Water Bottle Chamber

Build a homemade water gun or water balloon launcher and tell us about it.
me_really
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Water Bottle Chamber

Post by me_really » Sun Dec 13, 2009 1:07 am

Hi,
This is my first time posting, but not my first time reading posts. I gained some great info here before making my first homemade. Time to give back...

I didn't find info on these forums for how to attach readily-available water, coke, etc bottles as a chamber. I gave it a try using 1/2" pvc with great success! I took the expensive 3" PVC cap and reducer parts I purchased back to home depot for a refund :)

I will attach Picts later.

To attach the water bottle I simply primed (with purple primer) and then used a healthy amount of pvc cement on both the 3" long piece of 1/2" pvc and on the inside of the water bottle neck, then insetred the 3" piece. After joining the 1/2" pvc to the water bottle, I carefully tilted the assembly pvc-end-down to allow the excess cement inside the bottle to flow around the joint for added strength.

I haven't used the gun extensively yet, but I have pressurized and shot it at least 30 times with no pressure failures yet. :)
Attachments
h2oBottleChamber.png
gun_pumpout.png
gun_pumpin.png
Last edited by me_really on Sun Dec 13, 2009 1:09 am, edited 1 time in total.
Reason: add picts

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Drenchenator
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Re: Water Bottle Chamber

Post by Drenchenator » Sun Dec 13, 2009 2:09 am

Welcome to SSC, me_really!

I like many things about your homemade. The tubing barb for a nozzle should work well, and the pump looks very well done. You shouldn't expect any leaks from any of your PVC parts because you used PVC primer, so I wouldn't expect any.

But there's a reason why you didn't see threads about attaching soda bottles as pressure chambers: It's usually a bad idea. Though they are designed for some pressure, they usually won't take much to burst. They burst easily because the plastic too thin and because the bottle's geometry is irregular.

That's not to say that you shouldn't use bottles. Just use them carefully. In Europe, PVC is rare, so many builders resort to copper water guns with soda bottle chambers. This is understandable because there isn't much else to do.

Regardless of the bottle's strength, if the fitting to attach the bottle is bad, you might have just build a bottle rocket. To be frank, your bottle attachment joints can just slip right off. Don't fret though; I'm sure there's a fitting that you can screw the bottle into if you must use bottles.

Still, 3" PVC is dirt cheap in the US and would make a much better pressure chamber. Was there a particular reason you used soda bottles for the pressure chambers? Was 2" or 3" PVC unavailable to you?

Still, it's a good build overall; I'm just wondering about the choice of materials.
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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Sun Dec 13, 2009 2:15 am

Nice APH design gun! Its very clean and well done! How big is the backpack?

One thing I'd watch out for: the water bottle. The coke one will probably be fine, but the water one is not pressure-rated. It might work, but I'd do something different.

I like this a lot. What size nozzle do you use and how much range do you get with it?

:-)
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cantab
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Re: Water Bottle Chamber

Post by cantab » Sun Dec 13, 2009 2:41 pm

Such a slip-over fitting is something I've considered. Drenchenator is right that one possible failure mode is for it to shoot off like a rocket - I've heard of this happening with other people who used bottle pressure chambers. To be honest, that's probably less dangerous than the bottle exploding, but still not something you want to happen.
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me_really
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Re: Water Bottle Chamber

Post by me_really » Sun Dec 13, 2009 4:36 pm

Thanks for the replies and I appreciate the warnings about potential bottle failures.

The reason I went with water/coke bottles is cost and weight. The 3" pvc pieces were costly and relatively heavy.

I'm not a hard-core user (don't even have a backpack). I don't regret making it from available bottles, although I agree the coke bottle is a better choice for strength.

I'm considering making a trigger by using a 12V solenoid valve and battery pack connected to a momentary switch/button. Have you guys ever tried that?

Thanks again.

I am an ME (really).

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Drenchenator
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Re: Water Bottle Chamber

Post by Drenchenator » Sun Dec 13, 2009 6:31 pm

I just noticed the green string. That's a great idea. So many people have built homemade water guns and have complained that the pump can pop out. I guess that solves that problem. Great idea!
I'm considering making a trigger by using a 12V solenoid valve and battery pack connected to a momentary switch/button. Have you guys ever tried that?
I think nobody has done that for a water gun -- it's been discussed, though -- but I know it works because they it works for Nerf guns; there's no reason it can't work for a water gun.

Still, most builders avoid solenoids in water guns because solenoids destroy good water flow. Expect your gun's performance to decrease if you use them. Ball valves are really the best for performance, but some people hate them (Don't worry; I'm in that camp too.). Still, if you just want to have fun and have a easy to use water gun, a solenoid valve is fine for that.

But this raises a question about costs. If you deemed 3" PVC too expensive -- I certainly don't view it as that -- why buy a solenoid, which will cost around 20 USD where I live? Do you just want an easy trigger?
Last edited by Drenchenator on Mon Dec 14, 2009 2:12 am, edited 1 time in total.
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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Sun Dec 13, 2009 9:06 pm

An easy trigger is very affective in combat because of the tap shots possible. I also think me_really's bottles are .5 liter each so he doesn't want to waste his water quickly with just a liter to use.

Im not very experienced with those valves, but I do know that they open more quickly.

Me_Really's project is very clean and well done. But I still want to know what size nozzle and range.
The name's Juch, just Juch.
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me_really
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Re: Water Bottle Chamber

Post by me_really » Mon Dec 14, 2009 2:03 am

Drench,
You're good. Yes, the green string is to keep the pump from coming out. It's very effective and pretty easy to implement.

I do agree about the cost of the solenoid trigger. Definitely takes it to the next level cost-wise and will impact the performance. I tend to think it would make others green with envy though... because I expect it would change the whole feel in a positive way.

I've thought of two ways to implement....

1) The easiest would be to have the water flow while the button is pressed and stop when you let your finger off.

2) The more-desirable (for me) would be to have it fell like most real guns... and put out a short pulse of water with one pull of the trigger. That implies some circuitry to cut off the solenoid voltage after XX milli-seconds.

I actually purchased a solenoid to play around with. I'll post when/if I get around to the implementation.

---

Juch,
My nozzle is 3/8". I get about 45 feet out of it when held at ~45degrees. The stream is not real tight (breaks apart fairly soon after leaving the nozzle). It would give someone within 30 feet a decent drenching. ...with the ball valve.

Regards.

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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Mon Dec 14, 2009 12:59 pm

That's a good sized nozzle, even though I'd play around with others to get the best range possible. 45 probably out-ranges most of the guns anyway (except for the 98s) so this isn't a big deal, but isn't it awesome to shoot someone 50 feet or more away easily?

I don't know much about solenoids so I'll let someone else talk to you 'bout that.
The name's Juch, just Juch.
Also known as Commander JuchJawsTurtles, commander of the C0BALT TiDE team in The Ocean Volcano Union.
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Drenchenator
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Re: Water Bottle Chamber

Post by Drenchenator » Mon Dec 14, 2009 3:26 pm

1) The easiest would be to have the water flow while the button is pressed and stop when you let your finger off.
That would definitely be the easiest.
2) The more-desirable (for me) would be to have it fell like most real guns... and put out a short pulse of water with one pull of the trigger. That implies some circuitry to cut off the solenoid voltage after XX milli-seconds.
With electrical circuits this plan is completely possible, but I don't think anyone has done something like this with a water gun.

I don't know how much you know about circuits, but a simple RC circuit could do this is you know exactly how many volts the solenoid needs to stay open. But this would just turn off the solenoid. You'd still have to take your finger off the button to recharge the capacitor to let you shoot again.

So you'd probably would need an op amp in there somewhere to help make a square wave generator. A square wave would work here because it would just pulse on an off. I don't remember the exact kind of circuitry you would need for this off the top of my head, but I'm sure we can look it up.
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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Tue Dec 15, 2009 6:16 pm

This is interesting, but just be careful. Water and electricity do not mix well. And part of the reason I am more concerned than usual is because if the bottle explodes, and water gets in the circuit, it would be quite shocking! It would be safer if you switched to heavy-duty pipes, which have small chances of exploding even at high pressures.
The name's Juch, just Juch.
Also known as Commander JuchJawsTurtles, commander of the C0BALT TiDE team in The Ocean Volcano Union.
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me_really
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Re: Water Bottle Chamber

Post by me_really » Mon Dec 21, 2009 2:11 am

Juch,
We're talking about low voltage (12V) DC. Not much of a hazzard. You would certainly want to waterproof the electrical part though.

However, if we were to try and use 120V AC with a transformer to feed the DC voltage, then yes, we would need to be careful to keep the transformer away from the water. However, 120V AC implies you have to use an extension cord which takes away portability anyway.

I was leaning more toward using a 12 volt battery to charge up a cap in some circuit appropriate for this application (like the RC circuit Drench mentions).

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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Mon Dec 21, 2009 2:15 am

I'd just be careful because of the risk of the water bottle breaking. Cover the electric part with something waterproof, possibly a plastic bag.

Also, YAY! It's my 200th post!
The name's Juch, just Juch.
Also known as Commander JuchJawsTurtles, commander of the C0BALT TiDE team in The Ocean Volcano Union.
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Drenchenator
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Re: Water Bottle Chamber

Post by Drenchenator » Mon Dec 21, 2009 3:55 am

Cover the electric part with something waterproof, possibly a plastic bag.
A plastic bag isn't a sturdy solution. I suggest you buy a small cup, perhaps even a urine cup if you could get one. I used one on a simple circuit I had to make in high school, and it worked well. It's large enough for a resistor, capacitor, and a nine volt. And it's guaranteed to be water proof so that the -- um -- "contents" don't leave accidentally.

Keep us updated me_really! This is a nice project.
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JuchTurtles
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Re: Water Bottle Chamber

Post by JuchTurtles » Tue Dec 22, 2009 9:16 pm

How is it going? Have you put the solenoid into effect yet? Have you made any changes?
The name's Juch, just Juch.
Also known as Commander JuchJawsTurtles, commander of the C0BALT TiDE team in The Ocean Volcano Union.
SPLASH! You're dead!

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