SpudFiles

Hi spudders, I am currently in the process of finishing up my first piston valve launcher based on the design of mrredrooster (not sure of his spudfiles username). Here is the exact link if you are interested:

Anyway, I constructed the gun and the valve. It took a couple of tries, but I got the piston working perfectly and sealing off the barrel. Victory! In his video to store the air he uses a fire extinguisher. I didn't have a fire extinguisher at the time so I just used a water bottle with some teflon tape. While obviously not a permanent or very safe solution, the water bottle held air fairly well and showed me that the valve worked. I decided to make a more permanent solution, but not with a fire extinguisher because I thought they were a little bit too expensive. Instead I used a sturdy plastic container from a sprayer. I pumped it up and there were no leaks anywhere and it looked like everything was going well, but when I pulled the ball valve nothing happened. I tried it again and same results. There were no leaks and the piston was still working perfectly. I then reverted back to the water bottle and it shot. And then I went back to the sprayer semi-permanent solution and it didn't work. Anybody have ideas as to why it didn't work?
Here is a picture of the thing:

Is the water bottle significantly bigger than the plastic container? It could be that air from the chamber is leaking through the ball valve, and with a smaller volume there simply isn't enough pressure to open the piston significantly.

How tight is your piston?

Actually, the water bottle is significantly smaller than the plastic container. You can't really see it in the picture but the plastic container is actually quite large. The piston is pretty tight, but it is well lubricated.

What pressure are you using, since it's smaller you could be venting all the air instead or triggering the piston, I had this problem on one of mine

I am using 70 psi with the plastic container in the picture, not sure what I was using with the water bottle. Something much lower. Now that I look at the container, I'm thinking that maybe the problem is with the piston allowing enough air into the plastic container and the small bottle only requires a little bit of air.

Did you cut a large groove in the piston, if so your venting all the air, try rebuilding the piston wirthout the groove

I previously had the groove in my piston, but that didn't work. The piston that I'm currently using has no groove.