Post by herman on Mar 6, 2020 13:27:52 GMT -8
I have recently built a piston DH reg and thought you guys would be interested. Here is the text of the thread I started on VDH, I would have posted it with the photos here but I don't use any of the on line photo storage sites (I am correct that photos can no longer be posted directly here am I not??) so I can't include photos.
To my knowledge, a piston double hose has never produced, until now. Healthways was planning on introducing a piston double hose, you can find a drawing of it in one of their catalogs but to my knowledge it never was produced.
Looking for another reg to build and since no piston double hose regs had been produced, it seemed like the thing to do. Rather than building completely from scratch, I decided to see if there were piston regs that could serve as the first stage. An axial flow reg would better suit my needs as modifying an angled reg like a MK-5 would not lend itself to making a clean looking reg. Few axial flow piston regs were ever produced but 2 candidates, the Tusa R100/350/390 series and the Sherwood 3105 were found. These regs are axial flow, balanced and the design made it perfect for what I had in mind. They are both discontinued models and are not too common. I finally found examples of both. After rebuilding both to make sure I was starting with a working reg, it was time to choose one. After some self-debate and a coin toss, the Tusa was chosen. The project started off with these base materials including DA cans but later I acquired a set of prototype gray AK cans from Bryan. Many thanks to him for them.
Now that the first stage was chosen, the second stage and body design were needed. I borrowed a good bit of design from the Kraken for this project. The body is made out of Delrin, a tough and durable plastic that is great to machine. Plus, it’s a lot less expensive than brass, if….when…I screwed up a piece of material, cheaper is better. It might not the best material for the job but it better suited my needs, plus it does not need plating. To keep things simple and since I had made HPRs in the past, I decided to use a HPR for the second stage. With the basic design in mind and some simple CAD drawings in hand, it was time to start on the reg body. This turned out to be an interesting machining challenge.
A length of 2 ¾ delrin stock that was cut into a 1 ½ slice then was put in the lathe and trued up
The process of machining is often times more about how to hold a part and what order the machining operations must to be done in than about the actual machining process. You must get the steps in the right order in your head before starting to cut material. Often times you need to keep material on your work that “obviously needs to be removed now” until later. This turned out to be the case with this part. The internal side of the part had to be completely finished before cutting the external side, otherwise it would be more difficult hold the part later in the machining process. Walking through the process mentally before starting to cut is essential.
After truing up, threads were cut to accommodate a USD style body ring and an oring grove was cut to seal the body to the cans. Moving to the mill, locating slots for the cans and the opening for the second stage was located, machined and threaded. The LP seat design was borrowed from the Kraken, I had some left over parts from the early prototypes and since the second stage was a HPR, it seemed like a good option.
Now that the internal side of the body was complete, it was back to the lathe for work on the external side, this is where things start to get interesting. Because everything on this side is offset from center, a 4 jaw chuck had to be used to hold the part. Holding a part off center in a lathe is an experience I had not had before. It takes a good bit of trial and error to get a proper grip on the part and to get it properly set in the chuck without hitting something. Once set up, it’s a bit unnerving to watch the part spinning around so far off center
With the part set in the chuck, the hole where the first stage was to be installed in was made. This involved creating a proper sized hole then threading it. Threading a blind hole to the bottom is an interesting challenge. An oring groove was also cut for the oring that seals the first stage to the body.
Photo threading
Now the excess material on the body had to be removed. Again this was an offset cut made in the 4 jaw chuck.
Back on the mill, the air passages for the second stage and LP ports were drilled and threaded. Three LP ports were placed around the body at 120 degs. These were for the LP inflator and octo plus one extra. The body was installed in the cans and the position the first 2 holes were marked, these needed to be in line with the can horns, the third use split the difference. These proved to be adequate during the sea trials, more could be added if needed.
And now for testing. The first stage was installed in the body, a HPR and LP seat installed and the LP ports plugged. An IP gauge was installed in one port and the reg pressurized. IT WORKED!! Well, at least IP is good and nothing blew up. The assembly was submerged and checked for leaks, none !. This first stage has unusually big ambient ports which are shown in the manuals plugged with special plugs, this reg did not come with them so I made some just for looks.
Finally, the body was installed in the gray AK cans with black hoses and a gray Voit mouthpiece.
I had a dive trip planned for Bonaire so the reg got put into the luggage for sea trials. The reg was given a first test in shallow water with a trusted dive buddy close by. After about 20 minutes in shallow water, the reg did so well I moved deeper. The first dive was 60 minutes to a max depth of 50 ft. The reg was taken on several more dives for a total of 3 ½ hours of bottom time. The max depth was around 60 ft., not that the reg would not have worked deeper, that was just as deep as I cared to go, most of the nice stuff on Bonaire is above 50 ft. The reg performed great and is a wonderful addition to my unique DH collection. It still needs some kind of label and I am really looking at Robs blue hoses for it but otherwise it’s done. Now there is a working piston double hose regulator in the world. Stay tuned for the Sherwood model……or maybe a totally different model, I have had another idea!
