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It's time for the big one... help me out

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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It's time for the big one... help me out

Unread postAuthor: spudkpi » Sun Aug 13, 2006 10:16 am

I have built 4 cannons so far... 1 combustion and 3 pneumatics. I like pneumatics much much more for many reasons (more powerful, easier to build, cooler sound shen shot, etc. lol) but now I want to move to the next level in my spudding career and i'm considering building a massive pneumatic cannon. I want to build a co-axial cannon with a large 4'' chamber and cleanout cap but what i'm not sure of is what barrel size i should use to shoot normal spuds... whether it should be 1.5'' or 2''. I am also unsure of whether I should use a piston or a diaphragm and which would be easier. I have made one coaxial piston valve and it took me quite a while to get a good piston and good seal but now it works every time. I was going to use a modded sprinkler valve to relieve the pilot but I would like some input on the barrel size and whether or not to use a diaphragm or piston... I want to be able to shoot it right at 1/4 to 1/2 mile with a spud or other object, hopefully it's possible... i'm ready for the big one! Thanks.
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cannon big boy.JPG
This is a sketch with a piston... what do u think?
cannon big boy.JPG (9.56 KiB) Viewed 1631 times
Last edited by spudkpi on Sun Aug 13, 2006 11:49 am, edited 1 time in total.
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Unread postAuthor: noname » Sun Aug 13, 2006 10:35 am

Just use a 10' length of 2" for the barrel and a 10' length of 4" for the chamber.
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Unread postAuthor: spudkpi » Sun Aug 13, 2006 10:53 am

Ok is that a good C:B ratio? And what about the valve diaphragm or piston?
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Unread postAuthor: noname » Sun Aug 13, 2006 11:29 am

C:B ratios don't matter very much with pneumatics, but this will be 3.5:1 or around that. Doesn't really matter if you do piston or diaphragm, that's your choice.
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Unread postAuthor: spudkpi » Sun Aug 13, 2006 12:59 pm

Well ive never made a diaphragm cannon before. Are they easier to get to seal than piston cannons? And which would be more efficient for a cannon this size?
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Unread postAuthor: Torch » Sun Aug 13, 2006 1:07 pm

I wouldnt go for a diaphragm. I tryed that once on a large scale gun like this and couldnt get it to seal and it was all set up right..From what i've read pistons can be much better then a disk of rubber. But dont hold me to that since I am still a noob. :)
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Unread postAuthor: ProfessorAmadeus » Sun Aug 13, 2006 1:54 pm

Yeah i like pistons more also. For some reason they are easier to make. It would be cool if you coul get a ten foot golfball barrel. That would go 1/4 of a mile.
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Unread postAuthor: spudkpi » Sun Aug 13, 2006 2:02 pm

Yea 10ft golf ball barrel would be very cool... are there any sch 40 pvc sizes that fit gold balls? I know that sleeved 2'' works but i dont exactly have good access to a table saw to cut the strip out to sleeve it...
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Unread postAuthor: Torch » Sun Aug 13, 2006 2:06 pm

Well, 1.5in SCH 40 pvc will fit golfballs with the shell removed. They will slide down but I would use wadding to seal it correctly.
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Unread postAuthor: spudkpi » Sun Aug 13, 2006 2:09 pm

Yea i dont want to have to bother with taking off the shells of the golf balls though thats too much of a hastle...i'm off to home depot to buy a 3'' coupler to start on the piston...
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Unread postAuthor: runningawaypyro » Wed Aug 30, 2006 4:42 pm

um how do you get the shells of golfballs?
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Unread postAuthor: SpudStuff » Wed Aug 30, 2006 5:30 pm

Cut it in an x shape then peel off the shell with pliers.
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Unread postAuthor: Shrimphead » Wed Aug 30, 2006 5:36 pm

Don't use a cleanout cap! They aren't pressure rated.
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Unread postAuthor: runningawaypyro » Wed Aug 30, 2006 5:39 pm

should i use a hacksaw>
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Unread postAuthor: Infernal2 » Sat Sep 30, 2006 8:50 pm

You can.... And if you want an easy fix for cutting pipe I use a bosh 4" hand grinder with a masonry blade. You can also outfit a dremel with a 1" cutting disc. Then you simply use a chalk line to make two straight lines and cut them.
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