LGM Posted October 15, 2007 Share Posted October 15, 2007 The other day I made a piston valved gun with a .5" barrel and a 1.5" chamber. It is coaxial and the valve is reduced to 1.25" so I can use a 3/4" endcap as a piston. All in all I am quite proud of it and will probably post pictures of it later. The thing that interests me right now is as I was dropping a crab apple in the barrel I did something I normally didn't and just let it drop the whole way. The weight of it hitting was enough to trigger the valve, at least partially, and the apple flew out with quite some force. I was wondering how much pressure is generated when shells up to about 2" (as big as I'm going for right now) are fired, I have other cannons to lauch bigger ones (4" pumpkin gun in the works) but I am interested in this method for now. Link to comment Share on other sites More sharing options...
frogy Posted October 16, 2007 Share Posted October 16, 2007 Hmm... lol... you need to think that through... Air + Fuse = NullAir + Lit Fuse = Possible Lit Fuse You can't really time it right unless you light the fuse and drop it in... I have a "coaxial" with a burst disk of aluminum foil that can be broken by throwing down a bouncy ball, golf ball, whatever... Also had another coaxial setup with a light spring that could be pushed back easily and stayed open from the air flow... Unless your running a hybrid (coupler broke on mine ) your not going to be lifting any heavy shells... 1", 1.75", and maybe a 2" Link to comment Share on other sites More sharing options...
jacob Posted October 16, 2007 Share Posted October 16, 2007 As Frogy said, the only real problem with air lifting shells is igniting the time fuse, i've made a coaxial air cannon with a 2'' by 2' (i think, can't remember excalty) chamber and a 1/2'' barrel and was amazed with it's power, i shot a 68cal blow gun dart that fit in the barrel just loosely through about a 1'' piece of wood, so i think power wouldn't be an issue, it's fuseing that makes this hard to do, plus the risk of PVC shrapnel, and reloading might be inconvenient with compressed air, however disney world seems to do it successfully so i guess it can be done, albeit probably more expensive then traditional methods. Link to comment Share on other sites More sharing options...
frogy Posted October 16, 2007 Share Posted October 16, 2007 Disney World doesn't use conventional fuses though... Their "fuses" are actually RC microchips that are controlled from a main computer\launch panel that is computer coordinated and are precisely launched by hundreds of air cannons and precisely detonated at proper apogee with their special detonator things Link to comment Share on other sites More sharing options...
tentacles Posted October 16, 2007 Share Posted October 16, 2007 I've been wondering what kind of batteries they use for those, etc - it just seems to me they're swapping a little BP so they can blow up a watch battery in midair along with a fiberglass PCB or something. Link to comment Share on other sites More sharing options...
Mumbles Posted October 16, 2007 Share Posted October 16, 2007 Pretty much they are. The only cool thing I heard about it was that it allows them to start the show silently. The air lauch system with no fuse give no sparks, and little noise at the crowd level until it goes off. Besides, disney was paying $600 a SHELL for one they used in the finale. Only one shot a night, and they dropped $600 for it. Money isn't really a deterent for them obviously. Link to comment Share on other sites More sharing options...
flying fish Posted October 17, 2007 Share Posted October 17, 2007 This is a topic that I've been interested in... If you have an electronic valve (perhaps a sprinkler valve), couldn't you wire up some circuit that triggers the valve to the cannon a given amount of time after triggering an e-match (or as I would use, just a nichrome wire sticking through the fuse)? I realize that these sort of projects generally end up becoming more complicated than they initially sound. But if I ever become serious about airlifting fireworks, that's probably where I will start (after figuring out how to build a successfull pneumatic cannon of course). I also figure that, even without a chip inside the shell, and an e-match lighting the time fuse instead...the fuse could still probably be hidden to facilitate your regular "surprise fireworks". Link to comment Share on other sites More sharing options...
frogy Posted October 17, 2007 Share Posted October 17, 2007 Yes it will work if you set it up right... I have a sprinkler valve pneumatic with a double sprinkle setup... One for the valve and then another to trigger the valve... I'm not sure if your up with the sprinkler valve know-how... But the electric solenoid on the sprinkler valve does not have a big enough exhaust hole to allow the diaphragm to open fast enough for efficient launching... Normally a blow gun type valve is tapped into a 1/8"-1/2" hole used as the exhaust trigger.... One of my valves is setup with a sprinkler valve on the sprinkler valve... The exhaust sprinkler does use the stock solenoid to trigger itself, because it doesn't matter how fast it opens as long as it provides proper airflow for the firing valve... You would think that if the exhaust valve opens slowly it still wouldn't trigger fast enough, but this is not true. With the solenoid the problem isn't really in it not opening fast enough, but with it having to small of an exhaust hole... Of course you could just spend $100 or something on a 1/2" solenoid, but I'd rather get another $10 sprinkler valve I was thinking... (not always good when I do that ) another benefit of air lifting is no flowerpots, unless your shell is actually so terrible that it gets ripped apart by the air, it will have no problems of the flames from the lift breaking through... One problem of air lifting is igniting comets though... you will have to QM from the time fuse to the comet... Link to comment Share on other sites More sharing options...
NightHawkInLight Posted October 17, 2007 Share Posted October 17, 2007 Maybe a simple enough answer would be a burst disc cannon with a flammable/meltable disc, such as saran wrap. The shell would be built like a normal shell with the exception of no lift. Quickmatch would lead all the way to the timefuse and a 'special bottom side comet'. When the fuse and comet were ignited it would quickly melt the disc and....well it's not hard to guess what comes next. This setup would require no electronics unless you wanted an ematch. Link to comment Share on other sites More sharing options...
Tweetybird88 Posted October 17, 2007 Share Posted October 17, 2007 Besides, disney was paying $600 a SHELL for one they used in the finale. Only one shot a night, and they dropped $600 for it. Money isn't really a deterent for them obviously. I would rather have them drop their food prices down instead of a giant $600 a night shell. Can any one say $4.50 for low quality ice cream in the shape of mickey the mouse! Link to comment Share on other sites More sharing options...
Mumbles Posted October 17, 2007 Share Posted October 17, 2007 Wasn't even that big. Single break 8" shell I think. Link to comment Share on other sites More sharing options...
PyroMedia Posted September 15, 2008 Share Posted September 15, 2008 Sorry for bringing up an old topic, but couldnt you use a pullstring ignitor attached on a pin instde the mortar to a fuse? Link to comment Share on other sites More sharing options...
Arthur Posted September 16, 2008 Share Posted September 16, 2008 This topic has been widely researched in the UK too. However though all things are possible regarding valves tubes and gas pressure, we can easily loft a dummy shell to a repeatable altitude, there is little value in air lifting if the available shells already have lift and fuse attatched. We get shells from China quite cheaply or we get British made (Kimbolton) shells very expensively. Getting shells with a special fusing system built in specially made with no lift bag would reduce all the benefits of the huge volume Chinese manufacture. Trying to get a new design through UN classification and DOT HSE approval would cost some importer a fortune, then there is the problem of having a power source coming DOWN somewhere after each shot. I've been surprised by the odd insert case hitting me on the firing site but I do NOT want to feel an AA cell (0.5 cal?) battery/bullet descending from 1000 feet. Add to everything else, if every small firework company had to discard all their $10 card or plastic tubes and buy a fire computer and a hundred gas powered mortars with valves and possibly a compressor or two...... It'a a perfect idea (except the descending batteries) for the Disney shoe where there is a show on a fixed site every night, and the mortars are replaced as needed. Also Disney will get huge quantities of fireworks specially made and have their own magazines full of their own unique items. Does anyone have a copy of the news release that came out when Disney started this? The link I once had is now broken, obviously it's no lnoger "news". ONe of the scientists here might solve the "ignition by gas pressure" challenge cheaply, but would anyone here want to buy "special" shells and mortars for way over the usual price. Removing the lift cup and powder removes less cost than the cost of making a smaller batch of something different. Now if you were prepared to order in multiples of a million then things would change! BUT there would still be a million batteries somewhere for environment groups to find. -probably knowing the Chinese they may be mercury batteries too and these KILL if accidentally swallowed by a child. Link to comment Share on other sites More sharing options...
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