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How did he build this?

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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How did he build this?

Unread postAuthor: Live1nce » Mon Jul 23, 2012 11:52 pm

Just was browsing through the internet, and happened to run into this

http://www.arniesairsoft.co.uk/?filnavn ... custom.htm

Does anyone have any idea how he built this? If you look closely at the back of the cannon, it looks like he has done a bit of lathe work if i'm not mistaken. Looks like some kind of custom coaxial or toolies piston design. I would really like to build something nice and sleek like this one.
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Unread postAuthor: Zorlord » Tue Jul 24, 2012 12:13 am

That's essentially what im trying to create with my m72, just not as "milsim". What i came up with is a linear design using a toolies piston. What he probably did was the same thing, except housed everything in 2.5 or 3" pipe and then stuck that into the body of the at4. On the back it looks like it could be the very end of a male 1/4 quick connect, so he may have that connected to a tube and then that to a blowgun. As far as air supply goes perhaps there's another connection we cannot see due to the angle that would connected to a tank that's housed in the back of the at4 shell.
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Unread postAuthor: Live1nce » Tue Jul 24, 2012 11:02 am

http://www.arniesairsoft.co.uk/projects ... vX.MP3.avi

Judging by the sound of it in this video, it sounds like there is a port releasing air before it shoots. I wish i knew how the AT4 Firing mechanics worked. Does the push button system run all the way to the back of the tube, because the port release valve has to be located in the back somewhere.
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Unread postAuthor: Zorlord » Tue Jul 24, 2012 12:11 pm

Also, if they didnt build it like a spud gun, what a lot of airsofters do is mount a airsoft m203 round into the back and then it's possible to unthread the fill valve and hook up a hpa tank directly into the shell, so the only thing you have to do is reset the pin in the back of the valve to fire another round
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 24, 2012 12:22 pm

Zorlord wrote:Also, if they didnt build it like a spud gun, what a lot of airsofters do is mount a airsoft m203 round into the back and then it's possible to unthread the fill valve and hook up a hpa tank directly into the shell, so the only thing you have to do is reset the pin in the back of the valve to fire another round


http://www.crewchiefpb.com/main/index.p ... 4&Itemid=1
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Unread postAuthor: Zorlord » Tue Jul 24, 2012 12:33 pm

jackssmirkingrevenge wrote:
Zorlord wrote:Also, if they didnt build it like a spud gun, what a lot of airsofters do is mount a airsoft m203 round into the back and then it's possible to unthread the fill valve and hook up a hpa tank directly into the shell, so the only thing you have to do is reset the pin in the back of the valve to fire another round


http://www.crewchiefpb.com/main/index.p ... 4&Itemid=1


Essentially that, thanks. i knew I saw it somewhere before! haha. The only hassle with this design is that there are only one or two m203 shells that you can use that can hold enough pressure to shoot the rocket (madbull and sthunder i believe are the brands). Also, the m203's tend to fail after a couple rounds, and need to re-assembled/reset. They blow orings and lose ball bearings like it's their job.
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Unread postAuthor: ramses » Tue Jul 24, 2012 6:57 pm

I can think of 2 ways, but is probably the "clide style" one.

Clide Style:
+ better flow
+ more streamlined
+ no solder/braze/epoxy
+more serviceable
-heavy piston
-must run pilot line to the back (mechanical or large pilot volume in hose)
-probably needs floating o ring check valve
-piston needs additional stabilization (a la coaxial barrel support type thing (not shown)



D_hall style
+ light piston
+no piston seal necessary
+pilot port near trigger area
+ easy to ghetto rig with epoxy
- not really servicable (without going to great lengths)
-hole in chamber wall
- marginally less flow



With high pressure (300 psi + maybe, a standard tee valve could be used used along with a smaller chamber, allowing a longer barrel and therefore higher velocity at a given maximum acceleration.
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Unread postAuthor: Technician1002 » Tue Jul 24, 2012 9:28 pm

They have no muzzle end photos. It is possible it is a coax design like my Mouse Musket.
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Unread postAuthor: MrCrowley » Tue Jul 24, 2012 11:09 pm

ramses wrote:D_hall style
+ light piston
+no piston seal necessary
+pilot port near trigger area
+ easy to ghetto rig with epoxy
- not really servicable (without going to great lengths)
-hole in chamber wall
- marginally less flow

Did D_Hall make a valve like that? I remember I drew up a very similar design years ago; always wanted to know if someone had ever tried it.
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Unread postAuthor: Technician1002 » Tue Jul 24, 2012 11:20 pm

I was just looking closely at this picture; Direct links to photo prohibited.
http://www.arniesairsoft.co.uk/projects ... /at4-l.jpg
It looks to be a coax design since he mentioned a piston. There is room for a piston in the breech and the chamber does not go quite the full length of the barrel.
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Unread postAuthor: ramses » Thu Jul 26, 2012 10:04 pm

MrCrowley wrote:
ramses wrote:D_hall style
+ light piston
+no piston seal necessary
+pilot port near trigger area
+ easy to ghetto rig with epoxy
- not really servicable (without going to great lengths)
-hole in chamber wall
- marginally less flow

Did D_Hall make a valve like that? I remember I drew up a very similar design years ago; always wanted to know if someone had ever tried it.


Yeah (sort of). He made that pneubmatic canon that he shot the watermelon in HD, >5000 fps video. I was hoping JSR would provide a link, since I didn't feel like searching.

I think he had a conventional tee valve, but ran the pilot line through the chamber for ergonomics/aesthetics.
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 26, 2012 11:50 pm

ramses wrote:Yeah (sort of). He made that pneubmatic canon that he shot the watermelon in HD, >5000 fps video. I was hoping JSR would provide a link, since I didn't feel like searching.

I think he had a conventional tee valve, but ran the pilot line through the chamber for ergonomics/aesthetics.


Fine, yeesh. http://www.spudfiles.com/forums/john-daly-t20239.html
Did D_Hall make a valve like that?


No.

I remember I drew up a very similar design years ago; always wanted to know if someone had ever tried it.


You did: http://www.spudfiles.com/forums/linear- ... 14957.html
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Unread postAuthor: Live1nce » Fri Jul 27, 2012 2:40 am

I really like that mouse musket design! :)
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Unread postAuthor: ramses » Fri Jul 27, 2012 11:28 am

Live1nce wrote:I really like that mouse musket design! :)


The issue is, depending on how big of a barrel you want, (diameter), you will have a fairly small chamber volume with restricted flow due to a tube-shaped column of air. Also, some part of the barrel (even if it is reduced to ~1" diameter) must go all the way to the back of the launcher, adding dead volume and using chamber space.

what I called the "D_hall style" valve (sorry, MrCrowley) has the issue of a few hundred pounds of force acting on the piston slide assembly trying to push it away from the barrel. It can be supported, but this reduces flow.
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