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making a mini pneumatic

Posted: Thu Sep 13, 2007 8:13 am
by f.c
ive started designing a mini pneumatic but theres some trouble ggdt shows errors when i input the info so can someone please tell me if this gun will work well.


1 inch chamber which is 6 inches long.
3/4 (15 mm ?) barrel which is 12 inches long.
and a ball valve.

im planning to use this gun at around 80 psi so will it be powerfulish for its size ?

Posted: Thu Sep 13, 2007 8:39 am
by jackssmirkingrevenge
im planning to use this gun at around 80 psi so will it be powerfulish for its size ?
It's tiny, it has an inefficient valve and you're planning relatively low pressure - in short, not really. What kind of power are you expecting?

Posted: Thu Sep 13, 2007 8:51 am
by f.c
using it for mock paint ball wars. and shooting m and m's at stuff. how could i improve it. ( instead of changing valves as other valves can be bulky.)

id be happy to increase the barrel and or chamber length.

im also thinking of upping it to 100 psi.

Posted: Thu Sep 13, 2007 8:55 am
by jackssmirkingrevenge
be happy to increase the barrel and or chamber length.
It's a simple as that, if you want to keep the same valve then your options to increase power are longer barrel, larger chamber and more pressure - increase those parameters to the most you're willing to live with.

Posted: Thu Sep 13, 2007 8:58 am
by f.c
ggdt says i can get over 100 fps with the gun. im thinking of incorporating a burst disk also. what valve is a ball valve in ggdt. and what is the best ratio for a pneumatic.

Posted: Thu Sep 13, 2007 9:08 am
by jackssmirkingrevenge
You can't realistically model a ball valve in GGDT because you cannot predict how fast you're going to open it.

A burst disk would be very beneficial for power though.

Posted: Thu Sep 13, 2007 11:36 am
by spud yeti
Yeah, I would definitely use a burst disk valve, or a coaxial piston valve.

Posted: Thu Sep 13, 2007 11:48 am
by Fnord
Er.. sprinkler valve? It would be easier than all of the above.
If you want to keep the speed below 250fps you might not even need to mod it.

Also, you can't expect to hit anything more than 20ft away when twisting a ball valve.

Posted: Thu Sep 13, 2007 11:51 am
by spud yeti
If you want to keep the speed below 250fps you might not even need to mod it.
Or just keep low pressures and/or low volume chamber. Good idea though

Posted: Thu Sep 13, 2007 3:48 pm
by f.c
i need to keep the cost of it ultra low also as i plan on mass production.

spring powered ball valve and a burst disk.

Posted: Fri Sep 14, 2007 2:10 am
by Pyro Ninja
I say a 25mm sprinkler valve, only $22.60 at bunnings........my 15mm ball valve cost $13.......but yeah go for a sprinkler valve, they are pretty good, and no movement when opening...

But if you still want to make a ballvalve gun...theres one

Posted: Fri Sep 14, 2007 2:18 am
by mtronic
and shooting m and m's at stuff.
NOOOOOOOOO oh the humanity....poor little m&ms lol

Good luck with the cannon, as others have said maybe a sprinkler valve would be best because your gonna need to be able to shoot with accuracy if you are going to pb with it. Ball valves are hell inaccurate :( I used to use one, but won't ever go back to using them.

Its up to you though.

Posted: Fri Sep 14, 2007 2:26 am
by Novacastrian
I have never used a ball valve as a trigger, nor will i.
They suck dogs balls :lol:

Edit: That sounded a bit harsh, oh well.

Posted: Fri Sep 14, 2007 4:17 am
by Hubb
and shooting m and m's at stuff.
Yeah, I can just picture the little red guy flying through the air and smacking his pretty little face against a wooden fence or something.

Posted: Fri Sep 14, 2007 7:34 am
by f.c
ive modified the ball valve so it turns so easily it is not funny. im using 1 meter of 25mm pipe for chamber and 1 meter of 15 mm for barrel. is this ratio ok ?