SpudFiles

Note from MrCrowley: This topic has been split from here as JSR's hijack eventually took over the thread.

I decided to make something conceptually similar, currently have a prototype valve curing. It has a schrader fill port so I can attach it to my paintball tank setup with 4mm porting and a solid rubber piston, spring loaded and piloted by another schrader.

If it works well enough, I'm tempted to give a Monsoon style gas piston a go...



Looks something like this internally, testing later today

it might be diffcult to get it to work correctly.. and even if you do I think there are just too many seals, friction and stuff that can render this design impractical

I am not saying that you can't get it to work... but I'd even try to build it without machined parts


Have you ever tested the design I used on my semi autos ? you see... I realize that I am really no good when it comes to building something with my own hands, yet they did work...
I think that with your skillzzzz you could build amazing gun based on that design...
I am not talking about using off the shelf parts, air cylinder and such I am using them for my own convenience... you can build your own air cylinders using... uhmm epoxied syringes etc.

Forget the cartridges, imagine it was just a sleeve covering an opening in the barrel , you would only need one relatively weak spring (the Monsoon in contrast has to cock a 3000 psi hammer valve) and with a big enough piston you should get enough energy to overcome friction. If you have just 20 psi on a 0.75" diameter piston at the point pressure reaches it, there's around 4 kilograms of force on it, more than enough to simply cycle a sleeve.

I know I've talked down this system as implausible in the past but with fast valves and high pressures I'm pretty confident it could be made to work.

If you have just 20 psi on a 0.75" diameter piston at the point pressure reaches it, there's around 4 kilograms of force on it, more than enough to simply cycle a sleeve

wouldn't it be a better idea to put the piston closer to the valve ? air would have more time to act on the piston and it would be easier to connect it with the sleeve

I hope it will be a success but I still think that what I wrote earlier is right

POLAND_SPUD wrote:wouldn't it be a better idea to put the piston closer to the valve ? air would have more time to act on the piston and it would be easier to connect it with the sleeve

Yes, but it would be at the expense of power, and we can't have that

I hope it will be a success but I still think that what I wrote earlier is right

To be honest I might not even try it, I'm perfectly happy with the tee breech, especially for semi-auto. I think it would only be viable if used with cartridges, maybe a future project Tried the prototype valve out filling from the chamber with a shock pump, it seems to work well enough. Tomorrow it's back to work so I'll give it a good bake in the laboratory oven and then we'll see how it likes 850 psi

update: here it is in action hooked up to my compressor at 100 psi:

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One surprise is how quickly it resets with higher pressures and flows. Intuitively I thought feeding pressure more slowly would let it equalise and seal quicker when feeding through the chamber but it appears the opposite is true.

Yes, but it would be at the expense of power, and we can't have that

uhmm yes but I suspect that the piston will barely move by the time the projectile is at the muzzle... so yeah you will lose some power but if you concentrate on reducing dead volume there the performance loss might be almost negligible

but on the other hand if all you want is power you should try the design I mentioned in my first post... I've got a design that should work great with cartridges... pic included

Interesting, basically a pneumatically driven version of the Girandoni breech...



It is however contingent on a sufficient pressure drop in the chamber.

One surprise is how quickly it resets with higher pressures and flows. Intuitively I thought feeding pressure more slowly would let it equalise and seal quicker when feeding through the chamber but it appears the opposite is true.

I could have told you that.How else do you think I got 15 shots out of Shatterhand.I had to deliberately weight down the hammer to get " deep" shots..

It is however contingent on a sufficient pressure drop in the chamber

yes that's the biggest disadvantage of this particular design and all designs that use chamber pressure to cycle ammo... finding a 3 way valve that can handle more than ~500 psi can be really difficult

I think I found one that performs well but I still have to do more testing as soon as I get a new fridge compressor...

hydraulic spool valves might also be the right solution


but I've been also thinking about having two separate circuits on a gun.. one for HP (the main valve) and a LP one for controlling (opening) the main valve as well as operating the air cylinder... I've already listed advantages of this idea in the the thread I linked to above... but what do you think of it ??

pic included

EDIT
ohh damn it.. typos in the pic... sorry

As declared earlier, valve will be baked at 50 degrees for a whole workday in the lab tomorrow and later tested at 55 bar, results will be posted within 24 hours.

PUI btw, I really should get some rest, work in 2 hours... happy new year! feck...

Hmm can't wAit to see the results jsr!!! It seems similar to something I proposed awhile back.... I'll have to try and find the thread in the morningx

Here's the valve coupled to a stainless chamber, if I can get ten good shots out of it then it would be perfect - considering it has much smaller porting (4mm) than Brian's setup and will be charged to 55 bar I would think that it should have more than that.

Currently baking in the oven, it will be tested in a few hours.

Brian, is your hammer valve single or double action? Do you have to cock the hammer manually for every shot or does the trigger cock the hammer every time you pull it?

K.I.S.S means nothing to me wrote:but I've been also thinking about having two separate circuits on a gun.. one for HP (the main valve) and a LP one for controlling (opening) the main valve as well as operating the air cylinder... I've already listed advantages of this idea in the the thread I linked to above... but what do you think of it ?

I think two separate circuits is pushing on the limits of complexity, it looks workable but not something I'd go for. I think the solution for a multishot lies in the FX style system, one that uses the air generated to shoot the projectile to cycle the bolt, ideally after the projectile has left the muzzle. That's what I like about the Monsoon, it's not using any more air than a normal 30 ft/lb PCP, just recycling air that would otherwise have been wasted out of the muzzle.

Interesting... It seem kindb of... Small

JDP12 wrote:It seem kind of... Small

You say "small", I say "concealable"

Let me get something first.. This is your prototype of the blowback with piston in the Barrel like you drew up in the previous page correct?