"Build Your Own Diving Lung", Revisited in 2018 & 2019

[Vancetp]

I got a great deal on a super clean Bendix oxygen diluter. CRAP!!! I really wasn't going to do this..... Maybe I'll be satisfied with just looking at how it works.

Keep us informed!

It is really doubtful it will go anywhere. I don't like the metal bellows in the first stage, and am concerned about how long it can last w/o fatiguing. If it could be adapted to a rubber diaphragm, that would be better, but that takes the whole thing beyond what would have been done in that era.

Besides, I already have poor breathing, dangerous regulators in my collection!

[antique diver]

Trying not to be the wet blanket on this thread, but the discussion of DSV on this forum section is beyond the scope of Classic Vintage Diving. The OP discussion on the Bendix is fine, but addition of DSVs (might be the new one for the Argonaut?) is NOT. You could discuss the DSV's use on other forum sections.

I agree... thanks for keeping us on course.

[Vancetp]

Got the diluter today. Cool.

I took it apart, and found a pretty decent diaphragm, but probably unusable for diving. Bill has done a pretty amazing analysis of how the thing works, which I'm grateful for, seeing as how the thing is pretty convoluted in some ways.

I can't help but think there's a way around that bellows, which seems to me to be the weakest link. I think a smart feller with a will could find a way to use a rubber diaphragm setup to replace that hot mess...

Speaking of the first stage, and I say this with no knowledge of its potential; is the low output of the regulator to the diver a problem with the second stage? The orifice is small, and I'm wondering if the second stage is throttled by the small opening. As I understand the way this thing works, at this early stage, the 2nd stage output can be modified so it is piped directly into the air horn. Bill modded the complicated stock setup to do this.

But, if you caused the can to be charged by a secondary jet(s) and used a venturi aimed into the air horn, might you pick up more volume from an under-utilized first stage?

[Vancetp]

Got the diluter today. Cool.

I took it apart, and found a pretty decent diaphragm, but probably unusable for diving. Bill has done a pretty amazing analysis of how the thing works, which I'm grateful for, seeing as how the thing is pretty convoluted in some ways.

I can't help but think there's a way around that bellows, which seems to me to be the weakest link. I think a smart feller with a will could find a way to use a rubber diaphragm setup to replace that hot mess...

Speaking of the first stage, and I say this with no knowledge of its potential; is the low output of the regulator to the diver a problem with the second stage? The orifice is small, and I'm wondering if the second stage is throttled by the small opening. As I understand the way this thing works, at this early stage, the 2nd stage output can be modified so it is piped directly into the air horn. Bill modded the complicated stock setup to do this.

But, if you used a venturi aimed into the air horn and added secondary jet(s) to charge the can , might you pick up more volume from an under-utilized first stage?

[antique diver]

I don't think the first stage bellows is really of that much concern for a catastrophic failure. In use it really doesn't flex very much to open the HP seat. As well as that system was designed for its intended use I think the whole thing must be pretty bullet proof for the aviation industry to rely on it. On the other hand I am keeping an open mind on that, so keep me informed on that subject.

As far as danger goes, the whole shebang is not designed to dive with anyway, is inherently dangerous in that use, and warrants a pretty good dose of caution to use underwater. I dive it with the assumption that something in it could fail at any time, causing either a loss of or over-abundance of air flow. I keep hearing the words of John Coffee, and would never subject mine to 3000 psi service (as he did) for fear of a loud noise and disappearing parts. I'm sticking to 1800 psi.

I look forward to hearing more about your project!

[Vancetp]

I don't think the first stage bellows is really of that much concern for a catastrophic failure. In use it really doesn't flex very much to open the HP seat. As well as that system was designed for its intended use I think the whole thing must be pretty bullet proof for the aviation industry to rely on it. On the other hand I am keeping an open mind on that, so keep me informed on that subject.

As far as danger goes, the whole shebang is not designed to dive with anyway, is inherently dangerous in that use, and warrants a pretty good dose of caution to use underwater. I dive it with the assumption that something in it could fail at any time, causing either a loss of or over-abundance of air flow. I keep hearing the words of John Coffee, and would never subject mine to 3000 psi service (as he did) for fear of a loud noise and disappearing parts. I'm sticking to 1800 psi.

I look forward to hearing more about your project!

When electronics burn up, it's called "letting the black smoke out". I wonder what the equivalent saying would be with regulators?

I suppose your assessment of the bellows is correct. However, we don't have a ready supply of replacements.

I've been thinking about your exhaust issue. Why not plumb the duckbill so it crosses the center of the domed cover instead of off to the side?

[antique diver]

About the duckbill location.... I placed it to one side for a couple of reasons. Initially it was chosen for the convenience factor. There was an unused opening at that location where I had removed the gas metering and mixing apparatus, I sealed it up internally and used it as a secure mounting device for the copper tee that the duckbill was attached to. Also I reasoned that the exhaust valve in that position would be at virtually the same level as the demand diaphragm, and that would help prevent a free flowing exhaust that could possibly occur with it in a position just above the dome. That would place it almost an inch above the diaphragm in a lower water pressure location when in a swimming position, maybe inviting a free flow.

I had seen photos of earlier conversions that placed it where you mentioned, and also noticed that the commercially sold Seahorse conversion placed it there as well. It just seemed easier to utilize the unused opening to the side as a mounting place instead.

I was pleased with the chosen location to my left of center performance wise. An added unusual bonus was that I could roll to my right side down and decrease the inhalation effort if I needed a little extra flow.

I had intended to test the other duckbill location for a comparison, but since I like the way it was working I just left it alone.

[Vancetp]

I'm all for going with what works!

[Vancetp]

Started my own diluter conversion. I wasn't going to do it, but covid social distancing has made me look for more projects. I have a few ideas to make it work better than the PopSci unit. Some are based on Bill's excellent conversion, but I have a couple of new ideas. I'm posting the long version on VSS, but will update here as I go.