Figures for creating an APH

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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Joined: Sun Aug 03, 2008 6:57 am

Figures for creating an APH

Post by JPT » Sun Aug 03, 2008 7:49 am

I am new to this forum. I recently digged out my old stock soakers from the attic and it made great fun.

To have even more fun I decided to build a soaker myself.
While there are a lot of guides and tutorials, I was not able to find any figures yet.
Please do not say "that depends on what you want to have". I want to have something that feels like my XP150 without its drawbacks.
It would be fine if it had a range similar or superior to my SS100. I do not want to have a specialist eg for sniping or flooding.

Size of PC and Pump
When you think about volumes, eg. the volume of the pressure chamber or the pump you need a hint from experienced people which proportion will work fine.

My old soakers are a SS100 and an XP150. They show both ends of what is possible.
Using the SS100 you have to pump like insane, because the pressure chamber has a volume of 400 ml, while the pump only has 20 ml (and the diameter is low). You never ever reach a point were pumping is not possible any more. The valve will have opened long before.
Pumping up the XP150 only needs you to pump a few times. But you soon reach a point, where you just cannot move the pump any more.

So what do you suggest?
My idea is a PC volume of about 300 to 500 ml, a pump pipe of either 16mm=>1/2" or 20 mm (outer) diameter, and with a lenght of maybe 15 cm.
Should I change some of these figures?

Size of the soaker
I tried to attach the water reservoir to the gun itself. But if you plan a reservoir of 1 liter, the gun will have a size of at least 35 x 35 cm (14").
Is it possible to handle soakers of that size? Or will you hate it?
I think I will use some standard PET water bottles on my back... should I?

What is a good size for the nozzle?

Max Pressure
What is the pressure I have to expect?
Most of my parts have a specification of 16 bar (230 psi). Some only reach 10 bar (145 psi).
A few that I could try to avoid reach "only" 5 bar (70 psi).
There are some transparent PVC pipes available that do not take much pressure. But it might look great. :-)

So what pressure are we usually talking about, when pumping manually?

How much PVC glue will I need? Should I buy 125g or 480g?
Should I buy the "PVC cleaner" they offer?
Did anybody integrate a manometer in his soaker?

Posts: 339
Joined: Sat Apr 21, 2007 3:01 pm
Location: Virginia

Re: Figures for creating an APH

Post by Silence » Sun Aug 03, 2008 11:15 am

Welcome to!

Here's a zipped spreadsheet that relates pump force, various pump sizes, and pressure. You should expect about 50 PSI if you're using 1/2" Schedule 40 PVC. But...judging from the units you've mentioned, I'm guessing you're British, which means PVC may be hard to find where you live. That's a big assumption though so I'm probably wrong.

1/2" PVC is a good compromise. You won't get much pressure and range with 3/4" PVC and you'll have to do a lot more pumping with anything smaller. As for pump length, that's entirely up to you. I don't like the "number of pumps" statistic - "distance pumped" works much better, as many short pumps and a few long ones essentially equate to the same thing. I'd go with the longest distance you're comfortable with, probably closer to 25 cm. And if you want specifics, you'll have to do measurements yourself, simply because we don't have XP 150s in front of ourselves.

For the pressure chamber(s), you should be fine with 4 to 6 inches of 3" PVC or 8 to 12 inches of 2" PVC (in two pressure chambers if you go with the longer length). That's fairly small for an APH but it's sufficient and it should be closer to the XP 150.

14" is not very large at all. In fact, I'm not sure how you could fit a pump, reservoir, and pressure chambers into a square that small. If you want a backpack, using water bottles should work well. To make a hose connection, you could cut a hole in the cap and glue a hose barb to that, or try to use a threaded fitting that connects directly to the bottle, like this. Apparently a 3/4" female hose thread fitting works perfectly.

A 1/4" or 3/8" nozzle should work best at most pressures. If in doubt, use hose barbs with suitable inner diameters (which aren't labelled) or metal pipe nipples instead of drilled PVC endcaps (at least, unless you have a drill press).

Transparent PVC's pressure shouldn't be a problem, but the price may with larger diameters. As I said above, expect something around 50 PSI.

You probably won't need much glue. Definitely buy primer though. Here's a good, well, primer on solvent welding PVC in homemade water guns.

I don't know if anybody has integrated a pressure meter, but it's not hard. Ben has used a pressure meter on his regulated air homemades, and water guns (like SuperCannon II) that use air pumps can use the gauges in those pumps. If you just want a manometer to see how much pressure you can attain with the water gun, you can screw it onto the nozzle selecter instead of a nozzle to see, temporarily. If you want to see how much water is left while you're using the water gun, that's not a problem because you can see the water level through the pressure chamber PVC.

Good luck with the build! B)

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Joined: Sun Aug 03, 2008 6:57 am

Re: Figures for creating an APH

Post by JPT » Sun Aug 03, 2008 12:34 pm

Thank you, Silence.

Your post helps a lot, but I believe I have to think some details over again. Will have a look at the spreadsheet.

Actually I am from Germany. I didn't know my English was that good :-) Thanks.
And luckily I found an online store for osmotic stuff that sells PVC pipes at reasonable prices:
Using this stuff I will probably end up at 70 Euro.
On saturday I was at the local hardware store. If I would buy there, it would cost 200 Euro!

25 cm pump length. I will give it a try.

For pressure chambers I planned to use two (or three) chambers from 2" (5cm) pipes, because of the pressure allowed.
But if you expect "only" 50 PSI, I may take larger ones.
In height maybe 4".
BTW, what is Schedule 40 PVC? Is it the pressure rating? All PVC the store offers is rated 16 bar (230 PSI) except a few parts, eg. the large diameter pipes.

well, you are right, I forgot the length of nozzle attachment and pump :-)
I need a software to draw...

For connecting the bottles I have a great idea.
Do you know the Gardena garden hose stuff?
And do you know those water rockets sold at ebay?
You can buy adaptors from water bottle to gardena. so you can simply click your bottle on. :)
From there you may use standard Gardena hose connectors to attach to your soaker.

I did not find primer anywhere. Only the "cleaner", I wrote about. What is the primer supposed to do?

That's it for today.


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Joined: Sun Aug 03, 2008 6:57 am

Re: Figures for creating an APH

Post by JPT » Sun Aug 03, 2008 1:07 pm

What about this?
aph.jpg (90.1 KiB) Viewed 2242 times

Posts: 339
Joined: Sat Apr 21, 2007 3:01 pm
Location: Virginia

Re: Figures for creating an APH

Post by Silence » Sun Aug 03, 2008 1:23 pm

Your English is great. :)

It's good that you found a source of PVC in Europe, and that it's pressure rated too. Schedule 40 refers to the thickness of the pipe. All pipe with the same specified size (like 2") has the same outer diameter (OD), but the inner diameter varies. Here are a few thickness, ordered by increasing thickness and decreasing innerdiameter (ID):
  • thinwall
  • Schedule 40
  • Schedule 80
  • Schedule 120 (very rare)
Naturally, the pressure rating increases for each one. Thinwall isn't pressure rated at all. Schedule 120 is only really found with large diameters like 6", 8", or 12", where you need more thickness to get sufficient pressure. Of course, that type of pipe ends up being very expensive and heavy, and it still doesn't hold much pressure.

PVC also has different types of structure on a molecular level:
  • cellular core, or cell core
  • solid core
Cell core has little holes in the PVC that makes it lighter, but it loses the pressure rating. All pressure rated pipe is solid core.

That's a lot of (irrelevant) information, but you asked. :P

Using a Gardena hose attachment should work well. You will need a Gardena hose to PVC fitting (either threaded or socket, which means you can stick PVC pipe in directly) to connect the hose to the water gun. If you can't find the right fitting, try using a different type of hose that you can connect instead. Because there's no real pressure held in the backpack, you don't need a very tight seal between the hose and the reservoir. Even duct tape should be sufficient.

Technically, there are three chemicals that should be used in solvent welding:
  • cleaner - cleans dirt and grime off the pipe. It's usually not necessary.
  • primer - softens the PVC to help the cement do its job. It usually is a good idea.
  • cement - chemically melts the PVC so that, once solidified, the pipe and fitting are one piece.
Primer (the purple compound in the pictures) isn't necessary but you should use it. Sometimes cleaner and primer are combined and sold in one container.

Your diagram looks good. Make sure you use pipe saddles instead of filed tees on the pipe that holds the pump and barrel together near the ball valve.

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