SpudFiles

Just a thought:

It seems like you could buy a 1/4" QEV for a lot less than a 1" QEV. But a 1/4" valve doesn't help if you have a 1" barrel. (just looking at mcmaster, a 1/4" QEV is $10 cheaper than a 3/4" QEV)

Ball valves are much cheaper than QEVs, but they're slow, and spring loading only gets you so far. They do have the most ideal flow, though; no right angles or turbulence.

Why not combine the best of both worlds? Making a small, single acting piston doesn't seem too hard. A 1/4" QEV should flow enough to move a small piston enough to open a ball valve. No need to reset any springs.

I admit it's a little cumbersome or unnecessary, but it's just a thought, and I hadn't seen it done before.

I wonder what the theoretical fastest opening time for a ball valve is.

It's been done before, can't find the bloody link but I remember the cannon was a horrid shade of blue.

Why stop there, have a double acting cylinder and a three way ball valve et voila, semi/full auto!

You certainly could use a 3-way ball valve to do fill/fire. Semi-auto with a 1" barrel does sound pretty interesting, although it would use up so much air...

It would be interesting to find out what chamber, barrel, and pressure results in launching a tennis ball at reasonable serving speed, and the highest-flow regulator you can get (maybe multiple in parallel)...intense tennis practice anyone?

aEx155 wrote:You certainly could use a 3-way ball valve to do fill/fire. Semi-auto with a 1" barrel does sound pretty interesting, although it would use up so much air...

In theory with a three way valve, the inner volume of the ball valve itself could be the "chamber"... if you're using high pressure this would still result in worthwhile performance.

I don't think it's a good idea.... yeah I know it involves 3 way valves but still it isn't a good idea

a 1/4" QEV is $10 cheaper than a 3/4" QEV

that's not much you know?
if you don't want to buy a QEV then just build a QDV

@POLAND_SPUD
What is the difference between a 1/4" QEV and a 2" QEV then? Because this would theoretically work in that application too. It seems like a small air cylinder and a ball valve is much easier to manage than figuring out o-rings and a piston on a QDV. (I had the worst time fitting o-rings for inside 1-1/4" PVC; I ended up just cutting some larger ones down and gluing them and that resulted in some small leaks but it barely worked)

On a slightly related note:

Would a QDV function similarly if you use a small valve to feed air from the chamber to the space between the projectile and the piston?

I would think that would allow for higher performance, as it equates to pulling on the piston using an air cylinder; you might need a really tight fit on the projectile though.

my point is... if you're no good at building stuff as I am just get a 3/4" QEV - they are fairly cheap and will offer higher performance than a 2" BV

yeah finding the right o-rings is a PITA

A ball valve gives the "ideal flow" when it is fully opened but in most cases the projectile will have left the barrel before the valve is fully opened.

A pneumatic ram will mean you can open a larger valve faster but I think the opening time won't be much smaller than a good spring set up.

I'm pretty sure I recorded an opening time of 25ms on my 1/2 BV rifle and the spring tension isn't particularly high. But most projectiles with any decent amount of pressure will have left the barrel in less than 10ms.

I remember quite a nice air ram canon on USKGC, reasonably large bore too.

After some digging through the bowels of the interwebs, found it!

Website is dead but dug up some pictures though mark's site:

aEx155 wrote: A 1/4" QEV should flow enough to move a small piston enough to open a ball valve. No need to reset any springs.

Why not delete the QEV as it seems a bit redundant? The ball valve on the gun below is actuated by pneumatic cylinder and controlled by a 3-way solenoid valve. You could use a push button valve for a trigger rather than a solenoid.