Designing Powerful Water Guns for Distance Propulsion

[Midnightblue69]

Good morning, I always walk on egg shells posting what is probably a redundant question on a forum. I have been reading for two days and there is a ton of physics information out there on the subject but most of it doesn't truly address the mechanics of what I am looking for.

In a very simplified explanation, I am wanting to build a powerful water gun. In the end I am wanting to propel more viscous liquids than water but for R&D I am sticking to water. The end goal and this is my entire forcus at the moment is to be able to put a stream of water as far away as I can. For where I am at I am using 2" diameter DOM tubing for a tank, either a piston or bladder to apply pressure using 100-200psi compressed air and roughly a 1/4" minimum nozzle constriction. What would my nozzle look like? Again my primary concern is how far I can make the water reach. Am I correct in thinking that a bigger diameter tank would equate to more pressure/distance? One of my big questions is nozzle taper leading up to the constriction, what are the benefits of more or less taper hence nozzle length as it relates to water distance? Would I get significantly more distance decreasing my constriction orifice? Is there an ideal diameter in relation to my tank. I know there is an encyclopedia of science relating to most factors here but I'm relly needing nuts and bolts answers with it to help wrap my head around the subject for visualization. I know there are many other variables that affect the end product such as tank/nozzle resistance, air density and a host of others but those things being constant, I want to focus on nozzle design and sheer distance Much thanks!

-BTW my end goal is to build a device to propel liquid scents into areas for animal research without disrupting the area with human scents, specifically we have a family of spotted skunks in my part of Virgina that is extremely rare and I want to get as much trail video as I can before hard winter sets in, I also have a machine shop so I have a fair amount of latitude in design, either steel or PVC

 

[Nugatory]

No matter how you start the liquid moving, the distance it will reach depends on the speed with which it is moving and how quickly it loses that speed due to air resistance. Fast-moving liquids tend to lose energy into the air very quickly (there's a reason why firefighters try to get their hoses as close to the fire as possible, and it's not because they enjoy risking their lives).

I find myself wondering if you shouldn't be considering a ballistic projectile approach instead - think water balloon, or because you have a machine shop, thin-walled containers that will rupture on impact.

(BTW, thank you for telling us why you wanted to solve this problem - makes for a much more productive discussion).

 

[Midnightblue69]

Hi Nugatory, TY for the response! I'd contemplated a projectile and to keep them delicate they have challenges all their own. The relationship between launching force and impact force are usually not that far off, getting one to reliably break apart on impact yet yet not break when launched is tough. Kinda like the egg toss. I'm very confident it could be done but in the interest of simple and reliable I wanted to try a precharged liquid launch. I have a hand held pneumatic golf ball cannon I built and I adapted that to use the 50g Co2 cartridges when I'm not at a compressor, I was contemplating an adaptation of something like it. A scaled down firehose is actually what I've been picturing, just using a rigid pipe instead. If I could make a proportional model, I'd be very happy. Might run down to the firehouse with calipers and pin blocks LOL