Scrapheap challenge watergun

Build a homemade water gun or water balloon launcher and tell us about it.
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Dougw
Posts: 1
Joined: Mon Oct 20, 2008 4:55 pm

Scrapheap challenge watergun

Post by Dougw » Mon Oct 20, 2008 5:02 pm

Hello everyone,

This maybe a slightly odd request. I am part of a team that has to build a water collection and dispersion device from scrap materials as part of a competition.

We are aiming to build a water gun that is hand powered (hand pump to create/store pressure) and draws water from a drum or other collection device.

We would need to fire approx 30 -40 ft with low volume, but high pressure (like a pressure washer)

Does anybody know of any good designs that we could adapt to build from scrap (2 litre coke bottles and a bicycle pump for example)??????

Any help or suggestions welcome.

Thanks

D

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SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Re: Scrapheap challenge watergun

Post by SSCBen » Mon Oct 20, 2008 7:13 pm

Welcome to SSC!

Any variation of this water gun or aEx's water gun would be fine. Just be aware that the pressures can't get too high. I'd stop at 80 psi to stay on the safe side. If you intend to use higher pressures than that be sure to test the bottles first (if it blows up in a fail safe environment that's better than with a person next to it) and still have a safety factor.

If you have scrap PVC then use that. It'd be safer at high pressures.

aEx155
Posts: 325
Joined: Sun Apr 27, 2008 3:13 am

Re: Scrapheap challenge watergun

Post by aEx155 » Mon Oct 20, 2008 11:06 pm

You're not going to be able to get "pressure washer pressures" unless you have a pressure washer or pressure washer equivalent, so I'd rethink things like that...At most, I'd say you'll get around 80 PSI from a bicycle pump.

If you're thinking of going any higher, then you might want to think of going for something stronger than plastic soda bottles (max pressure is 100 PSI, but that may be going over already), otherwise, you may have an explosion hazard.

There are several ways you could stem off the details you gave; are you going for distance, shot time, output, or mainly pressure?

For distance;
Look around the Physics section for the nozzles article, and anything else that applies to increasing range. Try to get the highest flow/laminar"ity" (straightest flow path) so your stream will go further. Look into stream additives.

For shot time:
Try to get the largest tank you possibly can, or some kind of pump that you can power. (you probably could make an air powered one from PVC if you have valves and such). That way, your water doesn't get used up fast. Look into reducing nozzle size to the bare minimum.

For output:
Basically the same as going for shot time, but with nozzle size being large instead of small. You want the most possible water flowing out of the nozzle, so keep it simple. Try a Supercannon 2 approach. (the shot time thing is so you have a sustainable stream, rather than an APH-riot blast type thing(unless that' all you need))

For pressure;
Work on getting things rated for pressure; you most likely end up with something you fill with water, pressurize with air, then fire, since pumping air is the easiest way to get high pressure.

You can also try for any combination of those approaches, most of which can be achieved with "scrapheap pieces". My homemade is a great example of a gun made from "scrapheap pieces", but it still works pretty great. The soda bottles, which are basically the most important part, are the only thing I didn't buy.

Any clarification needed could probably be provided, so don't be afraid to ask questions.

Hope that helps.

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Silence
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Joined: Sun Apr 09, 2006 9:01 pm

Re: Scrapheap challenge watergun

Post by Silence » Fri Oct 24, 2008 12:15 am

Ben linked to a couple of relevant designs. Scale it up with more water bottles and larger tubing if you can and if you want more output and range. And make sure you use epoxy unless you can actually find a perfectly-sealing fitting.

I'm wondering what you'll use for the valve, though.

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cps zer0
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Joined: Thu Aug 07, 2008 6:52 pm

Re: Scrapheap challenge watergun

Post by cps zer0 » Sun Nov 16, 2008 8:11 pm

what is the competition?
armory: 3 aph's 2 max d 3000's 1 supercannon2 1 cps 2 xp 215's and a cheap pr gun

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