ergo Piston gun

[Cosmic Muffin]

Gday all.

this is my piston rifle, made entirely from brass and galvanized steel fittings (minus the PVC elbow, getting rid of that). i think i have finally mastered the piston valve, this time i dint have to try 1000 designs to get it working
piston is just half an AA battery with some bike tyre inner tube rubber epoxied on.
i wanted the chamber small so i could pump it up with a normal bike pump, which ill put bellow the barrel, or somehow in that PVC on top. the barrel is way too short, so i haven't bothered with damage pics until i get at least 1m of copper for the barrel. needs some sights and other random bits and pieces, just wanted to let you guys know what Ive been doing recently. its gonna get a paint job soon too, and a new fill valve, to replace that ugly epoxy fillet elbow.

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<a href="http://tinypic.com" target="_blank"><img src="http://i40.tinypic.com/hwifwk.jpg" border="0" alt="Image and video hosting by TinyPic"></a>

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[Technician1002]

I like the layout. The trigger location and stock rock.

[mark.f]

...Ergo, piston gun.

Sorry, couldn't help playing with grammar.

Very nice gun, too.

[Cosmic Muffin]

oh im sorry
cheers guys, just waiting for some paint

[jackssmirkingrevenge]

Nice, the stock is evocative of the SL8, I'm sure it was of some inspiration

[Cosmic Muffin]

haha thats exactly right Jack.
i loved the look of that gun. i cut the stock ages ago but never found a use for it. but im very satisfied with this build. just made a nice iron sight for it so ill put some pics up of that soon.

[far_cry]

hey nice looking gun mate
and the piston is a half AA battery , then the seat is very small this will chock the air .bad flow

[Cosmic Muffin]

the seat what?.. can you explain that a bit more. cheers

[spot]

The seat of a piston is the surface of the sealing face of the piston that is covered by the barrel (in a barrel sealing piston valve).

[jmadden91]

@spot
He wasnt asking what a seat is.

@Cosmic Muffin
far cry was saying that if your piston is only the diameter of a AA battery the seat must also not have a very large diameter which could restrict the air flow

[Cosmic Muffin]

well the seat is 10mm then.

[rikukiakuchiki777]

Are you filling from the chamber? how does that work, wouldn't the flow of air push the piston back before pilot area is pressurized?

*sigh*.. I hate trying to figure out how peoples pneumatics work.

[jackssmirkingrevenge]

Are you filling from the chamber? How does that work, wouldn't the flow of air push the piston back before pilot area is pressurised.

If you fill slowy and your piston has a spring behind it then this is entirely possible. Don't forget that almost all sprinkler valve pneumatics are filled from the chamber, not pilot area.

[rikukiakuchiki777]

If you fill slowy and your piston has a spring behind it then this is entirely possible.

Once again, thank you JSR. Would 100psi be too fast to work?

[Cosmic Muffin]

i dont see how that would cause it not to work riku.
i just hold the gun barrel down while filling, so the piston seals off the barrel. once its passed 5psi it doesnt move.
ill put a spring in there....eventually