improvise.....gotcha.....(wink)......

[Derin]

if this becomes a double post,sorry but where do you find the 100mm pipe?I only have 75mm and 50mm which is not pressure rated(both of them)

[conrad2468]

dude one word "ICE!"

[ATCdude]

In your instructions, you say not to use a bell reducer from 3-1.5". But in this picture you use one. I'm guessing it's safe enough to use for this project then? Otherwise, what type of reducer would you recommend?

[matthewbeckler]

Sorry for the confusion. I just updated the instructable to reflect the warnings of a knowledgeable user, who posted some information that bell reducers are normally not pressure-rated. This user suggests using regular slip bushings to adapt the pipe size down to your valve size. You are correct, a few years ago when I built this cannon and wrote up the instructable, I used a bell reducer. I've built 5/6 cannons of this design, all with bell reducers, and I have had no problems with any of their bell reducers. Your mileage may vary, so it's probably safer to go with regular, pressure-rated slip bushings instead.

[ATCdude]

Cool Thanks! I'm going to start building it today and see how it works when the glue has set.

[conor1148]

my inline orbit sprinkler valve wont work, i send current to it and i hear the solenoid clicking but it wont open, i have to stick my finger in the valve to open it

[matthewbeckler]

Hello, These kind of valve won't open on their own. They need some pressure from water or air in order to activate them. The clicking you hear from the solenoid is all you need at this point to know that it's working. Once you have a working fluid such as water or air, then it should open as expected.

[conor1148]

by the way my valve is a 1" orbit inline, its not exactly like yours

[conor1148]

how much pressure is needed?

[matthewbeckler]

I'd be willing to be that the inline valves are still a "diaphram" valve like my u-shaped valve is. I really don't know how much pressure is required, but there is a spring in there holding the valve shut, so you need enough surface area x pressure to overcome the spring force. I kind of doubt that you'd be able to open the valve just by blowing into it.

[conor1148]

alright thanks! i took my valve apart and its just like you said, i just finished putting toghether the electronics and i just need one more piece and it will be finished, after i glue it all toghether

[matthewbeckler]

Awesome. Let us know how it works out.

[conor1148]

thanks, im still a little iffy on the valve working right but i glued everything and teflon tapped the valve so if it still doesn't work removal should be as painless as possible

[blugyblug]

SCHEDULE 40 DOES NOT MEAN PRESSURE RATED... ffs its a thickness rating. You actually have to look for sometime like "200PSI" on the pipe. Or if you are Australian/British, PN 12 or higher. (PN12 is 175PSI.)

[Derin]

one of my couplers say "10 Atm"how much psi is that

[Derin]

ty for the info

[blugyblug]

Atm=Atmospheres.
I think it means that it is 10 times the Atmospheric pressure on Earth, which is 14 psi. Simple maths 10x14=140psi.
Search google/wikipedia to make sure...Wikipedia has a good table for comparing psi/atm/psig blah blah.

[matthewbeckler]

10 atmospheres is about 147 psi.

Google is pretty handy for these sorts of unit conversions:

How to use google search ror unit conversions

[bigbob12345]

That bell reducer is NOT PRESSURE RATED!!!! seriously, it could blow up at any time to those people that want to make the cannon in the instructable, fine just make sure to use a pressure rated coupler bushing setup. If it didnt have the bell reducer I would say nice cannon.

[matthewbeckler]

Do you have any links to reputable information concerning this? It seems like a pretty important deal whether or not these are pressure rated, so I'm very interested to see some more information. Did you talk to a manufacturer or plumber? Please let us know all that you know, and where you got your information. Thanks!

[bigbob12345]

Well you should probably read this
http://www.spudfiles.com/spud_wiki/index.php?title=Identifying_Pressure_Rated_PVC

And I get all my information mainly from a spudgun forum called http://www.spudfiles.com/
I am an active member there under the same username as here.
And I see that you made this instructable quite a while ago and I'm assuming your cannon has not blown up yet.
I find that surprising, though you probably dont have any scratches on the bell reducer and you most likely did a good pvc cementing job.

I myself have experienced DWV go boom, it isnt a joke.

And dont mistake me for a spudgun genious, im just a 14 year old that is experienced with these types of things.

[matthewbeckler]

Well done. Thank you for the information. I'll go put a note up above in the instructable. I have built about 6 of these cannons, all with bell reducers as pictured above, and have had no problems with any of them. I'll check later today to see if my current cannon's bell reducer has the "NSF-PW" marking on the fitting. I must say, you have very good writing skills for being a 14 year old. Congratulations. Most adults on the internet seem to prefer writing without proper capitalization or punctuation, and it's nice to see that some people still know how to use English properly.

[neeewwww!!!]

Can I replace the Sprinkler Valve... to a Ball Valve?

[matthewbeckler]

Sure. One thing to remember is that the speed of opening, that is, how quickly you can go from totally closed to totally open, influences how much 'power' your cannon has. One advantage of an electric value (especially a modified sprinkler valve) is that the valve can open much more quickly than a ball valve.

[neeewwww!!!]

Yeah... I know about this... But where I live Sprinkler Valve is too expensive... So I use the cheaper one ;) - Back to the project I guess I will use an Iron Forged Chamber, like a Fire extinguisher connected to the Iron Ball Valve and the PVC Barrel or a CPVC Thermal Pipe 24kgf/cm2 @ normal temperature conditions - Im very afraid about pipe explosions... It will get heavy... better than some plastic spikes at my eye - The biggest problem is how to install the Tire Valve Stem into the Iron Chamber Im just thinking about the design too... Sry about my bad english... Second language ftw ;D

[boredwifiguy]

if you wanted a real cannon then you should use 2 1\2 inch black pipe used for gas lines. take 2 3' sections.put a 2 1\2" ball valve inbetween the two and cap off one end. i believe they might sell caps with the built in air thing. but if not find a muffler shop and have one welded in. should be good for verry high pressures. but the kick will be big as well so maybe an old school cannon mount would be best.

[matthewbeckler]

True, that kind of metal pipe would be able to handle enormous pressures, but I wonder about how quickly you could open such a large ball valve. The faster the valve opens, the larger the impulse the projectile receives from the in-rush of high-pressure air. That's the reason that a bunch of spud gun research is directed towards high-speed, high-flow pneumatic valves.

If I get bored later, I'd like to look into the math to justify the "faster valves = further shot" argument.

[The N3rD]

I had an old cannon that had a ball valve. I pumped it to 150 PSI and it barely shot a piece of chalk over 200 feet horizontally. I built my new one, though,(with regular sprinkler valve, unmodded) and at 80 PSI, It shot a AA battery 350+ feet straight up!

[Hetzau]

Nice cannon. My friend and i are thinking of making an aircannon for a science project and i find this page lol. How exactly do you fire the thing? I see a sprinkler valve like that at my home improvment store website and it seems to me that you fire it by pushing down the button on the bigger side? That doesnt seem right to me though because you have a wire there. can someone please explain? thanks

[Hetzau]

well, i just tried it after i built it. It doesnt work. I connected the wires of the solenoid to a sprinkler thingie that has the same brand (orbit). I have this button thing that makes the circuit complete that i use as a trigger. When i push the "trigger" the thing turns on and starts buzzing but i cant blow through it. any ideas? thanks

[The N3rD]

Did you connect the valve in the right direction? there should be arrows pointing in the direction of the rquired airflow, indicating input and output. Also, try using two nine volt batteries to open the vale. Mine would not open until I used two, and it works fairly well.

[frankinator]

you can blow through it if it works but only if you modify it with a blow gun look up modifying a sprinkler valve on google it cost about 5 dollars extra but its worth not having to replace the battery every week or so.

[matthewbeckler]

You're probably not going to be able to blow air through the valve, even when it's open. There is still a spring holding the diaphragm shut that you need to overcome. On my valves, you can actually flip the little switch on the side, and it'll manually open the valve. Good luck!

[Lftndbt]

Solenoid valve operates on an electronic actuator, releases pressure on one side of the diaphram allowing flow through of water/air in this case.

[Hetzau]

xD, my dad told me the same thing and so i hooked it up. it works! My friend and i shot marshmellows about 100+ feet and this was with 40 psi. We hit a board about 25 feet away and the 1 and 1/4 inch marshmellow was smushed into a half inch marshmellow LOL thanks for your help guys

[The N3rD]

My cannon looks exactly like this (only bigger) and i mounted a handle on it with a button to shoot. only problem is that firing is not instant, it kinda leaks for a millisecond. after shooting, does yours make smaller and smaller blasts until empty?

[Loveofchaos]

im thinking that possibly a small-ish (get creative, but use appropriate voltage) capacitor. i saw a capacitor used on an air cannon. I believe I will give you the instantaneous firing you are looking for.

[diydude]

How bout' an electric cigarette lighter ignighter? That could be used in a pressurized cannon without any leakage issues. The only opening needed would be for the projectile opening.

[The N3rD]

That wouldn't do anything, because this is a pneumatic cannon. Pneumatic means air-powered. There isn't any combustion going on, and it removes the need for spark, flame, or non-burnable ammo. Check out spud guns, you could use a cigarette lighter on one of those.

[Derin]

i use tangit for pvc it works good and requires no primer for smaller ones i use heat machines to weld them

[Derin]

and also tangit is weatherproof

[blugyblug]

Modify the sprinkler valves.
They open 5x faster.
To find a tutorial go Here and Here
For the first one, click on design library and "Orbit watermaster modification"

[ELITE HAMSTER]

last year at a snow camp in bsa i saw someone with this shoot me with this but he used snowballs. ive been looking everywhere for how to make it. thank you thank you! its time for my revenge!!!

[blugyblug]

Some PVC pipes have a foam core...Now thats just stupid. Very nice cannon though

[steven123654]

I would suggest using ABS pipe because it does not burst under pressure it only splits witch is safer,I've built one like this and they are powerful

[frankinator]

Abs pipe is not the safer choice, I use schedual 40 pvc. Abs pipe is not pressure rated it can burst at relatively low pressures pvc is pressure rated. With pvc you know how high you can go.

[steven123654]

atualy your talking about cellulose abs witch is not pressure rated but if you use scedule 40 abs (witch you may not have round)it is safer like for me a reno depot they have it but home depot does'int i dont no it may be the location but i know for sure hat pressure rated ABS (scedule 40 or 80)it safer wen it burst

[frankinator]

the only place we have to go where I live is true value and I guess they just have cellulose abs so I assumed that is what you meant sorry at any case I built a cannon the other day out of galvanized we have it laying around the garage and I welded some together and made a 500 cubic inch chamber I've already tested it with my air compressor up to 300psi I'm hoping for at least a 1/3 mile with this one

[steven123654]

cool you should post sound cool

[steven123654]

I would suggest using ABS pipe because it does not burst under pressure it only slits witch is safer,I've built one like this and they are powerful

[olvegrn]

very nice job. I made one like this in 2000, but didn't think to put a gauge right on it! TIME TO MODIFY FOR ME! THANKS!

[Ammosmoke]

And another thing, NOTHING will protect you from a PVC pipe bursting while under pressure. On a spudfiles.com, a member conducted a test, using controlled conditions to see if any of the commonly recommended things worked. Jeans leg, failed. Chicken wire, failed. (Even worse because it made flying metal) Duct tape, failed. Fiberglass tape, failed. All of them at once, failed!! Just use the proper stuff, ie pressure rated pipe AND fittings, and you will be ok.

[Ammosmoke]

Ok, for one, never go past the rated amount on the pipe, even if it is for a test. It will weaken the pipe, making the likelyhood of failure much greater. And you don't want to use the electric solenoids from the sprinkler valves. They are slow and have very little flow. If you mod the sprinkler valve, you will get much better performance. Visit spudfiles.com to find out how to do that properly. And, actually a 2:1 barrel ratio is ideal. 2 being the volume of the chamber. If you have a sprinkler valve that is modded, you can go to 3:1 even.

[nugget659]

The safest way to pressure test this is to fill the pressure chamber as completely as possible with water and then pressurize. Water will not expand with a sudden pressure drop and send PVC shrapnel everywhere. DO NOT PRESSURE TEST WITH AIR. Remember that PVC shrapnel is bad for your eyes...

[TheMadScientist]

pvc shrapnel is bad for you period

[organicengines]

There is a kind of packing tape that has fiberglass filaments in it. it is very strong and it might be usefull for wrapping the pressure chamber. PVC is often used for compressed air lines in peoples shops, but the main problem is that it becomes brittle over time, and then blows up, especially if exposed to sunligt, so keep an eye on it.

[sparkyss]

you can use duck tape to. so it wont shater

[oinkoinkzoopals]

i seriosly dout that duct tape would make a difference

[greenbriel]

Would tape really work? Seems like shards of PVC could still fly off the tape pretty easily. Have you tested it to failure? I was thinking of wrapping the chamber in a thin metal drainpipe I saw at Lowes. Anyway, cool project, I have two valves arriving this week, and PVC is ready to go.

[Spookiefish]

you can cut the leg from an old pair of blue jeans and place it over the pressure chamber. this would prevent any injury from flying pvc fragments

[greenbriel]

Maybe I'm paranoid (probably not a bad idea when dealing with potential explosions that leave X-Ray invisible shards in you! :), but I'd still worry, even with jeans. I finally managed to puzzle together the fittings I need from Lowes, so I'm going to start PVC welding this weekend.

To hopefully make the chamber a bit safer, I bought a 3" x 24" piece of galvanized pipe for 2 bucks and change. Something like this stuff
http://www.acehardware.com/product/index.jsp?productId=1274082&cp=1254880.1255015.1306408&parentPage=family&searchId=1306408
I plan to fill the space between the chamber and the pipe with wadding (maybe wrapping in old jeans!, and the putting 4 or 5 pipe clamps around the whole thing. More aesthetically pleasing that way too :)

[cokebottle tuque]

pvc has a fairly high PSI rating on it i would find the piece of pipe that has the lowest ratting(it will be the largest diameter piece) then cap it some 30 PSI below that. i have had several of my home made air canons up to 120 PSI. and not to give any one any bad ideas but that light wait drainage pvc that has no PSI ratting on it has been up to 80 PSI with out incident but its still not a good idea.

[matthewbeckler]

Cokebottle Tuque, Thanks for the tip. You'll notice that the largest pipe I've used, the 3" diameter, has a pressure rating of 260 psi. I normally only fill it to about 60 psi, and never above 100, so I should have a safety factor of more than double. Also, my particular valve has a limit of 125, so hopefully, in an accidental over-pressurization, the valve will (non-dangerously) fail and release the pressure well before the pressure chamber will explosively fail. Also, the air compressor I have is not very good, and the maximum pressure it can create is 100 psi, so I'm not too worried. I've heard that some people pressure test their pressure chambers with water from the garden hose. They get an adapter to convert from hose threads to a tire filler connection, and pressurize their chambers that way. They said that if a tank is weak and bursts, that in only cracks and then sprays out all the water. I'm not sure if that works, comments are welcome.

[crabber]

About testing to destruction - the method of filling w/water & then overpressurizing to above what you will use is the safest way. This is how pipefitters do critical testing. Since water does not compress an appreciable amount, you are not storing energy in it the way you do when you compress air. One way to do the testing is to fill your chamber completely w/water and them pressurize it w/air. If it blows, only the air will expand, releasing energy. My brother told me about breaking things filled with water @1000 p.s.i. and only producing a crack and a trickle of water. Be aware, however that Murphy's law is always in effect (what can go wrong will) and that Murphy is an optimist - protect yourself with distance, barriers, protective clothing and ear protection anytime you push the limits. Also I see people talking about using non-rated pipe- DON'T EVER DO THAT! Rated pipe (schedule 40 and schedule 80) is available in any size you could want. Check the net. Check your speciality plumbing retailers. I just spent more than I intended to because I went w/schedule 80, because I am experimenting and want to push the limits, but want to stay within the pressure rating of the materials. More $ ? Yes, but I like my eyes, ears fingers face, etc. Saving a few bucks is not worth risking it! Incidentally, the pneumatic gun I am building is out of extra tough stuff, but I am also looking for a reasonably priced pressure relief valve as an extra safety. If I can't find one I like, they are a little tricky to bild and get right, but I may try it. I have also considered putting in a "weak link", similar to having your valve fail safely. This would be a small lower-rated pipe connected to the camber pressure, inside a higher rated pipe that was vented to ambient pressure. It should blow before the main chamber could, venting the whole thing before it could explode catastropically. Comments are welcome here, too.

[killerjackalope]

thry an air tools shop or somewhere that sells compressors and you can get them... they are extremely safe and reliable due to the fact that an exploding compressor tank is a more than loud we blew an old tank we used as a reservoir in the back room when we changed compressors for the day the usual one needed an engine swap honda 8hps have a 10 year life expectancy at my guess but the other compressor was a fearsome peice of kit it sang and hummed when running at 250 PSI ye olde tanke was made for a meagre 150 and never went past 120 and the shrapnel and explosion basically destroyed the back room. Unfortunately you haven't mentioned the accompanying shockwaves from an exploding air reservoir. a 120PSI tyre blowing at 130PSI gives you approx 3days bedrest and I was 20feet away please for the love of god don't go over kill on your PSI ratings a safe bet is 10% below ratings sorry for the long comment and story but it was worth mention as I know firsthand the power of compressed air the compressor safety valves are very safe and reliable and work for year on end

[matthewbeckler]

Yeah, I've not been able to find any good pressure-relief valves, although there is one on my (pretty crappy) air compressor. I've not tested it, but it's useful to get the extra air out of the compressor's tank at the end of the day.

[zuixro]

Awesome instructable. By the way, I have heard that you can cut PVC with just a piece of string. I haven't ever tried it, but you old it between your hands, and make a sawing saw the pipe with it. I hear it works faster than a hacksaw or hand saw.

[srwoodruff]

I heard the same myself and decided to try it. Lo and behold it works! It has to be cotton string though (the kind used in construction to measure lines) because nylon string will melt and bind with the pvc. I was very impressed with how clean the cuts are as well. Just be sure to keep well ventilated when cutting with string as small amounts of HCl gas can be emitted from the heat upon the pvc.

[matthewbeckler]

So, what you're saying is, that you can take a piece of cotton string and 'saw' through PVC pipe by moving it back and forth, like you were using a real saw? It cuts with the frictional heat, you say? I'll have to try that sometime. How does the cut look? Is it smooth/straight?

[srwoodruff]

yes indeedy. My cuts were actually very smooth. Mainly probably because of the heat effects. I wouldn't say it was necessarily faster than a hacksaw, but something definitely worth experimenting with. I'll try and get some pics of a trial up soon.

[killerjackalope]

my system involved a piece of resistance wire and a battery... i rigged it up for cutting pieces of ploystyrene during an art project but it turned out to cut pvc pipe fast and clean only a variable resistor a hacksaw handle and a lantern battery would be a much better configuration than pliers and croc clips going to the wires

[presurizedbottle]

My friend was presure testing his home made air cannon and it exploded at about 102psi, thank god he put a lead x-ray coat over the compession chamber! These things can be very dangerous, so use extreme caution. the shratonal went in to the aspalt!!! I hear 2liter bottles are good compression chambers supposebly able to hold 200psi.

[killerjackalope]

120psi is the safest max for them some will explode at 130 some at 190 they're not perfectly manufactured

[hg341]

no they get like 180 or so

[helzangel]

i was thinking of making a 2 chamber back mount hand hek=ld air cannon if i get the time to make it and post it ill will

[binnie]

if it exploded wraped up in gaffatape would the pieces still shatter and like stab you and all?

[monsterpoof]

my brother and i build small trolling motor powered speed boats like eight feet long and mess around on the river with them...we got this crazy notion to build some air cannons and mount them on swivel stands on the front of our boats and fly down the river shooting apples, and tennis balls, and such at each other.....should be fun

[bunky11]

Is this better than a combustion potatoe cannon?

[arex]

fuel-driven cannons rarely exceed 15psi, unless you're using scary stuff like acetylene.

[frankrede]

Thats not true. Even with deodorant they can reach 50 psi with a good fuel/air ratio. WIth metered propane you can reach 90 psi.

[matthewbeckler]

So...uh...how exactly do you measure the pressure of a combustion cannon?

[frankrede]

You have to use a pressure guage,drain cock, and a one way check valve.

[n-saur]

believe it or not, pneumatic cannons are substantially more powerful. They can be made even more powerful if you modify the sprikler valve to be actuated with a blowgun.

[snakeblack8]

I have a 2 inch by 1 1/2 foot chamber and i fill it up to 110 psi

[Mr.Bean]

i don't think you need even close to that amount of psi

[RobbGodshaw]

you coulsd have saved some time money and girth by getting a 1/4NPT pressore guauge drilling a hole and screwig it in

[bunky11]

Hey, This is EXTREMELY COOL. I have made lots of bizzare stuff in the past. A Spudzooka type project is what I am currently interested in. Seeing your cannon has got me seriously interested. Now, which is more powerful your design with air or a combustion conventional type of spud gun if both are of about the same physical size? How far would you expect a 100 psi charge to fire say a sock projectile? Thanks, Bunky.

[matthewbeckler]

Hey, In town, where my house is located, in a subdivision type thing, I usually only fill up to 40-60 psi. Using the rolled up and zip-tied wet sock projectile, I'd estimate that at 100 psi, it'd go a pretty long ways, probably at least a standard city block. As to the never-ending combustion vs. compression debate, I personally prefer pneumatics for the following reasons: 1. Safety: I know exactly how much pressure is in the system, and I don't have to worry about timing sprays of fuel. All I have to look at is the nice pressure gauge. 2. Consistency: Again, for a given pressure, I get pretty much the same range and target. 3. Power: Related to consistency, I have friends who swear they can get more range out of their combustion cannons, but it seems to take a lot of trials, and requires a lot of luck as to the amount of fuel as well as the mixing of the fuel and air in the combustion chamber. Basically, if the maximum power of a combustion cannon on a good day, with lots of luck, is X, then I'm more than happy to consistently get 90% of X every time.

[Sequoiaboy]

I can't find a pressure gauge with 1" pipe thread (most that i find are 1/4" or 1/8")... Where did you find the gauge or an adapter to fit the 1"?

[hivoltage]

i made something like this. but with two chambers. they sit below the barrel.

[classicrocker12]

by the way, pvc can become brittle at temperatures below freezing so be careful. oddly, tennis balls fit very well into 2.5" pipe. i think most people should be able to figure out how to make that barrel with pipe fittings. with the U-shaped valve, though, one will need to use a pipe nipple between the air chamber and the valve, because the fittings on the barrel and chamber will run into each other. as far as a barrel-to-chaber ratio, most people like a 2:1 chamber-to-barrel ratio (chamber twice the size of barrel i nvolume) and anything above 3:1 is a waste. i have made 3 air-powered cannons, and i like having a u-shaped air chamber. This makes it nicer to hold, and also has a large chamber volume in case im using my 3" or 4" barrel. for my glue, i like Christy's Red Hot Blue Glue. its a one-step glue that effectively 'welds' pipe together. its blue and seems like a bit more of a knockout smell than most normal pipe cement, but its great. i know my joints are good, so i usually use my gun around 80 PSI, and i max out at 90 PSI for safety, both with valve failure and joint failure (the pipe i use is rated for over 200 PSI). http://www.spudtech.com is hands-down the best spudgun site, with references, plans, info, parts, and you can buy prebuilt guns from him, too.

[dev1201]

My brother made a cannon similar to this. Instead of the pressure guage on the cannon, it is on the compressed air pump we use to fill the chamber. Put it up to 80-90 psi, load a rock w/ a foam sabo, and fire clear through a THICK piece of plywood. I wouldn't reccomend going to 80-90 psi unless you've taken the proper precautions in construction. But it is funny as hell!

[Fark 2111]

is this cannon air or combustion??

[matthewbeckler]

This cannon runs on compressed air.

[pdileo]

I am actually building something very similar but i cant get the valve to open. What power source did you use? I tried using extra ac adapters with very similar volt and amp rating but the valve wont open.

[matthewbeckler]

pdileo: On my valves, they have a manual pressure release, it's a little lever near the solenoid (black thing). I've never really needed/liked the electric operation, except for remote firing. If you connect three, 9-volt batteries in series, it should open the solenoid.

[Ledmik]

The "Orbit" pressure valve you used is made for a hose-bib. Garden hose threads or more course than pipe threads. The smaller threads however should be either 3/8" or 1/4" pipe thread. I would use a tee with a 1/2" thread and a brass bushing down to the size of the smaller thread on the pressure gauge. You could probably also fit your fill valve between the bushing and pressure gauge. That would eliminate the problem of weekening the cap by drilling a hole in it.

[RobbGodshaw]

from my experience in air cannnons the compression chamber should be roughly the same volume as the barrel, anything else is wasted pipe, air, money and weight

[matthewbeckler]

migetman121: I've heard lots of different "ideal chamber-to-barrel" ratios from many different people. I've never calculated the ratios for my cannons, but I do like having the chamber and barrel the same length, as I can bind them together, which makes it more compact and easy to carry.

[jdege]

I have no idea what pressures its rated at, if it's rated for pressure at all. But it is designed to support people.

http://www.apiplastics.com/pvc_pipe_furniture_pipe_coex_extrusion_capstock.html

[matthewbeckler]

Hmm...I can't find any mention of a pressure rating...I really wouldn't want to use this pipe, UV resistant it may be. It just doesn't seem to be made for holding pressure. Interesting material though...

[jdege]

There are two basic grades of PVC pipe - plumbing and furniture grade. Plumbing-grade PVC is not intended to bear weight, and it's not intended to be left out in the sun. Exposed to UV, it gets weak and brittle. Furniture-grade has UV protectants. (And it doesn't have that ugly purple printing, either.) Seems to me that furniture-grade would be a better choice for this project.

[matthewbeckler]

jdege: I've never heard of furniture grade PVC. Do you know if it's pressure rated?

[Sofocation]

i made one, simpler, but works fine, if ypu want i cant send you some photos now i want to make yours regards, sofocation

[baitisj]

My friends and I made PVC pneumatic cannons much the same as yours, including using a tire stem in the PVC end cap. We routinely pressurized one of the cannons to over 160 PSI, despite the solenoid being rated at 125PSI. The point of failure of the cannons was always the end-cap: drilling a hole in the center of the end-cap *significantly* reduced the pressure rating of the cap. Visible stress fractures always occurred at the end cap first, so be very careful when inflating the system from the end-cap.

The most apparent point affecting performance was the volume output of the solenoid. The solenoid aperature was quite small in our cannons. I would suggest using two or more in parallel to allow more gas to flow per unit time.

Our favorite thing to do was to shoot water colums. This was very dangerous because of the mass of the water column in the cannon: a VERY surprising amount of reaction force "gun-kick" due to the mass of the water being propelled out of the system. However, watching a three-inch column of water rise 15 ft into the air is quite an aesthetic :)

[greybeard]

If you want to pinpoint leaks in any pressurized gas system, apply soapy water around your joints and fittings with a sponge, or foam brush after you've pressurized the vessle. The escaping gas will produce bubbles. Cheap, quick and easy. I use this technique when I change hoses or tanks on my oxy/acetylene and oxy/propane torch setups.

[matthewbeckler]

Wow, that is an awesome idea. Why didn't I think of that. I'll have to try that soon on my cannon. Thanks again!

[Moogle]

Coextruded cellular core is glorified styrofoam. Take a look at the cross section of almost any PVC pipe you can find over 3". It's got a 1mm thin layer of solid pvc, a thick section of vaugly translucent hard foam, and another layer of solid pvc. If the pressure chamber fails, it turns to shrapnel. Jeans or jackets won't stop it. It's *probably* ok for low pressures if you treat it well. It made me too nervous the last time I built one, so I reinforced the body by placing pipe joiners with the inside lip filed down (repair patches don't have the lip but are much more expensive) around the entire chamber. Double walls == good. Your pressure chamber is faar to long for that to be practical here though.

If you want a safer way to play with it, you can turn it into a downright nasty watergun by getting a rubber cap and cutting an astrisk of slits into it. Use a funnel to fill the barrel with water, and the cap will hold it in until you fire, and the pressure will flex the rubber outward turning it into a nozzel. Just make sure you tighten down the collar on the rubber cap really well. And still don't fire it at people! Mine had a smaller chamber vs barrel volume than yours and anything over 60 PSI would make it shoot clouds instead of a water stream.

[Moogle]

BTW, the comment about coextruded cellular core is just in general, FYI for anyone else building one. It's all I've ever been able to find in Home Despot or Lowes. I noticed you actually have pressure rated 3"? Where did you find it? I haven't been able to find any, but then I haven't gone to specialty plumbing shops.

[matthewbeckler]

Moogle, Just as a note, I purposely didn't buy the cellular core extruded pipe. I got all my pipe at a Menards store, they're really big in Wisconsin, not sure if they are anywhere else in the country, but the largest 'real' (i.e. not cellular core) PVC they sell is the 3" diameter pipe I bough. I had to buy 10 feet of it, but I've been cutting it down to make cannons. Thanks for the heads-up with cellular core, I'm going to add a warning about that in the safety warning step.

[Moogle]

It might be a better idea to put the fill valve on the side of the endcap where it overlaps, so you're going through a double wall. It should be a lot stronger there.

[kai_h]

You're right about the PVC Cement that you're using. The first part is the primer that removes any surface coating and slightly softens the PVC, a cleaner really, and the second part melts the surface, but is extremely volatile, so it evaporates quickly, causing the two melted surfaces to be chemically welded together - effectively becoming one piece of PVC with no seam.