Step 8: Drill and tap the valve's hole

I decided to drill a hole in the top of the propane tank, so the entire thing looks streamlined. It took a while to drill through the top, and its harder to tap, but it's worth the better look. For this one, I just went straight in with the big drill.
When you're done, this hole will be hard as hell to tap. You'll need LOTS of wd40, i used half a can, and you'll need to do a reverse turn every 3 turns. I even managed to dull my tap on it. Oh well, gives me a good reason to return it, I guess.

Anyways, once you're done tapping, you should put some Teflon tape on, and screw in the valve. I had to grind the handle down a little, so it doesn't hit the tank on the way down.
<p>Use a real tank with NPT thread. You are so dumb. If you do this, use a fire extinguisher and hydro test adapter or steel/copper pipe for the chamber. When drilling, you may ignite remaining propane fumes. The fittings can also blow off. The quality is like a kindergardner poked holes in the tank and then used a glue stick to glue fittings on top of the holes.</p>
Your techniques and use of tools is laughable and DANGEROUS. Messing with cylinders is ill-advised. Find a drill press next time. Next version how about a stock, sights and forestock? Its a decent try (for an 8th grader...)
Actually using a propane/oxygen or any metal tank that actually handle pressures much higher than 150 PSI are a hell of alot safer than PVC! PVC if over pressured shatters into billions of pieces and can embed itself into your body. A metal container would most likely rip at the weld seams before it would explode. ABS is bar far the best to use because it rips instead of blowing into millions of shreds. the only downside is its pressure rating is much lower than PVC. BTW SCH20 PVC is rated at 300psi and typical oxygen tanks are rated 500-1000 psi. My paint ball CO2 tank is constantly pressurized and unpressurized at 3000 psi! Oh yea and CO2 tanks get cold when they depressurize, WELL below freezing!!!! they can handle it well.(that being the pressurized tank side). Moving on to the barrel... the idea of the PVC pressure test cap you used was a bad idea... but the barrel is never pressurized enough to do harm... that said, if you can shove something down the barrel, the air that is about to escape will shove back out of the barrel with very little PSI, nothing to fret about. Ive got a Bachelor's of Science in Aerospace Engineering at Auburn University in Alabama and live in the Engineering Rocket City a.k.a Huntsville AL, don't EVEN Question me!
p.s. lay off on cvxdes, he's just making an instructable that for the most part is safe. although drilling into a propane tank is a bad idea because one spark = boom, follow watterppk's advice and drill underwater or use an air compressor and blow it out for a long time.<br/>
propane tanks are 100% fuel environments unless theres something wrong with the valve. propane + No oxygen = NO explosion. if anything adding compressed air would be a very bad idea<br/>
I agree partially, but to create an explosion you need heat or a spark. decompressing air actually takes away heat. Besides i meant like using a blower nosle to blow out the propane tank after all the propane has been released and the propane tank valve has been removed, no compression at all.
Bachelors in Aerospace Engineering- OK Jr. High spelling- not so good Ex. Nozzel instead of Nosel. Don't they have Nozzels on Rockets? ;-0
Not for all explosions, if that's what you were saying. I have overpressured a piece of PVC and it blew up, with no spark. But you are right about the latter.
Technically, it didn't blow up. It shattered prom overpressurivation, and if there was a boom sound, it was escaping air.
could you maybe use a fire extinguisher (cylinder) instead of a propane tank?
where would you get a tv that big?
I have found that propane and oxygen tanks are 3/4 in threads. I use this instead of the 1/4in thing. By the way this cannon is great especially version 2.0 but i would recommend an oxygen tank.
or an empty fire extinguisher
ooooppps I was wrong, propane tanks do not have 3/4 threads. And no, instead of using the oxygen tank that I recomended use a footlong peice of 2 in galvanized steel with a cap on the end. I would also recomend using an "over under" design that includes a quick exhaust valve. This is how my newest cannon is designed and it shoots potatoes and tennisballs over 160 meters.
That's not looking to be safe. Propane tanks are dangerous, much MUCH safer to just make a container from some 3&nbsp;inch pipe.&nbsp;And it is probably hard to open the valve, so you will jerk the gun and then your aim will be off.,
you can buy a snowball gun from hammacher schlemmer. <a rel="nofollow" href="http://www.hammacher.com/publish/76244.asp?promo=to_action">http://www.hammacher.com/publish/76244.asp?promo=to_action</a><br/>
This is just a thing i heard but appareantly when your tapping you cant use oil or lubricants as it puts pressure on both side of the threads top and bottom making it harder this also works with bolts
I would suggest not using pvc for a snowball cannon ,even if it is only the barrel, because when cold pvc gets very brittle and explodes easily.
u got to make it good then look good!!!!!! or else its a bunch of PVC glued or whatever to some propane tank......life isnt bland dude, make it pretty!!!
I made a potato cannon, and I spray painted it black with red accents over it. It's sweet.
I agree with frollard. PVC is deathly weak in the cold and it could definitely shatter without warning.
only when its under pressure
Umm...so? The barrel will still contain positive pressure, if only for a moment (as opposed to minutes for the tank). It doesn't take long for the PVC to splinter.
yes but the barrel is only pressurized for a fraction of a second and even then its a fraction of the initial psi (especially in this setup with a low flow valve). i realize it doesn't take long for pvc to splinter but it takes longer than milliseconds when its being used within it pressure rating
PVC's weakness in the cold is a well-known phenomenon. Google it, or even better, leave a piece of it out in the cold and strike it with a hammer. It doesn't really matter how long the pressure stays in the barrel. PVC is weaker in the cold because it isn't very flexible; it's brittle. In other words, it shatters when the molecules are barely displaced. Also, the pressure rating you mention always specifies the temperature. It's usually 70 to 75 degrees Fahrenheit. You may also want to consider what would happen should a pressurized snowball cannon be dropped. If it happens, which is likely with slippery gloves on, parts will certainly snap. A PVC snowball cannon is a bad idea. Don't use it.
the barrel it under maybe 40psi (more likely 20psi) of pressure for a fraction of a second there is no way in hell it could possibly fail on this set up, PERIOD! i know PVC is brittle when cold, i have first hand knowledge of how it preforms, i used if to form ice projectiles once. you describe it as it were more fragile than glass its not, even when its below freezing. sure if you leave it in the cold and smash it with a hammer it will break, lots of things break when hit with hammers. a hammer exerts far greater force than those exerted on the barrel during firing. i would be concerned if a PVC chamber was used, but a barrel is harmless. if it were to fracture there would not even be enough force to propel the fragments at anything near harmful speeds. A PVC BARREL IS PERFECTLY SAFE FOR THIS GUN SO LONG AS ONE DOES NOT TRY TO FIRE IT IN AN ATMOSPHERE RICH WITH LIQUID NITROGEN (because flash freezing pvc would be the only possible way to fracture PVC in the manner you are talking about)
Just wrap the barrel with Duct tape if your worried... Problem solved....
alpha1dksays: Just wrap the barrel with Duct tape if your worried... Problem solved.... exactly.
duct tape. the way to go!
I don't see any empirical justification for using duct tape. Nothing suggests it would help besides the bandwagon belief that it can fix anything.
exactly my point.
It will keep it together if it shatters dumbass...
"the barrel it under maybe 40psi (more likely 20psi) of pressure for a fraction of a second" Why do you say that? Sure the pressure in the barrel will be a little less than that in the chamber, but it will still probably peak at 100 PSI or so. And unless you've calculated the chamber pressure using N-S or the Gas Gun Design Tool, the safest estimation is the maximum one. You may also want to reconsider how long it takes for PVC to break. Crystalline solids shatter when molecules are displaced even a little bit. It doesn't take much time for shattering. For example, hammers deliver significant force because the contact time is quite small. "you describe it as it were more fragile than glass its not, even when its below freezing." Depends on what type of glass you're talking about and how fast it was cooled. "if it were to fracture there would not even be enough force to propel the fragments at anything near harmful speeds." Why not?
final nail in coffin for pvc in the cold. i was watching country fried videos on cmt and woudn't you know they had a potato gun being used in the cold, as i told my friend about pvc not lasting in the cold the video itself shows the camera going out of focus and people rushing to help the &quot;shooter&quot; the pvc gun cracked apart upon firing. i can't find the video yet, but the website at cmt had the episode info which i am posting here (tivo, youtube searches anyone???)http://www.cmt.com/pictures/country-fried-home-videos-rollin-your-own/1552865/2353396/photo.jhtml. remember this stuff is only fun as long as you play it safe. cheers.<br/>
I dont know how many times I have to say this... but the pvc is only in the BARREL. With this set up, it is impossible for the PVC to rupture. Simply impossible. There's no pressure on the PVC, there's nothing pushing on it. All the pressure pushes on the snowball, not the PVC. I've shot it off enough times and the barrel is still good.
Well, not really. If you had a tight enough seal with the snowball, then there might be pressure, but what are the odds of that?
ok, just to be abundantly clear, note i said "pvc in the cold" I am not necessarily against your gun or your instructable, matter of fact, your gun may never fail from the cold, however the issue here is that pvc does shatter in the cold, and if enough people make them out of pvc in the winter then it is bound to shatter, again may be not your gun in your location ever, but someone, somewhere else will potentially get hurt. in the cmt video i referenced before, the shattering happened upon firing and it was the barrel that broke apart, granted they were shooting a potato in the cold but you have to understand people are not thinking too much and just want to have fun. so please do not take this as an attack on you or your instructable, only as suggestion to make a fun instructable safer under all circumstances including weather!!!! cheers! I think the collective has come up with other alterntives to pvc in the cold so let's try them out. part of the fun is putting up your creation for review and suggestions to make it better. most projects here have had some tweaking done to them by rest of us and that's what makes this place great, we do care. Later
Ok, no offense taken.
I can't believe he drilled a propane tank without purging it.
Hmmmm... couldn't someone just take a perfectly good tennis ball mortar and only have to worry about snowball diameter? I know that it wouldn't go very far, but it would be quite a bit cheaper. I do, however, like this idea. Hurling snowballs at high velocities (for a snowball) sounds like it could fit itself into my budget... if we ever get snow long enough for that.
Listen to irwinner, seriously, hes they guy that made this crazy 25mm Pneumatic Sniper Rifle that could probably own urs... 0o
you guys are a bunch of morons, what do you think a potato canon is made out of. PVC.
I just finished making my own snowball gun before i saw this. I respect your ingenuity however i prefer to stick to more conventional methods. I made a 1.5"pvc stock/chamber with a modded sprinkler valve(no duct tape.) I hate to be the jerk who criticizes but the 1/4 npt greatly reduces the flow, you dont really want 1/4" going to 2" I would never go with something 1/2 the width of the barrel. Also, that cap you used it supposed to be used for pressure application, buy an actually pvc endcap, it wont break. Thats a nice idea to mod the ball valve, but if you had a larger size ball valve you would yeild the same results. For optimum results, use a sprinkler valve, piston, or qev.
A sprinkler valve isn't going to withstand 120 PSI. And no, it doesn't reduce flow. It's really powerful, and 120 PSI coming out of 1/4 inch is WAY more powerful than 30 psi from your PVC tank. In the second version I did get a real cap, the first one was crap. I thought I'd save a few dollars. Also, my duct tape his nothing do do with the setup, just so that the tank and the barrel can be supported, and all the pressure isn't on the joints. Thank you for the criticism, though. It did give me some ideas for my next one.
i disagree still, a sprinkler valve is still comfortable up around 100 psi. and still 1/4 at 120 psi is still not as powerful as 1&quot; at 30 psi. psi is how many pounds of force act on 1 square inch. therefore the inside area of 1 inch pvc (my valve is 1 inch) is .83 inches<sup>2 if you multiply that by 60 pounds per square inch (which i run mine at) and you get 50 pounds of force. 1/4&quot; npt has an inside diameter of around .2inches</sup>2 times 120psi=24 pounds of force. This is 2x as powerful and is compunded by the fact the modded sprinkler valves open around 10x as fast as hand opening traditional ball valves.<br/>
Just because it's comfortable at 100 PSI, doesn't mean it wont explode, especially when i put it up to 120. Just because it can take it, doesn't mean you should try. And mine opens with drill power, as you see in step 7. It may not be as fast as your sprinkler valve, but its fast enough. Also, your math has no logic behind it. And I must add, just because you made a snowball cannon that you think is the best in the world, doesn't mean it is. I'd like to see a video of yours firing off, see if it doesn't just roll out of the barrel.
a sprinkler valve can take 100 psi easy, (they are hydro tested to atleast 125psi the last time i checked which means they can actually go a lot higher than that) the ball valve you are using acts a huge bottleneck. koolaidma3's math does make sense, the smaller diameter the valve the less air can flow, the lower the air flow the lower the pressure acting on the projectile is. think of it this way (this is not an accurate representation it is just meant to get the point across), with ball valve is emptying a swimming pool through a drinking straw, with a sprinkler valve your emptying that same swimming pool through a fire hose (well actually it would probably be larger that a fire hose). by the time all the air has gone through the ball valve the snowball has already left the barrel, now a sprinkler valve has much better flow and can put a lot more power behind the snowball before it leaves the barrel.<br/><br/>i have made about 5 cannons with sprinkler valves and the oldest has gone three years without failure (when it is used its used at above 100 psi). one of them is on this website here is a link<br/><br/><a href="http://www.instructables.com/id/25MM-Pneumatic-Sniper-Rifle/">http://www.instructables.com/id/25MM-Pneumatic-Sniper-Rifle/</a><br/><br/>in the video the projectile made a clean hole through both sides of the box and kept going, it never was found. i have embedded nail darts in trees 100ft away with this gun. unfortunately it is too cold to use it outside at this time of year so all i have to shoot at it old text books (and it has done considerably large amounts of damage to them). <br/><br/>i do no suggest using PVC in the winter (becuase it tends to become very weak and sometimes explode) so i have to say the metal parts were a wise choice, although you should get atleast a 1/2 ball valve.<br/><br/>
Whoa, gang, hold on, there is a huge difference in pressure ratings when discussing a compressible gas (!KINETIC ENERGY! WARNING) was a non-compressible liquid. Just because you have used the valve 3 yrs w/o failure does not mean it is safe. It just means you aren't injured yet. When using a gas instead of a liquid you immediately should derate all pressure fittings meant for fluids (PVC, ABS, etc) by 75%. Since cvxdes is really not pressurizing the barrel with an implacable object, I won't go into the additional derating the end cap should have since you have mechanically altered it. IF it was an all plastic contract (including air storage tank) personally I would being doing a 'whoa, hold on there pard...' again! Back to the point, having spoken with the sprinkler valve folks (my biz manufactures effects, I know a tiny bit about air cannons) they cringed at the idea of gas pressurizing their valves, period. It is simply an unsafe practice to run that sort of PSI (100+) behind it. You can buy decent gas rated solenoid valves for a little more that 2x the cost of a sprinkler valve, in my mind, 20 bucks buys a lot of peace (and piece) of mind (and no missing spleen!) cvxdes, did you think about unchaining yourself from the compressor? Using a tire inflator tank (reserve tank) to refill that tiny propane tank could probably fill 40-50 times off a 10 gallon. Better yet, grab the CO2 tank from the keg, and use that....10# bottle @ 1300 psi will provide you a few hundred shots.
yes i realize you need to lower rate the pipe and fittings because it was meant for liquids not gas. but it ends up being by 50% for PVC and 75% ABS (ABS really shouldn't be used on pneumatics). even at that 1" sch 40 PVC is rated at 450psi, so it would be perfectly safe to use 100 psi gas in it. 2" PVC is rated at about 250 psi, so once again it would be fine to use 100 psi gas in it. and it would be fine to use a sprinkler valve at that kind of pressure because they are intentionally rated lower. this has to do with the solenoid, if to much pressure it put in the valve in its stock form the solenoid could fire without the electrical pulse which is meant to fire it. of course the cringed when you told them about pressurizing the sprinkler valves they don't want to get sued. long before the body of the valve fails the diaphragm or the threads (for the compression fitting) will. either way the valve will fire and theres small chance you get hit with a piece of metal, nothing that will give you more than a small bruise. i would like to see a 1" solenoid for $20, can you give me any proof of this claim, a link possibly? CO2 is stored at 800-900 psi the only way it could get up to 1300 psi (in a standard non bulk tank) is by putting it in an oven.
Schedules don't change for different materials, schedules are wall thickness to attain pressure rating. PVC sched 40 is not rated for 450psi, it is as stated 140psi@73 degrees, a static rating. Whether plastic, steel, glass, transparent aluminum.... doesn't make a difference. Derating is a consistent value too, you don't change the application of it to suit your mood. Why is there NO HARD PLASTIC PIPE rated for gas use??? Harvel and Chemtrol tried, and recalled their products years ago. Again I am trying to get you to understand that GAS and FLUID have different properties, gas, heavily compressible, until it reaches a liquid state. Liquid, barely compressible if at all. Simple physics. The "you say so" principle doesn't apply. Having been in the presence of rupturing gas bearing PVC lines, I hope to never be again. Things like sprinkler valves are rated lower because they are manufactured for as cheap as possible to meet the stated specs (150PSi (2x muni water pressure), not because they care all that much about liability. Also designed to be run on muni pressure (typically 60-70PSI) transporting water (non-compressible, remember) so if it fails, is squirts, not explodes. These manufacturers operate and are insured under the premise that the valves will be underground in a reinforced box spewing water. Not in under someones armpit spewing shrapnel (not splinters) from rapidly decompressing gas. Please reread the remark about buying a gas rated valve. Double the price of a sprinkler valve, and that is rounding up to 20 for the valve at Lowes (13.59 for 3/4" or 1" ) , that puts a valve at 40 (20 bucks for peace of mind). I did not state 1", in air cannons, 1/2" will suffice (recall decompressing gases?) yep, commercial 1/2" gas rated solenoid valves are at that price point. You can find commercial suppliers or just hit up ebay. CO2 is contained higher than 800-900psi, steel CO2 bottles are typically rated at either 1800 or 2100 PSI. Aluminum bottles, 1500-1800, unless you invest in specialty tanks. I have steel and aluminum bottles in my place right now, both charged at 1300psi, one is 5# one is 20#. No way are they stored in an oven.

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