UDS-1 System

[John C. Ratliff]

Are there any UDS-1 System divers out there? I picked up one of these systems last year, and have now fixed the major engineering problems. I've enjoyed diving it now, and will share my knowledge of this system if anyone is interested. It has a lot of pluses, even though it was unsuccessful commercially.

For those who have never heard of it, this is the Unified Diving System that US Divers put together in the 1970's. It combined a triple tank system holding 105 cubic feet of air in aluminum cylinders, and uniquely combined the first stage of the diving regulator in the valve. The valve has huge openings, so that air is fed to the first stage unrestricted, and this unit can be breathed to zero tank pressure without breathing resistance being felt (which can be a bit scary, if you think about it).

But this is a beautifully designed system, except for the harness and balance problems, which doomed it. Dive shops hated it as it takes a lot to break it down and put it back together. So if there is anyone else out there with one, I'd like to hear from you.

SeaRat

 

[Bob3]

I had the chance to pick one up last year, passed on it 'cuz of the tanks' alloy. (the crispy kind)

 

[pescador775]

I believe USD made two models of UDS. The earlier type incorporated inverted tanks, the first stage into the valve manifold and included semi permanent filling attachment, low pressure hose and SPG hose. I seem to remember a later mod that had a triple manifold and regulator mounted in the conventional manner on top.

What changes/modifications did you make? Are first stage parts available?

 

[John C. Ratliff]

This unit had severe balance problems. I had to do several pool dives to figure them out, and found that adding 6 pounds of ballast to the top of the system (interior) corrected that problem.

I have my own BC design, and I incorporated the UDS-1's harness into my harness design. The way it is normally set up, the waist strap is way too low. It really was made for the European system which did not include a waist strap, but had the crotch strap hooped into the weight belt. Mine now eliminates the waist strap, and hooks into hip attachment points on my Para-Sea BC.

The parts are mostly Conshelf first stage, and the regular USD metal Conshelf/Calypso second stage, with the exception of the high pressure diaphragm. Instead of a diaphragm, it uses an enlarged "O" ring piston, which also is unique.

USD has no documentation on the unit; that apparently was destroyed in a fire in the 1980's, and they offer no service on it whatsoever.

My cylinders passed their hydro with no problem, and passed a visual this month. The valves are all-aluminum, so there is little potential for metal interactions/corrosion. The cylinders also have a much larger opening than normal, one inch, I believe. This allows for the larger diameter openings in the valve. I also do not believe that the type of aluminum in the cylinder is the same as the problem aluminum cylinders now being inspected. My documentations states that the aluminum is 6351-T aluminum alloy.

SeaRat

 

[Bob3]

The 6351-T alloy is the flavor with sustainled load cracking issues, the triple bottle unit I passed on was made out of the stuff.

 

[pescador775]

Yes, the UDS was made under DOT SP 6498 which is 6351 alloy. However, I've never heard of a cracking problem inside the smallish tanks with the big neck opening. The forces on the neck are greater due to the large opening and hence, the aluminum shoulder and neck were made really thick in relation to the tank diameter. Crack theory lays suspicion on this but I bet the chances of a problem are very remote.

The valve manifold is aluminum and much thicker walled than a comparable brass manifold. Also, the diameters are larger to accomodate the internal parts. Hence, the necks were also made larger to be compatible with the manifold design. It has nothing to do with air flow. Makes for easy visual though.

Kudos for the mods, very sensible. Even with the aluminum manifold, the balance problems tended to make the UDS bounce off the shoulders and feel really light. One solution was to find two plastic coated 'bullet' weights, drill them and insert a long bolt with large fender washer. The bolt goes between the tank and the weight is tightened against the washer with a nut. I remember that the small hook on the crotch strap would detach itself in a minute. Sounds like you fixed it. BTW, the BC mods sound interesting. Trying to picture it.

I checked my locker and found a complete UDS manifold, brand new. Let me know if you need parts. I had converted the three tanks to a conventional triple arrangement for use with a double hose regulator. It's a long story involving a machinist and a blacksmith.

Edit: I forgot to mention that the tank neck and valve thread of the UDS was factory coated with teflon powder or paste. Some sort of lubricant is required on the threads.

Pesky

 

[John C. Ratliff]

I just spent several hours working on the UDS-1, putting it back together after VIPing the tanks. What a chore! But it was kinda fun figuring out how those intrepid USD engineers decided to design this thing. In the water, it's now great. But tearing it apart, and especially putting it back together again is a real pain.

SeaRat

 

[John C. Ratliff]

For those of you who have never seen the UDS-1, I'm going to show several photos of the system.

This first one shows the problems related to its buoyance/balance problems.

SeaRat

 

[John C. Ratliff]

Here's what the system looks like underwater after I reworked the system, and balanced it with 6 pounds on the top. As I explained above, I incorporated my own harness design to overcome the UDS-1's harness design problems, mentioned above.

SeaRat

 

[DeOppressoLiber]

I've got a US Divers triple manifold tank system, but mine is Gray and uses a standard reg set up. Anyone have any idea what the heck I've got? It has no harness, but does have to large diameter female thread receptacles on the back, kind of like having bands for doubles, one hole over the other. Anyone???