co-axel diaphragm PROBLEM/material (pics)

[theRIAA]

summary of below: intertube for diaphragm? posible materials?

just finished building a nice gun out of 2" and 3/4" SCH 80 PVC. its a "co-axel diaphragm" and i have no expreience with it at all. it uses a blowgun to engage and scratener valve to fill. i made the diaphragm out of intertube (big ones you go down a snowy hill in, and i dont think its working. it wont engage at 3-20 psi (cant go higher, my valve leaks, ill fix it) it works at super low psi just fine. the intertube seems to be stretching out into the barrel. i screw the rubber up directly to the barrel (the 3/4" barrel is 1/3 way into the female threads on the 2" tank...this is ok right?)

if an intertube will not work, is there anything easy to get for diaphragm material (send me a link if you want, i already searched the forums). if intertube will work, tell me what im doing worng.

links to co-axel diaphram information sites would be appreciated!

some PICS to get u all exited

diaphragm seen below oreo box... kindox looks like oreo

HOLE where valve goes lol

back is NOT dead space, damn HD didnt have any 2" ENDCAPS!?!?! filled it w/ water putty.... dead space is bad right?

[Benny]

its not dead space, its the pilot, but its good that you filled it in, because its less pilot to exaust by the blowgun,by my experiance innertubes dont seal very well.

[McThrust]

im making a cannon nearly exact to this one (except with a 1/2 inch barrel) and i was wondering does it matter where you stick the blowgun? because this is the first co-axial that ive seen that has the blowgun on the side of the pipe rather than the direct back (or endcap).

[theRIAA]

blowgun has to be BEHIND diaphragm


thanks, i think the air is just rushing past the endcap and not sealing, this could be beacuse the intertube just dosent seal or the intertube is actualy getting smaller in diameter, when it is "sucked" a little into the barel

what can i use?!?!

[sgort87]

Use a sheet of rubber sold at the hardware store. They sell them with gaskets and such so you can make your own custom gaskets and washers.

[spudshot]

you know thats conduit PVC right? made for underground wires, not pressure.

[McThrust]

is that a schrader adapter i see at the bottom of that trigger? if so that would be blocking and therefore stopping the air from being exhausted.

[)DEMON(]

i dont think that is a component for that gun

[sgort87]

2" conduit and under will hold up fine.

[theRIAA]

you know thats conduit PVC right? made for underground wires, not pressure.

i always over-presure test my guns before i use them,
whats the diffrence in material of conduit and regular PVC?
it was heavy as hell

[sgort87]

The density and plasticizing methods are different between them. Conduit PVC does not go through the same procedures as pressur-rated PVC. It is more brittle and could even be foamy like cellular core.

[noname]

Just go to a hardware store like gort said. Usually you can buy separate small sheets or sheets by the foot. At the Ace near where I live they have like 6 different types of rubber sheets in huge rolls.

[frogy]

Look at the other Coaxials, they use a carriage bolt \ bolt with nuts washers and rubber.

N=Nut
W=Washer
R=Rubber


Bolt ==[N][W][R][W][N]==[N][W][R][W][N]===============[N][W][R][W][N]=

[Killjoy]

if you can't fin the rubber sheet, look for rubber caps for pipe, every homedepot and almost every Ace hardware ive been to has had them, they're thick rubber and all you have to do is cut it to fit. (and it should be thick enough not to get sucked into the barrel). they also cost about 3 bucks or less.