Designing a gun, will it work?

Build a homemade water gun or water balloon launcher and tell us about it.
eternal46845
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Designing a gun, will it work?

Post by eternal46845 » Tue Apr 01, 2008 5:21 pm

Hello all, I've designed a gun, but I'd like for you all to look it over and makre sure it will work before I build it, and what I might expect for distance and volume output. I have attached a quick MS Paint Jpeg to look at. Hopefully it is pretty clear...

Questions:

How large should I make my pump (length + inner diameter) I don't want to be pumping this thing up all day.

The main tank will be 4" Sch 40 PVC...about 2' of it, so how big should the outer pressure tanks be to optimize pump / pressure / other stuff?

Possible output at what nozzle diameter?

Size of PVC connections I should use and size of tubing to optimum flow?

Any other suggestions?
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watergun.JPG

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Drenchenator
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Re: Designing a gun, will it work?

Post by Drenchenator » Tue Apr 01, 2008 8:36 pm

This gun should work provided the pump is functional and the tubing that says "to nozzle" leads to a firing valve and nozzle setup. It should have performance similar to a single chamber APH.

I'd recommend a 1/2" schedule 40 PVC pump as long as you'd like it; I'd probably go for at least 15 inches. With this setup, you can move 1.5L in about 20 pumps. Don't make the pump out of 3/4" PVC; it becomes much harder to pump at higher pressures. For more information on pumping issues, read this article and this article.

I have no idea based on the current information how large your pressure chambers should be. Likely, I'd recommend building them out of 3" PVC and making them about 6" long. Your reservoir is rather small for what I'm assuming is a backpack, so I'd actually recommend making it at least 40 inches long and still 4" PVC--this way it's capacity is about 8L.

If you want to, you can make both the pressure chambers two feet long and have no reservoir. From there, you can just use the water pump to pump water into the chambers and power the gun from a filling station.

This gun could be build out of 3/4" PVC if you want performance similar to the APH. It's very similar to the APH; in fact, you could say it's an APH in a backpack at this point. The APH outputs about 10 ounces a second with a 1/4" nozzle, and about 1 ounce a second with a 1/16", from what I remember, which an effective range of 55 feet.

For best results, you should use a rather wide tubing to lead to you firing devices--any restrictions in the flow will greatly reduce performance. 3/4" vinyl should do the trick since it's about the same size as the rigid tubing I recommend before.
Last edited by Drenchenator on Tue Apr 01, 2008 10:41 pm, edited 1 time in total.
The Drenchenator, also known as Lt. Col. Drench.

eternal46845
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Re: Designing a gun, will it work?

Post by eternal46845 » Tue Apr 01, 2008 9:30 pm

Thanks for the reply. This gun is designed to be mobile. I'm building it for a Cub Scout Pack, and I plan on blasting many a scout during summer camp. Being they will also have guns (most likely store bought) I need to be mobile.

I'd like to have the handset small yet durable...hence the reservoir and the pressure tanks on the back. I envision the handset to be nothimg more than a pump, a ball socket, and a nozzle. Much like the APH, just minus the reservoirs on the handset.

Could I have two pressure tanks, pump fed...something like the attached picture?
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2tank.jpg

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Drenchenator
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Re: Designing a gun, will it work?

Post by Drenchenator » Tue Apr 01, 2008 9:42 pm

That work would well, but only one pump is required. Just remember to fill the gun with water before pressurizing it with an air pump.

Edit: Never mind the stuff about CAP, or constant air pressure. I just got confused because it was, well, in all caps. Ben told me you were referring to a cap as in the cap of a bottle.
Last edited by Drenchenator on Tue Apr 01, 2008 10:41 pm, edited 1 time in total.
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Silence
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Re: Designing a gun, will it work?

Post by Silence » Tue Apr 01, 2008 10:57 pm

Drench, "CAP" was probably just meant to be "cap". It's marked right next to the reservoir cap, I think. I too got confused for a moment when after seeing the diagram.

A 40" tall reservoir? I guess it depends on your tastes. If you follow the second design, you could get lots of volume in little height, which makes more sense to me.

As Drenchenator said, you may as well use a single pump. Use a tee to join both reservoirs at the top, then above that, have a pump, two check valves, and the input.

The final problem is dropoff. Air pressure systems lose pressure and range as you fire - less water in the pressure chambers means the air inside is compressed less. It's not much of a problem with conventional soakers, as you can pump and repressurize on the fly. But here you want the pressure to last.

I would suggest going with a CPS bladder like the one used in SuperCPS. If you have running water and a hose by the battlefield, you can use fittings that let the gun fill directly from the hose like with Leftovers, but with a backpack.

Most water guns without pumps on the handset fill directly from the hose using this method (Super Soaker's SuperCharger series: Splashzooka, Power Pak, and Big Trouble). The exception is the Water Warriors AquaPak/HydraPak, which is like your design but is simpler because it has a pressurized reservoir.

mr. dude
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Re: Designing a gun, will it work?

Post by mr. dude » Tue Apr 01, 2008 11:04 pm

Most water guns without pumps on the handset fill directly from the hose using this method (Super Soaker's SuperCharger series: Splashzooka, Power Pak, and Big Trouble). The exception is the Water Warriors AquaPak/HydraPak, which is like your design but is simpler because it has a pressurized reservoir.
HydraPak is a spherical CPS ;)
I don't have much else to add to this...

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Silence
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Re: Designing a gun, will it work?

Post by Silence » Tue Apr 01, 2008 11:19 pm

Oh whoops, thanks for the correction. :cool:

Looking at iSoaker's AquaPak/HydraPak review, it looks like the water gun is identical to eternal's first design, but with CPS pressure chambers. Eternal, you could probably model the dimensions of your water gun off the HydraPak if you want to go with that format.

eternal46845
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Re: Designing a gun, will it work?

Post by eternal46845 » Wed Apr 02, 2008 12:27 pm

Ok, taking into effect the bladder system and dual reservoirs, my somewhat questionable MS Paint skills have come up with the attached design. Pump outstroke pulls water from reservoirs, and in-stroke pushes water into the bladder...the tubing isn't going to look like it does on the drawing, I just kinda turned the connectors to the side to show how it connects. Note that the tube coming from the left reservoir does not attach to the outflow to the nozzle...it kinda goes behind it.
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Silence
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Re: Designing a gun, will it work?

Post by Silence » Wed Apr 02, 2008 9:02 pm

I see what you've done - clear enough. I'm guessing the cross will be behind the rest, in the third dimension, but hidden from this angle. You could still use only one intake check valve if you rearrange the parts, but that's just a small detail.

I had forgotten that multiple bladders is bad, as over time, one will weaken and expand before the other. It is better to have only one CPS chamber, so you got that right too.

But now you'll need to split the output tube into two parts if you want two hand pieces. Is that still the plan? If so, then another problem arises: limited flow. CPS doesn't allow for very high flow except with really wide tubing. Your design will work with small and medium nozzles though. I'm guessing you don't need high output - that would mean low shot time and having to take off the backpack to pump.

If you do want two hand pieces, then you could have just two CPS chambers that you fill individually, with optional pumps if there's no hose available. It doesn't really matter since there are a lot of options.

eternal46845
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Re: Designing a gun, will it work?

Post by eternal46845 » Thu Apr 03, 2008 12:01 pm

Just need one hand piece. I was planning on using 3/8 inch rubber hose for the path between the backpack and hand piece...or do you suggest wider to accomodate the CPS bladder?

I guess my final design will be similar to the SuperCPS, just with the bladder in the backpack, not the hand piece. Trying to keep the hand piece relatively small.

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Silence
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Re: Designing a gun, will it work?

Post by Silence » Fri Apr 04, 2008 1:02 am

Nothing wrong with a small hand piece. :cool:

I would suggest 1/2" tubing for the hose; also, consider using clear vinyl tubing for the connector. You wouldn't want rubber for that part anyway as it would expand; perhaps we should note that in the articles.

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SSCBen
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Re: Designing a gun, will it work?

Post by SSCBen » Fri Apr 04, 2008 3:11 am

If you're going to be using a CPS bladder, use a tube at least the diameter of the barb. Typical barb sizes for CPS bladders are 1/2 inch and 5/8 inch. Either tubing size is commonly available in home improvement stores.
I had forgotten that multiple bladders is bad, as over time, one will weaken and expand before the other. It is better to have only one CPS chamber, so you got that right too.
I'm not completely sure about that. I think I said that before, but I never tested it. If you build the gun with multiple brand new tubes and replace them all simultaneously, you should not run into the problem of one expanding while the others don't because all of them will experience the same wear. If the tubes don't work initially then something might be wrong. But I think most tubes are close enough to work.

Let me reiterate that I've never tested multiple tubes out and I have no idea if it will work. I don't know if the Super Soakers that used that design (the PowerPak) had better quality control or that no better quality control was needed.

sbell25
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Re: Designing a gun, will it work?

Post by sbell25 » Fri Apr 04, 2008 6:02 am

The Powerpak's multiple bladders work because their expansion is limited by the case. Once the weakest bladder fills up it's own PC case, the water has nowhere to go but inside the stronger bladders. I'd say that having multiple bladders wouldn't work so well if they weren't limited like that.

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SSCBen
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Re: Designing a gun, will it work?

Post by SSCBen » Fri Apr 04, 2008 12:54 pm

Does the PowerPak fill one bladder and then the next? I've never seen one and I'm wondering now. I assumed they all filled simultaneously.

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SSCBen
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Re: Designing a gun, will it work?

Post by SSCBen » Sun Apr 06, 2008 3:58 pm

How's the project going? Any progress? Have you started buying the parts? It seems to be to be a perfectly reasonable design that should work nicely, so you should be able to build it no problem. ;)

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