Vintage Double Hose

Several months ago I had Bryan fit my DA with a Phoenix nozzle. I sent it back to Bryan for adjustment since it breathed hard, especially at depth. He repaired it and the breathing at depth problem was solved, but it still breathed harder than I thought it should - actually my Mares Abyss breathed easier.

I readjusted the IP and the 2nd stage and got it tuned just short of freeflow, but still was not happy with the cracking pressure. I checked it directly from the inlet hose and it seemed fine - about .5" wc, but still it did not breathe easily from the mouthpiece. When diving, I always felt like I had to suck hard to get the air flowing.

Last week I decided to purchase some yellow hoses and a new USN mouthpiece from Sam. When I went to install them last night, I took the existing mouthpiece and breathed through it and found what I think was my problem. The exhaust valve opened easily when I breathed out, but the inlet valve was hard to inhale through (and even "popped" on opening). I switched the valves in the old mouthpiiece and it breathed much easier - inhalation effort was almost nothing.

I made sure to install them in the same configuration in the new mouthpiece and when I got everything assembled, the PRAM breathed like I thought it should - almost pushing air into my mouth on inhalation.

I examined the valve, both the rubber and cage, that seemed to cause the problem, but could find nothing obvious and it works fine on the exhaust side. Maybe the rubber stem that goes through the cage is a little tight on that valve.

All I know is now I want to get back to the quarry and confirm that it is operating the way I think it should - this is going to be a long week and a half.

This has happened to me also. The rubber cage valves are fairly stiff and sometimes they can cause hard breathing. I have several sets of silicone cage valves and the difference is HUGE. This is another of the reasons that some of us have been playing with different mouthpieces and looking for rebreather mouthpieces or contemplating using the new Mistral mouthpiece, they have larger and softer cage valves in them which flow more air with less effort.

Most of the black rubber cage valves work just fine and are essentially the equall of what was installed in them originally, occasionally one seems a bit stiffer than others as you have found and that valve should be discarded and replaced.

I do not have a current source of silicone valves. If anyone has a source please let us know.

A hard breathing regulartor-- the cage valves are immediantly suspect.

Again, the standard black valves are fine and function adequately.

James

The pictures below are of several experimental mouthpiece valves.
I am trying different types of silicon film, mostly 0.010 inches thick, but different durometers and surface texture.

I am hopping to reduce the flow resistance using our standard vintage mouthpiece.

So far my results are good, but not great.

The new Mistral mouthpiece still has the least breathing resistance, but I don’t like how big it is. Even with a nice comfortable mouthpiece bite, I don’t like the feel of the big assembly.

http://cgi.ebay.com/Vintage-Scuba-Doubl ... dZViewItem

is an ebay link for silicone valves.

I just got some valves from Dan and they were pretty good too.

http://www.vintagescubasupply.com/hoses.html

The silicone valves I am talking about are clear (slightly whitish) and are very soft compared to those pictured in the links, those are all neoprene.

James

Nemrod wrote:The silicone valves I am talking about are clear (slightly whitish) and are very soft compared to those pictured in the links, those are all neoprene.

James

Are the ones you are referring to similar to the one on the top right of my pictures?

I am fairly sure the ones Ron was selling (they are gone) are black silicon. I bought some a while back and I think that is what he told me. They work well, but that clear one in the pictures works a bit better.

The ones I am making from silicon film work slightly better than either, but I need better instruments to get better data. I am measuring fairly accurate suction, but I need a flow meter or a consistent flow pump.

I have been looking at a metered suction venturi pump (with flow meter) from Peter-built (scubatools.com), but it is expensive.

So Luis when are you going into silicone valve production? WHne will you have them for sale? We need the info.

The valves Luis is making are similar to some I have made recently using his idea. The silicone sheet is cut out and a hole punched in the center and a small stainless bolt with nylon washer is pushed through the center and through the cage valve housing. I am not entirely satisfied with these as they do not breath as well as the purpose made ones I got from Dan and other places. I think it is the lack of space between the silicone sheet and the cage valve spokes. The sheet is flat--a true mushroom valve is domed and only the feather edge rests on the cage valve housing. The vintage valves and reproductions oddly are flat, not true mushroom valves. I find that the domed silicone valves I use will leak slightly because there is so little sealing surface at the perimeter of the cage valve housing.

If you have never done it, remove the cage valves and breath from the regulator and then put them back in. You should see a fairl large difference in effort. Ideally the valve should be invisible in the system.

James

One other things that I have encountered that caused hard breathing--on exhaust side --is that the cuff of the hose had been over trimmed and was restricting the air flow.

James