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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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Spaceman Spiff
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Post by Spaceman Spiff » Mon Nov 26, 2007 7:03 pm

Hey guys! I assume that I am free to modify an existing pump or compressor to create higher pressure.

I had a brainstorm inspired from something I saw on Mythbusters and I have tested it with some cheap 12V car tire compressors and I can easily now double the output without stressing them. I intend to submit my design to the fabrication contest whenever that starts. I am getting a friend who can weld to help me build a nicer version. When you see how easy it is you're going to slap your forehead and say "D'OH!" 8)


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rockets42
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Post by rockets42 » Mon Nov 26, 2007 9:37 pm

KCParkinson wrote:So you're saying we can get air from a scuba tank for "practice"? What do you mean by "practice"?
Yes, they don't mind you spending money on a tank for practice, but they also don't want you to have to buy an expensive compressor for the competition to be fair to others. So instead if you want the sort of performance you get from your tank for entry into the competition you should build a high pressure compressor yourself.
Hey guys! I assume that I am free to modify an existing pump or compressor to create higher pressure.
Please be very careful when attempting this, homebuilt compressors can be extremely dangerous.



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Post by rockets42 » Mon Nov 26, 2007 9:41 pm

Team Seneca wrote:I don't care if everybody wants to keep their ideas secret so nobody copies, but I don't understand the need to post pictures of a air tank. We aren't allowed to use them to make rocket bodies, and we can't use them to bypass the compressor design part of the competition.

I hope this isn't a sign of rules changes. I'm not interested in hitting a moving target.
I expect the rocket is not made out of the tank body, rather, its probably the one sitting on the table in the same picture.



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Post by The Mooseheads » Mon Nov 26, 2007 10:35 pm

rockets42 wrote:
KCParkinson wrote:So you're saying we can get air from a scuba tank for "practice"? What do you mean by "practice"?
Yes, they don't mind you spending money on a tank for practice, but they also don't want you to have to buy an expensive compressor for the competition to be fair to others. So instead if you want the sort of performance you get from your tank for entry into the competition you should build a high pressure compressor yourself.
Uhhh... I think the idea is to make it so people who already had tanks could test drive their rockets before going for a record. It could be a good way to test a rocket design before tackling the pump design, rather than taking on all the challenges in one fell swoop.

It also seems likely that someone who already had a compressor wouldn't want to downgrade to a tank.

P.S. Do you EVER have anything constructive to say?


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Post by rockets42 » Mon Nov 26, 2007 11:04 pm

The Mooseheads wrote:
P.S. Do you EVER have anything constructive to say?
Sorry Rick, I didn't mean for that to sound so negative. After I re-read it, I agree, it sounded a bit off. I'll be more careful.

I just wanted to point out that do-it-yourself compressors are dangerous, especially for those on limited budgets where people will cut corners or use sub-par materials. While we discuss safety of rockets themselves not having metal parts and being 50 feet away, not a lot of consideration is given to the fact that you might be standing next to your homebuilt compressor when a metal fitting on it fails at full pressure injuring yourself or someone near you.

I hope spaceman that the design idea is just some kind of lever extension for a hand pump, as "just having a friend weld up" a high pressure component without understanding heat affected zones could result in an unpleasant result.



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Post by The Mooseheads » Wed Nov 28, 2007 12:24 am

rockets42 wrote:
The Mooseheads wrote:
P.S. Do you EVER have anything constructive to say?
Sorry Rick, I didn't mean for that to sound so negative. After I re-read it, I agree, it sounded a bit off. I'll be more careful.

I just wanted to point out that do-it-yourself compressors are dangerous, especially for those on limited budgets where people will cut corners or use sub-par materials. While we discuss safety of rockets themselves not having metal parts and being 50 feet away, not a lot of consideration is given to the fact that you might be standing next to your homebuilt compressor when a metal fitting on it fails at full pressure injuring yourself or someone near you.

I hope spaceman that the design idea is just some kind of lever extension for a hand pump, as "just having a friend weld up" a high pressure component without understanding heat affected zones could result in an unpleasant result.
Okey dokey then. I think I see where you're coming from. I hope Spaceman comes around to explain how safe his design is.

Coincidentally, this thought has just recently been considered. The latest safety rules draft Lisa posted a few days ago has a section in it about safety precautions required for homemade pressurized components, so people will not be endangered by faulty designs or workmanship in any of the parts they make themselves.


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Spaceman Spiff
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Post by Spaceman Spiff » Wed Nov 28, 2007 2:56 pm

rockets42 wrote: I hope spaceman that the design idea is just some kind of lever extension for a hand pump, as "just having a friend weld up" a high pressure component without understanding heat affected zones could result in an unpleasant result.
Thanks for your concern but I feel quite safe with my design. My fried is a retired U.S. Navy welder who worked on nuclear subs at the Naval Submarine Base in New London CT. I am 10000% sure that he knows what he's doing.

But I will also follow whatever safety regulations I need to follow, just to be extra safe. Especially if spectators are around.


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Post by Tim Chen » Wed Nov 28, 2007 5:10 pm

By the way, Mark and I have wrapped our 3000PSI stirrup pump with 1/4" copper tube and we circulate cold water through that and it cools so efficiently that we're going to attempt to motorize it. We have not altered the pump itself, just added to it.


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