Highest pressure you've seen?

Build a homemade water gun or water balloon launcher and tell us about it.
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kevinthenerd
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Highest pressure you've seen?

Post by kevinthenerd » Wed Apr 05, 2006 4:17 am

I was thinking about making a very high pressure water gun. Has anyone ever heard how well galvanized pipe works for such high pressure conditions? I was thinking of using 1/2" or 3/4" galvanized pipe, but I can't think of what to use for a high pressure air reservoir. (There's a certain advantage of studying mechanical engineering: I can find out if my design is safe before I even build it!)

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SSCBen
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Post by SSCBen » Wed Apr 05, 2006 10:26 pm

How much pressure are you looking for? From what I have read, you are familiar with the capabilities of the pipe available to you. Just remember that anything over 200 PSI (more like 130 PSI actually) won't be safe for a water gun. Essentially, if you need to use metal pipe, your water gun probably isn't going to be safe at those pressures, but, of yo. Pressure is a poor way to achieve distance and power, so look to make your designs efficient if you intended to use a lot of pressure.

A member a while back (in 2003?) named Xray did do a test at 350 PSI using a propane tank - the two galloons + in the chamber emptied in apparently less than 5 seconds with a very small nozzle.

If you don't mean to have a water gun that can be shot at people, I'm sure that metal pipe would be perfectly suited for a big and powerful water gun designed for performance. ;)

ben@sscentral.org / Please read this before emailing or PMing me

Do not ask me water gun questions by email or PM. Please post the question at the forum. Private questions and suggestions are welcome by PM and email. Also, I do not sell or buy water guns online.

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kevinthenerd
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Post by kevinthenerd » Wed Apr 05, 2006 11:31 pm

Ben wrote:How much pressure are you looking for? From what I have read, you are familiar with the capabilities of the pipe available to you. Just remember that anything over 200 PSI (more like 130 PSI actually) won't be safe for a water gun. Essentially, if you need to use metal pipe, your water gun probably isn't going to be safe at those pressures, but, of yo. Pressure is a poor way to achieve distance and power, so look to make your designs efficient if you intended to use a lot of pressure.

A member a while back (in 2003?) named Xray did do a test at 350 PSI using a propane tank - the two galloons + in the chamber emptied in apparently less than 5 seconds with a very small nozzle.

If you don't mean to have a water gun that can be shot at people, I'm sure that metal pipe would be perfectly suited for a big and powerful water gun designed for performance. ;)


I don't intend this for point-blank use. In the medical field they use small streams of high pressure water that can inject stuff into you without even using needles. Fire hoses are used for crowd control. In the extreme case, tsunamis cause entire cities to be leveled. I know water is capable of a lot of damage.

I intend this for extreme-range sniping. By the time it gets to the person, they won't be able to tell where it came from, and it will have slowed down and dispersed enough for it to just feel like a $1 squirtgun close up.

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SSCBen
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Post by SSCBen » Sat Apr 08, 2006 3:48 pm

I'm not worried about the stream hurting someone from a distance. I am worried about the stream hurting someone closer or the pressure being too high. Hopefully you understand, and I think you do. ;)

I don't think that you realize how much power is required to make a water gun shoot over 70 feet. It is completely possible, but it would take the right design and a lot of pressure. I think I might have linked to my design in another reply of mine to one of your comments... let me know if I hadn't.

ben@sscentral.org / Please read this before emailing or PMing me

Do not ask me water gun questions by email or PM. Please post the question at the forum. Private questions and suggestions are welcome by PM and email. Also, I do not sell or buy water guns online.

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kevinthenerd
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Post by kevinthenerd » Sat Apr 08, 2006 5:26 pm

Ben wrote:I'm not worried about the stream hurting someone from a distance. I am worried about the stream hurting someone closer or the pressure being too high. Hopefully you understand, and I think you do. ;)

I don't think that you realize how much power is required to make a water gun shoot over 70 feet. It is completely possible, but it would take the right design and a lot of pressure. I think I might have linked to my design in another reply of mine to one of your comments... let me know if I hadn't.


Would 200 psi with a custom machined nozzle do the trick? That would be well within the limits of galvanized pipe.

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SSCBen
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Post by SSCBen » Sat Apr 08, 2006 6:14 pm

Yes, that should be enough. Just make sure that your nozzle is conical (like fire hose nozzles, which you can buy online) and you use the "linear design" practice. Because of the price of plastic fire hose nozzles ($5 - 10 depending on the size of the nozzle), custom machining a nozzle would be unnecessary. The linear design practice essentially states that all water to be shot must follow a straight and unobstructed line from the pressure chamber to the nozzle. This practice prevents unnecessary turbulence from being created. It also means that ball valves or any valve that allows for straight, unobstructed flow should be the valve of choice.

Look at my "Supercannon II" design for my take on a smaller-scale version of what you will be doing. Note that I will use a piston to separate the air and water so that the water gun can be shot at any angle. If you are finding that your piston is leaking, you'll have to either change the design or improve the piston's ability to hold pressure. One person who made a piston water gun used two pistons for that reason.

Also, I think that I should tell you that much of what I discuss in my incomplete "Water nozzle physics" article are methods for improving flow and stream lamination from a poorly laminated stream and flow. With a design that creates laminar flow from the start, you'll avoid having to use things such as straws in the nozzle and get better performance. :)

Looks to me that you're going to win my "achieve a distance of 70 feet" challenge by a long shot!

ben@sscentral.org / Please read this before emailing or PMing me

Do not ask me water gun questions by email or PM. Please post the question at the forum. Private questions and suggestions are welcome by PM and email. Also, I do not sell or buy water guns online.

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