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Valveless launcher

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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Valveless launcher

Unread postAuthor: POLAND_SPUD » Sat Jun 05, 2010 6:18 am

Most of you are familiar with the concept of the valveless launcher...
Theoretically it can offer the best performance (similar to that of a burst disk gun) but the idea hasn't been thoroughly testes

Here is my design that I am going to build... I am mostly worried about feeding and avoiding double feds... I know it can be a problem but instead of using any elaborate mechanism I want to build the simplest gun first. The theory is pretty sound (I hope):

As soon as the valve is actuated air flows to the chamebr filled with ammo and one round reaches the o-ring detent where it forms an air tight seal
When the pressure reaches ~300 psi the pressure acting on the BB pushes it through the detent....
As a result of this the pressure inside the chamber drops but at the same time another BB gets stuck at the o-ring detent and it stays there until the pressure reaches 300 psi... at that point the whole cycle repeats


any ideas? suggestions? questions ?
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Unread postAuthor: jrrdw » Sat Jun 05, 2010 6:29 am

I can see the o-ring wearing out or getting damaged very fast. To hold back high pressure it will have to be mostly in the barrel with very little surface being in a holding groove.

Maybe a sealing sabot held by a check ball or two being spring loaded. Use a screw behind the spring for adjustability in the power range.
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Unread postAuthor: Crna Legija » Sat Jun 05, 2010 7:07 am

i think it will be hard getting the bb to pop out at 300psi without adjustable dent
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Unread postAuthor: jhalek90 » Sat Jun 05, 2010 8:23 am

Well, i tried with with a vortex BBMG, and seeing as what you have is BASICALLY a cloud bbmg let me offer some advise.

1. It does indeed work.
2. you will burn through o-rings every few hundred shots.
3. a simple adjustable detent is easy to make with a spring a bolt an airsoft bb and a tight bore barrel. (if you want a diagram just ask.)


I say go for it... all my tests were at about 50 psi with 6mm bbs and a HPA tank. Very fast ROF about half of a non-detent-ed BBMG.

I am interested to see what a 300psi valveless launcher preforms like. haha
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POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: clemsonguy1125 » Sat Jun 05, 2010 8:54 am

What about replacing the oring with aquarium tubing, thats what JSR did on his CO2 inflator pistol prototype, the bbs were going through at 200psi if I remember right.
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Unread postAuthor: deathbyDWV » Sat Jun 05, 2010 9:34 am

It already looks good to me. My only suggestion would be something so the o-ring doesn't wear out so fast. Maybe aquarium tubing like Clemson said...



Oh btw... Technically, this gun still has a valve... :lol:
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Unread postAuthor: Gun Freak » Sat Jun 05, 2010 9:41 am

deathbyDWV wrote:Oh btw... Technically, this gun still has a valve... :lol:


And I don't understand why it has to be a three way, can't it just be a blowgun or a spring loaded ball valve? Isn't the air just being wasted when the valve is in the closed position?
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Unread postAuthor: jackssmirkingrevenge » Sat Jun 05, 2010 10:31 am

Finally he sees the light :)

Essentially it's what I did here, no double feed problems - though projectile size and weight coupled with valve flow might cause feeding issues without the benefit of a vortex block to agitate the BBs in an guided fashion - what ammunition were you planning on?

A simple o-ring detent is not going to give you much in the way of adjustability, I had a number of projects where seal was so tight that the projectile wouldn't "pop" even at 850 psi, so I would recommend an o-ring for sealing but also a ball detent to adjust firing pressure.
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Unread postAuthor: POLAND_SPUD » Sat Jun 05, 2010 10:52 am

And I don't understand why it has to be a three way
I think it will increase safety.. after each burst the gun won't be left pressurised but instead the 3 way will vent it

what ammunition were you planning on?

either 4.5, 5.5 or 6 mm bbs
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Unread postAuthor: Lockednloaded » Sat Jun 05, 2010 12:19 pm

I saw a diagram earlier IIRC it was jsr's, but basically it was a piece of hose running through a compression tee and on the top side of the tee is a fill valve/regulator. This way you can adjust the detent by adding air pressure in the tee. I have never seen it work, but the concept seems sound
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Unread postAuthor: jackssmirkingrevenge » Sat Jun 05, 2010 12:36 pm

POLAND_SPUD wrote:either 4.5, 5.5 or 6 mm bbs


I would recommend going for a smaller calibre the higher ROF you want to achieve, think "braaaap" 7.62mm minigun versus "dakka dakk dakka" 20mm cannon :)

I saw a diagram earlier IIRC it was jsr's


Actually, it wasJimmy's.

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Unread postAuthor: deathbyDWV » Sat Jun 05, 2010 1:55 pm

Ok I now understand why you would use the three way valve. I wasn't getting that but good idea...
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Unread postAuthor: Crna Legija » Mon Jun 07, 2010 7:55 am

you could put a hose clamp over the aquarium tubing to get adjustblity that you need.
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Unread postAuthor: POLAND_SPUD » Mon Jun 07, 2010 10:15 am

the o-ring seal is adjustable... I have a sort of compression fitting adapted from a tap head/bonnet...
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Unread postAuthor: kozak6 » Wed Jun 09, 2010 2:11 am

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