Some of you may remember my homemade adjustable oprv, which if I remember correctly, has since been revised and improved by Venom. I'm not sure how many of you made them, but I know that mine always gave me trouble. It always took forever for the valve to release air from my 4B (which is also due to the high volume of a 4B). After the initial pop, it would literally hiss, sometimes not even audibly, for the next 5 minutes until it reached equilibrium. Intially I thought this was simply a problem with my design. I tried all sorts of things - I added 1/4" o-rings to the valve to create a perfect sealing face for the BB. Didn't work. I mixed and matched springs. Didn't work. I changed out the sheath for the whole assembly. Again, didn't work.
Essentially I just got frustrated with the project altogether, and I tossed it. I figured my valves were just dysfunctional. So I got my handes on a 4B pump head, and gutted it for the OPV valve. That I fitted with a barbed fitting, and hooked it up to the 4B. Same problem. Having modded for several years now and knowing how many more mistakes I make when I'm angry, I set down my tool and went and did something else. And didn't really come back to it. Unitl later...
Several months ago, I was examining a 3k pump assembly for no particular reason. When it hit me... nerf blasters always put their OPRV's in the pump heads. But why do that? Certainly it would be easier from an engineering standpoint to attach them to the actual tanks, where space isn't as much of a constraint. The answers pretty simple: putting the valve BEFORE the check valve leading to the tank solves all the problems I've been encountering. For one, the air in the pump tube isn't constantly under >atmospheric pressure when pumping the blaster. Only in spurts. More importantly, the check valve cuts off the tank from the relief valve, so the tank never leaks! I felt soooo stupid when I realized this, Hasbro had been doing it forever and I just rediscovered the concept.
Recently I got kinda back into nerf, and was getting my primaries ready for the summer wars that I'm going to try to get out to. My 4B, the most reliable thing ever, was in pristine shape, as usual. But holding it made me remember the really scary sound it made when it shot, and how frightened some people got from it, knowing it was plugged (it has a ball pump installed). So I decided to change that. I've found that people will feel much more comfortable around blasters with OPRV's, even if they're shooting harder than other plugged blasters (like 2k's and 1.5k's). So I installed one from a 4B pump head in the manner I described above.
The valve is position right at the end of the ball pump's stroke in a little gap of deadspace that occurs right before the check valve. I simply drilled a hole and superglued in the tip of the barbed fitting I had put on the valve long ago. No vinyl tubing necessary. The hot glue is there for structural support, NOT for sealing.
When the blaster's all closed up, you can see how the back end of the relief valve is exposed for easy access and adjustments.
VIDEO DEMO OF THE VALVE IN ACTION
One more thing: although I did this on a 4B, the concept is universal. It can be done on any air gun, provided there's enough space between the check valve and the pump, and that the new valve introduces a trivial amount of deadspace.
Edited by TantumBull, 05 July 2011 - 02:07 AM.