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A valveless pneumatic?

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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A valveless pneumatic?

Unread postAuthor: High-PSI » Fri Oct 15, 2010 5:30 am

Hey Guys,

I was thinking........ In my 2" gun discussion, we got into CV values and the benefits of fast acting valves versus high flow valves and I got to thinking and came up with a couple ideas;

#1 What about a totally valveless system? Picture a common combustion cannon layout (but not used as a combustion cannon) using an O-ringed projectile similar to the UHMW slugs. This O-ringed slug would be, in effect, the piston of an air valve. The slug would be slid down the barrel and latched in place with some sort of extremely beefy latching system (obviously air tight system) to hold the slug in place. Air up the tank and release the slug. There would be no flow restriction what-so-ever and there would be no valve opening delay at all. The latch could be released by way of a pneumatic ram. Latch release time is really not important because the slug would not start moving untill the latch is completely unlatched. Does this sound crazy?

#2 The other option is to use a pneumatically released ball valve, but, in the interest of delaying slug movement to allow more time for the ball valve to open, the slug could be a very tight fit in the back of the barrel. Perhaps tight enough to withstand maybe 50psi or so. That way the ball valve would begin opening, but the slug would delay its journey just long enough for the valve to open further (all the way?). This would, in effect, decrease barrel length required for a given FPS due to having much more pressure acting on the slug before it begins moving. Either that, or more velocity for a given barrel length. Oh, the slug would only fit tightly into the rear most portion of the barrel. The fit would loosten as the slug moves forward slighly to reduce drag in the barrel.

Thoughts?

Matt
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Unread postAuthor: Crna Legija » Fri Oct 15, 2010 5:57 am

jsr and POLAND_SPUD have played around with the idea in full out for a while now
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 15, 2010 6:20 am

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Unread postAuthor: ThornsofTime » Fri Oct 15, 2010 6:26 am

My take on the whole thing.

You got me designing in paint again lol
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 15, 2010 6:31 am

ThornsofTime wrote:My take on the whole thing.


Ah, but is the servo pressure rated ;)

For a single shot launcher, amechanical latch would be a lot easier to make ;)
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Unread postAuthor: ThornsofTime » Fri Oct 15, 2010 7:29 am

@JSR- lol guess you beat me to the punch huh... I was working paint and then posted with out hitting your links :( oh well... great minds think alike i guess. Yes I agree that your mechanical latch idea would be better, however I think that you would be replacing that o-ring that seals the bb quite often, as bbs usually have pits in them that would be rough on that kind of seal.

Basically... I like your latch, but my ammo w/O-ring. Would make ammo a pain in the ass im aware, but larger caliber is nice... and the ammo would look cool as hell and have much more oompf.
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 15, 2010 7:41 am

ThornsofTime wrote:JSR- lol guess you beat me to the punch huh...


Welcome to spudfiles :)

larger caliber is nice... and the ammo would look cool as hell and have much more oompf.


To be honest I don't know why someone hasn't tried one of the USG rounds in a valveless setup, if only I had the downrange space :roll:
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Unread postAuthor: ThornsofTime » Fri Oct 15, 2010 7:45 am

lol @ ready-made ammo. not cheap... but thats bad ass. Makes me want to make some of those rounds in a smaller caliber with some FAT O-rings and a rifled barrel. I wonder how accurate they could be...
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Unread postAuthor: Technician1002 » Fri Oct 15, 2010 10:05 am

:roll: A QDV with the piston pushed forward does this. I launched the piston out of my ABS cannon once. My newer cannons have mechanical limits to prevent it.
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Unread postAuthor: POLAND_SPUD » Fri Oct 15, 2010 10:10 am

For a single shot launcher, a mechanical latch would be a lot easier to make
I know some of you knew I'd mention this but... have you considered using an air cylinder ??


In this design the air cylinder can act as both the loading mechanism and the firing mechanism
Image

1. First the air cylinder retracts and takes one round from the magazine
2. Then it extends almost all the way and the round seals
3. The air cylinder extends all the way out when air is released from the other side of it. The gun fires and the air cylinder starts to retract
4. The whole cycle starts from the very beginning

I can draw a diagram of the complete gun if you're interested
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 15, 2010 10:35 am

POLAND_SPUD wrote:have you considered using an air cylinder?


What about the air ram operating a detent in this sort of setup:

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Unread postAuthor: Technician1002 » Fri Oct 15, 2010 11:07 am

A dual detent will be needed for single fire.
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Unread postAuthor: SpudFarm » Fri Oct 15, 2010 11:50 am

Wouldn't a burst disk have just about exactly the same specs if looking away from loading time?

It's easier to make a quick changing system for a burst disk then making something that has to load, seal and hold the projectile in place.

A big sheet of burst disk material that is clamped between a flange setup controlled by some powerful servos.
Just open, move the disk material and close to fire another shot.

Just the first thing that came to my mind when reading this, seems to "complex" to be a practical way of firing, you will also need fairly precisely made projectiles that easily overtakes the price of burst disk material in any larger caliber then 6mm (Perhaps 8mm BBs).

(Sorry if this has been said before, there is to much discussion on the matter to read through it all without any particular interest on the topic)
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Unread postAuthor: POLAND_SPUD » Fri Oct 15, 2010 4:33 pm

@JSR
naah that isn't the best design... sure it might work but it's a lot better idea to use the air cylinder like in your design that I posted... damn you can have ejecting shells !! YAY!!

Well not to mention that it just needs an aircylinder to both load the ammo and send it down the barrel
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Unread postAuthor: POLAND_SPUD » Mon Oct 18, 2010 4:23 am

Now that I think of it... I'll have to test the detent and the loading mech for the POLSKA_HYBRYDA :wink: (BTW thx for inventing the name) so I might as well test this too
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