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High pressure piston valve

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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Unread postAuthor: jackssmirkingrevenge » Thu Nov 15, 2007 3:24 am

looking good, apart for the tortuous pilot volume route.
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Unread postAuthor: rna_duelers » Thu Nov 15, 2007 4:01 am

2nd that with jack,that pilot valve route is huge and in-efficient why not go for a ball valve like said before and have the fill point and pilot in one unit.
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Unread postAuthor: daccel » Thu Nov 15, 2007 4:20 am

Twitch, I appreciate the concern, but I don't see the problem with using fittings and valves under the rated pressure. What failed on yours, did the pipe burst or threads strip out? I want to make this safe, so if you see a weak spot by all means suggest how I can imrove it, but frankly, if no one pushed the envelope we would still all be using pvc ball valve cannons at 120psi. Not that there's anything wrong with those, that was my first cannon.

Jack, it's never small enough is it :roll: :). I may be able to connect the pw valve directly to the tee and figure out a trigger mechanism so the handle stays where it is, or directly to the bushing and fill backwards through the pw valve - that's probably the best way, eh?

edit: Sorry rna, didn't see your post. I don't want to use a ball valve because it will ruin the ergonomics. But hopefully I can pull out the pw valve and remote trigger it from the original handle. Point taken on efficiency.
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Last edited by daccel on Thu Nov 15, 2007 4:32 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 15, 2007 4:23 am

Jack, it's never small enough is it


You're making the effort to build with high spec materials for use at high pressure, why settle for a mediocre design? Also, don't forget that the air escaping through the pilot is going to be loud in its own right, so even for your ears' sake it should be as little volume as possible.
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Unread postAuthor: spanerman » Thu Nov 15, 2007 5:20 am

looking good...but the pilot volum is huge compared to the chamber.....cut it downcan you fill/pilot with the PW handle? like have a fill valve on the back of the handle?
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Unread postAuthor: TwitchTheAussie » Thu Nov 15, 2007 7:30 am

daccel wrote:Twitch, I appreciate the concern, but I don't see the problem with using fittings and valves under the rated pressure. What failed on yours, did the pipe burst or threads strip out?


One word; Recoil.
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Unread postAuthor: chaos » Thu Nov 15, 2007 7:57 am

jackssmirkingrevenge wrote:Also, don't forget that the air escaping through the pilot is going to be loud in its own right, so even for your ears' sake it should be as little volume as possible.


this would be probably worth looking into in that perspective, i also would imagine that pressure even in a small volume would be deafening: SMC pneumatics Exhaust Muffler
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 15, 2007 8:03 am

I think it's better exhausing into an expansion chamber (maybe into the silencer itself) than through a muffler, as the latter might impede flow and reduce performance.
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Unread postAuthor: Brian the brain » Thu Nov 15, 2007 1:35 pm

1500 psi is what I call overkill...It will generate so much power you won;t know what to do with it.
Forget about handheld anyway.
My cannon ( currently disassembled) was so powerful, nothing I shot out could be seen.( at 2" that is)

I used a pretty short barrel, so I could have increased power by using a longer one.
I used 23 bar .( 21 bar is about 300 psi)
At 9 bar I could shoot a spud through plywood...


I predict 1500 psi will be scary! I mean..just scary...not fun ánd scary.

My cannon was more fear than fun, wich is why I only showed peple shots up to 9 bar.
Good luck, I doubt you will shoot it much..
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Ragnarok » Thu Nov 15, 2007 1:56 pm

I have a similar situation, ammo becomes next to invisible when you are firing at higher pressures.

It's still fun, but you are slightly on edge before the shot in case of a ricochet or other problems. You can have great fun with only 30 psi or so - combustions manage with only about that.
300 psi is very powerful, and although there's still fun in it, the subconscious concerns can take something out of the experience, so a lot of the time, I use under half that, possibly even down to a tenth (HEAL can operate down below 1 bar, but 30 psi is more reliable).

Less destructive, but also less work (quicker to fill), less worrying, and more than enough to enjoy yourself. And you might stand a chance of seeing a blur in the air when you fire into the distance - at 300 psi, all you get is recoil.

300 psi I can enjoy, fifteen hundred I would be standing well back from.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Brian the brain » Thu Nov 15, 2007 2:14 pm

Not that you shouldn't try...I'm busy building a 900 psi strafer...so..

Just remember, more pressure doesn't neccesarily mean more fun.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 15, 2007 2:19 pm

Agreed with the above, for large bores (over 0.75"), typical compressor pressures of 150 psi or so provide more than enough power if you have a good valve and long enough barrel.

High pressures come into their own really when you're dealing with small calibre (BB, airsoft etc.) launchers - still, doesn't mean I don't want to see videos of daccel's prototype in action :D
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Unread postAuthor: spanerman » Thu Nov 15, 2007 2:42 pm

naaa, high pressur/large bore..is the future.....like DYI's triggers burst dicks......
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 15, 2007 2:52 pm

spanerman wrote:naaa, high pressur/large bore..is the future.....like DYI's triggers burst dicks......


That implies bulky, heavy, noisy and hard to refill - I think we'll see more high pressure one-offs but PVC will still the the king of spudding ;)
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Unread postAuthor: Solar » Thu Nov 15, 2007 3:39 pm

High pressure is great for reducing the size of your expansion chamber for force equal to lower pressures with high volume. High volume with high pressures does get interesting quickly. The current operating pressure of my launcher is 300psi with the limiting factor being the trigger valve rating. The main firing valve is rated to 1200psi with the limiting factor there being the o-rings. REMEMBER THIS FACT!!!! : High pressure air alone can cause death from brain embolisms. DO NOT have any exhaust port for high pressure air placed where it could come into contact or even within direct line of your skin. Air will pass directly through your skin and into the blood stream at those pressures.
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