APH question

Build a homemade water gun or water balloon launcher and tell us about it.
psicicle
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APH question

Post by psicicle » Sat Mar 31, 2007 3:15 am

How are you supposed to fill the PCs with water? Don't you need to cement them on?

mr. dude
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Post by mr. dude » Sat Mar 31, 2007 3:29 am

That's what the pump is for. Each stroke of the pump takes water out of the reservoir and into the PCs.
Another common method requires a shrader valve. You fill the PCs up through the ball valve, and then pump up to pressure with a bike pump. The first method is the one used in the APH.

psicicle
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Post by psicicle » Sat Mar 31, 2007 2:41 pm

in the design there doesn't seem to be any resovoir though.

Im using this one:
http://www.sscentral.org/tech/homemades/aph.php

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joannaardway
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Post by joannaardway » Sat Mar 31, 2007 2:53 pm

That design uses a water backpack as a reservior - attached via a long hose.
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psicicle
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Post by psicicle » Sat Mar 31, 2007 5:22 pm

hmmm, would it work if I made the PCs the resovoir because I accidenally got a T-bend thing with threads. If I connected the check valve to nothing, would it pump air in?

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DX
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Post by DX » Sat Mar 31, 2007 8:04 pm

That design requires the use of a homemade backpack. PCs cannot act as reservoirs except in one-shot water cannons. For an APH, you need a separate reservoir, either backback or attached [onboard].

You can build an onboard reservoir if you don't have the materials for a backpack. There are a lot of different ways to set one up, examples:

Image
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Other image won't load due to word filter [it affects urls as well]
Last edited by DX on Sat Mar 31, 2007 8:17 pm, edited 1 time in total.
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joannaardway
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Post by joannaardway » Sat Mar 31, 2007 8:25 pm

Ah - the ever present word filter.

Just a moment:

soakermedia.net/images/n0x0b_killer_homemade.jpg

If you want to view the other image, copy that url to your address bar, just remove the x that's in red.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

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Silence
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Post by Silence » Sun Apr 01, 2007 9:49 pm

Yeah, I'm fairly sure a revised version of the APH article will mention the backpack more.

What you're referring to is a pressurized reservoir (PR) water gun. Basically, there's a tank with a cap in it, and a pump that draws in air. The problem with these is the fact that it takes many pumps to pressurize the reservoir, at least at first, because the reservoir is far larger than the pressure chamber (PC) of a regular gun.

psicicle
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Post by psicicle » Sun Apr 15, 2007 2:06 am

another thing- how should I build the pump? I get the gist of it but some pictures would help. The ones with the onboard resovoir helped a lot, thanks everyone.

also, what nozzles should I have and how should I make them?

edit: never mind about the nozzle, I found the search button finally, but pump info would still help

edit: is a pressure gauge useful in an APH?

edit: how strong does PVC cement hold; I used primer first of course and liberal cement and wiped off the excess like on the can. It will probably be somewhat imperfect though so I just need an estimate. Would it be roughly as much as the PVC?
Last edited by psicicle on Sun Apr 15, 2007 1:13 pm, edited 1 time in total.

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SSCBen
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Post by SSCBen » Sun Apr 15, 2007 1:52 pm

Don't follow the pump construction in the APH guide. It is easier to make a wooden pump and a wooden pump seals better. I'll write a small guide to making wooden pumps within the next few days. If I don't get to it because I'm busy, someone like DX will help you out. ;)

Nozzles are easy to make. All you have to do is drill a hole in a PVC threaded endcap. To switch nozzles, all you do is screw off one nozzle and screw the new one on. I've been working on a rotating nozzle selector too, but I haven't had the time to finish it. The rotating one will be on the website when I get around to updating it.

As for whether or not a pressure gauge is useful, it depends on how well you can tell how hard the pump is. Using some more reducers to attach a pressure gauge to the top of one PC would be quicker and more convenient than trying to pump to get a good picture of how full the PCs are. You could mount the gauge on a part with water and still get a reading, but I'm not sure if the inside of the gauge will rust. The main reason I did not include a gauge in this water gun was due to cost however. A gauge costs typically $7 at our local Lowes, and the parts needed to mount it should cost at least an additional $5 over the endcap they replace. If you want to try this out and want some better explanations, let us know and we can help.

I've read that PVC cement bonds are slightly weaker than the PVC itself, but I am fairly confident the pressure figures written on the pipe include PVC cement because the only way you could bond the pipes would be with PVC cement (aside from a torch, and no one uses one for PVC). The PVC cement literally melts the plastic together so it becomes one solid piece, so I would imagine it is about as strong as the PVC itself. Even still, the pressure figures on the pipe are already conservative, so I wouldn't worry about anything. Water guns typically don't even approach half of the pressure rating.

I also would not suggest applying too much PVC cement. The fittings will push it out from under the fitting and you'll just end up wasting a lot of cement. I would suggest following the instructions on the can. Typically they say apply two or three coats on the ends, and then twisting the fitting onto the pipe as you push it down to spread out the cement. After that, they usually say to hold the fitting onto the pipe for about 20 seconds to prevent it from popping off while the bond is it's weakest.

Hope this helped! :)

psicicle
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Post by psicicle » Sun Apr 15, 2007 2:55 pm

should I just replace the aluminum rod with a dowel of the same size?

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Silence
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Post by Silence » Sun Apr 15, 2007 6:18 pm

A dowel should work fine, but I'd wait for Ben's article. He knows what he's doing. :cool:

Some people have used metal pipe nipples for their nozzles because their streams are much cleaner. Ask somebody at the store to show you where they are. You might want to get 1/4" and 3/8" pieces for nozzles, as well as standard endcaps.

If you can easily see the water inside the PCs, I'm thinking there's a better way to do a pressure gauge. Buy the pressure gauge and pieces if you want to do this, but screw the gauge on as a nozzle and leave the ball valve open as you pump. Make marks on the PC to show how much pressure there is when filled to a certain point.

You can actually skip the gauge if you just need a rough estimation of the pressure. Using Boyle's law, you can determine the correlation between how much air volume is in the PC and how much pressure there is. Making marks will let you easily see how much pressure there is while in battle.

However, I suspect you won't really find a pressure gauge useful. Just make sure you shoot short bursts and keep the pressure up by occasional pumping. There's also very little dropoff.

I'm fairly sure people have tested PVC and found that pieces rated to 200 or 300 PSI have found them safe up to over 500 PSI or so. Don't quote me on it though. I still would not ever take any PVC above half of its rated pressure, not that it's possible with a standard pump.

When applying the PVC cement, just make sure you use primer first, apply the cement thoroughly (although not excessively - just make sure there's an even coat), and twist the joints as you slide them in. That should yield a complete, strong joint.

Wipe off the cement that gets squeezed out. Looks cleaner, helps allow the parts underneath to dry, and doesn't warp or weaken the PVC that it squeezes onto.

psicicle
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Post by psicicle » Wed Apr 18, 2007 12:41 am

where will I find the post? Also, I'd appreciate it if someone could help me make this better version now, because I have a trip to lowes scheduled tomorrow (Wednesday) or direct me to a website.

By the way, I've put together the pressure chamber half of the gun so far! Pretty excited

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Silence
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Post by Silence » Wed Apr 18, 2007 2:19 am

I can only imagine the good pump Ben's referring to is his brother's homemade one, in this thread at waterwarfare.com.

Duct tape should work as well as CPVC. If necessary, you could create a groove for the O-ring - I have no experience here, so I hope Duxburian (who's recently had success) will answer this.

Good luck with the rest of the homemade!

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DX
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Post by DX » Wed Apr 18, 2007 2:57 am

http://www.geocities.com/m15399/pumps.html

^Only guide as of now. Forgot about that site have we? :rolleyes: My own article on pumps is so ancient that it's not even worth posting.
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