chamber volume question

[ilovefire]

sorry if this is a bit of an annoying question but i am making a coax with a 5mm bore and 50cm barrel and want to know what would be a good chamber volume be for say a max of 400psi and maybe a min of 300psi, i would like power but i only have a shock pump so ill need to take that into consideration
thanks

[MrCrowley]

Probably something as small as a 20mm tube 100mm long would suffice. I would GGDT it, but I'm busy at the moment. Perhaps you can try GGDT it yourself?

P.S - GGDT (gas gun design tool) is a tool developed by D_Hall (a member on spudfiles) to model guns in the designing stage to see how they would perform in real life. Check the Spudwiki for more info or google "GGDT" and check out his website (complete with FAQ section and such).

[ilovefire]

Probably something as small as a 20mm tube 100mm long would suffice. I would GGDT it, but I'm busy at the moment. Perhaps you can try GGDT it yourself?

P.S - GGDT (gas gun design tool) is a tool developed by D_Hall (a member on spudfiles) to model guns in the designing stage to see how they would perform in real life. Check the Spudwiki for more info or google "GGDT" and check out his website (complete with FAQ section and such).

thank you for your help, i did look into it a bit but dose it work on a mac?

edit: sorry sould have looked before i posted, found the answer

[MrCrowley]

Hmm doesn't seem that way:

Are you ever gonna release a version for the Macintosh?
No. GGDT is a hobby; nothing more. I have made exactly zero dollars and zero cents for all the work I've put into it. With motivation like that, I don't see the point in buying a new computer just so I can do the port and make a few folks happy. What you CAN do, however, is run a Windows emulator on your Macintosh. There's a free one called "Guest PC." Feel free to download it.

Running a few rough coaxial piston valved launchers in GGDT using your barrel, 400PSI, a 20mmx100mm chamber, 2cm piston and an air rifle pellet I get about 285m/s, if you double the chamber size you get a few extra m/s in performance. From a rough calculation, a chamber 20mmx100mm seems fairly effecient.

[ilovefire]

Hmm doesn't seem that way:

Are you ever gonna release a version for the Macintosh?
No. GGDT is a hobby; nothing more. I have made exactly zero dollars and zero cents for all the work I've put into it. With motivation like that, I don't see the point in buying a new computer just so I can do the port and make a few folks happy. What you CAN do, however, is run a Windows emulator on your Macintosh. There's a free one called "Guest PC." Feel free to download it.

Running a few rough coaxial piston valved launchers in GGDT using your barrel, 400PSI, a 20mmx100mm chamber, 2cm piston and an air rifle pellet I get about 285m/s, if you double the chamber size you get a few extra m/s in performance. From a rough calculation, a chamber 20mmx100mm seems fairly effecient.

thank you very much for your help and patience you have helped me alot

[MrCrowley]

For aesthetic or ergonomic reasons you may make the chamber bigger or longer or both, just letting you know that a chamber only 20mmx100mm big, is big enough to get some pretty decent performance.
If you doubled the barrel length but kept everything else the same, you could get around 330m/s (though take this with a grain of salt as I believe GGDT can run in to a few problems around the 'subsonic approaching supersonic' area). No doubt you'll see a huge increase in performance over the 50cm barrel though.

[ilovefire]

For aesthetic or ergonomic reasons you may make the chamber bigger or longer or both, just letting you know that a chamber only 20mmx100mm big, is big enough to get some pretty decent performance.
If you doubled the barrel length but kept everything else the same, you could get around 330m/s (though take this with a grain of salt as I believe GGDT can run in to a few problems around the 'subsonic approaching supersonic' area). No doubt you'll see a huge increase in performance over the 50cm barrel though.

you have just answered some of the other questions that i had without me even having to ask them, you dont know just how grateful i am that there is someone willing to go out of there way to help a stranger
thank you

[MrCrowley]

you dont know just how grateful i am that there is someone willing to go out of there way to help a stranger

I don't mind helping out someone from across the ditch, you aussies need all the help you can get

[Crna Legija]

Only if you would run for PM

[ilovefire]

Only if you would run for PM

yea that whole thing is a mess, glad i dont have to vote

oh and would a 10mm x 450mm chamber be able to get me that 280m/s?
thanks, it would be a great help

[chinnerz]

Only if you would run for PM

Made me lol


Any ways isn't the rule for chamber volume no less then half or more than double the barrel volume?? Could have sworn that was the rule :/

[ilovefire]

Any ways isn't the rule for chamber volume no less then half or more than double the barrel volume?? Could have sworn that was the rule :/

i once used my pen gun to shoot a ball bearing of of 5mm x 900mm barrel a 400psi mind you it probly didnt have any major power but it went pretty far

[MrCrowley]

oh and would a 10mm x 450mm chamber be able to get me that 280m/s?
thanks, it would be a great help

Yup, GGDT says so.