Sun May 22, 2016 8:01 am
Life has gotten in the way of my shop time recently but that is getting much better now so once I catch up with my tools, I can get back on this. Here are some of the issues I have found,
The material in the metal part of the original seat is molded in. Removing it is going to be a bear short of using a solvent to dissolve it but more to the point, you can't just press something back in. The new "insert" will have to be either molded back in, sealed with an oring or glued/bonded in some way, otherwise you will never get it to seal, it IS going to leak. Cost wise, this would be a much more expensive option plus you would have to find a number of seats to convert.
Making a one piece seat in some material like nylon is going to be the best bet. I need to experiment more but so far delrin seems to be too hard for this application and Teflon is too soft....I had a Teflon seat extrude under pressure. I have has some success with nylon....I did a lot of seat experimenting a while back so I have those materials on hand. The 2 issues I am having are getting a good seal and balancing. I have no idea what the actual amount of balancing was in the original so I may be getting "normal" results. Looking at the geometry of the seat it does not appear that it would be as balanced as a standard USD seat. As it turned out, a lot (most ??) of my sealing issues were due to the hard seat stem. At least on the one I have, it is a good bit smaller than a normal USD HP seat stem and under the proper diameter to seal with the standard Orings used in USD balance chambers. I doubled up the orings and that seemed to "fix" the problem but I am beginning to believe that many of the sealing issues with these regs was not the seat but rather the balance chamber oring to seat interface.....unless you know what to look for, determining which is the issue is difficult. To get a reliable seal different orings are going to be needed.....I am wondering if the originals were actually metric....another thing I need to look into.
The next question is what the goal here is? Restore it to original with repro parts or just get it diving again. Restoring it is going to be a little difficult and expensive to do. With the limited number of regs and even more limited the number of folks wanting to restore one, the cost will be high. If on the other hand, if getting it back into diving condition is the goal, I think there is a better approach. Install standard USD/AL HP hard and soft seats and designing/ making a new pin. A replacement pin is a lot easier to manufacture and a lot cheaper. A simple kit could easily be made for the conversion and from then on, service will be easy. I am pretty sure this approach will work but again, it would have to be looked at closely to make sure the dimensions are correct....off hand I do not recall the diameter of the original seat. Even if the standard hard seat is not the correct diameter, a slightly different sized version of would be a lot easier to produce than an original style one.
Herman