US Divers UDS-1 system

[DaleC]

Thanks for the science lesson Luis

Rich, I'm pretty sure you are confusing the UDS-1 system with the ABS system. The UDS had tanks with 1" valve openings. Either that manifold is also an oddball size or you have the 30cuft tanks that came with the triple manifold you showed earlier. The UDS tanks were 35cuft.

 

[John C. Ratliff]

UDS-1 Streamlining

View attachment 110500Rich, those tanks are not UDS-1 tanks. Those have a very characteristic look, and were painted green. I have a different "take" on the streamlining of the UDS-1, based upon several years of diving the rig and modifying the weight characteristics and harness to make it work correctly. As it came from the factory, the unit is very unsatisfactory. It does not "ride" well on the diver because of its weighting and harness design. Let me explain; the unit is poorly balanced, as the valve is at the bottom and the top has tanks without any weight. This makes the unit want to ride up in the water, off the diver's back. Here is what I wrote on the VSS website about the UDS-1:

I'll talk of the down-side, and why they were not successful first. The UDS-1 had several design defects unrelated to their design as a breathing machine. Here are the defects:
--The unit was not well balanced as it was marketed. The valves are on the bottom of the unit, and without re-balancing using weights, the top tends to float off the diver's back and provide lots of resistance to normal swimming.

--The harness system was a combination of the US system, with a waist strap, and the European (probably La Spirotechnique) system where no waist strap was used. Therefore, the when worn with the waist strap around the waist, they were too high. When worn normally, the waist strap was around the hips, and too low.​

Basically, in order to balance the unit I placed 6 pounds of lead bullet weights (two) between the two cylinders on top. This allowed the unit to ride correctly just under my shoulders, and down on my back (not like the first photo that is enclosed, but like the second one). If the waist strap is removed, as is mentioned above, and the buckle from the waist strap used as a weight belt without connection to the UDS-1, the system will ride correctly.

Now, a bit more on the physics of the streamlining and use in scuba. Luis is correct in what he states about streamlining, but I would point out that the shorter tanks, with a fairing, sit lower on the shoulders and therefore do not catch the water as much if worn as described above instead of as the unit came from USD. The other factor in streamlining has to do with the surface area exposed to the water. With the three cylinders sitting below the shoulders, they present a much smaller cross-sectional area than does a "normal" 100 cubic foot single cylinder when viewed head-on. In addition, for a rotation movement, the three cylinders will present much lower surface area to the roll than a single, huge tank on a diver's back. So in current (the Clackamas River) the UDS-1 worked very, very well. It was one of those "dream machines" when diving it, but one of those maintenance nightmares when servicing it.

Currently, I cannot get my cylinders hydroed, so it sits disassembled in my garage.

SeaRat
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[kingairpilot]

John,
I've got a call into my local shop here in SW Florida (ive moved in the last 6 months). Anyway, this guy claims to have worked on the UDS in the past and might...MIGHT have some spares for it. Now, just got to get around the hydro problem. Hopefully you get yours back in action sood.

Cheers,
ka

 

[DMC777]

Hi Guys,I may be able to shed some additional light on the UDS-1 System. I maintained and dove one of these for several years. There are times when I greatly miss the System, but not necessiarly the maintenance. I made several changes to the unit to overcome some of the inherent design problems.As far as leaking; as mentioned previously, there were two primary areas that leaked. These were the filler hose and the manifold link sections between the tanks. First, the manifold links. There were two types. The early type was of a military gray/green anodizing consistent with the colors of the cyinders and the main manifold. These leaked steady bubbles that collected in the casing that would change your bouyancy on it's schedule. The remedy for this was to acutly tilt head down while swimming, and the collected air would exhaust through the four large holes in the bottom of the pack. US Divers came out with a second run of manifold links to remedy this. These links were anodized black in color. My experience was that these also leaked, but much, much less. I tried a number of specialized "O" rings, but the problem was clearly a clearance issue in the design. I resolved the problem by carefully drilling a series of 5/16-inch holes (spaced 1/4-inch apart) through the ABS casing at the top handle inside surface area. This automatically exhausted any leaked air. I resolved the problem with the filler hose by installing a Whitey precision stainless high pressure needle valve that intercepted the filler hose at the top of the pack. I placed the valve on the surface -inside the top handle to keep it out of the way. I had no more problems following these modifications. There were many pluses to the UDS-1. The first stage regulator (integral with the manifold) breathed very easy. The pack with it's 103 cu. ft. volume moved through the water with little drag, and the system was only slightly buoyant when close to empty. The ABS casing on the UDS-1 was very durable and would take a significant bump with no damage. I hope that this information is of help.DMC777

 

[simplediver247]

I had the machine shop make a new brass fitting that supports my LP Hose, Octo & Reg. It replaced that bad original aluminum fitting it came with also to resolve that filler hose problem we came up with a very simple replacement and used a standard tank valve. Will upload pictures shortly. I do believe this is the only triple UDS 1 in use in South East Asia and there's only 1 other diver here in the Philippines using Double Hose Regs. My 18 year old Niece really liked the UDS 1 and my 15 year old Nephew had lots of fun with double 50s.