Water Warriors Stingray - tighter cap

[cantab]

Another dead simple mod here. The WW Stingray has a lug on the gun, which engages with one on the cap, limiting how much the cap can be screwed on. The result is the gun is prone to leaking from there when pressure is high.

So, I just filed the lug off! There's a second, smaller bump on the opposite side of the cap thread, I filed that too. (You could file the lugs on the cap instead I think, but I found the gun easier to hold steady)

Now, albeit with some effort, the reservoir cap can be tightened by about an extra half a turn. This gives two advantages. 1) The gun no longer leaks. 2) Maximum obtainable pressure seems just a little higher.

I was already very happy with this gun's range and power for its size; now it doesn't leak, it's even better.

[Silence]

That's a creative tweak. It's easy to follow, but do you have any images of the cap? At any rate, I'd be happy to upload this to the site with your permission.

So the pressure release valve doesn't kick in, even with the extra pressure you can build up without leaking?

[cantab]

iSoaker.com suggests the pressure release valve IS the cap. I'm not sure if that's true - I think there might be another PRV valve that does kick in, since the pressure increase is only slight (if it exists at all).

[Ben]

Interesting modification. Seems simple enough and it sounds like it works well. If BBT did use a real PRV I'm wondering why they even had the lug to begin with. Sounds like more trouble than it's worth.

[Silence]

Are you guesstimating the pressure increase based on pump force or on range? Range is approximately proportional to the cube root (or worse) of pressure, so a slight increase in range comes from a massive increase in pressure.

[cantab]

Both really - neither changes much.
Then again, the pump's pumping air. Will that make it become less effective if the reservoir pressure is higher?

[Silence]

It shouldn't really matter. However, in a poorly designed water gun there could be an automatic pressure limit thanks to "dead space" between the end of the pump plunger and the check valve. When you pump, the compressed air sits in the dead space unless it has enough pressure for enough to seep through the check valve (which is usually the case). But if the pressurized reservoir already has high pressure, that air may just compress and decompress as you pump. A good check valve design will place the second check valve right next to the pump so that you won't really get to that point. Of course, some of the air still sits in the dead space, so you won't be pumping much air anyway.

In water guns that pump water, that isn't really a problem. Water doesn't compress, so the entire volume can't just sit in the dead space - it has to go through the check valve.