Point-Defense water gun

Build a homemade water gun or water balloon launcher and tell us about it.
eqo31
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Joined: Mon Aug 23, 2010 4:44 am

Point-Defense water gun

Post by eqo31 » Mon Aug 23, 2010 5:01 am

I'm currently building a heavy duty water gun that is meant more for point defense than assault - but I still need to be able to move around, and would like to seek some input from the more experienced members on:

1. Your experiences with the trade off between weight and mobility.
2. How to minimize costs when using large diameter PVC. 4" fittings are almost $10 a piece, and 4" schedule 80 pipe is about $10 / foot. Reduce then fit? Any other layouts that minimize fittings?
3. Suggestions for nozzles, streamlining, and anything else.

The current plan:

Constant pressure setup.
3 separate 2 feet long sections of 4" PVC will make up the core reservoir.
Each of the 4" PVC will have a 4"->2" reducer up top, then a 2"->3/4" reducer. This will then connect to an elbow, and eventally a cross. Since a cross has 4 openings, and 3 of these are hooked up to the 4" reservoir tubes, the 4th outlet on top will be hooked up to the pressure system (described momentarily).

Ascii art version:

Top view:
...O
O-|-[]
...O

O = 4" PVC reservoir, 2 feet long
[] = 19 cubic feet scuba cylinder. This is about 4.5" in diameter, and 1.5 feet long

On the bottom, identical setup. Except the 4th outlet on the bottom will be connected to a garden hose, which will then be connected to a garden sprayer.

The pressure system will be a 3000psi 19 cu feet aluminum cylinder, with the first stage regulator bringing the pressure down to a constant 130psi. It will be attached via a system of adapters like: SCUBA -> 1/4" NPT -> 1/2" NPT -> 3/4" Garden hose -> 3/4" PVC.

All of this is encased in a backpacking backpack.


System operation:
The pressure system will be connected via a PVC quick connect fitting, which can be removed when filling.

Basically, turning on the air source will keep the entire system pressurized to 130 psi for the duration of the battle. As air pressure drops in the system, the first stage regulator will feed more air in to balance it. Water gun volume will be roughly 0.80 cubic feet (6 gallons), so the cylinder should be able to power two full fills before running out of air.

Planned System stats:
Water reservoirs - 6 gallons (48 pounds of water)
Pressure system - 20 lbs including mounting brackets, air, and regulators
Add in backpack and accessories, and we're looking at 75-80lbs of gear.
Last edited by eqo31 on Mon Aug 23, 2010 5:06 am, edited 1 time in total.

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mysterio
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Re: Point-Defense water gun

Post by mysterio » Mon Aug 23, 2010 5:13 am

Welcome to Super Soaker Central! (I'm not the most knowledgeable member here, but as far as water reservoirs go, use ABS. its lighter and cheaper.) Also, dont use a garden sprayer, It kills the lamination. just use a ball valve. Otherwise, really awesome concept.

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SEAL
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Re: Point-Defense water gun

Post by SEAL » Mon Aug 23, 2010 12:08 pm

Really? I thought ABS was more expensive then PVC. At least where I live.

So this design has 3 reservoirs?
Captain of the Catskill Mountain S.E.A.L.s (Soaker Elite Assault Legion.)

eqo31
Posts: 6
Joined: Mon Aug 23, 2010 4:44 am

Re: Point-Defense water gun

Post by eqo31 » Mon Aug 23, 2010 3:53 pm

ABS locally is alot cheaper than PVC - however, the ABS I can find locally isn't pressure rated. In my current design, the entire reservoir is pressurized, so I have to stick to PVC.

Currently, the only way I can get it to hold 6 gallons of water without being insanely long is to use three 4" reservoirs at 2 feet long a piece. By clustering them together like the ascii image above, it's not terribly thick either. I'd prefer to use some sort of pressure rated tank, but haven't found any yet. I'm trying to avoid adding separate pressurization chamber, because then it would require pumping - and pumping to 130psi repeatedly is not fun.

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cantab
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Re: Point-Defense water gun

Post by cantab » Mon Aug 23, 2010 6:01 pm

I'd say that's seriously heavy, although of course it gets lighter as you shoot.

One thing to bear in mind - is the flow rate on the regulator enough? It's all very well it producing 130 psi, but if it can't put air in as fast as the water is being shot out you'll suffer pressure drop. I don't know what kind of flow rate these things produce.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

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zeda.beta
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Re: Point-Defense water gun

Post by zeda.beta » Mon Aug 23, 2010 11:23 pm

Okay, first, don't pressurize the entire reservoir unless you want to have to re-pressurize the whole thing in the middle of a fight.
Second, the garden nozzle takes the energy and reduces it by forcing it through a 90 degree turn.
Otherwise, good concept.
I reject your reality and substitute my own.
Quack damn you.

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cantab
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Re: Point-Defense water gun

Post by cantab » Tue Aug 24, 2010 12:12 am

Well the pressure is provided by a compressed air tank. Once you exhaust the reservoirs, you close the regulator, vent the remaining air from the chambers, fill with water, and reopen the regulator. Then you're ready to fire again.
Once the air cylinder is empty, it needs recharging, which will take time. But it will last many reservoir-loads of water before that happens.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

eqo31
Posts: 6
Joined: Mon Aug 23, 2010 4:44 am

Re: Point-Defense water gun

Post by eqo31 » Sat Aug 28, 2010 4:57 am

Cantab - the flow rate on the regulator is roughly 6 gallons per second at normal atmospheric pressure. So at 130 psi, that's roughly 2.5 liters per second. Hopefully that is sufficient, though I will probably have to try a smaller nozzle - thanks for this tip, it's very helpful. I've also dropped the design to 4 gallons to lighten up the weight a bit.

zeda, I tried a few designs which doesn't pressurize the full reservoir, but to utilize the compressed air cylinder, that requires manual pumping of the water into a staging chamber that needs venting each time.

- The air cylinder is very small, and will only last 2 reservoir fulls. However, it's mounted via quick release and can be swapped out like ammunition. I only wish I can suck in water using compressed air somehow.

Anyways, using these suggestions, I've ordered my parts. Man this stuff is heavy! I hope I can stand up with it fully loaded.

Here's a picture of the parts attached, but not cemented in yet.

Image

The tops will connect via a cross to the air tank. The bottoms will be arranged the same way, but connect via a cross to the flexible pvc hose. (which now uses a ball nozzle per this board's wisdom).

Wish me luck!
Last edited by eqo31 on Sat Aug 28, 2010 5:16 am, edited 1 time in total.

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cantab
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Re: Point-Defense water gun

Post by cantab » Sat Aug 28, 2010 2:27 pm

eqo31 wrote:I only wish I can suck in water using compressed air somehow.
Compressed air engine coupled to a water pump. But based on the small amount of air you mentioned you probably can't waste it. Although it might be possible to have the air drive the pump and then go on into the pressure chamber, simultaneously drawing in water and pressurising it. But that will be really complicated and hard to get right.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

eqo31
Posts: 6
Joined: Mon Aug 23, 2010 4:44 am

Re: Point-Defense water gun

Post by eqo31 » Sat Aug 28, 2010 10:21 pm

And 3 solid hours of work later...

Image

Just need to wait overnight for the cement to dry before testing it now. In this picture, the nozzle isn't connected - because it's on the hose for testing.

I found a pretty cool alternative to the laminated nozzle. A 1/4" NPT quick disconnect plug, when used backwards (so the QD part is the nozzle) gives a thick laminated stream - all for under a buck.

Using this nozzle with my garden hose of 40 psi:
- I can place water 45 feet when shooting diagonally like artillery.
- Fires 8.5 oz of water per second (filled a 5 gallon bucket and divided time)

I can't wait to test this nozzle at 130 psi.

Here's a picture showing the stream in the nozzle:
Image

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mysterio
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Re: Point-Defense water gun

Post by mysterio » Sat Aug 28, 2010 10:31 pm

that looks like a beast. you should try out the homemade lamination nozzle.

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cantab
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Re: Point-Defense water gun

Post by cantab » Sat Aug 28, 2010 11:40 pm

Don't expect massively greater range with 130 psi. You get diminishing returns with increasing pressure. I'd expect no more than 60 feet with that nozzle.

Once you have the gun finished, I'd suggest experimenting with the regulator, you might be able to reduce the operating pressure to make the air cylinder last longer without losing noticeable performance. Ben used 100 psi on his Supercannon II; the performance came from having a massive stream that thus has more momentum and is slowed less by air resistance.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

eqo31
Posts: 6
Joined: Mon Aug 23, 2010 4:44 am

Re: Point-Defense water gun

Post by eqo31 » Sun Aug 29, 2010 12:03 am

Yeah, now that I think about it, while I don't remember much from fluid dynamics, it should end up around 45*[130^(1/3) / 40^(1/3)] = 67 feet theoretical.... minus earlier terminal velocity probably puts it around 60 in practice.

Edit: Hmm, now if only I can reduce the viscosity of water. I wonder if a drop or two of dish detergent might help.

Since my nozzle is currently a standard 3/4 FPT, I'm thinking of putting a Y-splitter on the front so I can chose on the fly whether to do a fire hose or the current 1/4" nozzle. Point defense isn't very useful if a cannon can outrange you, but at the same time, I need to last longer than a 5 second blast. Sigh. Reality always has to burst my bubble. We'll see how tweaking goes tomorrow.

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cantab
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Re: Point-Defense water gun

Post by cantab » Sun Aug 29, 2010 10:36 am

eqo31 wrote:Edit: Hmm, now if only I can reduce the viscosity of water. I wonder if a drop or two of dish detergent might help.
Ben got five feet extra from Supercannon II by adding 5% glycerin to the water.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

eqo31
Posts: 6
Joined: Mon Aug 23, 2010 4:44 am

Re: Point-Defense water gun

Post by eqo31 » Mon Aug 30, 2010 2:23 am

Haven't had the time to start tweaking - It seems like cantab hit the nail on the head with regulator thoroghput - as pressure increases, flow is too fast for the regulator to keep up. This means the riot blast needs a pause half way, and the 1/4" nozzle is too wide - pressure drops to and stays at 60psi.

The flow at higher pressures was extremely turbulent - I think I'll try the other project mentioned for more laminar output.
Last edited by eqo31 on Fri Aug 12, 2016 7:17 am, edited 1 time in total.

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