British newbie seeking more power

[Ben]

I hadn't remembered that discussion at NerfHaven SilentGuy but now I do. If that's how accumulator tanks really work then I'm intrigued. It's not as constant as regulated air pressure or rubber CPS but I bet it's close enough. Edit: I reread my posts there and I'm coming across as a complete asshole to me now. In retrospect I shouldn't do that.

Bladder tanks do seem a little less "homemade" I suppose but if they work I don't have a problem using them. I'm fine with using available parts. Machining and such would be best I think but wouldn't be "homemade" though still built by an individual. You build with a goal in mind I suppose, like Biopyro said.

I'm thinking with two one liter bladder tanks and a 3/4 inch wye I could make a pretty nice water gun. Luckily they built the tank I'm considering to have some sort of mounting system built in, which would simplify the building process. I can use a 3/4 inch valve and fittings with 1/2 inch bladder tanks because two 1/2 inch pipes at a common flow speed have more flow than a single 3/4 inch pipe at the same flow speed. This gives me a 3/4 inch internal diameter with 1/2 inch parts.

[Silence]

Yep, bladder tanks make sense if you have a more pragmatic goal in mind. I've got no problem with that. I guess I build with different goals in mind, too. I like the challenge of building (not that I've done much...I'm more experienced outside of water guns) more than using what I've built, so paying top dollar to get suitable parts doesn't fit the bill.

Ben: Never too late to apologize. Actually, I'm totally serious about it. He'll forgive you.

[Biopyro]

Well, I'm back with an update. The huge delay was the fact that I couldn't find a pipe with a larger bore than 13mm to connect the tank and the gun apparatus. This would have meant there would be no point in using 22mm pipe because the resevoir flow would have been choked.
I found one of these (19mm) for £10 and I plan to unscrew it to fill the tank.
I'm writing up the instructable now and hopefully I'll be finished by christmas (packed work schedule atm).
Reading through the original plan suprises me how much it has changed, but I take this as a sign for good.

One thing I have realised too late, is the cricled in red. When the valves are off then the water will
A) drip out over everything over several minutes (also wasting water) and
B) take a few seconds refill before water fires from the nozzle.
This dead space is nearly 150mls and I have no way to stop it.
How bad do you think this will be?

[cantab]

Dead space is unavoidable. But I doubt it will be an issue. Keep the nozzle angled up when carrying it, and the water won't drip out. prime your gun by a quick tap shot before the battle starts.

[Silence]

It's actually not too big an issue. With smaller nozzles, air can't get in while the water's getting out, so the water can't leak because that would create a vacuum inside. But even with larger nozzles, I haven't really noticed a problem. Water guns tend to be wet from filling anyway.

[Biopyro]

Well, problems again, only minor but still.
The ballvalve which now conects to the tank has a handle which is too long, so I can't open it all the way. I tested it anyway (using the ballvalve to fire out of the tank) and wow. It wasn't full at all but I got a good 5 seconds of very spread (because the BV was only 1/4 open) high flow. looking good!
I also ordered a wrong part so i plan to get a new BV when I re-order it!

[cantab]

Hmmm...is it that the valve is bumping into something? If so, you could always adjust the position a bit, eg rotate about the pipe axis so the handle is angled to miss whatever's in the way.

[Biopyro]

Wow. I am both very happy and annoyed at the same time. I hooked it all up, but saw that I could save myself some trouble by moving the ball valve as you suggested (I didn't think I could before).

Happy because:
I can connect the ball valve to the hose, which connects to the tank, and stop there. If I want a nozzle, I just screw in a 3/4" cap with a hole in it. The whole 8l (I think, I thought it would take longer than 30 secs to fill!) empties in about 4 seconds at 30psi with a range of about 8m. I plan to up the pressure and double check it's full, but I think thats good performance so far.
If I want the pressure higher than the mains, I just fill it then pump it, but I suspect this will be enough for now, since you can really
feel the recoil.
Also happy because I have just finished a great new spudgun, and may be able to easily solve a problem on an even better old one!

But annoyed because this does mean, that I have spent around £30 for nothing on the twenty-five 22mm copper tees I bought, the solder and pipe I used, and the 2 ball valves. I will recycle them (perhaps into a new spudgun) because I just don't need the handset.

Here are the first pics. I will get some more and a better video when it is light, perhaps at the weekend.
Why it wouldn't open all the way

The new assembly


I almost feel like this is too simple. It is so good and will be able to absolutely drench people, as well as delivering nice controlled blasts, yet so simple, with only 3 parts!

Youtube video

[devvo]

Are you using mains pressure to fill and pressurize the expansion vessel?

[Biopyro]

Yep, that power is 100% mains pressure. I think the test video was about just above 2 bar.

[Silence]

Well, there's probably some unfilled space in the tank, perhaps explaining why it didn't take so long to fill it. Or maybe there's just more flow than expected.

Turn the ball valve around, or cut/file off the rim that stops the handle from turning in the other direction, so that you can open it completely. And for more range, consider using a smaller nozzle...a 1/4" or 3/8" pipe nipple might be better at that pressure, especially since the hose barbs might limit flow.

[cantab]

Originally Posted by Silence

Turn the ball valve around, or cut/file off the rim that stops the handle from turning in the other direction, so that you can open it completely.

Note the two photos there. He's already moved the valve to the nozzle end of the hose, instead of the pressure vessel end. Which is the better way to do it anyway, since that loses the substantial dead space from firing valve to nozzle, that would delay first shot.

It's getting what sounds like basically an 8m range riot blast, which is pretty good. With a good stream nozzle (like a laminator) I reckon 15m (CPS 2000 range) should be attainable.

[Biopyro]

I was thinking of using a caulk tube nozzle for a more laminar small flow nozzle, would that be good enough (It's a cone shape which, I estimate to be about 2.5cm long when cut to a 6mm bore nozzle).
It is a riot blast by every definition. I suspect it would sting!
That laminator looks like a good idea, I reckon I could reproduce it for that extra range. Do you think it could be done with narrower straws for a narrower nozzle? I can get ~3mm ID straws easily so I may try that, because the plan is to have the normal nozzle, and then just be able to unscrew it for the riot blast (for which range is less of an issue)

Turbulence is caused by the water particles colliding with each other in a large stream, so making many smaller streams is beneficial.
^Is that correct?

What size should I fit- the expansion is 4% of water heaters capacity. There is only room inside an expansion tank for half the total volume, as it needs room for the compressed air and diaphragm. So the best basis is to fit one that is 10% of the total water heater capacity.

Just found this while searching ebay shame but my results do back it up. When i release all pressure from the tank, it is much heavier, but cannot hold enough air to exhaust the whole tank. I plan to experiment with the pressure for the best results.

Is 3/8" too big for a standard nozzle?

[Ben]

The narrower the straws, the more benefit the laminators have in laminating the stream. However, you'll eventually start restricting the flow. Experiment to see what works best. Be sure to test before adding laminators because they don't always increase range.

Turbulence and stream size are two different things. You worry about turbulence before the water exits the nozzle. While having larger diameter pipe does allow for more turbulence to develop, the increase in flow from the larger pipe increases performance much more.

Smaller streams have less mass and are affected by drag much more than larger streams. However, larger steams move slower. The ideal nozzle orifices diameter for range generally is somewhere between large and small orifices for those two reasons.

As for a 3/8 inch nozzle, it's hard to say how a nozzle will perform because there are too many variables with water guns, but according to my rough math you could expect about 800 mL/s of water flow from that.

I'm looking forward to the instructable. Accumulator tanks seem to make water guns that are powerful and dead simple to construct so I should probably look more into them when I have more free time.

[cantab]

Originally Posted by Biopyro

I was thinking of using a caulk tube nozzle for a more laminar small flow nozzle, would that be good enough (It's a cone shape which, I estimate to be about 2.5cm long when cut to a 6mm bore nozzle).

Just a note that the very last part of the nozzle (I'd say roughly one to two diameters from the end) should be straight internally. If it's conical right to the very end it may not work too well, though I've tested too few nozzles to be sure.