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Post by antique diver on Mar 7, 2023 14:26:42 GMT -8
Preview: Re: "Build Your Own Diving Lung", Revisited in 2023 Five years into tinkering with the Bendix "Diving Lung", I still couldn't leave well enough alone. I had it working better than ever last year, after a slight modification that added some additional throw of the demand lever. It was only noticeably easier in shallow diving in 20-25' depths, but still dangerously difficult by 42' (which was deeper than I had originally planned to use it anyway). I had an additional modification in mind, but since it was already working pretty well at shallow depths I was reluctant to try something different that might make it worse, and might be irreversible. So, along came the opportunity to do some horse trading with Vance for new-looking 1942 Bendix, and I had that as a fall-back reg if I screwed up the original beyond repair! The problem that I had faced with my original Bendix was that the mechanism controlling the HP poppet worked backward for diving application. The aviation use required the Oxygen poppet to open wider and flow a greater percentage of that gas as elevation increased. So when diving the pressure sensing device did the opposite... closing the poppet more and more as depth increased. I knew that, and had fiddled with the mechanical linkage adjustment many times still hoping for some improvement, but knowing it was unlikely to ever happen. What I had wanted to try was to completely remove the HP Oxygen poppet and some related parts. So with a whole new backup Bendix I felt bold enough to try the new modification on my original unit. The results were everything I had hoped for on the test bench. The separate inline regulator (acting as first stage supplying 450 psi) that I had been using required a significant pressure reduction and some hours of tinkering to get the right balance of pressure and breathing performance. At first it actually had too much venturi effect. Trial and error found a comfortable balance at about 190 psi. Cracking effort is under 0.8", and sustained flow at heavy breath is lower than that. I'm pretty sure these figures will hold up in actual diving conditions, and hoping to give it a try soon. Photo shows some of the old parts removed during several years of trial and error. The small white objects that look like a revolver cylinders are the original hp poppets:  Side by side old and new Bendix conversion. The duckbill has much less exhalation resistance than the Duckbill Eliminator, and will be my valve of choice:  |
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Post by nikeajax on Mar 7, 2023 14:40:39 GMT -8
Bill, thanks for keeping us in the loop; sounds like you're having a lot of fun totally geekin' out!
JB
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Post by antique diver on Jul 11, 2023 17:20:28 GMT -8
As reported in March, I had entirely removed the high pressure poppet and had a very encouraging improvement in performance on the test bench. I finally got to test it in open water, diving with Seawolf, who was equipped with his recently refurbished set of vintage 38's and a nice simple little US Divers Aquamatic (USD's first single hose regulator, and so simple that it has no purge button). He found the doubles with the vintage style harness to be very comfortable and stable in position. The Aquamatic breathed ok at first but became a little wet breathing later in the dive. I'll check it out later. Maybe some debris under the exhale valve or (or loose lips). As expected, the Bendix Diving Lung breathed easier than before, but the decreased flow restriction caused an unexpected increase in the venturi effect. That made it a bit unstable and was prone to some blow-by out the exhaust during normal inhalation. Also, I had a little wet breathing due to not sufficiently tightening the back cover against it's gasket. It was manageable anyway, but not pleasant. Back on the bench I bored out the hp "volcano" orifice to allow easier flow with a much lower intermediate pressure, thinking that might get the venturi under control. Took the IP down from about 200 to 120 psi, and the venturi was more appropriate. Cracking effort was lowered to about 0.5" as well, (down from 0.8") since the second stage is upstream. Venturi was under better control, but still lively, the way I like it. Of course, underwater use may not return the same results... but I'm optimistic! Learned a lot this time, and will be going back to the water soon. Here's the little HP orifice. Second photo shows it when I got through experimenting with orifice sizes.   Here's Seawolf attaching my Aquamatic to his cool 38's. Looks like he isn't quite convinced this is a good idea... maybe not enough hoses?  I'm about to test the Diving Lung. I thought it was sorta vintage dive looking to carry a speargun for battle with the big fishes we hoped to see:  Seawolf thought the Aquamatic worked pretty well, but a little wet. I'll have to check out the exhaling valve.  I survived the test dives with an over-exuberant venturi, and a bit of wet air. I think I got those issues resolved today. Visibility was about 3-4' and an ugly green, so I went with black & white and a 130 degree lens.  |
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Post by nikeajax on Jul 12, 2023 7:58:26 GMT -8
Daaaang son, very cool! You should try making Rainer's regulator now...  JB |
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Post by antique diver on Jul 12, 2023 12:15:49 GMT -8
Daaaang son, very cool! You should try making Rainer's regulator now... JB Thanks JB Well, I may retire from making wildcat breathing devices after this... or maybe not. There is something else I've been thinking about for a while.  |
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Post by vance on Jul 12, 2023 13:25:34 GMT -8
I hope you never retire from hotrods. They are so much fun!
You have worked miracles with the Bendix. I never imagined I'd hear that there's too much venturi! That is crazy. I hope you bend your imagination to other new projects.
Good work, Bill.
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Post by vance on Jul 12, 2023 13:34:26 GMT -8
I still have a Bendix diluter in a box, 3/4 modded for scuba. I might pick it up again, but, I'm not that interested in using it as a second stage with a remote first. But who knows when interest might pop up?
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Post by nikeajax on Jul 12, 2023 13:37:35 GMT -8
Well, I may retire from making wildcat breathing devices after this... or maybe not. Nice try, tell us another story buuuuddy! I wanna see what your next project is  JB |
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cg43
Senior Diver
Posts: 91
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Post by cg43 on Jul 12, 2023 14:13:40 GMT -8
Hi Bill
Please messure the distance from the center of your inhale diaphragma to the outer edge
of your duckbill . Something about 5 inch ?
The cracking suction 2.stage is 0,5 inch , cracking duckbll 0,5 inch , if aquastop mouthpiece 1 inch
for cracking two flappervalves , all together 2 inches . 3 inches missing .
Right sight and head down (duckbill up) the reg. will freefloat , you are violating the Cousteaou/Gagnan
rule (center exhale distance to center inhale smal) to much !
Another question is how perfect does an exhale valve close ?
In Lothar's webside I found an interesting discusion Duckbill vs Duckbill eliminator between John , Luis and other .
I missed the question how watertight is the valve and how quick is it watertight .
You can find out by cancel the automatic drying .Remove the flappervalves in the aquastop mouthpiece
and dive in an position mouthpiece dowm exhalevalve high .
And (or) watch an duckbill and an muschroom valve closing speed .
Greetings Rainer
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Post by antique diver on Jul 12, 2023 14:39:22 GMT -8
I hope you never retire from hotrods. They are so much fun! You have worked miracles with the Bendix. I never imagined I'd hear that there's too much venturi! That is crazy. I hope you bend your imagination to other new projects. Good work, Bill. Thank you Phil! I too never imagined there would ever be too much venturi after my first test dives on this beast in 2018! I took it into a pool for the first cautious testing with the diaphragm held in place by a conventional rubber band, and the exhalation going back into the main body (shared space with the inhalation) before exiting the body via a duckbill (also held by a rubber band) to my left side. Had a little water leak as moisture built up in the main body, gurgle-hack-burp, but it was somewhat cleared out by rolling left side down and blowing. It was not a good plan having the exhalation going back into a common body with incoming air... never mind what the dangerous Popular Science article showed! If someone followed all those directions they would be really lucky to survive a day of diving! Our friend, Scuba Lawyer tells of his father using aviation Oxygen diluter regulators in the Pacific in WW2. Happily, he survived, but it's doubtful that all users of homemade conversions were that lucky. I made a lot of changes before going to open water, including excluding the exhalation from entering main body, and securing the diaphragm with a very tightly snug oring. So the first cautious lake dive found the reg to be very smooth and easy on a gentle inhalation and calm breathing rate in 15' of depth, but it got seriously restrictive if upping the exertion level or going below 20'. Anyway, over the years I kept trying to improve the overall performance with various success, finally getting to breathe well enough to get to 42' without being too seriously starved for air. More recent tweaks have been way more successful, and I think the next lake trip might satisfy my demands. |
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Post by antique diver on Jul 12, 2023 14:51:47 GMT -8
Hi Bill Please messure the distance from the center of your inhale diaphragma to the outer edge of your duckbill . Something about 5 inch ? The cracking suction 2.stage is 0,5 inch , cracking duckbll 0,5 inch , if aquastop mouthpiece 1 inch for cracking two flappervalves , all together 2 inches . 3 inches missing . Right sight and head down (duckbill up) the reg. will freefloat , you are violating the Cousteaou/Gagnan rule (center exhale distance to center inhale smal) to much ! Another question is how perfect does an exhale valve close ? In Lothar's webside I found an interesting discusion Duckbill vs Duckbill eliminator between John , Luis and other . I missed the question how watertight is the valve and how quick is it watertight . You can find out by cancel the automatic drying .Remove the flappervalves in the aquastop mouthpiece and dive in an position mouthpiece dowm exhalevalve high . And (or) watch an duckbill and an muschroom valve closing speed . Greetings Rainer Hello Rainer, good points you make. Yes, the duckbill is a bit far from where I would like it, and it seems to dribble more air than the more restrictive Duckbill Eliminator that I also use at times. I might even try a stiffer mushroom valve in the DBE. So as it is, my horizontal position in the water with left shoulder a bit lower works out ok. Not the ideal situation, but we must remember this whole crazy gadget was never ever meant to go underwater at all. It has its little faults as is, but I don't find it totally annoying in the type of use I give it. I just kinda overlook the extra bubbles if I shift position a bit now and then. Still, I may see what I can do as an improvement some time this summer. I appreciate you interest and input, and certainly welcome any suggestions you would like to add! Thank you! BT |
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cg43
Senior Diver
Posts: 91
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Post by cg43 on Jul 12, 2023 15:46:49 GMT -8
Hello Bill
If it is not your own goal to build a reg. that worked in any position the same it is ok.
I sometimes dive with a Aquabell shallowwaterhelmet .
It's a great fun even the position in the water is very restricted .
Tuning your inhale :
Low cracking suction and strong ventury are not ideal for your design .
That restrict's your position withhout freeflow more than nessesary .
Find a compromise between easy breathing and possible position without freeflow .
Greetings Rainer
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Post by antique diver on Jul 12, 2023 15:59:13 GMT -8
Hey Rainer, I forgot to answer your question about distance from diaphragm center to outer edge of duckbill.
From diaphragm center to outside edge of duckbill is 4.5". Viewing the body from side shows the Duckbill edge to be below the Diaphragm by 1.5", so that helps a little bit when swimming horizontally.
With the Duckbill eliminator installed the outer edge is 4" from diaphragm center, and the sealing surface of it is about 1.625" lower than the diaphragm when viewed horizontally.
Considering I will probably use the DBE most of the time, I can probably configure it about 0.75" closer to the can without any major work.
Anyway, I don't use much air, and a little air leakage at times isn't going to be a big issue with the shallow and simple dives I'll be doing with the rig. Mostly 20-30', and when I do push the depth limits I will be carrying an extra air source by my side.
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Post by antique diver on Jul 12, 2023 16:04:12 GMT -8
Well, I may retire from making wildcat breathing devices after this... or maybe not. Nice try, tell us another story buuuuddy! I wanna see what your next project is JB Wellll... you are about to talk me into another configuration with Bendix #2. Maybe. Thanks chum  |
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Post by vance on Jul 13, 2023 7:09:53 GMT -8
This might not work for reasons I can't think of (and you may have already explained it), but why don't you simply rotate the copper exhaust fitting so the DBE or DB crosses the center of the cover?
Since Ft. Worth is expected to get to 115 degrees F this week, testing in the lake should be a better alternative than bench testing. Take care in that heat, Bill!
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