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My new Howitzer I call Howie

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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My new Howitzer I call Howie

Unread postAuthor: Jared Haehnel » Fri Feb 22, 2008 9:50 pm

I was inspired by spud tech's giant 2x4 hurler. So I'm planning on biulding my next pneumatic big. I want to be able to luanch anything out of this thing a good long ways. (I've got plenty of room)
I've got a plan all drawn out. I've got two five foot 4 inch chambers that would hold some where in the order of 1300 cubic inches of air. Two 1" inline valves rated up to 150 psi connected to a 2" tee the plugs into the back of breech. I'll also put a 2" thread adapter on for interchable barrel for when I want to launch something bigger. Basically the whole works of a luxary spud planter.
Now this beast (I call Howie) is still in the drawing phase. I figure if I'm going to biuld now's the time since I work at ACE and get 20 percent off all hareware, plumbing ect. 8) So I would like some input to perfect the design. I'm basicaly trying to luanch a spud as far as I can with compressed air with out having to spend more then 200 bucks. Right now The cost is around 130 with my discount. When I figure in the cost of a ten foot barrel. I suspect the barrel how ever wil need to be longer depending on what diameter bore I go with.
Yes, it sounds crazy. But I love this stuff. I got hooked when I biult my first combustion luancher when I was a freshman in high school. Any input would be awesome
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Unread postAuthor: MrCrowley » Fri Feb 22, 2008 9:53 pm

Go with Piston valves, my only input for now.
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Unread postAuthor: Jared Haehnel » Fri Feb 22, 2008 10:00 pm

Sorry about the paragraphs it didn't quite come out like I had typed it. I'll fix when I'm on a computerwith a faster connection (dial up sucks)

Yeah I thought of a piston valve. I guesss I never understood the real advantage of them. I'm guessing more flow. And if I biult one could I get by with just one?
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Unread postAuthor: MrCrowley » Fri Feb 22, 2008 10:11 pm

I would say you could get away with a 4" one for both chambers easily enough.
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Unread postAuthor: rna_duelers » Fri Feb 22, 2008 10:12 pm

Well you can build one to any size you want,so you can get away with using only 1 piston valve easily.Build a 2" porting valve into a 3" Tee and you will have great power,or even a 3" porting in a 4" Tee because of the 4" pipe you have as your chamber.They will have MUCH greater flow then 1" valves upwards of 10x the flow in comparison.
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Unread postAuthor: sjog » Fri Feb 22, 2008 10:57 pm

How can you name a piece of paper?
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Unread postAuthor: MrCrowley » Fri Feb 22, 2008 11:04 pm

sjog wrote:How can you name a piece of paper?

Are you referring to how he called it Howie though it's still in planning stages?

Who cares, personally I don't name projects till I finish them but no need to post about it. :?
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 23, 2008 1:07 am

MrCrowley wrote:Who cares, personally I don't name projects till I finish them but no need to post about it. :?


Names are for friends :D
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Unread postAuthor: Jared Haehnel » Sat Feb 23, 2008 11:09 am

It's sounds better when you can call it something besides my new spud gun project.

I guess I'm going to have to do some reasearch with the piston valves. Say I biult one with a 3" porting valve in a 4" tee like rna-duelers suggested. How would I enter the demensions into the ggdt program to see the difference. Rough demesions would be fine I just need a general idea.

Oh and what is the ball park efficiency of an average piston vave? Probably a loaded question but what is your guys experiance with it?
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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 3:16 pm

Depends, but don't worry. A 4" housed piston valve has far more flow then 2x 1" sprinkler valves. The performance will be hugely increased. No doubt.
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Unread postAuthor: Lentamentalisk » Sat Feb 23, 2008 3:58 pm

lets do the math, assuming perfect flow with no restrictions:

two 1" valves 2 x pi x 1/2 x 1/2 = 1.57sq.in

one 3" valve pi x 1.5 x 1.5 = 7.07sq.in

thats almost 5x the flow, plus sprinkler valves are generaly much worse than max efficiency...

make your own valve
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Unread postAuthor: Sticky_Tape » Sat Feb 23, 2008 4:45 pm

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Unread postAuthor: Jared Haehnel » Mon Feb 25, 2008 7:25 am

Thanks for the link. I've got a design in the working right now that I think should work. 4" housing with a 3" dia piston. I'll use the sprinkler valves to actuate the piston valve.

Since I've already got them might as well use them. It will allow for remote triggering. I might back it up with ball valves if I want to use it with pressures higher then rating of the sprinkler valves

I'm planning on using 1/2 felt as the piston rings however I haven't quite figure out what I'm going to use as the seal with the seat. Probably rubber. Has any one tried cork?

The piston its self I was thinking of making out of 3" pvc or I've thought of using the blue rigid foam since its very light and not of the surfaces will be in contact with the wall or the seat it should hold up just fine. I would layer the blue board in the similar way I make my sabots. I can also make it more easily to the dimensions of the tee.

When I ran it through GGDT it was incredible to see the difference in barrel velocity and thus the projected distance.

Let me know if you have an suggestions
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Unread postAuthor: lockmanslammin » Mon Feb 25, 2008 2:04 pm

Use rubber for your seat seal. If your going to use felt for rings around the piston you should goop em' up real good with grease.

Good luck on your project... by the way good choice on going with the piston valve.
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Unread postAuthor: Jared Haehnel » Mon Feb 25, 2008 2:09 pm

Thanks lock. I'll be posting pictures once I get it done may be a couple months though.
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