Valve for firing water?

[psycix]

Found it!!
This thing looks beastly

I'm not sure how it works, it might be some kind of coax though.

I think its laughable that their most powerful watercannon is about equal of complexity as a moderate spudgun.
I mean, seriously guys, is that the best you can do? Ever heard of high pressures?

Fishboy,
Its nothing more then a chamber filled with water, and a piston in the end.
As air enters the back end of the chamber, the piston is pushed forward and the water is pushed out.

[btrettel]

There's a few reasons why water guns don't get more powerful. I won't say they don't get more complex because they do. The water gun being discussed is actually the simplest design--a single pressurized reservoir.

Most people don't need, want, or can attain more power. You forget that the average hobbyist wants to shoot these guns at people. As Supercannon II matches the power of a small fire truck, it's way too powerful as is for safety reasons. Conserving water is also important in water fights, so it's not even practical.

Anyway, with an efficient design, after about 60 psia you can barely increase range. You get diminishing returns. Getting over 70 feet of range is a challenge--getting over 80 and 90 is very very significantly more difficult. I've been told (by an engineer at a water gun company) that to get a water gun to shoot over 100 feet you'd need 200+ psi and a certain amount of water (I forget the details) and even that might not be powerful enough.

Let me reiterate that the design has to be right. High pressures do not necessarily make an extremely powerful gun. Supercannon II at 60 psi will shoot much farther than a pressure washer at 2000 psi.

You can make a more powerful water gun (and someone did) but it'd be the same design scaled up. You'd have to use significantly higher pressures and wider pipes, which translates into much more expensive materials. This is why I don't particularly care to make one more powerful even though I'd find it interesting. Someone with a ton of money to spend should jump on this.

[psycix]

As a spudder, I'm simply looking into achieving maximum power.

that to get a water gun to shoot over 100 feet you'd need 200+ psi and a certain amount of water (I forget the details)

Could you search the details for me?
I am thinking 450 psi. (Or MOAR!)

[jeepkahn]

The key to acheiving distance with water is the outlet, to increase range you have to make sure your outlet doesn't "shred" the surface tension of the water stream, and at a certain point pressure increases make it virtually impossible to maintain a surface film on the water be projected, and once you break the surface film all bets are off...

[jeepkahn]

can a mod delete this, my machine glitched and double posted...

[btrettel]

As a spudder, I'm simply looking into achieving maximum power.

that to get a water gun to shoot over 100 feet you'd need 200+ psi and a certain amount of water (I forget the details)

Could you search the details for me?
I am thinking 450 psi. (Or MOAR!)

Sorry. That email was lost long ago. 4 gallons or more of water at 450 psi with a layout that is similar to my Supercannon II should be more than adequate. You'll have to experiment with nozzle orifice sizes too... I'm willing to bet an orifice 0.7 inches or wider will be optimal.

Don't forget about the pressure ratio too. If your pressure drops too much you won't get too good performance (from the low pressure ratio). If you don't care about practicality, look into getting a 3:1 to 4:1 air-water ratio so the pressure is more consistent. You don't need to keep the air in a straight pipe too--look into attaching the gun to a larger gas chamber. This'll let you use the entire length of your straight pipe for water.

Another thing if you're going to try this (and please do): recoil is a bitch. Don't forget that you're practically shooting a rocket off without takeoff. Make sure whatever you make is in a stable configuration or else it'll hit someone/something and/or turn into a rocket. Recoil force is the nozzle orifice area multiplied by the pressure differential if it'll help you design something.

jeepkahn is correct, which is why you want to minimize turbulence and have a conical shaped nozzle of the right diameter. That's why I used a cheap plastic fire hose nozzle.

You also could increase the viscosity of the water by adding stuff like glycerin. Glycerin gets expensive. I've been told pool chemicals can do similar things too.

[psycix]

which is why you want to minimize turbulence and have a conical shaped nozzle of the right diameter.

I can machine stuff

Another thing if you're going to try this (and please do): recoil is a [female doggy].

I know. It is one of the reasons for building it.

Though Im not sure when. Its just on the list of "things i want to build someday"
Could be this summer, next summer or over 30 years.
But eventually, I will build it.