I don't have anything to go on other than the breakdown drawing that USD provided with the user pamphlet. I have broken down the valve, and made some photos of it, but have no USD documentation about it. I asked Aqualung, and they said that they lost all their documentation on the UDS-1 in a fire in the 1980s. There is one fellow (iainhsm) who posted on this thread about having original UDS-1 drawings as a subcontractor, and maybe he can help.
I haven't gotten out to the van yet to look at the interstage pressure (later this morning I'll do that). But my wife got up very early this morning, and I was laying half-asleep in bed and thinking about the UDS-1 and your problems. I think I may have an answer for your.
First, this is a "modified Conshelf" design for the first stage in the manifold according to the spec sheet I received with the UDS-1 system. Therefore, the repair manual for the Conshelf first stage should work for you to use in maintaining the UDS-1 first stage.
Now, about the problems you are having. I think that U.S. Divers designers went to the O-ring piston rather than a diaphragm for this regulator because they made the manifold entirely out of aluminum. I think they were concerned about the holding capasity of the metal over time, and decided to use the piston instead (this is speculation on my part).
Your problem may be with the orientation of the piston inside the manifold. Take a look at this photo:
There is a notch in the piston's center that should hold the head of the pin that pushes against the seat. The sharp point of the pin should be aimed at the HP seat. This notch serves as the "top hat" that is used on other, diaphragm first stages. If you have the piston reversed, then the pin would not be stable and the O-ring on the piston might not seal properly either. It is worth a check.
One other thing--I did not pull apart the HP seat when I did my maintenance. I simply put a bit of silicone grease onto the pin before inserting it into the HP seat area. I don't really know what that mechanism looks like, but I do know that there are a few O-rings in there that go around the pin. So greasing the pin would grease these O-rings. I believe this is how the balancing mechanism works to make this a balanced first stage.
If you look up the diagrams of the first stage of either the Royal Aquamaster, or the Conshelf XII or Conshelf SE, you can see how this mechanism works (it's the same in all these regulators).
I'll look up the LP pressure on my UDS-1 later this morning. I hope this helps you in your work to get your UDS-1 up and running. I may be diving mine later today (but it's raining pretty hard--so maybe, maybe...).
So far, I have not received the new O-ring you mention above.
The interstage Pressure on my UDS-1 is set at 132 psi. This is where these 1085-00 second stages seem to like it. The UDS-1 really performed well on a dive I made about two years ago to 90 feet in the Seattle area.
Thanks for all the help and diagrams. I was trying to stabilize the ip this morning with no luck, I've installed a New Hp seat in this unit. It seems when I turn on the valve and pressurize the regulator it holds air, but as soon as I start to purge the regulator the ip rises above 150 and air begins to leak out beyond the o-ring. I can't figure this out other than to assume the o-ring is just to far gone to hold back any pressure. That Parker Buna o-ring is a hard bugger to find, its not anything USD had made specifically for the UDS. I've found o-rings with the correct OD and thickness but its that small hole in the center that making finding a replacement difficult as they just don't have anything in the books with that size of hole. I may have to call parker in England to find this Bugger.
It sounds like you have a high pressure leak of the seat, and not an O-ring seating problem with the piston. If it holds initially, and then leaks after the IP raises above 150 psi, I think it is being lifted out of it's seating area by HP air, and the air is bypassing. Under similar circumstances for a Conshelf SE, if the HP air couldn't purge fast enough through the downstream second stage, the diaphragm could burst (probably would not, as the second stages can bypass quite a lot). But on the UDS-1, if you are getting a lifting of the piston out of its area, it probably should leak. Look at your new HP seat for scaring, at the pin for being bent, or at O-rings within the HP seat assembly. If you go to
You can download the new manual for the Royal Aquamaster. It will show how the seat fits, and probably be pretty accurate for the USD-1 too (although the UDS-1 probably has a different nozzle, it probably also has the same parts interior to the HP seat). Anyway, I would suspect the HP seat rather than the O-ring on the piston.
After some trial and error, we found the problem to be a worn yoke were the seat was not seating that allowed the hp air to bypass into the outer lp chamber and out passed the o-ring. found a newer yoke and the problem is solved.
For those of you who have been reading my dive log this year, you know that I dove the UDS-1 about a week ago, and used my ScubaPro A.I.R. I regulator on it. I even modified the A.I.R. I, by adding a second LP hose to the second stage. I followed the old directions on my ScubaPro Addendum to the TECHNICAL MANUAL for SCUBAPRO REGULATORS (Cat. 45-101-187):
The hose may be connected to either the right-hand or the left-hand port of tthe regulator. The unused port must, of course, be capped with the provided plug. Commercial or advanced divers requiring improved flow performance at depth can connect the A.I.R. I Second Stage to the first stage with two hoses, one over each shoulder. Maximum flow performance and safety can be achieved by attaching the A.I.R. I Second Stage to two independent first stages, which, in turn, are mounted on separate high-pressure cylinders.
I tried this with the UDS-1 and the A.I.R. I second stage, with two LP hoses to the regulator. It was a tremendous breathing machine. I have only dived it once in this configuration, but it really felt good. I needed it to perform well, as I was in very heavy current in the Clackamas River. I did not test it an extremely low tank pressures, exiting with 900 psi and the J-valve not released.
I think this may be the best breathing machine yet devised. Here are the reasons:
--The valves for the three tanks have huge openings which allow extremely large amounts of air to pass through.
--The regulator is integral with the valve, so there are no restrictions to flow sometimes associated with attaching the first stage to the valve.
--There are three (sometimes two--when the third cylinder is withholding air due to the J-valve) cylinders providing air to the manifold.
--The A.I.R. I accepts two separate LP hoses, with the resulting increase of diameter. This is restricted somewhat by the single hose feeding them from the valve to the top of the unit, but having more volume to draw from, and having the two hoses right in the second stage mechanism, seems a big plus (and ScubaPro says so above).
What do you think? Could this be the best open circuit SCUBA ever conceived?
Could be? But I would love to try the "2 hose" Air I with my vintage Watergill FSDS first stage, for those that dont remember this rig, it was about the size of a MKVII and had 2 totally independent first stages built into one unit. Wonder how the performance would be? Now you will have me spending money on ebay looking for a Air I, THANKS!
Post by sea.explorer on May 3, 2005 9:10:04 GMT -8
I may have a challenger for the best open circuit scuba system. I will be giving a talk on it at Wazee in Aug, and I will have two units on hand. You should come with your ultimate UDS-1 and we can have a friendly showdown. Stay tuned for details -Ryan
"A little less conversation a little more action..." -Elvis