Pop off valves

[Major Collins]

With pop off valves do they just pop once and let the extra air out in 1 go or will it pop numerous times letting the pressure ?

[usdiver63]

numerous times and then they reseat themselves, you can either pull them manually or they go off at a preset pressure.

[cannon monkey]

not 100% sure on this but when my buddy pulled his open it stayed open until he pushed it closed

[mobile chernobyl]

They only self-close when the "pop-off" pressure is no longer present in the tank.

pop-off_true = If pressure in tank > pop-off pressure

Your also likely to experience a bit of hysteresis in a pop-off valve due to the mass flow of air.

[usdiver63]

some are built that way and some are built with a spring to allow for reseating.

[jackssmirkingrevenge]

In short, if you want pop-pop-pop-pop, you need to be feeding air into a tank at a slightly slower rate than the pop-off can empty it.

[Major Collins]

In short, if you want pop-pop-pop-pop, you need to be feeding air into a tank at a slightly slower rate than the pop-off can empty it.

how do i do this ? smaller ports to reduce flow?

has anyone played around with this particular type of pop off ?

http://www.ebay.com.au/itm/80-PSI-AIR-C ... 814wt_1110

[al-xg]

You could also make something like this:





The air from the tank is fed into the inlet of the pop-off valve, the oulet of the pop-off valve is fed to the pilot volume, and the threaded port of the pop-off valve is also connected to the pilot volume.

[Major Collins]

hrmmmm looks quite good. I do like how its more efficient but with my lack of resources could prove a bit challenging to make

[al-xg]

Yeah, the drawing does not reflect practical solution for manufacturing.


JSR has made many similar systems with some bits of tube and epoxy resin.
I reckon one could even make a copper pipe/brass fitting/soldered version also.

[jackssmirkingrevenge]

JSR has made many similar systems with some bits of tube and epoxy resin.

and rubber bands and lollypop sticks...

[Major Collins]

looking at the pop off al-xg posted i though it would be a little difficult to fit onto an airgun without it being awkward due to the air inlet and outlet so i threw this sketch together of an inline popoff based on the previous one... any flaws?

[Gun Freak]

How are you going to get the spool in the body?

[Major Collins]

i would make these 1/4 threads... i could probably tap one side ,insert the spool and spring and then add the nipple and then solder it in

[al-xg]

Yes there is a problem, the piston isn't balanced.

The air from the tank will be pushing the piston to the left helping the spring.
Because it has a larger area to push on than the pilot side , the pop-off valve will never fire.