On to third version of the demand diaphragm, and I think this one will work out just fine. Haven't done an in-water test yet as several other modifications need attention first.
I can't believe that I was so anxious to try it that I breathed through that old-old-old hose without washing it out... tasted "very vintage".
It cracks too easy for diving use, but must have been really nice in its intended use. Cracks at about -0.3" WP, so I will either need a stronger demand valve spring or maybe just another coat or two of silicone on the diaphragm to get it up suitable for diving use. Now that sounds great, but the not-so-good news is that the air volume available is a little disappointing, and that's why I don't want to adjust the intermediate pressure downward. Unless I can improve the flow this reg will be limited to slow easy shallow diving, but that's ok just as long as I can make it work and come back alive.
Removing a restrictive multi-part venturi device noticeably improved the flow volume. I realized that the venturi device on this regulator was designed only to pull in atmospheric air through a sophisticated altitude sensitive automatic gas mixing device. More about that later, but that really cool mixing system had to be removed for diving use as it would have just allowed water to mix with the diving gas. So, that particular venturi was of absolutely no benefit to breathing underwater, and was just causing a flow reduction in the modified for diving config. I'm really starting to have fun with this thing now.
Pausing for now, but will be working on the hose loop and exhaling valve soon. Will have to do a little amateur machining to make an adapter for the duckbill. It will look really goofy out in the open, just as shown in the magazine article, but I will go with that for the first version. I hope to come up with a better system later, but keeping it simple as possible for now.
Diaphragm in place and being temporarily held by rubber band for testing. It will be tied in place with wraps of thread like the original once everything is adjusted to suit me. May need to access lever height adjustment under the diaph and no easy way to reach it once it's tied on and the thread wraps siliconed over.
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