Vintage Double Hose

What do we have here gents? The tanks barely have necks for the 1/2” manifold, but round bottoms. Manifolds stamped 1955 , tank 9-56 and 11-56

They look like very early aluminum tanks made for the Navy.

They were made from seamless aluminum pipe. The ends were formed by a roll-forming process. The center of the round bottom was closed with a plug. You can verify this by looking inside.

They are not DOT cylinders.

I do not have them in my possession, but I assumed that is what they were, I have seen the later aluminum’s with the plug, but nothing this early. Interesting to see.

Yes, they are interesting.

Personally I don't like tapered tank threads at all. And the concept of having tapered threads in an aluminum is IMHO a bad combination.

luis wrote: ↑

Sat Aug 24, 2019 9:21 am

Yes, they are interesting.

Personally I don't like tapered tank threads at all. And the concept of having tapered threads in an aluminum is IMHO a bad combination.

I'm with Luis. The tapered threads put increasing outward pressure on the inside thread diameter the further they are screwed in. While there are many modern aluminum pressurized devices that utilize the NPT (national pipe taper) threads, they are likely of a different alloy. I do not know the alloy of those old Navy cylinders, but knowing that many other aluminum cylinders in the 1970's and through 88-89 were made with an alloy that proved to be susceptible to neck cracks, the Navy ones are highly suspect in my opinion. The later aluminum cylinders used straight threads with oring sealing, which did not tend to substantially stress the neck, but many of them still cracked at that area anyway.

The cylinders you showed would be great to have in your collection, but I wouldn't be comfortable filling them. Probably would have a hard time finding someone to hydro them anyway.

Luis nailed it. Those tanks are shone in the Navy Aqua Lung instruction book Nav-Ships 394-0056. I had a copy a copy of the book that I bought when I bought my first Aqua Lung in 1957, over the years it has gone missing.

The tanks were made by rolling closed the ends of 6061 alloy pipe. Since rolling the ends do not completely close them a plug was used in the bottom to seal it. I have a set of the similar later tanks but with the now standard 3/4" straight O ring sealed thread but they still have the plugs in the bottom.
They can not now be stamped with the hydro tester ID number because they are not DOT certified. A hydro shop did test mine but did not stamp them. If you can fill your own tanks they can be used.
This is the first set I have ever seen other than in old Navy photos. A nice find for a collector.

Like Captain mention, these are made from 6061-T6 seamless pipe.

A while back I sent Bryan PDF copies of the Mil specs for these tanks and for the Mil standard steel 72 (the same as our regular civilian steel 72, but with a bit more traceability).

The specs are under the Manuals and Catalogs in a folder labeled U.S. Navy Manuals.

The revision I found is for the later aluminum cylinders with the more familiar neck and straight 3/4” pipe threads with O-ring seal.

I have not heard of any cracking on any of the 6061 alloy aluminum cylinders (modern or this unique Navy version), but I just think that tapered threads in an aluminum cylinder is a bad combination.

There are probably very few of this particular type of cylinder around, so as a collector’s item they are a great find.

NO Neck Navy Tanks , 1950's era. I have a set and a 70's set with neck.