XL water gun

FishBoy · Sun Nov 30, 2008 2:45 pm

Ok, in my town, on the offical first day of summer we have the Beach Bum Parade; basically, a humongous, beer-fueled water fight. Anyway, I was bored today and this design popped into my head. It consists of a 3" x 2'-3' Air/water chamber, and a spray nozzle setup. It is filled via a constant water feed from a garden hose, and pressurized by a regulated air compressor. Tips, comments, and suggested improvements will be greatly appreciatedl.

rp181 · Sun Nov 30, 2008 3:52 pm

Your going to need more pressure. Water lines here are pressurized at 100psi, just to reach it's destination, though im not sure about other place. This would be useful if you want to get "bursts" of water, so fill, disconnect hose, and pressurize then.

john bunsenburner · Sun Nov 30, 2008 4:01 pm

We have a similar water fight in poland around easter, hey polski spud, come here and help out, i want to make use of an idea like that...When i was small i tried hollowing out a huge log(50 by 50cm and 5m long) with a pocket knife, fill it with diesel and air, shaking the cannon created, insert water bllon, light through a hole and pray... Simple but i was about 10then...Yes i was always mad... oh and of coare the hollowing out part was a slight flaw i came across...I when out there and...cam back with a bucket over my head at about 6°C(Gdansk in april is COLD)

Biopyro · Sun Nov 30, 2008 4:02 pm

I have been making one of these and as such I've put a lot[\i] of research in. My design started off a little like yours and has now come down to a fully portable 6L hose pipe/ water gun, which doesn't need pumping because it runs straight off mains pressure.
Your compressor will not need to go above 50-60psi, unless you are planning to jetwash your opponents. other than that, your design is fine so long as you are happy being constantly connected to a compressor.

FishBoy · Sun Nov 30, 2008 4:05 pm

@ Biopro- care to elaborate on your design?

Biopyro · Sun Nov 30, 2008 4:21 pm

It's almost too simple and I spent a lot of money on parts I didn't need in the end. It consists of -

* An accumulator tank. This is used for removing air from central heating systems, and has adjustable pressure/volume. Mine is too small at 8l (holds 3l of water, so I plan to get an 18L one (£20))
* a 19mm bore Flexible water hose, covered in braided stanless steel. It's 3/4" thread goes straight onto the tank.
* A 3/4" ball valve, which acts as the trigger.

At the moment, it empties the tank in 4 seconds with no nozzle, but I plan to take it down to a much smaller hole

FishBoy · Sun Nov 30, 2008 9:51 pm

sweet, got any videos?

john bunsenburner · Mon Dec 01, 2008 2:29 am

Speaking for my self i like the idea of jet washing oppentent(random junkies of the street are fine too)... Some one here said that they have about 100psi on those water pipe lines...How about we power a future gun with presureized water... would that work?

Biopyro · Mon Dec 01, 2008 4:49 am

[youtube]EI3U6DMJzes[/youtube]
Just a shot I did to time it, it looks a lot better in full daylight, but you get the point.
It's about 2.3L in that video at 2bar which is mains pressure. I highly doubt that anyone gets 100psi mains pressure though!

john bunsenburner · Mon Dec 01, 2008 6:09 am

Here in switzerland where someplaces are at 100m above see and some at 4000m a.s. we have 5bar pressure on our mains,could i use that in any way? Oh and the url did not come out too well...

btrettel · Mon Dec 01, 2008 8:12 am

john bunsenburner wrote:Speaking for my self i like the idea of jet washing oppentent(random junkies of the street are fine too)... Some one here said that they have about 100psi on those water pipe lines...How about we power a future gun with presureized water... would that work?

Pressurizing water takes very little energy, so you wouldn't get any useful work out of it. Pressurizing a gas is necessary in water guns unless you use an elastic bladder, spring, or something similar to store energy.

john bunsenburner · Mon Dec 01, 2008 8:18 am

but is i have water at 100psi and air at 100psi i have to have the same amount of energy

btrettel · Mon Dec 01, 2008 8:21 am

That's not true. The main difference is that it takes energy to change the volume of a gas. Water is an incompressible liquid so there can not be any significant change in the volume, so it takes less energy to get to that point.

I could pull out a thermodynamics textbook and give you more precise figures but it's just for illustration. There is no useful energy in pressurizing water unless you have it as steam.

john bunsenburner · Mon Dec 01, 2008 9:03 am

Ok, i was just thinking that 5bar are 5bar(if i let water at a pressur of 5bar run into an air filled container with a ball valve on the side and then opened it i would have air at 5bar streaming out, which would be really useful i guess as i coul futher pressureize it from there...)

btrettel · Thu Dec 04, 2008 8:08 am

Pressure and energy are two different concepts entirely.

The air will be at 5 bar initially. But the water doesn't expand like the air does so that 5 bar will drop extremely quickly. Again, this has to do with the amount of energy it took to get to those states and the fact that water is an incompressible liquid.