Vintage Double Hose

I searched the posts but did not find the info for this. What will I need to test the IP on the Snark, other than the obvious IP guage? Would I use the safety relief port or is there an adapter to replace the screw cap on the LP port?

I have never checked the IP on (or serviced) a Nemrod but reading the manual, it makes reference to checking the IP at 2 different places, at the LP orifice and at the exterior plug for the LP seat. The exterior port would be the easiest. You could also check it at the relief valve but as part of the test proceedure you are susposed to set it which precludes using that port. In either case you are going to need some kind adapter....and these are going to be metric. I have never seen one for sale or seen one for that matter.

Looking at some other parts breakdowns I have, I see a different design on the spring port cover, one seems to have a port built in it....the question there is what is thread, imperal or metric. I know the relief valve port is metric so my bet is it's metric.

The 3rd stage of the Snark III was actually a overpressure valve for the 1st stage as I am sure you know. The last of the models had both a low pressure and a high pressure port. The low pressure port was just an addition to the raised area from which the overpressure valve was attached. My late model seen here has a splitter in the low pressure port. You can take a reading of the 1st stage IP by accessing the overpressure valve port. Just unscrew it and put in any low pressure hose with your IP gauge attached.

The service manual I have tells you that the overpresssure valve needs to be set at 210. I wouldnt be able to do this if I were using that port for the first stage IP. I emailed Enrique about parts so maybe he knows about an adapter. I like what this guy is doing to his.

http://www.seveke.de/tauchen/technik/3heute-nemrod.htm

This may also be the place I found the service manual.

Exactly how you are going to set the over pressure to that psi value is interesting. But you can take it out set your IP gauge in its place and adjust your IP to your chosen value. Remember the 2nd stage is an upstream system, thus high IP will result in more difficult breathing, consider the USD Mistral. But, once you set your IP, then put in the over pressure valve back in and see if it holds. If not, it is set too low. Screw it in a bit to increase the release pressure.

Lots of new info for me..I had not seen that model of the Snark before...and I got the newer manual to add to my collection.
Setting the OPV is simple once you have a IP gauge connected (assuming you are not using the OPV port), just turn the Ip up to the pop off pressure recommended, see if it works and if it does turn the IP back down to normal. The old manual calls for an IP of 120 with a OPV activation of 150, both a good bit lower than the later model. I suspect the lower IP would be better from a breathing perspective
I dug my Snark out of it's very deep round-to-it pile and did come checking. The second stage cover is 18mm x1mm and the OPV is 9mm x1mm so adaptes will be necessary to connect any imperial fittings. There are some really neat mods to the Snark and other regs on that board....wish I read German.
Poking around the German site was interesting. I found reference to you Allan, Luis and myself plus some very interesting DIY regs.

Tauchen.seveke.de/technik/kompaktregler/nemrod/snark3silver-repair-eng.pdf

This should be link to the manual I have. I just searched snark 3 repair manual and this came up. For the other webpage I had to download a translator for my phone to be able to read it. Im glad you guys understand all this stuff because I still have alot to learn.

Going by memory, It seems to me that I got the recommended IP from Enrique Dauner and it was expressed in BAR. After doing the conversion, it worked out to about 145 PSI. I removed the "3rd stage/over pressure valve" and replaced it with an LP hose which I was able to attach an IP gauge to. I set my Snark III Silver's IP to 145 PSI that way, replaced the over pressure valve and have been diving it for about 5 years. In all that time it has been an excellent breathing reg and one of my favorites. I've dove that reg every where in all kinds of conditions from ice to warm water and it never misses a beat. Great Reg! I am eternally grateful to Enrique for his tech support and parts support for getting my Snark III Silver back in action. It was an ebay purchase and was really rugged when I started with it. When I finished, it was and is a real jewel!

Jim

Jim, did you have to use a metric to imperial adapter or does it thread right in?

No adapter needed. My LP hose screwed right in.

What has interested me in the Snark III is that the basic design was available from the late 1950s until 1998 or 1999. The unbalanced 1st stage coupled with an upstream second stage was unusual. Simple, reasonably efficient design. However, why didn't Nemrod (Seamless) convert the 1st stage to a balanced system? Schematics show that the 1st stage is very similar to most unbalanced diaphragm models. It would not have been much of a step to go balanced.

simonbeans wrote:What has interested me in the Snark III is that the basic design was available from the late 1950s until 1998 or 1999. The unbalanced 1st stage coupled with an upstream second stage was unusual. Simple, reasonably efficient design. However, why didn't Nemrod (Seamless) convert the 1st stage to a balanced system? Schematics show that the 1st stage is very similar to most unbalanced diaphragm models. It would not have been much of a step to go balanced.

The upstream second stage with the large mechanical advantage of this lever design is not very sensitive to IP changes.

As you mentioned earlier, this second stage design has some similarities to the design of the vintage Mistral regulator. The vintage Mistral works with large tank pressure changes (from full to empty tank pressure, roughly from 2500 psi down to 300 psi or less).

The percentage of IP swing for the non-balanced diaphragm first stage (in the Snark III) is going to be much less than the percentage change a Mistral has to work with. Changing the first stage to a balanced design doesn’t add much to this design.

What tank pressure is best for setting the IP?