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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.

Another internal grip launcher

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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SaskAlex
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Another internal grip launcher

Post by SaskAlex » Thu Dec 03, 2009 6:35 pm

Well someone was interested in one of my launchers, so here it is, Old Faithful. Despite it's complexity, I've been using it for years without failure* and with little maintenance. It will launch anything with a standard bottle neck. You release the bottle by taking pressure off of the air line. You can do this at whatever pressure you desire (well actually, due to friction of the internal parts, it usually has to be over about 50 psi). I think the pictures do a decent job of explaining it, but feel free to ask questions.

I should also say one thing about safety. I think having no release cord is a good safety feature, because there is no chance of pulling the launcher over at launch. However, by releasing when you depressurize the airline, there is no aborting once you start pumping up your rocket. Make sure you are in a good location and everything is safe before you begin pumping!

*Actually, the lower PVC tee failed on me one day. I often launched as high as 200 psi. This failure happened at about 150. I have since been using an all metal version, but the principles are all the same. I think the PVC version would be fine, just use a metal tee because if you get cheap fittings they will be the weak point. The main "action" section of the PVC version seems to be quite robust. As always, make sure you're far enough away in the event that it fails. PVC really does shatter when it fails.

Alex
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U.S. Water Rockets1
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Re: Another internal grip launcher

Post by U.S. Water Rockets1 » Sat Dec 05, 2009 11:56 pm

SaskAlex wrote:Well someone was interested in one of my launchers, so here it is, Old Faithful. Despite it's complexity, I've been using it for years without failure* and with little maintenance. It will launch anything with a standard bottle neck. You release the bottle by taking pressure off of the air line. You can do this at whatever pressure you desire (well actually, due to friction of the internal parts, it usually has to be over about 50 psi). I think the pictures do a decent job of explaining it, but feel free to ask questions.

I should also say one thing about safety. I think having no release cord is a good safety feature, because there is no chance of pulling the launcher over at launch. However, by releasing when you depressurize the airline, there is no aborting once you start pumping up your rocket. Make sure you are in a good location and everything is safe before you begin pumping!

*Actually, the lower PVC tee failed on me one day. I often launched as high as 200 psi. This failure happened at about 150. I have since been using an all metal version, but the principles are all the same. I think the PVC version would be fine, just use a metal tee because if you get cheap fittings they will be the weak point. The main "action" section of the PVC version seems to be quite robust. As always, make sure you're far enough away in the event that it fails. PVC really does shatter when it fails.

Alex

Very nicely done!

Other designs have been tried which use an expanding ball bearing setup based on the typical hose quick connect, but nobody has thus far been able to make a reliable actuator because the previous attempts seemed to try and move the actuator by passing it through the inlet pipe wall. The actuator seal where it exits the pipe was always a weak point.

You've done a great job designing out the mechanical pass through. Very good designing work!


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ninja_iga
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Re: Another internal grip launcher

Post by ninja_iga » Sun Dec 06, 2009 2:53 am

wow, this one's pretty good too :)


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WTF
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Re: Another internal grip launcher

Post by WTF » Sat Jan 09, 2010 6:25 pm

Could this launcher work as a way to make a multiple stage water rocket? Most of the methods I have seen look really "hot or miss".



SaskAlex
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Re: Another internal grip launcher

Post by SaskAlex » Mon Jan 25, 2010 4:16 pm

WTF - it could, but it's really heavy. And it would be difficult to make much smaller. Also, you want a much smaller nozzle on your second stage. A lot of people have had consistent success with the "crushing sleeve mechanism". And if you want to make simple two stage rockets with limited pressure (around 150 psi) you should search on here for my "stupidly simple stager". Not much to go wrong with that one.

Alex



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rockets-in-brighton
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Re: Another internal grip launcher

Post by rockets-in-brighton » Mon Jan 25, 2010 5:53 pm

SaskAlex wrote:WTF - it could, but it's really heavy. And it would be difficult to make much smaller. Also, you want a much smaller nozzle on your second stage. A lot of people have had consistent success with the "crushing sleeve mechanism". And if you want to make simple two stage rockets with limited pressure (around 150 psi) you should search on here for my "stupidly simple stager". Not much to go wrong with that one.
For your convenience: http://www.wra2.org/forum/viewtopic.php?f=3&t=578.


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Tim Chen
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Re: Another internal grip launcher

Post by Tim Chen » Mon Jan 25, 2010 10:14 pm

SaskAlex wrote:WTF - it could, but it's really heavy. And it would be difficult to make much smaller. Also, you want a much smaller nozzle on your second stage. A lot of people have had consistent success with the "crushing sleeve mechanism". And if you want to make simple two stage rockets with limited pressure (around 150 psi) you should search on here for my "stupidly simple stager". Not much to go wrong with that one.

Alex
That's very true. You want a smaller nozzle on the main rocket because you don't need a lot of thrust to get moving. The boosters take care of that part!


Tim Chen
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