New Acquisition - 38's ?

[ScubaLawyer]

Just picked these up from a Craigslist ad for $20. Not exactly sure what I have. Assuming 38's. They are 1800 psi USN with a 1959 first hydro date. Yet another project.

[ScubaLawyer]

These are actually slightly taller (by a 1/4 inch or so) and have a slightly larger diameter than my Sportsways 1/2 " straight thread oring 42's. I'm wondering if they are 50's? Did they make steel 50's in 1959?

[SurfLung]

The dive shop up in Moorhead had a set of Twin 50s made from CO2 fire extinguisher tanks that we guessed were 50s. They had dimple feet bottoms, were 1800 psi, and stood a little taller that 38s. On the other hand, I have those surplus "Twin 48s" that are quite a bit taller than 38s.
viewtopic.php?f=41&t=9096 (PS - I got the "48" number from an old Scott Lung)


Another thought is that they may be something between 38 and 50 cf. I have an oxygen tank that is identical to a 38 but is about 2/3 as long. Diver Don actually has a set of twins in the 2/3 length. So maybe there's an in-between size in the other direction, say... 45 cf?

OR,... 1/4 inch difference in length is insignificant and you have Twin 38s!

[ScubaLawyer]

Thanks for the info Eben!  Of interest is that these 1800psi cylinders are almost exactly the same height and diameter of my USD twin MKII aluminum 3000psi 50's. That sort of intuitively tells me they ain't steel 50's.
 
I know it isn't exact science, and the wall thickness is likely different, but given the size similarity if I take the ratio of 3000psi/50cu.ft. as 1800psi/X, I get 30 cu.ft. as a very rough approximation. (Please feel free to correct me if my formula use is inappropriate, flawed or just crap but I'm not going to fill a cylinder with water to measure volume). So that makes me think they are probably not 42s or 45s either.

However, my Sportsways 42s are slightly physically smaller all the way around but they are 1880 psi so that makes some difference. So I figure these are 38s or possibly 42s. They are what they are and it likely makes no difference to world order but it's fun to do some detective work. Mark

[ScubaLawyer]

I thought the harness/single band on my set were just a homemade aberration but I found this photo on-line and it looks like it was a standard design.  Any clue as to what company made these harnesses?

[antique diver]

I thought the harness/single band on my set were just a homemade aberration but I found this photo on-line and it looks like it was a standard design.  Any clue as to what company made these harnesses?

I don't know who made that set, but I have seen similar harness attachments around the manifold on two old homemade rigs as well as on a Siebe Gorman doubles set that has manifold and valves at the bottom.

[ScubaLawyer]

When I started to dismantle the twins I put a little CLR on the tank stamps. The 1959 Hydro stamps were NOT the first hydro. One is dated October 1942 and the other one a year earlier, October 1941!

I love history and the fact one tank was made 2 months before Pearl Harbor was attacked and America wasn't even officially in WWII yet is just really cool. It predates the CG aqualung regulator as well!  These tanks were repurposed from some Navy use. Who knows what action they saw! Love it!

Now, let's see if they pass hydro.  Mark

1941


1942