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Another valve help topic, xD

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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Another valve help topic, xD

Unread postAuthor: nadjatee1996 » Fri Jan 21, 2011 10:52 pm

I haven't been active lately, due to finals, but hey, I'm back! After proposing my last idea, I need help yet again, incorporating JSR's valveless theory, I have a question. If my ammunition is 1CM wide, how wide does the barrel have to be to fire it? I lost the link to the valveless theory, sorry, but it goes something like this : ammunition acts as seal between barrel and air tank, when trigger is pulled back, air will literally FORCE the projectile out. Now, the part I need help with, if it literally forces it out?wouldn't that damage the barrel?
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Unread postAuthor: ilovefire » Fri Jan 21, 2011 11:06 pm

you have a barrel that has the same ID and the OD of your projectile and you use a O-ring detent to hold the bb until the desired pressure has been reached, not sure if this is the same link you looked at last time but take a look here
http://www.spudfiles.com/forums/valvele ... t8912.html
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why make it if it dosent shoot?
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Unread postAuthor: nadjatee1996 » Fri Jan 21, 2011 11:19 pm

ID?OD?O-ring detent?
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Unread postAuthor: Hotwired » Fri Jan 21, 2011 11:31 pm

Internal Diameter
Outer Diameter

The o-ring business just means an o-ring set in a groove inside the barrel which the projectile gets stuck on until the pressure behind is high enough to push it through the o-ring.

Once it's through the o-ring there's nothing stopping the projectile from being blasted down the barrel.
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Unread postAuthor: nadjatee1996 » Fri Jan 21, 2011 11:34 pm

Image
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Unread postAuthor: nadjatee1996 » Fri Jan 21, 2011 11:44 pm

Also, any recommendations for materials?
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Unread postAuthor: Gaderelguitarist » Fri Jan 21, 2011 11:57 pm

I'm not sure about your diagram. You intend the detent to be some sort of mechanical release for the bb?

The O ring detent would serve as your mechanical release, not the trigger. You could use a blowgun as your air valve, and that would simulate a trigger feel. The point is that the detent holds the bb in place while pressure builds up behind it. Once that pressure reaches a certain point, the bb is expelled through the o-ring and into the barrel. The speed of this process is dependent upon airflow rather than the cycling of mechanical pieces.
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so many muchness
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 22, 2011 12:10 am

nadjatee1996 wrote:any recommendations


Yes, Hotwired has been far too kind.

If you're asking questions like "If my ammunition is 1CM wide, how wide does the barrel have to be to fire it?" and "if it literally forces it out?wouldn't that damage the barrel?", your knowledge is still too limited to contemplate building such a project.

As recommended in your other thread, start with something less ambitious, to get familiar with the theory and operation of pneumatics, as well as the use of materials.

Have a look at this project.

It was put together by a 13 year old and the material cost him less than $20. It's a simple launcher to put together using standard parts and a bit of epoxy, and filled with a shock pump will give you very decent single shot power (or even bursts if you load it with steel or airsoft BBs.

[youtube]http://youtube.com/watch?v=f4CB7FUQX10[/youtube]
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Unread postAuthor: nadjatee1996 » Sat Jan 22, 2011 10:25 am

I know this one sounds ambitious too, but it seems easier in my mind, and I'm confident I can build it.What I meant for the detent released by the trigger was the sliding rod. Also, for the O-ring detent, wouldn't firing the gun repeatly damage the o-ring? You might not my ambitiousness JSR, but as far as I know, your the best on this site, I hope you help me out.


On a side note, all I'm missing for my really basic one shot pellet gun is the stupid shrader valve, I can't find it anywhere. (It's basically a Image with a modified muzzle and a hole on the bottom for the shrader valve
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Unread postAuthor: Gun Freak » Sat Jan 22, 2011 5:50 pm

You could get schraders at hardware stores or automotive stores. Also, I wouldn't feel comfortable putting pressure in one of those things through a schrader that is only in through a little hole with maybe some epoxy... Why don't you use a pipe nipple or something...
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Unread postAuthor: nadjatee1996 » Sat Jan 22, 2011 6:19 pm

I got a shrader now (actually two), thanks to my dad, who went to repair his car, I asked him to see if there was any there and lo, and behold, THERE WAS. Also, my ending for the Shrader is rubber, no threads, xD

I got no epoxy, super glue will have to do


Shrader valve

Image

Hole where the valve goes in

Image


Ok, I screwed up big time, the PVC pipe isn't 1 CM in diameter, its 0.6 inches(.5CM more), so I went out and bought a nice copper pipe (Yea, a few stores still open at 7:30PM), trying to figure out how to make it all fit now
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Last edited by nadjatee1996 on Sat Jan 22, 2011 7:12 pm, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Sun Jan 23, 2011 4:54 am

nadjatee1996 wrote:I got a shrader now (actually two), thanks to my dad, who went to repair his car, I asked him to see if there was any there and lo, and behold, THERE WAS. Also, my ending for the Shrader is rubber, no threads, xD


Schrader advice offered in your previous thread.

I got no epoxy, super glue will have to do


No it won't, buy some epoxy!

trying to figure out how to make it all fit now


See above ;)
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Unread postAuthor: nadjatee1996 » Sun Jan 23, 2011 11:04 am

Yea, the contact cement sucks, its not friggin' airtight

Anyone know how to say epoxy in Chinese?Or Korean?Or Japanese?

Found the epoxy, 8 bucks short, it costs eight bucks, guess how much money I have...
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Unread postAuthor: nadjatee1996 » Tue Jan 25, 2011 3:44 pm

Anyone tell me an estimation of the can's ability to hold air before exploding in my face?It's made of metal.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 4:45 pm

I wouldn't trust it much past 50 psi
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