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Piston in a Cross cannon

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Piston in a Cross cannon

Unread postAuthor: jhalek90 » Sat Sep 12, 2009 10:50 am

So heres what I got:
Barrel .5'' or 1''
chambers: APROX (1''x16'') each
Piston valve housed in a cross piece.... works juts like a t
Pilot... modded 1'' sprinkler valve.

This gun was clocked at 1200 FPS with my homeade chrony
http://www.spudfiles.com/forums/home-ma ... 19209.html


The barrel support is not prensent in the photos because i am currently designing a breech for it.

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Unread postAuthor: maverik94 » Sat Sep 12, 2009 11:43 am

Looks kinda weird, not very gun-like, but whatever floats youre boat right? I'm not a huge fan of pvc cannons, I prefer all metal canons, but it's not my choice.
what pressures and projectiles are you using? Also, I think your chrony might be messed up, 1200 fps in a pvc gun? I highly doubt it. Also, you claimed this gun could go .5 miles? Ehhhh, I must say I don't believe that.
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Last edited by maverik94 on Sat Sep 12, 2009 11:56 am, edited 1 time in total.
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Unread postAuthor: jook13 » Sat Sep 12, 2009 11:53 am

Its an interesting design, and I like the idea of a piston housed in a cross like that.

I am not seeing faster than speed of sound performance with a barrel that short, a pilot volume that large, and the low pressures you should be using with pvc. I think your homemade chrony needs some serious tweeking with a speed of 1200 fps.
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Unread postAuthor: mobile chernobyl » Sat Sep 12, 2009 11:55 am

Odd design for using a cross, do you use it to shot straight up? looks like the reservoir's would be used for the feet. Your pilot region is unnecessarily large as well, but if your using it to shoot straight up I can understand the extra ducting needed.

And 1200 FPS? might want to re-calibrate your chrony... that's a good number if your lucky with a metal or hybrid cannon...
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 12, 2009 12:13 pm

Looks like something out of star wars :)

1,200 fps with all the factors jook mentioned is highly unlikely at best, I would concur that your chrony's accuracy should be called into question.
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Unread postAuthor: jhalek90 » Sat Sep 12, 2009 12:31 pm

The 1200FPS reading needs further testing.... but bear in mind that the barrel i used for that test was WAY longer. probably around 5'
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Unread postAuthor: Technician1002 » Sat Sep 12, 2009 12:47 pm

jackssmirkingrevenge wrote:Looks like something out of star wars :)

1,200 fps with all the factors jook mentioned is highly unlikely at best, I would concur that your chrony's accuracy should be called into question.


I would just question the projectile weight. It may be possible with a Styrofoam plug. Anything more massive would be called into question.

Starwars didn't come to mind, a plastic low pressure version of the decimator with the sides rotated came to mind.
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Unread postAuthor: jackssmirkingrevenge » Sat Sep 12, 2009 2:45 pm

Technician1002 wrote:I would just question the projectile weight. It may be possible with a Styrofoam plug. Anything more massive would be called into question.


In the case of such a projectile, it would lose velocity very rapidly after exiting the barrel so the chrony would have to be practically at the muzzle, prone to blast interference.
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Unread postAuthor: jrrdw » Sat Sep 12, 2009 3:04 pm

I'm glad to see someone else getting into duel chamber design!!! Good start :wink: .
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Unread postAuthor: MrCrowley » Sat Sep 12, 2009 5:10 pm

Not the most efficient or powerful design you could've made out of those materials, but if it works and you're happy with it it's fine I guess :)

If you are interested in more power; a smaller pilot volume, a chamber that doesn't have to go through so many bends and twists and that longer barrel would help :)
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Unread postAuthor: mobile chernobyl » Sat Sep 12, 2009 11:30 pm

a 5' barrel is still not long enough, and certainly doesn't seem "WAY longer".

Also where do you live? I'm only asking because it seems as if you live in "under better than ideal conditions"-land because all of your results from your guns seem far superior to what other's on here can produce, some with arguably better built cannons with similar dimensions.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 13, 2009 4:15 am

jrrdw wrote:I'm glad to see someone else getting into duel chamber design!!! Good start :wink: .


Do you think they would be more effective than pistols at dawn:D

Actually the image of two gentlemen beating the living daylights out of eachother with sealed PVC tubes is most amusing :)
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Unread postAuthor: jhalek90 » Sun Sep 13, 2009 9:51 am

Technician1002 wrote:Starwars didn't come to mind, a plastic low pressure version of the decimator with the sides rotated came to mind.

Actually, I saw the decimator as the glue on this valve was drying... haha I thought i was being sorta original. But i guess not.

So, MrC Why would the air chambers be more efficient if i used an elbow... like most non-coaxial piston cannon, instead of the T i used now?
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Unread postAuthor: Ragnarok » Sun Sep 13, 2009 10:58 am

jackssmirkingrevenge wrote:Actually the image of two gentlemen beating the living daylights out of each other with sealed PVC tubes is most amusing.

Me and my various siblings once cut a bike inner tube into sections, filled each with water and set about hitting each other with those.

Much to our surprise, they didn't break. Consequently, much bruising was received by all the parties involved.
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Unread postAuthor: MrCrowley » Sun Sep 13, 2009 5:49 pm

So, MrC Why would the air chambers be more efficient if i used an elbow... like most non-coaxial piston cannon, instead of the T i used now?


When you open the valve, air has to travel both down and up from your 2 side chambers, then the air has to turn 90 degrees through that tee and then another 90 degrees through the cross in to the barrel, just means there's a lot of air turbulence and the air wont escape from the chamber and in to the barrel as fast.
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