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new valve system

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: airheadnoob » Sat Dec 06, 2008 5:29 am

I live in switzerland too! Also trying to build an air gun hahaha what a wierd coincidence[/quote]
cool but i dont live there any more :( but trust me it is so much easier to make it in swizz plus u can just go to zurich and go into a hobby stores and get a real air soft gun then just mod it and u got a real powerful 1
i went to zurich on a school camp (st George's) we were aloud out in the city
with out a teacher and shop i went into 1 and i saw 1 realy good 1 which i could of mode but i didnt know any german but a friend did and i asked him to buy it for me but he bitched out and yes it should b in the discussion board but im gona try a new 1 out
http://www.spudfiles.com/forums/pump-ac ... 15589.html
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Unread postAuthor: Technician1002 » Tue Apr 14, 2009 12:43 am

jackssmirkingrevenge wrote:Isn't this a pop-off valve? :?


***Edit *** :oops: Sorry.. Dead form My bad. Replied to a random cannon pic.

Not quite, It is a pressure relief valve. A pop off valve has a second larger diameter so when the valve opens, it lifts the wide part of the piston so the valve stays open until the pressure drops considerably. This one with the seat at the exit will simply vent and reseat at 1 pressure, not two.

Pop off valves are designed to remain closed and when they open, they blow all the way open and stay that way due to the increased piston area exposed to the discharge stream until the pressure is low enough to allow it to re-close, where it suddnly snaps back fully closed. They are often used on steam boilers. Old steam train movies show this valve operating. It's the jet of steam from the middle of the top of the boiler that sometimes vents or not.

This page shows the anatomey of a pop off valve;
http://www.stanleymotorcarriage.com/Parts/PopValve.htm
I hope it shows the difference from a relief valve.
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Unread postAuthor: jimmy101 » Tue Apr 14, 2009 12:23 pm

Technician1002 wrote:Pop off valves are designed to remain closed and when they open, they blow all the way open and stay that way due to the increased piston area exposed to the discharge stream until the pressure is low enough to allow it to re-close, where it suddnly snaps back fully closed. They are often used on steam boilers. Old steam train movies show this valve operating. It's the jet of steam from the middle of the top of the boiler that sometimes vents or not.

That's a great description. For steam boilers (or hot water heaters) the valves are actually also rated in BTU's which sounds kind of wierd. The rating is based on the energy release rate, not just the pressure they cycle at. The safety valve must be able to not only cycle when needed but it must also be able to release energy at a rate that is greater than the energy supply rate of the heat source. IIRC, typical hot water relief valves are rated at something like 10,000 to 50,000 BTUs
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 14, 2009 12:26 pm

Technician1002 wrote:Not quite, It is a pressure relief valve. A pop off valve has a second larger diameter so when the valve opens, it lifts the wide part of the piston so the valve stays open until the pressure drops considerably. This one with the seat at the exit will simply vent and reseat at 1 pressure, not two.


My bad, I used the wrong term. For the record, I'm very familar with how pop-offs work ;)
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