How To Build Your Own Diving Lung

[JamesBon92007]

Thanks. So far I found out they have a US Divers manifold and they are 2250 tanks. I'm still trying to find out the hydro dates but apparently I'm not on the same technological level as the seller (I don't know what an iPhone is and don't even have a cel phone).

Well, they are now sitting in my garage The original hydro date is 2-67 so that makes them newer than my oldest steel 72 (1963). The most recent hydro date is 1996. They have about 50 psi in them but the J-Valve does not stop the air flow when in the UP position so I'm thinking it may need a little work. The tanks appear to be galvanized and were brush-painted the pale yellow color. The paint is flaking off so removing the paint appears to be a better option than touching them up. The tanks measure about 18" from the bottom to where the neck begins and with a 72 measuring about 24" to the bottom of the neck that puts them at about 75% of the capacity of the 72s which would work out to about 54 cu/ft at 2475 psi (they are rated 2250 but the only "+" is on the first hydro date, I think). So, were 54s a common size? I've heard of 40s but these seem to be a little bigger than that. Also, the backpack has another backpack opposite the one that is actually used (with straps) and it looks like someone stuck it on there for a reason that has not yet become clear--maybe just so they would stand up (no boots on them). Plus the J-Valve Rod Clip is on the wrong side so I guess the backpack is on upside-down or something. The valve thread size appears to be standard (1 inch, is it?) so I think the manifold will fit on a couple of 72s without the need for any bushings. Should I strip them down to the galvanized finish or try to repaint them?

The hard part now is justifying spending the money to get the visual inspections and hydros plus they may need tumbling or whipping (not sure what that is). If they won't hold more air than a single 80 then the cost is probably gonna be more than double just to "look cool." But, if I can manage to come up with a nice, repairable double-hose reg then it would be irresistible. Or perhaps find an old O2 rig and make my own regulator!

I was gonna add a pic but now I don't see how.

 

[Thalassamania]

If you want the J-valve to work it is likely nothing more than the seat. But I'd not trust it, even with a rebuild, I'd use it, "always down."

 

[JamesBon92007]

I think I did it! Not a very good pic though.

I took apart the backpack and it's hollow, injection moulded (?) so I don't think the pack is all that old. Maybe late 70s or early 80s? It has black nylon web straps and stainless quick-release buckles. However, I have an old Aqua-Lung KAM "EZ" PAK that is for a single tank. There is a dimple moulded into it that looks like it might be where a hole is supposed to be drilled to accommodate a bolt for a double tank band. But, the hole needs to be directly in the middle (horizontally and vertically) for the bands (one double-band)that I have and the dimple is above center. Otherwise it looks like it would all fit together nicely and might make a better looking set. So, would I be doing the history of diving a disservice by drilling a hole in it, or is this "acceptable?" Is it likely that drilling it would weaken the plastic and cause cracking? It looks somewhat like bakelite. It still has the old yellowish, cloth straps and snaps for the quick-release on the chest strap but thankfully has a buckle for the waist strap. Other, newer backpacks I have look like they are designed to be used with two double-bands and are already drilled in two places.

Roger on the J-valve in the down position Thalassamania. I used to dive K-valves with no SPG and I'm still here. It's more like I just like to have everything working the way it's supposed to, even if I don't actually use it.

 

[Akimbo]

I think I did it! Not a very good pic though.

I took apart the backpack and it's hollow, injection moulded (?) so I don't think the pack is all that old. Maybe late 70s or early 80s? ...

Blow-molded, just like the ones you can still buy today.

 

[John C. Ratliff]

A lot of us who have dived J-valves use them with the valve mounted the opposite direction. Here, two US Navy divers show that there are two different positions that can be used for J-valves.

If you'll look closely at how the valves are used, all you need to do is to turn around the center section, and you have a reversed J-valve. This works well because the main cause of the J-valve not functioning correctly was it being knocked down by something the diver hit. With the J-valve in the "normal" position, it could easily be knocked down. With it reversed, it is now very difficult to knock down.

Scubapro actually made a valve which had the J-valve reversible, and advertised it as such in the mid- to late 1970s. It was used for a while in cave diving, and could be changed to reserve on a single tank either 300 psig or 600 psig. I have two of them and still use them, along with a set of double 45s with a reversed J-valve.

SeaRat

 

[duckbill]

Do you notice any restriction at all when switching the J-valve? It's possible that the innards have been removed. I know some dive shops still meddle with the good old stuff like that. They should be horse whipped, IMO. A j-valve should be a j-valve.

 

[JamesBon92007]

I have two other J-valves and both have resistance when turning it--pops into position. This one doesn't. Where's my whip?

 

[JamesBon92007]

AScubapro actually made a valve which had the J-valve reversible, and advertised it as such in the mid- to late 1970s. It was used for a while in cave diving, and could be changed to reserve on a single tank either 300 psig or 600 psig. I have two of them and still use them, along with a set of double 45s with a reversed J-valve.

SeaRat

Ahhh, I have one of those: Depth Compensated Adjustable Reserve. It was leaking in three places. It now only leaks out of the Depth Compensated Reserve adjustment. I don't have a small enough O-ring to fit it. Got any tips for overhauling these valves? I looked for a kit but didn't find any. I also could not find a service manual but I did find an exploded view diagram. Plus I tried reversing the lever and that worked just fine. I rather got the impression these valves are prone to leaks.

The good news is that it came with a freshly hydroed steel 72 that I got a very good deal on. I put a K-valve on the tank for now. If nothing else J-valves make better handles

 

[vintagediver]

Manganese is an alloy mixed in steel in the molten state. It would amount to only 12 or 14 % by weight max. Pure manganese would be too brittle and expensive to make tanks from.

Ben

Not true... high content manganese is not brittle at all but quite ductile when first smelted. It has the pecular property of becoming harder and tougher as it is worked. It is not any more expensive than mild steel in its pig state. The problem comes in when you hydro the tanks and find their yield becomes less and less over time. The elastic limit would be too variable after a few cycles.

 

[avidhunter]

for any given pressure, Wall thickness determines the stress level reached. Keeping the working stress level far enough below the elastic limit over time just means thick walls (relatively speaking). Granted that does reduce weight savings. it's all a trade.