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Simple Watergun Question

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Simple Watergun Question

Unread postAuthor: TheTrooper » Sun Jun 15, 2008 2:22 pm

When a 2-liter bottle is half-full with water, is it still safe to bring it to 100 psi?
Or would the water have some effect on the limit because its cutting the chamber volume in half?
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Once people start building spud guns they have two career options, they can be a weapons designer or a plumber. Hard choice isn't it.

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Unread postAuthor: benstern » Sun Jun 15, 2008 2:30 pm

I think so, although 100 psi might be pushing it. People into water rockets would be able to answer this better.
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Unread postAuthor: TheTrooper » Sun Jun 15, 2008 2:32 pm

Well when i did water rockets with 2-liter bottles, we used 80 psi to launch them, so i guess i should just keep it at 80. It's powerful enough already.
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Once people start building spud guns they have two career options, they can be a weapons designer or a plumber. Hard choice isn't it.

Projects Completed:
http://www.spudfiles.com/forums/viewtop ... tml#148488

http://www.spudfiles.com/forums/viewtop ... tml#190652
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Unread postAuthor: MaxuS the 2nd » Sun Jun 15, 2008 2:49 pm

Another simple watergun question..?

Why a watergun?
Is it because it's just something different?
I mean I could understand building a watergun that releases high pressure water quite slowly so it lasts for a while atleast...But the waterguns that are appearing on Spudfiles recently only fire water out in a short burst..
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Unread postAuthor: Biopyro » Sun Jun 15, 2008 2:50 pm

Water bottles which are used for fizzy drinks will easily hold 100psi. Filling them with water makes it much less dangerous because of the reduced energy stored. The volume halved just means you need half the number of pumps to reach the same pressure. Be wary of going over 70psi with a water gun because if a hose clip fails then you've got yourself an unintended water rocket!

Nice to see everyone taking a less dangerous twist to spudgunning this summer :P
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Unread postAuthor: iisthemuffin » Sun Jun 15, 2008 2:54 pm

In my enginneering class last year we built bottle rockets with a science class and they were safe up to 150 psi. They do tend to get dangerous that high but its not unsafe if you have the proper clamping equipment. I believe we launched them all at 120 without a problem.

EDIT - be sure to use pop bottles or carbonated drink bottles
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Last edited by iisthemuffin on Sun Jun 15, 2008 2:55 pm, edited 1 time in total.
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Unread postAuthor: MrCrowley » Sun Jun 15, 2008 2:55 pm

We went up to 160psi at school with our water rockets. My physics teacher didn't understand the risk, even though I told him that they could fail very easily at such a high pressure.
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Unread postAuthor: TheTrooper » Sun Jun 15, 2008 2:56 pm

if a hose clip fails then you've got yourself an unintended water rocket!


What do you mean by hose clip Biopyro?

Edit: Oh yeah heres my water gun http://www.spudfiles.com/forums/viewtop ... tml#190652
It shoots in long bursts.
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Once people start building spud guns they have two career options, they can be a weapons designer or a plumber. Hard choice isn't it.

Projects Completed:
http://www.spudfiles.com/forums/viewtop ... tml#148488

http://www.spudfiles.com/forums/viewtop ... tml#190652
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Unread postAuthor: Biopyro » Sun Jun 15, 2008 3:08 pm

A jubilee clip, I think they have a different name in the US.

That's a great cannon! A little simplified version of the one I'm planning :D
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Unread postAuthor: TheTrooper » Sun Jun 15, 2008 3:13 pm

Thanks Biopyro, your backpack water gun inspired me to build this simplified one. But remember, i can still add a second tank.

But I'm guessing its still safe to bring it up to 80-100 psi with the water still in there right?
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Once people start building spud guns they have two career options, they can be a weapons designer or a plumber. Hard choice isn't it.

Projects Completed:
http://www.spudfiles.com/forums/viewtop ... tml#148488

http://www.spudfiles.com/forums/viewtop ... tml#190652
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Unread postAuthor: Biopyro » Sun Jun 15, 2008 3:29 pm

Yeah looks fine, I think that hose would go first. Good thing about this is though you're more likely to get wet than injured. It may be worth measuring the performance increase with pressure. Above 60psi you tend to get diminishing returns.
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Unread postAuthor: TheTrooper » Sun Jun 15, 2008 3:37 pm

Thanks, good thing the hose has 100 psi safety rating.
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Once people start building spud guns they have two career options, they can be a weapons designer or a plumber. Hard choice isn't it.

Projects Completed:
http://www.spudfiles.com/forums/viewtop ... tml#148488

http://www.spudfiles.com/forums/viewtop ... tml#190652
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