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Build a homemade water gun or water balloon launcher and tell us about it.
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deserdog
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Joined: Wed Mar 14, 2007 4:46 pm

Hello, new here.

Post by deserdog » Wed Mar 14, 2007 5:17 pm

Hello. I am new here so I just wanted to ask a couple of questions. I have built between 1200 and 1300 prospecting tools called a gold sucker. It has a barrrel of 1 1/4 inch pvc and a plunger of 1 inch pvc, with an o-ring for a seal. I use teflon silicon spray for a lubricant. The length of the barrel all depends on how tall the customer is, so that they have an easy stroke length. While the gold sucker has different size nozzles for using to suck up material from cracks and crevices in bedrock of a river, what would be the best size nozzle for making a gold sucker into a water gun? Also if I want to make more just as water guns, would a bigger barrel and piston give me more pressure? And would the piston size make a difference in filling up the gun from a water supply?

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Silence
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Post by Silence » Wed Mar 14, 2007 8:44 pm

Welcome! Neat site, has good rankings for the "gold sucker" search term. ;)

If you wanted to shoot water out, you'd have a system similar to a river gun. You don't need a barrel though, just the plunger tube.

The best nozzle size depends on how much force you've got, although we have yet to bother creating a rule-of-thumb equation. Because the force differs because of user strength, even with an equation it would be difficult to determine the best nozzle size.

Trial-and-error has proved to be the best method. Most homemade water gun nozzle systems are just male threaded PVC adapters with female threaded endcaps with holes drilled in. The PVC size is usually 1/2" or 3/4". The hole size is usually 1/8" to 3/8".

So I would just slap a male adapter on and test different nozzle aperture diameter. I generally take two endcaps and alternate drilling, increasing the size (I drill through the old hole) until I see a decrease in range. I then use the endcap with more range.

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joannaardway
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Post by joannaardway » Wed Mar 14, 2007 10:29 pm

Hello. Welcome to SSC.

It certainly sounds like you've got some experience in a similar area, so I look forward to your contributions.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

deserdog
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Joined: Wed Mar 14, 2007 4:46 pm

Post by deserdog » Thu Mar 15, 2007 7:46 pm

I wish I had myth busters working on this one! They could set up 2 river guns, one with a 2 inch barrel and another with an 1 1/4 barrel, with the same lenghts and same size nozzles. Then have a pressure gauge at the bottom of each barrel to measure how much pressure a given force developes as the pistons are being pushed. Somehow I think it is more complicated then P =F/A, and how much flow at a given pressure through a set size of nozzle.

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SSCBen
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Post by SSCBen » Thu Mar 15, 2007 8:52 pm

Welcome to SSC!

Both pistons would have similar powers because what matters is force, not pressure. The force turns into a certain amount of mass being accelerated (the water beginning to move). The force is the same in both designs.

This rule is true for the most part in piston water guns, However, one should note that a design with an extremely small pipe diameter will be less powerful because the piston can't move fast enough to get the same water output as a larger diameter piston.

A guy who goes by the appropriate name of "waterzooka" figured out a few months ago that if you use hydraulics with a piston water gun, you can multiply the force. I think this was the best idea to come about water guns in recent times (I suggested that he patent the idea). You can read more about this design in it's thread.

Building a piston water gun isn't very hard or expensive, so if you're interested in comparing different diameters, feel free to. I'll tell you from experience that there shouldn't be much variation in the performance of each water gun though.

As for ideal nozzle orifice diameters, that's one efficiency issue more people are becoming aware of in recent times. All that can be done really is trial and error. However, I have noticed that (on a well designed water gun) a certain amount of force does seem to relate to an ideal nozzle diameter. After more study, I should be able to develop a formula to approximate ideal nozzle orifice diameter based upon the force applied.

:)

deserdog
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Joined: Wed Mar 14, 2007 4:46 pm

Post by deserdog » Tue Mar 20, 2007 2:13 am

This is quote: "Hence, he formulated Bernoulli's principle, which states that for all changes in movement, the sum of static and dynamic pressure in a fluid remain the same. A fluid at rest exerts static pressure, which is commonly meant by "pressure," as in "water pressure." As the fluid begins to move, however, a portion of the static pressure—proportional to the speed of the fluid—is converted to what is known as dynamic pressure, or the pressure of movement. In a cylindrical pipe, static pressure is exerted perpendicular to the surface of the container, whereas dynamic pressure is parallel to it."
In my thinking then, if one river gun starts out with a higher static pressure, when the fluid begins to flow, the one with the higher initial static prssure should have a higher flow if both river guns have the same size nozzles.
Has anyone ever done a controlled experiment with a given force on river guns with different sized pistons?

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Silence
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Post by Silence » Tue Mar 20, 2007 8:52 pm

Nobody's done an experiment as such. Partly because I'm lazy, and partly because the strength and angle used in each shot with a river gun can vary.

Pressure isn't as important with water guns as forces are. As Ben's said, his SuperCannon II gets nearly 80 feet of range with medium pressure and enormous water-air surface area. Most air pressure water guns get poor range with high pressure and low surface area.

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