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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.

T Series - Prototype

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tsumrall
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T Series - Prototype

Post by tsumrall » Fri Sep 07, 2007 9:37 am

The forward assembly mocked up.

Forgive the nose ... pure vanity but I just had to make one. Unlikely I will fly it.

For more images on this series

http://www.sumrallworks.com/rockets/mai ... My%20Stuff

scroll down to T Series - Prototype

Troll indeed!
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Tim Sumrall
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Mark Chen
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Re: T Series - Prototype

Post by Mark Chen » Sat Sep 08, 2007 5:24 pm

tsumrall wrote:
The forward assembly mocked up.

Forgive the nose ... pure vanity but I just had to make one. Unlikely I will fly it.

For more images on this series

http://www.sumrallworks.com/rockets/mai ... My%20Stuff

scroll down to T Series - Prototype

Troll indeed!
Nice looking work you have done there Tim.

Can I ask you what chems you are using? I have not seen a setup with two pistons ever before? What's the advantage of two pistons? More power in less space?


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Re: T Series - Prototype

Post by tsumrall » Mon Sep 10, 2007 9:53 am

[quote]Nice looking work you have done there Tim. [/quote]

Thanks. It's been fun. I started a power series nose cone this weekend. It looks pretty cool. I will also built a true hemisphere (boring to look at but is the best design).

[quote]Can I ask you what chems you are using? I have not seen a setup with two pistons ever before? What's the advantage of two pistons? More power in less space?[/quote]

I use distilled white vinegar and baking soda. The second piston is redundancy. Should the first fail to lift the nose off the second comes along to assist.

This is only a prototype and I'm considering one big system to ease some building contraints.


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Post by Mark Chen » Tue Sep 11, 2007 9:31 pm

I like the idea of the two piston deploy for backup. I can't imagine how you get it to work with only half the power and still deploy on the right time. Wouldn't it take twice as long and that could be a disaster if the rocket hit the ground before the chute was opened? Am I missing something, or did you solve that issue already?


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Post by tsumrall » Sun Sep 16, 2007 8:58 am

Mark Chen wrote:I like the idea of the two piston deploy for backup. I can't imagine how you get it to work with only half the power and still deploy on the right time. Wouldn't it take twice as long and that could be a disaster if the rocket hit the ground before the chute was opened? Am I missing something, or did you solve that issue already?
For now I'm using (testing) one very large device. Stroke is about 5 inches. By it's self I've got the timing to 7-8 seconds and can repeat it every time. When loaded in the forward assy it's tightly packed in and that adds 5-6 seconds. So I'm pushing the nose off in about 13 seconds which is nice. I did it 6 times yesterday all ranging between 12-14 seconds. Close enough and I'm not finished testing.

I've been playing with this for years and I've finally got consistent results.

Some tricks: keep all variables the same every time. An adjustment of a teaspoon if way too much. A stroke adjustment of 1/4" is way too much. Each piece must be cleaned and dried after each test. Pack methods must be the same each time. Keep the soda dry (I use rice to absorb moisture)

I've got pics but I'm waiting for the movie :)


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Post by tsumrall » Mon Sep 17, 2007 11:55 am

A few stills
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Post by Spaceman Spiff » Tue Sep 18, 2007 1:43 pm

tsumrall wrote:
Mark Chen wrote:I like the idea of the two piston deploy for backup. I can't imagine how you get it to work with only half the power and still deploy on the right time. Wouldn't it take twice as long and that could be a disaster if the rocket hit the ground before the chute was opened? Am I missing something, or did you solve that issue already?
For now I'm using (testing) one very large device. Stroke is about 5 inches. By it's self I've got the timing to 7-8 seconds and can repeat it every time. When loaded in the forward assy it's tightly packed in and that adds 5-6 seconds. So I'm pushing the nose off in about 13 seconds which is nice. I did it 6 times yesterday all ranging between 12-14 seconds. Close enough and I'm not finished testing.

I've been playing with this for years and I've finally got consistent results.

Some tricks: keep all variables the same every time. An adjustment of a teaspoon if way too much. A stroke adjustment of 1/4" is way too much. Each piece must be cleaned and dried after each test. Pack methods must be the same each time. Keep the soda dry (I use rice to absorb moisture)

I've got pics but I'm waiting for the movie :)
That looks like a sound deployment device. I'm anxious to see the movie as well. I think by making it larger that you improve the repeatability of the design by making the error variables less significant in the design. Does that agree with your thinking?

What I am saying is that a few milligrams of chem can be a significant error in a small piston chamber, but in a large volume chamber, errors in measuring get less critical. The same reduction in error would probably apply to the friction of the piston and resistance of the weight you are pushing off, etc.

Nice work!


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Post by tsumrall » Tue Oct 02, 2007 12:21 pm

Sorry no video yet. Camera is not working. Ram disk gets stuck :(
That looks like a sound deployment device. I'm anxious to see the movie as well. I think by making it larger that you improve the repeatability of the design by making the error variables less significant in the design. Does that agree with your thinking? What I am saying is that a few milligrams of chem can be a significant error in a small piston chamber, but in a large volume chamber, errors in measuring get less critical. The same reduction in error would probably apply to the friction of the piston and resistance of the weight you are pushing off, etc.
To be honest I had not thought of it in those terms, but I think you are right. Good call. 8)

I built large to get control of leaks more then anything. Soda bottle parts just don't cut it. I am simply testing so size doesn't matter much right now. Once I have precise control I will likely reduce the size and/or composition for weight reasons and then re-calibrate.
Nice work!
Thanks.


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Post by tsumrall » Tue Oct 02, 2007 12:30 pm

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Post by tsumrall » Wed Oct 03, 2007 10:31 am

This is a cross parachute I worked on over the past weekend. I built a half scale first to work out the steps and then this one. It spans 3 foot (5 sqft). Calculated descent rate for 1500 grams from 2000 feet is just under 20 ft per sec. Weight unknown but uncoated ripstop nylon is pretty light. The Army green is a bit of a bummer but I make my own camping gear and I've got lots. Dollar rack at Wal-Mart 8)


Construction pictures are here.

http://sumrallworks.com/rockets/xchute

Sorry no text instructions yet but I generally get to it.

Dang, can't believe I missed the shot of my sewing machine. :roll:
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