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SurfLung
Master Diver
Posts: 1763
Joined: Sat Jan 01, 2011 2:03 pm
First Name: Eben
Location: Alexandria, MN
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Ron's Snark III Rebuild

Sun Dec 10, 2017 2:03 pm

Ron's Snark III Rebuild
RonsSnarkIII01.JPG
- This is the 4th Snark III I have worked on and I learned the most about the mechanism from this one. The first two, I was trying real hard not to upset the existing settings and get them breathing properly with a minimum amount of disassembly. They both were in pretty good shape to begin with. The third one was Rich's Snark-A-Master that is a brand new Fireman's reg that worked perfectly right out of the box. We simply installed a DAAM exhaust can and DAAM hose loop to convert it to Scuba diving. This Snark III of Rons is the one I ended up completely disassembling, restoring old parts, substituting new and used parts, and learning how to adjust it... As I told Ron, "This is where I really got into trouble..." I ended up re-reading some of my forum notes on the first two regs to remember some aspects of the assembly. And so, I figure if I put what I learned on this one onto the forum, it may be a value to me again sometime.
- Ron sent me this reg and said it was free flowing when he turned on the air. When I hooked it up and checked for myself, it was flowing air alright. But, not like the torrent of a full free flow. It was more like a partially depressed 2nd stage lever. When I opened it up and tested the levers, the air would snap on and off... It would old on off for a moment and then slowly start giving air again. It looked to me like the 2nd stage seat was leaking. I have never worked on that before so the disassembly was an educational experience.
- The Snark III 2nd stage seat is upstream. There's a threaded push rod that goes through the middle and secures with a nut on the back side of the seat. The seat itself is a soft rubber donut that looks like it might be an O-ring but when you remove the threaded push rod from the center, you'll see its not an O-Ring. It had quite a deeply grooved and shriveled face that was probably causing the leak. I re-faced the seat by sanding it against 600 grit emory paper... Caution it is soft and cuts fast... And finished it against 1500 grit emory paper. With the seat smooth and flat, I reassembled the push rod and learned my first lesson about critical dimensions in the Snark III.
- The nut on the back of the push rod was not screwed down as far as it was before disassembly. And sure enough, this slight difference in position of the seat on the pushrod kept it from sealing. When I re-assembled with the nut screwed further down, the seat worked perfectly. I turned the air on, pushed the levers fast and slow... And the 2nd stage seat was now sealing perfectly with no leaks. I patted myself on the back.
--- Edit 12/11/17 --- I forgot to mention that I disassembled, cleaned and tested the Over Pressure Valve (OPV) at about this point. This is something I did on the first two Snark IIIs as well. Realizing the important safety aspects of the OPV. ---
- Well, the main thing wrong with the first two Snarks I worked on was that they were leaking around the High Pressure diaphragm. So I thought I better check this with some soapy water. Whoops! It was bubbling like crazy... Meaning it was leaking like the other two. No problem. I've done this before. Take it apart, clean off the shriveled paper gasket, install a VDH nylon gasket and put it pack together.
- Unfortunately, it wasn't so easy this time. I disassembled the HP diaphragm by unscrewing the retainer cap (without touching the adjustment screw). And... YIkes! The insides were corroded and full of gritty debris from a badly decomposed HP diaphragm. I noticed before that the Snark III HP Diaphragm is the same diameter as a DA Aqua Master HP Diaphragm. So, I wasn't hopeless just yet. The DAAM diaphragm is a little thicker I think. But the face where it meets the pushpad of the nozzle is in the same position regardless of how thick the diaphragm is. The Snark III diaphragm actually has 1 or more rubber washers on the back side that bring the edge thickness up to a similar thickness... So, maybe the DAAM diaphragm will work... I found a leftover used DAAM diaphragm in my parts box and it re-assembled into the Snark just fine.
- While I was this far, I figured I might as well service the nozzle. Mechanically, the Snark III nozzle looks almost identical to the DAAM nozzle. I remembered the nozzle gasket was thicker on the two previous Snarks but I didn't think it was on this one. (This was my 2nd lesson about critical dimensions in the Snark III). I cleaned the insides of the nozzle, polished with 0000 Steel wool, then re-faced the seat with 600 grit and then 1500 grit emory paper. On re-assembly I noticed the push pad and pin stick out farther on the Snark nozzle that they do on a DAAM nozzle. I replaced the nozzle gasket with a VDH nylon gasket and re-assembled everything for testing.
- Mounted on a 300 psi tank, I turned on the air and almost immediately a slowly accelerating leak of air began escaping out of the over pressure valve. This indicates a leaking or open 1st stage seat. I took it all apart and tested the nozzle hooked up to the tank all by itself... No leaks. So why was the nozzle open when it was assembled into the reg. I looked again at the original nozzle gasket and sure enough, it is 3X thicker than the new nylon gasket I replaced it with. So, I put the thicker gasket back on and Voila... No more leak. That tiny difference in gasket thickness is a critical dimension affecting the depth of depression that the pushpad and pin establish against the HP seat.
- Okay so this regulator not only has the original Nemrod hoses, mouthpiece, and hose clamps... The hoses are about 2x longer than normal. I've heard that replacing the Nemrod hoses with USD hose loop improves breathing ease a lot. Anyway, breathing out of this regulator was definitely more difficult than breathing from a DAAM. My personal Snarks have USD hoses and mouthpiece and they breathe with the same ease as a DAAM. I don't have an IP gauge for the Snark but I heard someplace that you can adjust it up until it free-flows and then back off.
- Proceeding with caution (I thought), I attached the reg to a 300 psi tank I began test breathing through the Snark III hoses. Turn off the air, release pressure, turn in the adjustment 1/4 turn, turn on the air, test breathe. The breathing ease improved with each adjustment until it was almost as good as my DAAM. But it never free flowed and I didn't feel right adjusting it any higher. And its a good thing, too!
- I next hooked the reg to a 2800 psi tank and as soon as I turned on the air, the over pressure valve released. And it kept releasing until I adjusted the IP screw WAY back... more than a full turn. Whew! I need to get an IP gauge for these Snarks!
- I test breathed it through the Nemrod hoses and its OKAY but not as good as a DAAM. On the other hand, I hooked up USD hoses and mouthpiece and there is a dramatic improvement. I think with an IP set by gauge and replacement of the hoses with USD, this thing will breathe super easy.
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SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

SheriffDiver
Master Diver
Posts: 194
Joined: Sun May 29, 2011 9:07 pm
First Name: John

Re: Ron's Snark III Rebuild

Sun Dec 10, 2017 7:38 pm

Thanks for doing all that Eben. Now we know why servicing them is problematic. I love the detail work on the cans of this regulator. Can wait to try it out.

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Herman
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Joined: Thu Oct 25, 2007 1:45 pm
Location: Raleigh NC

Re: Ron's Snark III Rebuild

Mon Dec 11, 2017 8:29 am

FYI Eben, the Snark second stages are up stream designs so unlike the down stream ones in USD/Voit regs they will NOT start to freeflow with excess pressure, instead they will seat tighter. That is the reason the Snark has an OPV. If a reg has an OPV there is a reason, 99% of the time it's because the second stage is an up stream design. You will find them on a lot of older Healthways regs, a dead give away that they originally had tilt valve seconds. Increasing the IP until the second freeflows is an alternative on regs if they have down stream second stages but it is never acceptable if the second stages are up stream like the Snark....in fact that is the way you test the OPV. These regs require an adapter and IP gauge to set them up.

As a side note, it is very important to test the OPV for proper operation and NEVER remove or defeat it. If it is removed or does not work properly and the first stage starts to leak something has to give, at some point the main diaphragm will rupture. IF this happens while diving, it makes an already bad situation (the second stage is likely jammed shut cutting off the divers air) worst.

While on the subject, the OPV has metric threads (10x 1) and while it's way too close for comfort with the standard 3/8x 24 it is not a standard 3/8 so 3/8 fittings should never be installed in the OPV port.
Herman

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SurfLung
Master Diver
Posts: 1763
Joined: Sat Jan 01, 2011 2:03 pm
First Name: Eben
Location: Alexandria, MN
Contact: Website

Re: Ron's Snark III Rebuild

Mon Dec 11, 2017 11:00 am

- I was trying to document everything I did with this regulator and Herman's comments about the Over Pressure Valve (OPV) reminded me that I forgot to mention servicing that. If you'll note above, I added an edit to include what I did with the OPV valve.
- Herman, I thought maybe you had an IP gauge I could order for the Snark III but didn't see one in your catalog. I HAVE one from Bryan that fits the hookah port of USD 2-Stage regs. I was thinking I might find an adaptor someplace. Then I was thinking maybe it should be a "T" connector so that the OPV could stay active? Such an arrangement would allow adjustment of the OPV as well as the IP... All gauge based.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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Herman
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Joined: Thu Oct 25, 2007 1:45 pm
Location: Raleigh NC

Re: Ron's Snark III Rebuild

Mon Dec 11, 2017 12:25 pm

I don't make an IP gauge or adapter for the Snark and as best as I know, none exist. The later Snarks had a standard lp port in to LP seat cover that could be used to test IP, the latest manual I have has this as part of the setup procedure. I would think finding one of those and seat covers using it as a test adapter would be your best bet.
The OPV port is metric so you will need a metric to SAE adapter before you can use any common scuba hoses or adapters. Since you would still need the OPV active unless you always had a down stream second stage attached, the adapter would need a male metric, a female metric (both gasket seals) and a SAE oring seal, that is going to be a real oddball which makes it a custom item.
Herman

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Vancetp
Master Diver
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Joined: Tue Oct 04, 2016 7:26 pm
First Name: Phillip
Location: Belmont CA

Re: Ron's Snark III Rebuild

Tue Mar 20, 2018 6:36 pm

So, Eben. You commented on my post about the Snark III rebuild I was doing on the proboards site where I showed the adapter I made that fits in the OPV hole to allow the use of a downstream second and BC hose. I found a source of brass m10 x 3/8unf adapters that work well, if you are interested in one. It is a brass hex thing about 2" long. The hex has to be machined down so it clears the box. It can be used to measure IP as well, of course. I use a gauge with an OPV, but you could also use a tee and a downstream second, I suppose.

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