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ScubaLawyer
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Scott Air Pak question

Mon Jun 27, 2016 8:42 pm

I keep seeing these mid-1980's steel Scott Air Paks for sale. They are 2015 psi (+10%). They are about 19 to 20 inches long. They are referred to as 30-minute air supplies.

My questions:

1. Do they have a standard 3/4" thread? If not, what do they have?

2. Are they comparable to an old steel 38 cu ft in volume?

Thought they might make a cool set of vintage-looking doubles if I stripped the paint and put on a Sea Hunt harness. All input is appreciated. Mark
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"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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antique diver
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Re: Scott Air Pak question

Mon Jun 27, 2016 9:12 pm

Mark, those may have been available in a couple of thread sizes. If you are lucky, they will have the SAE 3/4 (actual OD) x 16 thread (oring sealed). Just happens that the old early oring sealed Sportsways tanks and valves used that. Some of those valves are still around, and I personally like them. I don't recall any other Scuba valves being made in that thread size and pitch, but I could be wrong about that.

The 3/4" in this case is true OD sizing of the valve threads , not like the 3/4" NPS pipe thread sizing that is actually much larger.

The doubles that I was diving at Sea Hunt were like these, and outfitted with the cool Sportsways valves. Virtually identical in size and shape to the old 38's, they are a just a little heavier (maybe 2 pounds or so) than the 1800 psi 38's. Makes for more comfortable diving in my opinion. The additional pressure rating probably ends up making these about 41 to 42 cubic feet at 2215.

If you acquire some of these or can pull a valve and measure OD of the threads, let me know.
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Re: Scott Air Pak question

Mon Jun 27, 2016 10:06 pm

Thanks Bill,

I bet there are some spec sheets out there somewhere on these things. Would hate to get a thread size incompatible with a standard 3/4 valve. I'll investigate further.

I was suitably jealous of your rig at Sea Hunt Forever. Well done! Mark
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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antique diver
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Re: Scott Air Pak question

Tue Jun 28, 2016 7:11 am

Thanks, Mark

Can you get your hands on one long enough to pull the valve? Or at least an accurate OD on the tank neck? That would tell us a lot if we compare it to the ones I have. I still think they are probably the straight 3/4 x 16 actual size SAE thread which would allow using the appropriate Sportsways valves.

I hope I'm wrong, because it would be great if it would be the 3/4" NPS threads, with easy to find valves.
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crimediver
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Re: Scott Air Pak question

Tue Jun 28, 2016 10:44 pm

I also made a set of doubles using the Scott SCBA cylinders. It does not take the 3/4" straight thread. It uses a similar thread as the Sportsways. It is o-ring sealed.I used a set of bands from a steel 72 to dive them. I think the diameter of the tanks is about a tenth of an inch smaller than the 6.9 inch tank so I added a strip of rubber under the band of about 1/10 inch and it worked well. If I remember the rating was for 2216 psi. They were made by PST.

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captain
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Re: Scott Air Pak question

Wed Jun 29, 2016 10:17 am

We had bunches of them where I worked, none seemed to be 3/4" straight pipe thread used in scuba.
Captain

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Re: Scott Air Pak question

Wed Jun 29, 2016 11:12 am

Looks like Crime, Antique and Captain are on the same page. All good information. Thank you.
I emailed the company to see if they have any spec sheets for their older steel cylinders. Although they currently make an aluminum model, most of what they make now is a carbon fiber composite. My quest for information continues! Mark
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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