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I built this as yet untested unit in order to be used in conjuntion with this breech to provide a pulsed air supply. The theory is sound and has been used before, but in this case I built all the fittings from scratch. The relief valve pressure is adjustable by means of a bolt. The actual unit differs slightly from my original design concept in that air is fed to both into the pilot and firing chambers.

I've added another pouring of epoxy to reinforce the piston unit-chamber attachment, that should be dry in around 24 hours so watch this space.

Wow jack..... WOOOWWWW......

sure it wastes a little airflow but holy mother...... that thing looks like its going to work no matter what you do...

its relatively failsafe, and well, its way more compact and cool looking that a QEV and a pop-valve.

VH_man wrote:sure it wastes a little airflow but holy mother...... that thing looks like its going to work no matter what you do.

My worry is that the flow into the pilot chamber is too big, but in that case I can always crush the tube to restrict it, it will fit well with the overall ghetto appearance

My dilema now is, if it works, do I use it with the blow-forward valve, or shall I give the cartridge feed another go? Decisions, decisons...

wow, looks great. Is that drawing to scale? Because it looks like you have about a mile of piston travel. Are you sure that your rubber disc in the popoff valve wont just let the air slip by?
EDIT: Ignor the stupid question. wasnt thinking

I say make a conjuction between the blow-foward bolts and a cartridge feed system.......

just make the blow-foward bolt have an extractor/ejector on it so that when the bolt goes foward, it strips a shell off the magazine and puts it into the chamber, "Puffs" air through it, then moves back under spring power and ejects the casing out the side. upon the next "puff" another shell gets stripped off....

of course, thats over-coplicated. look at boltsniper.com for ways to make extractors/ejectors that work extremely well............ (ive made them i know...)

if i were you id keep it simple at first and just stick with the normal blow-foward bolt without the casings. the KISS principle is one you alwayyyyssss follow when engineering.........

mopherman wrote:Are you sure that your rubber disc in the popoff valve wont just let the air slip by?

I though that's how pop-off valves worked.

mopherman wrote:Is that drawing to scale?

*facepalm*

but yes, the piston travel is relatively huge and certainly defies the d/4 rule, I didn't want to make the pilot chamber too small so it wouldn't pressurise too quickly.

VH_man wrote:just make the blow-foward bolt have an extractor/ejector on it so that when the bolt goes foward, it strips a shell off the magazine and puts it into the chamber, "Puffs" air through it, then moves back under spring power and ejects the casing out the side. upon the next "puff" another shell gets stripped off....

The system used in my original cartridge design is pretty much as simple as it gets. i think the blow forward design would be more powerful, but dude, flying spent brass, it would be a dream come true, especially on full auto. Still, baby steps, let's see if the damn piston works first.

wow its ghetto and beautiful and the same time :love4: and i can't wait to see it attached to something, what pressure will you use it at?

ALIHISGREAT wrote:what pressure will you use it at?

The best my compressor can do, 110 psi.

well, what i was saying is that you can proboably make the blow-foward system work in conjunction with a shell loading/ejecting system that will yeild more power than just your cartridge prototype alone........

basically, hook a blow-foward bolt system to an AR15 style ejector/extractor, make shells that fit in, make a chamber the shells fit in, and make a magazine that you can strip the shells off of and WALA youve got a gun that works like a dream (in no way do i think thats easy)

in fact, i think i have an idea for a new marble gun at the moment involving shells...........

Ooooh can't wait to see if this works as planned

I'll be trying a pop of system when i get home this weekend, but i'll just use my 3/4" QEV with the piston put the wrong way round and a weak spring to hold it against the barrel (I still feel some kind of remorse about having a spring behind the piston, that tiny bit of lost power... )
the pop off valve will be fitted directly to the pilot port and it will be filled through the chamber.

If that doesn't work I'll fill through the pilot port...

I have a 16bar pop-off valve lying around, I'd love to use that, but pumping my 2L tank to 20bar takes just over 2minutes, and it will go under 16bar in a matter of seconds... (not to mention the pain in my palms after filling that thing a few times)

Well anyway, I hope this works out.

Wow it looks very nice and complicated... whenever I see your topics, I first see a complicated design, which I think is just a suggestion that soon the Spudfiles members will simplify in design to make it actually possible to build. But right below it is an actual working model of the design. I don't know, it just always impressed me.

From what I see, isn't this design basically a chamber, a piston, and a pop-safety valve? Sure it has some differences, but essentially isn't that what it functions as?

EDIT: Just realized my post made little sense and basically ignored what the other members said. Sorry for this one

rmich732 wrote:But right below it is an actual working model of the design.

we don't know for sure yet

From what I see, isn't this design basically a chamber, a piston, and a pop-safety valve? Sure it has some differences, but essentially isn't that what it functions as?

Precisely, which is why I mentioned in the orginal post:

The theory is sound and has been used before.

It's curing next to a heater as we speak, looks like it will be ready for testing some time tomorrow. Thanks for all the comments guys, will keep you updated on the results, whatever the outcome.

Ahhh wow

When ever I see these designs I always think, that is not possible with your average plumbing pipe, no way is that gonna get built, then I look over and see 'jackssmirkingrevenge' and think 'ah but of course'.

Great stuff yet again, bit big for you isn't it

If the department of defence comes knocking on your door, hold out for the big bucks! Youv'e allready earned it here at Spudfiles.

No brag, just fact!!!

holy... that's crazy, and your MS paint skills have improved since your cartridge feed post