schrader valve question

[Crna Legija]

will a schrader valve open if wit out pushing the pin in a pump as a check valve? and how much pressure would it take? im making a 200-300 psi pump is that enough? if not could i put a bigger piston on top?

[Gippeto]

A schrader valve will indeed open with air pressure alone.

The schrader valve that I tested, cracked open at 70psi.

The net result for you, would be that although you are putting the effort into your pump to generate 300psi, you will only be able to charge your chamber to 230psi.

A larger diameter piston will improve delivered volume, at the cost of an increase in the amount of force required to pump the air.

[boom_o_matic_2.0]

The net result for you, would be that although you are putting the effort into your pump to generate 300psi, you will only be able to charge your chamber to 230psi.

did you have to take the 70 off from the 300 due to the cracking pressure of the schrader?

[c11man]

yes thats why he he said 230psi. it might be possible to take it apart and remove/mod/put a different one in so that it has a weaker spring stengh and crack at a different pressure

[Crna Legija]

sweet thanks of that. the pump work and i tested it to 400 psi but i wont use my gun that hi. its like the one Gippeto made a how to about just i soldered a schrader valve instead and its great thank for the how to and of this help ill post it soon as i get my camera.

and i need a new psi gage i for got to open the ball valve and stated to pump and my gage dident go up and i open it the needle is like bendnt 2 full 360s

[john bunsenburner]

Could you not completly remove the spring, once you have air on one side the push should seal the shrader, then it works like a normal check valve.

[inonickname]

Yeh, except most aren't very serviceable.

Have a look around, you want something called "long valve stems" for schrader valves. They have an external spring which can be cut off for a 0 cracking pressure.

[john bunsenburner]

Ok, thanks for that!

Got an example on ebay or something?

[Crna Legija]

yer i wanted to but i have one this

http://www.geocities.com/cyqlist/springs1.jpg
the smaller one

[Crna Legija]

sorry for the duble post but i cant use edit

iv got one like this
http://www.geocities.com/cyqlist/springs1.jpg

[far_cry]

the small one .no one successes to get the spring out from it
i tried once and this dose not work with me

here a photo to see how exactly what he look inside

[Crna Legija]

thanks i tried to cut one up and it didn't work ether
i only lose 70 or so psi and my pump already pumped to 400psi and i wont go passed 300 in my gun so its fine thanks for all the help guys