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mortar

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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Unread postAuthor: koolaidman » Sun Oct 14, 2007 10:25 am

hey i thought of a kinda neat idea on how to make a realistic mortar. id start of with the launching tube which could be as simple as 3' of 1.5" with an endcap and two 1" legs. Id then stick a sharp nail into the endcap. The round could be a 3/4" tube with and endcap and schrader valve on top. then on the bottom it would have a male and female to wedge in a burst disk. the idea being that you could quickly drop in a pressurized round and it would fall to the bottom of the tube, the nail would puncture the disk and it would shoot out. for the disk, i just did a test with an oold innertube which seems to work. It seems pretty straight forward but please criticize.
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Unread postAuthor: jrrdw » Sun Oct 14, 2007 10:51 am

This basic idea has been floated through here probly 4 different times since i've been here. I've never built one or seen the other members post a completed one. Would be a fun launcher.
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Unread postAuthor: koolaidman » Sun Oct 14, 2007 11:26 am

cool, well i lost get some points for originality. Any other advise though? Are there better sizes for snugness between the fittings and the barrel?
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Unread postAuthor: jrrdw » Sun Oct 14, 2007 12:13 pm

When i check for fit, i grab a cap rite out of the bin/box and roll rite over to the pipe and check it for fit. That way i can pick it out myself and have exactly what i want. And that goes for anything i'm building. The hardware guys laugh when i roll in because they know i'm probly building something rite there on the floor before i buy!
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Unread postAuthor: MaxuS » Sun Oct 14, 2007 12:29 pm

It would be cool if you could pull it off successfully.
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Unread postAuthor: LikimysCrotchus5 » Sun Oct 14, 2007 12:44 pm

I do the same as jrrdw, i begin to put it together in the hardware store. I gives me avisual of what my cannon is going to look like. And the guys are really no help because they dont understand the concept of what your trying to build. So i have to look for the materials myself. But once you have been the long enough, you would probably know well enough where everything is you could probably work there :)
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Unread postAuthor: koolaidman » Sun Oct 14, 2007 12:55 pm

nah, i hear ya. I always dry fit peices there too and have made friends with all the employees in the plumbing aisle. They must all assume that i have a pvc fetish.
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Unread postAuthor: jrrdw » Sun Oct 14, 2007 1:38 pm

koolaidman wrote:nah, i hear ya. I always dry fit peices there too and have made friends with all the employees in the plumbing aisle. They must all assume that i have a pvc fetish.


I slipped and told one guy it was for a spud cannon and he told me he couldn't help me. "Those things are to dangerous", a boy down the street blah blah blah, "i'm not a boy" i told him, still said i can't help you. So thats when i said, i'll help myself dagnabit!
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Unread postAuthor: NewB » Sun Oct 14, 2007 1:54 pm

I told the a guy at Homedepo what I was doing. He laughed and said he used
eggs for ammo.
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Unread postAuthor: koolaidman » Sun Oct 14, 2007 8:55 pm

actually when i built my first combustion i put together the chamber and a home depot guy came up to me. He asked if I was building a potato gun, i said yes, and he pulled out printed plans from his pocket.
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Unread postAuthor: koolaidman » Sun Oct 21, 2007 3:02 pm

well that idea didnt really work. The mortar round didnt even leave the chamber. It worked perfectly in that the round slid down the tube and bursted when it hit the nail. It just didnt have enough power and for some reason i could only get the innertube disk up to 50 psi. It is rated for 80 so i figured it would go to like 100. if anyone has an idea for a disk material as thin as that tube, but stronger, please let me know.
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Unread postAuthor: ALIHISGREAT » Sun Oct 21, 2007 3:05 pm

i'm sure if you use the search then you can find lots of posts on burst disc material that would be suitable, you could probably use the thin aluminium from the side of a drinks can but i'm not sure what kind of pressure that bursts at.
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Unread postAuthor: DYI » Sun Oct 21, 2007 4:05 pm

The thin aluminum from pop cans is a great material for discs (it bursts around 250 psi in a 1.5" union), but it is a real b*tch to get it sealed, which is why I still haven't posted my burst disk gun.

The reason that this mortar had no power was inner tube rubber doesn't blast apart in a clean circle, it just rips open in the middle, greatly reducing the flow.

For the kind of pressures that bike pumps or household compressors can deliver, I would recomment aluminum foil. It is easy to seal, easy to cut, and cheap to buy. In a 1.5" union, 16 layer alu. foil disks usually burst at over 130 psi.
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