To calculate the pressure for any non-given value, use this equation, but note that the pressure can't go above 800 PSI (the vapor pressure of CO2).

4200/Chamber Volume In ci=Chamber Pressure in psi -OR- 4200/CV
-From CO2 Cartridge in the wiki.

Where does the constant, 4200, come from? I have a ...

well, i ended up leaving it in and moved the fill valve to a tee before the blow gun and the launcher works "great" now(i'm sure there's room for improvement). I used it this weekend at an airsoft event to launch foam rockets at an "enemy APC". Worked out pretty well, i was one of the few people ...

hmmm... tough decision

i think this piece is why it is honking though, it really slims the equalization hole down to like a needle...

plus i made this launcher intending to use 12g co2...

i'll try filling it with my bike pump, but i think i'm gonna go ahead and take it out

yeah, sorry.

epoxied the solenoid hole and tapped a hole in the center for a blowgun, couldn't find any leaks.

anyone ever seen one of these? it's like a little white tab with a pointed stud through the equalization hole holding it on to the diaphraghm. on closer inspection it's hollow, the tab ...

my 3/4" orbit sprinkler valve honks when i'm filling it, should i remove this white plastic filter-like thing from the existing equalization hole?

sorry for no pics, and i would have done a search, but my neighbors internet is really slow today XD

here's an image of my new piston design, i'm not sure what i want to use for the fill material since i need to drill a hole in it for the home made bb check valve...

http://i273.photobucket.com/albums/jj227/howzer36/airsoft/barrelsealingcheckvalvepistonlabels.jpg

edit: on second thought i may ...

yeah, i just went to lowe's about an hour and a half ago, I'm going to try a 1/2" inner barrel this time with the 2" chamber. I picked up another 1 1/4" cap and a 1 1/4" plug. I'm gonna cut them down this time to make it shorter, i think i might cut a groove in the cap for the o ring because the ...

Yeah, i'll have to rebuild the chamber... Can you use threaded pvc on a fill chamber? teflon tape/thread sealant should work right?

also, how should i attach o-rings to the piston? right now it is just a pvc cap w/ rubber washer, maybe glue a plug in it with a gap for the o-ring?

yeah, i'm looking at some 1/2" relief valves right now, i can really only find this one

http://www.amazon.com/Midwest-Control-SF50-200-200psi-Safety/dp/B0025Q2UAK

atleast thats the only one in the style i want... i wonder where i might find it locally...

how small can i make my pilot volume while ...

I guess i can do that to test it, but i want to keep my trigger setup...

sooo... do you think using a 1/2" barrel will work? i'd kinda like to keep this thing 2", when it's finished i want to make it look similar to a RPG7...

yeah, i'm thinking the chamber is going to have to be 3" with a 1" inner barrel...

or what if i use 1/2" pvc for the inner barrel to add more surface area to the main pressure side of the chamber?

you really think the pop-off doesn't have enough dump? i guess it does make more of a pfft instead of ...

I've made a coaxial launcher to launch nerf footballs for airsoft/paintball scenario games, but for some reason my piston won't release when i pull the trigger and all of the air escapes through the pop-off valve.
So far i've tested the gun at about 40 psi. I've only checked the pressure using a ...

yeah, i've checked out the burst disk cartridge, i might try that for a later design, but i'd like to get my hand at constructing launchers first, so I think a simple in-line sprinkler valve launcher is going to be a good start. Thanks for the info though, I just downloaded all of your pdfs.

yeah, at this point i'm almost thinking of making some kind of protective housing for the chamber, with shock absorbers.

I guess we just have different definitions of cheap :?

For my application that will work out perfectly. I plan on using it for Airsoft gaming, so I'd imagine I may use it 5-10 times in a day, or less. I don't see myself firing this thing more than 100 times in a year, so it's not really an issue ...