Re-thinking SCUBA History

[YankDownUnder]

On Monday night I attended a small gathering of the Historical Divers Society here in Melbourne. There were several video presentations. One of the videos was about the M4 Sherman tank discovered by sport divers off the coast of Italy. It was a duplex drive model, used to swim rivers and make amphibious assaults. It has large propellers and uses a rubber skirt to make it boat shaped and keep it's 37 tons afloat. Some of you may have seen this documentary, it was on cable TV some time ago.

Divers here in the Pacific see a lot of wrecks, and discovered, in a submerged tank was an escape SCUBA. It was the WWII version of a Spare Air. The tank was larger and the entire unit was badly corroded. We only saw pictures, which show a cylinder mounted regulator with an inhalation port and an exhaust port at the back of the regulator. It is a bit like the Drager Monomat. The rubber was gone of course, but the function of the variouis ports were obvious to anyone familiar with modern SCUBA.

When I spoke to Ted Eldred, developer of the first commercially successful single hose regulator, he said that many people were working on the idea at the time. I also knew and dived with the late Lionel Martin, who made SCUBA for our diving club back in the late 50s. Lionel used an oxygen welding reduction valve for his first stage and fabricated a workshop demand valve and used them on aircraft cylinders. He was instrumental in developing the world's second single hose regulator, the Sea Bee, by Air Dive sold in 1954. The company is still making SCUBA. While all of this is interesting, it appears that the US Army was making compressed air SCUBA for tank crew escape purposes 10 years before, during the island campaigns of the Pacific. The Cousteau SCUBA was pre-dated by Commeines in France, but perhaps this escape SCUBA goes back even further.

Do any of you know about this? It is new to me and I would like to know more. I was a tank platoon leader and I have seen many tanks and a lot of equipment, but I have never seen anything like the escape apparatus that was found.

[Phil]

You were probably looking at pics of a Mine Safety Appliances tracked vehicle (tank) bail-out set. They are a distinctive vegetable green color, have an air HP nut and nipple on the backside, 3/4" black corrugated hose about a foot long,an 'elbow' mouthpiece tee with a 'wishbone' isolation valve (a little different from a simple shut-off valve - when you flip the wire 'wishbone' over, the set is off but you can breathe ambient air without taking the mouthpiece out - this is from an MSA 'Navy' 02 rebreather set and was designed to purge the bag before a descent on 02).
These units were often converted for air lung demand use by substitution of an HP oxygen nut for the standard air nut and going directly onto and an oxygen valve (but using air) - or making or buying a yoke to fit either a medical 02 'pillar' valve (like a regular 'k' valve) or a SCUBA valve.
The major problem with these units was the orifice sizing - they breathed OK in shallow water, but were slow draggers at any thing past about 40 feet or so - but they did work deeper - but you couldn't (work. that is).
A secondary problem was the single hose - the exhaust air went back out through a small mushroom valve in the reg can (about the size of the early single hose second stage exhaust. This was easily fixed by blanking off the can exhaust (bolt,bent brass washer,innertube rubber washer, another bent brass washer and a nut). You could then use two long gas mask hoses (about 24") a 1" copper plumbing tee for the mouthpiece and clamp a short copper union and a flutter valve to the end of the exhaust hose and tie or clamp that end back at the reg. There were lots of different types of (02 mostly) demand regs available in the early 40's - (most notable is the AN6004 dilutor-demand aircraft reg which was the subject of a 'build your own Aqualung' article in a 1953 'Popular Science' mag. But they were usually upstream valve systems, made of aluminum, and designed for surface use - with very small orifice sizing. Any port in a storm, though. I had an MSA of this type as a back-up unit in the mid 50's and used it quite a bit. I drilled the HP orifice out (in the high school metal shop) - and that helped, but it leaked air a bit!
If anyone has a yen to see these units, I have a couple in good shape in my reg pile. Could take a pic. Best I've been able to find out, these units came into service in 1942/43 - about the same time as the original scaphandre autonome - but much later than the Commeinhes units.
I also converted an MSA oxygen rebreather to air use 'cause it was 2 stage and had a monster 1/4" second stage orifice in the demand counterlung. I made a lot of deep dives with this unit but it was really bulky when it sat on top of two 90 cu. ft. fire extinquisher bottles! Ah, the bad ol' days!
Regards
P.

[capn_tucker]

Wow, you've been diving since Noah was just an able seaman..
I don't feel nearly so old now..