Unconventional high power water gun designs

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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SSCBen
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Unconventional high power water gun designs

Postby SSCBen » Sat Jul 29, 2017 9:42 am

Conventional high power water guns use a valve between a pressure chamber and the nozzle. Firing valves are tricky for several reasons, and it's worth thinking of ways to avoid using them. First, anything more complex than a ball valve is too hard for most to build. (Pinch valves are an exception, but they are expensive and have not yet seen widespread use, but I am certain we'll see new designs in the future that use them.) Second, the valve tends to introduce turbulence into the flow. The ideal flow path has nothing in its way, whether seals or turns. This is hard to get in practice outside of ball valves and manual pistons.

There's also the related problem of water pumps. They are hard to make well. I am not aware of any off the shelf part that can be used as a hand water pump. It is possible to make a water gun with a separate (non-pressurized) reservoir and an air pump only that will move water from the reservoir to a higher pressure chamber. So it's worth thinking about how to replace a water pump with an air pump (easily available off the shelf) and some other mechanism (possibly air) to move the water from a non-pressurized reservoir to a reservoir, or make the water flow in another way.

The simplest way to meet this goals would be to have a water gun that's like a pressurized reservoir water gun, except that there is no valve on the nozzle end, and the only valve is an air valve that pressurizes the reservoir. When the trigger is pressed, a burst of water is released, and the stream will likely continue for some time after you stop holding the trigger because the pressure in the reservoir will still be higher. The efficiency and gun response time will become worse and worse as the reservoir empties.

A relatively simple modification of this design could help. Add a small pressure chamber attached directly to the reservoir with a high flow check valve, or alternatively a valve which is either manually opened to fill the pressure chamber or automatically opened after the (air) trigger is pressed. You can allow gravity to fill the pressure chamber. Firing is accomplished via an air valve that injects air into the pressure chamber, pushing the water out.

Getting constant pressure is easy in this design; just put a regulator on your air input line. A trigger is also easy (simple air valve) as are the pumps. Overall, I can see many advantages to this unconventional design.

The disadvantages are numerous, however. First, this would seem to require air to float on top of water. This limits the angles you can fire at, introduces turbulence into the flow, and may introduce air bubbles into the flow depending on the angle. If you use a regulator to get constant pressure then you'd have to vent the excess air after each shot. That could be unacceptable inefficient, but for what it's worth, the energy efficiency of bladders is only about 65% anyway, so perhaps it could be in that ballpark. There's also the issue of the time lag between air injection and firing. Chambers which are normally pressurized would have much less start up time. It might be possible to optimize this to the point where it's not an issue.

There's another component missing from these designs: preventing water from leaving through the nozzle. You need some sort of stopper or valve to do this. A firing valve would reintroduce all of the problems with valves that I'm trying to avoid, which is no good. The Buzz Bee Drench Force uses a stopper that moves out of the way when you fire, which seems like the simplest approach. The good news is that because the pressure is low, you don't need a particularly good seal. I would personally use something sliding rather than rotating, but perhaps Buzz Bee considered that and it did not work. One disadvantage of this component is that it limits you to just one nozzle size.

I could think of other ways to accomplish this goal as well. In particular, I spent a lot of time years ago designing a water gun that runs entirely on compressed air that used a complicated and expensive set of special air valves in addition to an air cylinder [I edited this sentence a bit to clarify what I meant better.]. It was rather fancy and designed to recycle some air to improve efficiency. Ultimately I decided that is too complex and probably wouldn't work that well anyway. I've also been toying with applying some valvelesss pulsejet concepts, but I don't know a lot about pulse jets at the moment and am not certain this would work.

Let's use this thread to discuss any unconventional or speculative water gun designs that may be worth building.

Edit: For the lack of a better name, let's call the design I mentioned AIGF (air injected, gravity filled) until someone can think of a better name. I also just had the realization someone might be able to make the Drench Force style valve work at higher pressures. If that's possible then that would be a good valve to use for water guns. No turbulence introduced in the valve. The manufacture might not be so hard either. You just need to seal a flat surface under pressure. I can think of one fast opening mechanism, too, though closing fast might be an issue.
Last edited by SSCBen on Mon Jul 31, 2017 5:54 pm, edited 1 time in total.
Reason: Edited a bit to clarify.

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Tim
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Re: Unconventional high power water gun designs

Postby Tim » Sun Jul 30, 2017 7:36 pm

Hi Ben,

I like where your head’s at. I also think watercrazy007 has some ideas worth bringing into the fold here. In particular, I like his shortened version of NightHawkInLight’s piston, but I’d stick with the original piston for 2” pipe due to its ease of manufacture.

Because I am promoting the use of a Piston, I don’t think a gravity-fed PC (Pressure Chamber) is the way to go. Instead, the Water Reservoir must be charged with low-pressure air, which will fill the PC with water and push back the Piston.

A manual 3-way Valve is needed to divert air from the Pump to the Water Reservoir when filling the PC & resetting the Piston. When this valve is turned to its alternate position, it would divert air from the Pump to the Air Reservoir. The second valve needed would be a 3-way Trigger-Operated Valve like I used on POPCAP. Without squeezing the trigger, the dry side of the Piston is vented to atmosphere to ensure responsive stream termination (pressure remains in the Air Reservoir). When the trigger is depressed, regulated air would flow from the Air Reservoir to the dry side of the Piston, causing water to shoot out of the blaster’s nozzle.

While filling & pushing back the piston, I’m wondering if a rubber friction plug will be adequate in place of a valve. It shouldn’t take too much pressure to push back the piston. More force (same PSI) will be applied to the piston because it will have a much greater surface area than the rubber plug. The plug would also remain in place when not firing to avoid losing water from the PC. When the trigger is depressed, the water pressure will eject the tethered plug. The plug should remain hanging from its tether in between closely-occurring tap shots. In a worst-case scenario, a ball valve (in line with the nozzle) would be used only when filling the PC with water. Firing the blaster would still require a mere squeeze of the trigger.

Below is the circuit I have in mind. I realize this may look more complex than you had in mind, but let’s not confuse circuit complexity with build complexity. This would not be a beginner build; however, I think it’s a build that all Admins & veterans of this forum could pull off with ease once provided thorough step-by-step instructions along with component sources.

Image

We have the technology to build this NOW. There's nothing to figure out other than whether or not a ball valve is truly required in line with the nozzle for PC filling only (not for firing). Any prototype should include this valve so the blaster can be tested either way.

Because I’m bucking the gravity-fed idea, the name AIGF would not cut it for what I am proposing. Perhaps MAPCAP would be a better catch-all (Manual Air Pump, Constant Air Pressure).

VR,

Tim

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Re: Unconventional high power water gun designs

Postby watercrazy007 » Mon Jul 31, 2017 7:36 am

Wow, I was just about to post how implementing a piston would be hard because of pushing it back and the air/water sources to make that happen, and on and on. Check, check, check, all that is solved, fantastic. There really is no way to exclude a piston without putting a 90 degree turn.

Does the 3-Way Valve, T-Handle go only to the C-1 and C-2 paths, or are all three paths open as you are turning the valve?

What if you attach the check valve end to the rubber plug, and use a ball valve instead of a check valve? That is, the plug end connects to the ball valve and water tank. It might be a pain (or impossible) to implement, but it would remove the tee that slightly blocks the flow.

To cut costs down, the 3-Way Valve, T-Handle may not need to be there. You could just have the air pump go to the air tank and air regulator, and after the air regulator, install a tee and a ball valve to go to the water tank. The low pressure can be set beforehand by the pressure regulator.

This is like a stream machine on steroids with how clean the flow path is. The range can be record breaking.

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Re: Unconventional50 high power water gun designs

Postby SSCBen » Mon Jul 31, 2017 7:17 pm

Thanks for your quick reply Tim. What you posted is a very interesting variation of my original more complicated design. I just found the thread where I posted that 3 years ago, so take a look at it. I discussed using a double acting air cylinder to move a piston, but you push the water directly into the pressure chamber, which is very clever. I had not thought of that at all. Avoiding the air cylinder would make the design a lot easier to build, cheaper, and smaller. It would be really hard to get the air cylinder design to work without spending a ton of money, actually. I had planned a design with a lever to get a mechanical advantage, but that didn't help much with using smaller cylinders. So, long story short, pressurizing the reservoir is a great idea, much better than using an air cylinder.

If I understand your design correctly then you'd have to press a button and put the cap back on to refill the pressure chamber. I'd much rather have these functions be automated so that all you need to do is pump and press one trigger. The trigger should be able to be fired in rapid succession. My goal would be to make each shot relatively small, say 30-100 mL. Enough to count for a "hit" and get good range.

With your approach, you can get tap shots without putting the plug back on, which is nice. But in doing so you'd have to vent the air side of the pressure chamber multiple times, which could waste a lot of air. (I focus a lot on wasting air as you probably can tell.)

If you have some sort of seal on the nozzle (not solved yet), you can do the trigger part with just one 4-way valve. I had planned to use a Clippard FV-5P valve for this. Making an air cylinder move from one side to the other is a standard application for these valves, and it's all the functionality you need for a basic design. Unfortunately this approach requires venting the entire water reservoir after each shot, so the air efficiency is bad. (If you are merely venting an air cylinder, it's not as bad.) If you want some extra efficiency, you have some options. You could add another regulator set to a very low pressure on the water reservoir side. You could also try air recycling (e.g., using some of the air leftover from the firing cycle for the filling cycle), but then you'll need more valves best I can tell.

Another way around the air efficiency problem with a 4-way valve is to have an intermediate reservoir which is fed from an unpressurized reservoir (perhaps by gravity). The intermediate reservoir takes the place of the water reservoir in your design. The volume of this reservoir would be small so that you won't lose as much when you vent the reservoir when it's nearly empty.

One potential problem with the pressurized reservoir is that it might make the weak "valve" used to seal the nozzle leak. This is one reason to prefer a suction based design like the air cylinder or springs HBWW had in his design. Also, given that the entire thing runs on compressed gas, it would be reasonable to use a pinch valve instead of the nozzle seal if needed. You'd lose the theoretically perfect stream and increase the cost and weight a fair amount, but it might be necessary. Then again, if you're going to use the pinch valve then it might be a better idea to make the system switch to pressurized right after filling somehow to decrease trigger lag from the air side of the piston not being pressurized when you press the trigger. A specially designed streamlined check valve might also work, but I'm not sure these are available off the shelf.

For a piston, it's also worth also thinking about something like a pump action shotgun. The firing is done via compressed air, but to fill the (small) PC you have to do one easy stroke. This avoids a lot of the difficulties mentioned.

Going back to my AIGF design, I can think of another disadvantage. Depending on how you inject air into the pressure chamber, you might create a lot of bubbles. It's important to inject air evenly (via guide vanes or screens?) to avoid that.

I'm going to think more about HBWW's idea to use springs for the filling in the Air Wiz A10 thread. I've also probably missed something, but here's what I could post in the time I had. I'll get a drawing up of my 4-way valve design later.

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Re: Unconventional high power water gun designs

Postby marauder » Tue Aug 01, 2017 9:48 am

This is an awesome idea. Even if it is not fully battle practical it would be fun and could lead to some improvements that we may want to keep for future homemades. Our biggest problem, IMHO, when it comes to innovation, is how small our group is. You can see through history that societies that are isolated do not advance nearly as quickly as large societies/societies that trade ideas rapidly with others. So, any idea is welcome, and I'd love to see this one into production.

I've been trying to get a Drench Force for a while now. They are so difficult to come across. I really want to examine this stopper.
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