400 psi valve?

[mopherman]

umm i dunno about a pvc barrel if it would explode... a pumpkin chunkin PVC barrel exploded once.. I'd just go with metal barrel to be safe

I doubt his barrel is 20 feet long and '10 in diameter. That barrel only broke because it was sagging and got snapped back by the projectile.
Edit: spelling!!!!!111111!!!!!!one!

[jackssmirkingrevenge]

dont use a schrader valve for the pilot. its too slow and those things are not rated for 400psi. just use a ball valve thats rated that high. pvc ball valves are rated for 150psi. brass/metal ball vavles are MUCH higher

400 psi mini-piston launcher with a schrader pilot for less than $50

1" piston with schrader pilot

[Brian the brain]

reducer-pipe-reducer.Hmmm...
Barrel in the center, coax style..small ( fasterand easier to open) metal ball valve as the pilot.This plus some teflon tape won't be too expensive.

In stead of a piston, in a coax, you can use a floating diaphram, aka a piece of circular metal, with a slab of rubber to coat it bolted on..( use a washer to keep it on tight)I you make it fit it will be as fast as a QEV...

1" barrel and 2" chamber diameter...

at 400 psi that means....you could accidentally kill or mame your neighbour three doors down without having to leave your warm lazy couch...


So be carefull with that kind of pressure!!
I only wonder how you plan to achieve that kind of pressure without spending some extra cash on either a (home built) HP pump or CO2/HPA setup.

[AlbinoSpud]

I already have a 400 psi shock pump so that isn't a prob, even though my arms would probably get sore after like 3 shots. And thanks Jack for the links. Winter Break Starts tomorrow!

Edit: is a floating diaphragm just like a really thin piston?

[Brian the brain]

Yeah it is..
It could be just a neoprene disc that fits the outer walls really snugly.
In your case however you will need to back it up by a metal plate and keep it from getting torn off that plate by a washer in front of it.A short bolt will keep it all in place.

The less mass a piston has, the faster it can move.
In this case...it rivals/equals a factory made Quick Exhaust Valve or QEV for short, if you do it right.

[AlbinoSpud]

gaaahh i just killed the epoxy piston

my dad said he'll help me tommorow

the epoxy stuck to the sides of the pipe even when i put pam on it... so i had to get it out with a hatchet

[mopherman]

gaaahh i just killed the epoxy piston

my dad said he'll help me tommorow

the epoxy stuck to the sides of the pipe even when i put pam on it... so i had to get it out with a hatchet

Make sure the epoxy isn't getting snagged on any seams that the pipe might have. Also, you should try wd40 when molding, It works beautifully and distributes well.

[dongfang]

Hi,

You could use a large ball valve as a trigger, or another home built piston or DFTV valve, just smaller. Or, design the whole thing as a DTFV (lathe requred), and use a small ball valve to control it. Pay attention to good damping then, and don´t stand right behind it when testing. One of my DFTVs had a tendency to shoot half of the piston out through the breech end!

Regards
Soren