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optimum barrel length

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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optimum barrel length

Unread postAuthor: brogdenlaxmiddie » Wed Jan 02, 2008 9:21 am

I was infering upon the best length for a pneumatic gun. For a gun w/ 16' of 4" pipe ( chambers (actually, its a dual chamber w/ 2x 8' sections))
, charged no more than 125 PSI, the barrel should be XXXX long? :?

so whats the best length of 2" pipe?
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 02, 2008 10:46 am

For that massive chamber volume, even if you go up to 50 feet of barrel length, performance will still be increasing, you can go up to 100 feet and still not see a drop in performance.
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Unread postAuthor: Carlman » Wed Jan 02, 2008 10:51 am

lol, 100' barrel, do it, do it, do it!
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Unread postAuthor: brogdenlaxmiddie » Wed Jan 02, 2008 11:04 am

hmmmmm sounds fun..... maybe i should try it. if i do, then it prolly would of broken a record for longest barrel... how frickin sweet would that be?..... but besides that, basically, the longer the barrel the better? What would the lenght do to the sound? im aiming at makeing the loudest damn thing i can.
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Unread postAuthor: bigbob12345 » Wed Jan 02, 2008 11:08 am

The ablolute best would be about 120ft long but there would be be hardly any difference between that and a 50ft barrel but if your looking to make noise a short barrel is the why to go
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Last edited by bigbob12345 on Wed Jan 02, 2008 11:10 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 02, 2008 11:09 am

The longer the barrel the better, until you reach a certain limit, and then power starts dropping off - in your case, the chamber is so huge that this limit is far beyond practicality, so make it as long as you can manage.

Longer barrels give the air more space to expand and lose pressure before exiting the muzzle, meaning it will be quieter. I wouldn't worry about it being silent though, with that volume and a good enough valve it will be very loud.
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Unread postAuthor: WOW!! » Wed Jan 02, 2008 12:44 pm

What type of valve(s) are you using?

For a C:B of 1:1.5 its 487.25"
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Unread postAuthor: jimmy101 » Wed Jan 02, 2008 1:10 pm

You might want to download a copy of GGDT (Gas Gun Design Tool).

Here is what I get with the default valve. The graph is barrel length on the horizontal axis and velocity on the vertical axis.

For the default valve, the optimal barrel is about 80 feet long. Shortening the barrel to just ~20' only drops the velocity by ~10%.
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Unread postAuthor: koolaidman » Wed Jan 02, 2008 7:44 pm

im not having any luck with that download. I downloaded the program and the two components into a folder then extracted the two, but its saying something is still missing in one of the components.
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Unread postAuthor: brogdenlaxmiddie » Wed Jan 02, 2008 8:29 pm

yeah i had to try it a couple of times.... did you put the extracts of the extracts into the same folder? thats what i did....
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Unread postAuthor: bigbob12345 » Wed Jan 02, 2008 9:03 pm

koolaidman wrote:im not having any luck with that download. I downloaded the program and the two components into a folder then extracted the two, but its saying something is still missing in one of the components.

Yea Im having the same problem with it.I dont now why it is happening. I followed all the instructions and I have tryed so many times I think I might just have to live without GGDT
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Unread postAuthor: tansit234 » Wed Jan 02, 2008 9:27 pm

1:2 or 1:1.5 is usually what I aim for. One of my guns is 1:3 just so I have the option of different barrels. Course its no big deal to have a bigger tank than you need. Some of my guns do fine with 1:1 and others do fine over 1:4. It depends on how scientific you want to get. I just want stuff that shoots stuff.
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Unread postAuthor: jimmy101 » Thu Jan 03, 2008 12:24 pm

To get GGDT to work you have to follow the installation instructions located at http://thehalls-in-bfe.com/GGDT/installation.html exactly.
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Unread postAuthor: koolaidman » Thu Jan 03, 2008 3:09 pm

yeah the extracts went to the same folder. i dunno i tried a good 5 times following them exactly, no luck.
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