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New JSR semi-auto prototype (split topic)

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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New JSR semi-auto prototype (split topic)

Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 1:50 am

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...

Image

Looks something like this internally, testing later today :)
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Unread postAuthor: POLAND_SPUD » Sun Jan 03, 2010 11:10 am

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.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 11:50 am

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.
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Unread postAuthor: POLAND_SPUD » Sun Jan 03, 2010 12:23 pm

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
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 12:52 pm

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 :P ;)

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 :twisted:

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



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.
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Last edited by jackssmirkingrevenge on Sun Feb 09, 2014 4:50 pm, edited 1 time in total.
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Unread postAuthor: POLAND_SPUD » Sun Jan 03, 2010 2:31 pm

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
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 2:38 pm

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

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It is however contingent on a sufficient pressure drop in the chamber.
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Unread postAuthor: Brian the brain » Sun Jan 03, 2010 3:37 pm

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..
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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: POLAND_SPUD » Sun Jan 03, 2010 4:43 pm

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
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 03, 2010 10:31 pm

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...
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Unread postAuthor: JDP12 » Sun Jan 03, 2010 11:02 pm

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
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 9:09 am

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.
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Unread postAuthor: JDP12 » Tue Jan 05, 2010 10:42 am

Interesting... It seem kindb of... Small
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 05, 2010 10:50 am

JDP12 wrote:It seem kind of... Small


You say "small", I say "concealable" :)
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Unread postAuthor: JDP12 » Tue Jan 05, 2010 11:03 am

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?
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