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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.

Adapting scuba regulator to Launcher

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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Frank
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Adapting scuba regulator to Launcher

Post by Frank » Mon Aug 23, 2010 9:12 pm

I tried the search function but didn't turn up any useful information on how to adapt a SCUBA tank and first-stage regulator to a launcher. I'm a newbie, and this is only my third post, so please forgive me if this subject has been discussed ad nauseum and I'm just too inept to find the post with the needed information.

The US Divers first-stage has three threaded fittings in the "high pressure" side one of which is occupied by the pressure gauge, and three on the "low" pressure side, where the second stage (regulator) would attach. Which do I want to get an adapter for, the high or the low? I'm assuming its the "low" pressure side... I have what I believe is a 5/8" standard high pressure hose rated to 300psi, 25 feet long, from Home Depot. Sorry, don't know the pitch off-hand. Fits into my launcher (about 3/4 finished (see picture).

Can anyone advise how to safely and efficiently marry a scuba tank first stage stage to this high pressure hose?

Thanks in advance.

Best to all,

Frank
Launcher.jpg
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SaskAlex
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Re: Adapting scuba regulator to Launcher

Post by SaskAlex » Mon Aug 23, 2010 11:16 pm

Well the end of your air hose is most likely an NPT (national pipe thread, I believe) fitting. These are tapered threads. If the SCUBA regulator also has NPT fittings then it will be easy, even if they are different sizes. I live in Canada and I'd go to Princess auto for the parts, but I don't think they have that store in the US. You could try home Depot, but you'd be better off if with a store that sells hydraulic equipment. They should have anything you'll need. Just take your stuff with you and see what fittings you need.



Frank
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Re: Adapting scuba regulator to Launcher

Post by Frank » Wed Aug 25, 2010 8:38 pm

SaskAlex: Yep...you were correct. There was no direct way to connect the hose to the regulator. I ended up with a three-way connector which accomodates a pressure gauge, the in-flow from the tank, and the out-flow to the launcher. To get the low pressure hose to the in-flow, I had to use a barbed 3/8" female connector. Getting the barb into the SCUBA hose was a pain, even with heating from boiling water and a heat gun. If it don't go, force it, I always say! :mrgreen:

In any event, it got done, and initial pressure testing of the launcher revealed one tiny leak, which will easily be addressed with pipe thread compound. Following the test of the launcher, I had seven (YAY!) successful 1 L bottle launches, three with air only (60, 90, 120 psi) and four with water of varying amounts with identical pressures (two at 60 psi). My son (age 24) and my wife (she'd kill me if I said her age on this forum!) watched, and were actually quite impressed!

We had a lot of fun! Our yard is 1.2 acres, and it was utterly breathless here. The bottle (no fins, just a plain old 1 L test bottle) really flew and landed surprisingly close to the launcher each time, except for once when it landed in the pool. My son Scott actually caught it once as it fluttered back down to within feet of where he stood. The sound wasn't too bad, either. I was worried it would be louder, as I live in a hoity-toity neighborhood where people are, well, snooty. :roll:

So...an auspicious beginning! I was delighted to see how easily controllable the pressure was from the SCUBA tank. I was afraid the tiny volumes of air would be difficult to regulate, but with only modest care, it proved quite easy! So...I'm stoked to build a REAL rocket. The principles behind the design and construction seem sufficiently challenging to keep me interested. I can see how people can start out for fun, and get serious about competing.

Thanks to all the forum members who have shared their information. The on-line wrocket community seems like a bunch of great folks. Really helpful! Got me off to a great start, so take a bow, one and all! I really appreciate how much flailing you saved me in launcher construction.

Best to all,

Frank



SaskAlex
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Re: Adapting scuba regulator to Launcher

Post by SaskAlex » Wed Aug 25, 2010 11:16 pm

Sounds great! A lot of people are really down on bottled gases, but I think they could be a good option if you know the dangers and how to handle them. I'd love to have a system like that for non-competition launches. Anyways, looks like you're hooked for good, so good luck with your rockets.



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U.S. Water Rockets1
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Re: Adapting scuba regulator to Launcher

Post by U.S. Water Rockets1 » Sat Aug 28, 2010 10:14 pm

Frank wrote:I tried the search function but didn't turn up any useful information on how to adapt a SCUBA tank and first-stage regulator to a launcher. I'm a newbie, and this is only my third post, so please forgive me if this subject has been discussed ad nauseum and I'm just too inept to find the post with the needed information.

The US Divers first-stage has three threaded fittings in the "high pressure" side one of which is occupied by the pressure gauge, and three on the "low" pressure side, where the second stage (regulator) would attach. Which do I want to get an adapter for, the high or the low? I'm assuming its the "low" pressure side... I have what I believe is a 5/8" standard high pressure hose rated to 300psi, 25 feet long, from Home Depot. Sorry, don't know the pitch off-hand. Fits into my launcher (about 3/4 finished (see picture).

Can anyone advise how to safely and efficiently marry a scuba tank first stage stage to this high pressure hose?

Thanks in advance.

Best to all,

Frank
Launcher.jpg
It seems that there are very few water rocket enthusiasts who live in coastal areas where SCUBA gear would be commonplace. For the most part, SCUBA enthusiasts are in a niche sport like us Water Rockets enthusiasts... so the overlap is pretty narrow. Don't be surprised if there are few people even in a popular hangout like this forum that know much about both.


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