This Old Scuba Shop

[Herman]

As many of you know I have a small machine shop where I make tools for working on regulators but what you may not know is I dabble in parts and accessories for dive regulators. I am not getting into the parts business and don't plan to make or sell them but I though you might like to see what I am up to and maybe get started on making some of your own parts. So if you guys enjoy the following thread, please chime in and let me know. If you do, then I plan to post more of my projects in the future. SO....to start this off... This Old Scuba Shop presents - Voit J Valve Seats.

[Herman]

A while back I won a Trieste on eBay and I have a Pegasus that both needed to be upgraded to include working J valves. I have some NOS Voit J valve seats but they are for the most part not serviceable, great to take measurements off of but not safe to use. With no suitable replacement parts available, to get my J valves working I would have to make replacement J valve seats. After some experimentation, I came up with a fairly easy way to make replacement J valve seats from quarter inch nylon stock. And before I start, no I’m not going to make them for sale, I really don’t want in the parts making business.
The required diameter of the seat needed to be slightly smaller than the stock ¼ inch I had, so first off I had to turn down the stock to .220 inch from the stock .250 inch.

Once the stock is down to size, I needed to create a T shaped pocket to capture the end of the original J valve seat carrier. First I bored a hole with a milling endmill and then used a custom tool to cut the T shaped slot.

One of the things that a lathe operator has to do is to fabricate cutters to do the job at hand, this is partly science and partly art, an art I am still just learning. The pocket required a T shaped undercut to hold the end of the seat carrier.

Once the pocket end of the seat was complete, the sealing surface had to be fabricated. The lathe was set up to cut a 30 deg cone on the end of the seat and at the same time separate seat from the stock.

Not an exact match but not too bad for a few minutes of lathe time and a couple of pennies of nylon stock. The left seat is a bad Voit seat taken out of my Trieste, note the missing center section. If you have any old Voits with these valves, you really need to dissemble them and remove the plastic parts. They can shatter and send pieces of plastic into the HP seat area, not a good thing while you are diving. By removing the plastic parts you will defeat the J valve function but at least you will not have to deal with a free flowing first stage in the middle of a dive due to chunks of fragmented J valve seat jammed into the HP seat. The center one is a NOS Voit seat and the right hand one is my version. Not as stylish but it works nicely as later testing proves and the nylon should last for many years.

Once the seats are made and installed, they had to be tested. This required me to come up with some way of testing the seats. I needed a way to start with around 500 psi in a tank, breath it down and watch the parameters of the regulator to determine if the seat was performing the way I wanted it to then easily reset the test jig if (make that when) I needed to change some design or setup of the seats. Obviously breathing down and refilling a 72 or 80 was not practical, this is what I came up with.

I used a center feeding yoke manifold , placing a full 80 on one side as my supply and a 13cf pony on the other side as my “low” tank, to that I attached my remote supply hose with a regulator at the other end. With this setup I can easily charge the pony by throttling the 80’s valve and watching the reg HP gauge until it reached the pressure I wanted, and then close the 80’s valve to isolate the pony. The J valve can be seen doing its job by watching the reaction of the IP with an inline IP gauge that I made for this project. As the tank pressure dropped past 500 psi I could see the IP start to dip more and more as I breathed on the second stage until around 300 psi when it would drop to zero and almost completely cut off air flow. Opening the J valve, the IP would return to normal until the tank dropped below the regs IP. After making a few adjustments to the design and turning a few more seats, I now have a Pegasus and a Trieste with working J valves.
Hope this segment of “This Old Dive Shop” has been entertaining and useful. If you guys like this sort of post, I will do more as time and projects permit. I have another project in the works so stay tuned.

[Herman]

Looks like larger photos is the first thing I need to change.

[SurfLung]

Hi Herman,
I would like to see some long yokes for DA Aqua Masters and Mistrals. They seem to be in severely short supply for Mistrals. Anyway, I saw (a few months back) where someone was modifying modern yokes to work on DH regs and I didn't think to take advantage of it at the time. Is this something you'd want to take up in your shop?

[Herman]

I don't stock them but it's fairly easy to modify other yokes. I modified several for Bryan a while back, he may still have some (for DA/RAMS). The yokes of early Conshelfs and Calypsos are direct replacements for the Mistral yokes but will not fit DA/RAMs without modification.

[ccyyss]

Thanks for posting this. I made my own seats for a vintage single hose first stage several months back, but no machining required. I'm a new member, but quickly acquiring VDH stuff. I rebuilt a RAM a couple of weeks ago, and just got a Mistral on ebay yesterday. I recently scored a suite of your tools.

I'm interested in the anything you might say about nylon versus teflon for seats in general.

[Herman]

Teflon is a good bit softer than nylon. I have had good luck making seats pressure test gauges with teflon but for seats that are under a lot more spring pressure or sharper orifice edges nylon seems to work better.

[gj1963]

Very interesting. Thanks for posting and l look forward to seeing more. I had wondered what others did with respect to the voit J seats. I have a couple that the seat is long gone on.

[antique diver]

Herman, I always enjoy your projects and appreciate your sharing your successes with us. I was wondering what I would do with all my Voit J-valve modules, and you have given me enough information to jump right in and follow your lead.

Thanks!
Bill

[Herman]

The "hard" part is getting the T shaped cavity into the seat. You really need to use some kind of accurate readout to get the depth and width correct because you only have a couple of thousandths to work with. Once you get the cavity right, the seat will just snap on. I tried using delrin and I think it would make a great seat but it's not stretchy enough to get over the end of the seat.....but I have not totally given up on it, heating it may be the trick to getting it on.