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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.

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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 » Wed May 23, 2007 12:15 pm

Tim Chen wrote:
Drag_Racer408a wrote:Tim about your earlier post about compressor getting too hot from running... I got an idea to keep it from burning up without putting different gears in it. I don't want to tell cause its really simple yet should work awsome!
Mark has two ideas. One is really simple, and the other is pretty simple. We're going to test them out. Hopefully the simplest one wins!
Would one of your ideas happen to be an electric fan?

:P


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Drag_Racer408a
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Post by Drag_Racer408a » Wed May 23, 2007 3:22 pm

No i got a water cooled idea.


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Post by HenningNT » Wed May 23, 2007 4:36 pm

I've got an idea:

Get a cheap high pressure washer. They are usually rated 110 - 130 bar.

Hook it up to a tank (which is hooked up to the launcher) capable of holding the desired launch pressure.

As the washer pumps water into the tank, the pressure rises.

Release water rocket...

The tank volume must be a multiple of the water rocket volume to get the desired launch pressure. For example a 2 liter water rocket launched at 20 bar would need a 20 liter tank capable of holding 20 bar...



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Tim Chen
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Post by Tim Chen » Wed May 23, 2007 9:11 pm

HenningNT wrote:I've got an idea:

Get a cheap high pressure washer. They are usually rated 110 - 130 bar.

Hook it up to a tank (which is hooked up to the launcher) capable of holding the desired launch pressure.

As the washer pumps water into the tank, the pressure rises.

Release water rocket...

The tank volume must be a multiple of the water rocket volume to get the desired launch pressure. For example a 2 liter water rocket launched at 20 bar would need a 20 liter tank capable of holding 20 bar...

It sounds like it would work. The water displaces the air and makes pressure...

There's got to be a catch. It's too simple. What am I missing?


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Post by Drag_Racer408a » Wed May 23, 2007 9:28 pm

Actually it is that simple except for the whole part of getting a 20 liter container to hold 120 bar. Thats a lot of pressure.


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Post by Tim Chen » Thu May 24, 2007 5:46 pm

Drag_Racer408a wrote:Actually it is that simple except for the whole part of getting a 20 liter container to hold 120 bar. Thats a lot of pressure.
If you can make a rocket that holds that amount then making a container for that air would seem pretty simple to me.

:P


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Post by Mark Chen » Sat May 26, 2007 11:09 am

Tim Chen wrote:
Drag_Racer408a wrote:Actually it is that simple except for the whole part of getting a 20 liter container to hold 120 bar. Thats a lot of pressure.
If you can make a rocket that holds that amount then making a container for that air would seem pretty simple to me.

:P
You have no idea how true you are, Tim!

Heh heh heh! :twisted:


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Post by HenningNT » Sun May 27, 2007 2:50 pm

Tim Chen wrote:
Drag_Racer408a wrote:Actually it is that simple except for the whole part of getting a 20 liter container to hold 120 bar. Thats a lot of pressure.
If you can make a rocket that holds that amount then making a container for that air would seem pretty simple to me.

:P
You could make a smaller tank, use some valves and a non-return valve. So you fill the tank up and empty it several times. Each cycle increases the pressure in the water rocket a bit.

The catch is probably that all your connected equipment and water rocket must endure much longer pressurization period. Glued bulkheads may fail...



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Post by Tim Chen » Sun May 27, 2007 4:23 pm

HenningNT wrote:
Tim Chen wrote:
Drag_Racer408a wrote:Actually it is that simple except for the whole part of getting a 20 liter container to hold 120 bar. Thats a lot of pressure.
If you can make a rocket that holds that amount then making a container for that air would seem pretty simple to me.

:P
You could make a smaller tank, use some valves and a non-return valve. So you fill the tank up and empty it several times. Each cycle increases the pressure in the water rocket a bit.

The catch is probably that all your connected equipment and water rocket must endure much longer pressurization period. Glued bulkheads may fail...
Do you really know that a longer time under pressure would make a rocket fail? I would imagine that if it can hold the pressure it can keep holding it. I think of it like a rope. If the rope can hold 500 pounds won't it hold 500 pounds indefinitly?


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Post by Drag_Racer408a » Sun May 27, 2007 7:03 pm

Yes you got the right idea but ropes do strech after many uses if you get what i am meaning.


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Post by HenningNT » Mon May 28, 2007 5:36 pm

Tim Chen wrote:Do you really know that a longer time under pressure would make a rocket fail? I would imagine that if it can hold the pressure it can keep holding it. I think of it like a rope. If the rope can hold 500 pounds won't it hold 500 pounds indefinitely?
Just guessing... Probably depends on the launch pressure. If it's "close" to the fail pressure, a prolonged pressurization period may make it fail.

If the rope has a break load at 5000 pounds then no problem. If the break load is at 510 pounds ... I wouldn't stand under it... ;-)



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