Healthways Double Hose Scuba Exhaust mods

[vance]

So the idea here is to produce a working exhaust system for the Healthways Scuba rev1. This is the one that utilizes the big exhaust diaphragm, a duckbill, and in some early ones, a rubberband-type cover for auxiliary drillings on the exhaust horn. There are several objectives, listed here in descending importance: producing viable parts an methods to breathe new life into the regulator, reliably sealing the air side of the body from water intrusion, and minimizing exhalation effort.

I am attempting to produce a workable duckbill first, which would pretty much eliminate the need for the molded exhaust diaphragm which is no longer available. This, I think, will allow the use of a thickish rubber cover of some type, silicone sheet, innertube rubber, etc., that does not have to seal the end of the exhaust horn by way of air pressure. In fact, my hope is that the cover does not come into contact with the horn at all. This would allow exhaled air to flow with less back pressure since it would not have to move the diaphragm away from the end of the air horn. More on this later.

The clearance between the inner surface of a membrane over the exhaust diaphragm flange (I put it this way for a reason) and the end of the air horn is about 1/8" (2-3mm?). Because of the way the original diaphragm was made, the center of the diaphragm surface was intentionally brought closer to the airhorn than a simple membrane stretched over the flange will be.



Note the drop in the center of the diaphragm! This brings the diaphragm nearly (if not directly) into contact with the horn. This seems to be a problem, if you're trying to utilize a replacement membrane with the original intent, which was to seal the end of the exhaust horn from water backing up into it. The contact surfaces are pretty far away from each other....

In practice, the diaphragm method did not work perfectly, and water entered the hose when the diver was in some positions. It is my understanding that Healthways introduced a duckbill later on to counter this tendency. My exhaust diaphragms are old, somewhat stiff, and somewhat mis-shaped, which probably exacerbates the problem when re-used. I have never seen an original duckbill that was even close to intact, much less usable.

As those of us who have these regulators know, there're no reproduction diaphragms available, nor any repro duckbills. This causes the intrepid to try other stuff. I've attempted to make duckbills from bike innertubes, cut up USD duckbills, and just now, molding from silicone. I have also used bike innertube rubber, and the palm of a latex dipped cloth work glove for the diaphragm. These ideas have all been attempted by others before me, with some success. Limited success, I think. The closest I've gotten to a workable duckbill before now was the cut down USD one. It doesn't close to my liking when installed. Maybe water pressure on it will close it tight, but I'm not happy with it.

So here's what I've done so far. I made a couple of plug molds out of an old broomstick handle, and varnished them.


They are slightly different sizes.

The idea was a simple dip process. I don't want to mess around with 3 piece molds...... yet.

Here's what happens after a couple of dips: 



Kind of crude, but in the ballpark!



In case you're wondering, this is the inside of my oven. It's too cold and wet here for the silicone to set up before it drips off excessively.

Installed:



It's a bit lumpy and uneven, but works on dry land. 1st attempt, ya know? I think the clip that held the original will cut the silicone too easily, so I'm thinking about gluing the duckbill in with silicone sealer or making a wider plastic retainer clip or something.

I will be making more, hopefully better ones, and will post my results here. I've learned a lot with this first attempt, mostly that I am my own worst enemy when it comes to this kind of thing. I can't let well enough alone and have to fiddle.

Back to my theory, and I'm sure that I'm missing something, misled, misguided, and generally FOS (I'm sure you will gently inform me about how all of the above are true, and why):

If you cover the big exhaust diaphragm flange with a thickish membrane (1/32 thick, maybe) and clamp it in place, the stretched membrane will be somewhat stiff, and will resist the air pressure on the air side of the body, rendering it useless for the original idea of sealing the exhaust horn. However, the thicker membrane should provide a safe, robust barrier between the air and water sides of the regulator. Thin flexible materials could fail catastrophically, which would be life threatening while the regulator was in use at depth. This will hopefully leave sufficient clearance between it and the exhaust horn for exhaled air to flow out without having to overcome the membrane's resistance. This is where I'm going to get shot down, most likely. It may not work that way, and the pressures will still be enough to deflect the membrane into the end of the horn.

I would prefer a solid cover, raised even farther away from the air horn, to overcome the potential seal of a flexible membrane. (One of these might just open up a path for a duckbill eliminator kina gizmo that would use a mushroom valve....) But that's for another day.

Please make suggestions, criticisms (be nice), and/or facts that might return me to reality. Please feel free to contribute any ideas you might have for working mods that actually adhere to the laws of physics!

Phil


        

[nikeajax]

Phil, one of the things I've been thinkin' 'bout is reinforcing the DB with nylon, like from pantyhose; it wouldn't need to come all the way to the end. This idea is very much in line with the original HW diaphragms too, which would make the tear resistant.

While reading your "John Ratliff" style text (at time massive amounts there of ) I figured out what it would take to make the DB-eliminator. When I can make a drawing, I'll PM you...

JB

[vance]

Yeah, I know. Lots of words. But, I'm trying to be specific about what I see are the problems and potential work-arounds.

I was thinking of a fabric imbedded in the silicone, and like you, thinking it would only need to be a wrap around the end to protect against the retainer. I'm not sure that it will allow enough stretchiness to work the part off the mold. I had to roll them inside out to get them off the form. Maybe sheer nylon like you suggest would work. The silicone is pretty tough. Not sure it requires re-inforcing. It just can't stand up to sharp edges.

I know the original duckbill was a form dipped in latex. What was the inner material? It looks like paper, maybe leather. Does anyone know the process for the rubber layer? Was it a hot dip? Someone was making hand dipped DB's back in 2006-ish, I heard. I'd like to know how they did it!

Phil

[vance]

Feb 20, 2017 14:18:10 GMT -8 nikeajax said:

........ While reading your "John Ratliff" style text (at time massive amounts there of ) .........

JB

Already! Fake comparison! So unfair!

[nikeajax]

Hey pal, if da shoo fitz

JB

[tomcatpc]

I like how the duckbill is looking so far, anyway it could be made longer and then have it fit the horn like a US Divers/Voit duckbill?
When I made mine from a rubber glove finger, I cut it as long as I could and used an internal clip and looped the end over the horn and tied it off with thread.
Mark

[vance]

Feb 20, 2017 21:24:26 GMT -8 tomcatpc said:

I like how the duckbill is looking so far, anyway it could be made longer and then have it fit the horn like a US Divers/Voit duckbill?
When I made mine from a rubber glove finger, I cut it as long as I could and used an internal clip and looped the end over the horn and tied it off with thread.
Mark

The wall thickness is too much for a fold-over, I think. It will definitely do it (they turned inside out when removing from the form), but getting the hose over it might prove difficult.

When I did this with a cut down USD DB, the hose would pull the fold-over down the horn and retract the DB. I solved this by gluing the fold over to the horn with a spot of RTV. Lubing might have been sufficient.

Tire tube ones are stiff enough to not slide like the USD material when the hose goes over, I found. 

I think just gluing this new silicone valve in at the end of the horn with a bit of RTV will suffice. 

[nikeajax]

Phil, 'glad you've got sumthin' to do while getting over, as my wife calls it, "the creeping crud!" Just as we were getting over one virus, we got version 2.0

Yeah, I think gluing that sucker in is a good idea. I'm hoping to make it to Jim's soon to see if he has the diaphragm I'm thinkin' 'bout!

JB

[vance]

I've been working on my silicone technique. This pair came out better. One is too small in diameter, so no more on that mold. Here's the new one:









And a new idea I'm trying out. This will probably elicit hoots of derision, but in a different configuration, it might have legs:





This will of course let in a 2-3 inch column of water if the exhaust diaphragm isn't sealing in all positions, but that's way better than a hoseful. Getting the exhaust hose in a comfortable position with this extension on it will probably require an elbow or some such to bring the hose around. I'm going to try it with the EPDM stretchy hoses to see if it even works.

I think the duckbill is probably far better overall, but I thought this would be a fun project.

Comments are welcome!

[nikeajax]

Phil good on you my friend--the fact that you are trying to be proactive says a lot, and not just bellyachin' 'bout the design of this reg!

JB

[vance]

Of course, the problems here are getting the exhaust mushroom as close to the end of the exhaust column as possible, and directing the hose toward the diver without a too ridiculous angle, and a too fragile extension.

I machined the body of the exhaust adapter so it fits inside the exhaust horn to reduce the amount of potential water intrusion into the horn, and to reduce the overall length of the adapter.

Also, the mushroom needs clearance inside the adapter so it doesn't get pushed by exhalation pressure into the reduced diameter of the adapter where it fits into the horn. A machined stop will be introduced into my next prototype. This one relies on a interference fit, which is probably ok, but a stop will make it idiot proof.

Various sealing strategies will be used at the joint of the adapter and the exhaust horn, and the joint of the adapter body where it fits over the wagon wheel. A rubber band cut from a bike tube will probably work for the ex horn, and I might just glue the adapter body. A replacement mushroom can probably be weaseled in even if it's glued. If I glue it, I should probably just glue the wagon wheel in, too.

The best part about this adapter is that the exhaust diaphragm is no longer necessary, and the hole can be replaced with a heavy duty rubber cover or some other material. You could even solder a metal cover over it, if you wanted.

Phil

[SeaRat]

I haven't read the entire thread yet, but will show you two duckbills I have used:


This is a cut-down USD duckbill for the Healthways SCUBA.


Here it is in the horn.


This is an original, intact Healthways duckbill for their SCUBA regulator.


Side view of the original Healthways duckbill.


Healthways enigneers kept it in place with a "C" clip that could be removed with needle-nose pliers.


Placement of the original Healthways duckbill within the horn/exhaust system before any cleaning, etc. of this regulator.

John

[nikeajax]

So, John, which work better? I'm guessing the USD because it allows more air to ekskape (escape)?

JB

[SeaRat]

Mar 8, 2017 18:44:26 GMT -8 nikeajax said:

So, John, which work better? I'm guessing the USD because it allows more air to ekskape (escape)?

JB

Phil and Jay,

I have some observations, and considerations about the exhaust. First, about Jay's question; this can be answered in a couple of ways. The first is by measurement, but I don't have the instrumentation to do so. The second is be examination of the different designs. The third is to subjectively evaluate each by diving them.

I will talk to the second, an examination of the two designs, first. Looking at the design of the Healthways SCUBA (original design), in the horizontal position the midpoint of the exhaust diaphragm is about 1 inch (2.2 cm) above the main diaphragm'S lowest point. Looking at the USD design, the duckbill is below the diaphragm, giving the Healthways design a bit over a 1 inch (2.2 cm) advantage in this horizontal position. That same 1 inch, or 2.2 cm advantage goes to the original Healthways design in a vertical position.

Now, the small Healthways duckbill is an afterthought put in when what Fred Roberts in Basic SCUBA described as an "exhaust imbalance" was discovered after production had started. But the duckbill was a backup to the main flexible exhaust diaphragm, as it was unneeded except in a head-down position, where water can intrude into the exhaust hose. In all other positions, air pressure on the exhaust diaphragm seals it to the exhaust tube. But the Healthways duckbill will introduce a slightly greater resistance, and therefore some slightly increased exhaust resistance and effort.

The third way is to dive this regulator in all these configurations, and subjectively evaluate them. I have found that the original exhaust diaphragm, or the exhaust disphramgm made out of a flexible membrane, to be the easiest exhaust I have ever used in a double hose regulator, easier that a Mistral/Aquamaster duckbill exhaust. Put the original exhaust duckbill valve into this regulator, and it will also breath very easily, as easy as or easier than the amistral/Aquamaster duckbill rprxhaust, but not quite as easy as without it.

Now, let's talk about the physics of Phil's proposal to place an immovable rubber/stainless cover where the exhaust diaphragm currently exists. If this is done, the duckbill then becomes the primary exhaust valve. But the duckbill is then located an inch of water pressure over the center of the diaphragm. If the demand levers are set for sensitive response by raising them as high as possible onto the demand diaphragm, the breaking pressure, especially at about 500 pasig tank pressure, will be about 1/2 inch, or 0.9 cm, But there is a 1 inch, or 2.2 cm "head" of water pressure already on it except in the head-down position. What this means is that in most positions, the modified Healthways SCUBA will leak air out of the exhaust in most positions.

That was the beauty of the Cousteau-Gagnan exhaust patent; the duckbill was below the center of the exhaust in almost all positions (except upside down). Newer duckbills are sometimes placed too shallow into the case of the UDA double hose regulators, so that the in some positions are a half inch to one inch above the center of the diaphragms, and they will also leak air slightly if really fine tuned.

The Healthways designers were able to overcome the USD patent wit h a unique design which used air pressure from inside the case to seal the exhaust diaphragm by this same one-inch pressure differential in the Healthways SCUBA regulator. This is why I created my Hybrid Healthways SCUBA regulator, which incorporated the original, unique and epvery easy exhaust system with the Gold Label Venturi of the third generation of these regulators.

Here is a calculation I made last year on the Healthways exhaust diaphragm:


What this calculation shows is that the pressure on the exhaust diaphragm is about the equivalent of putting a two once lead weight on that exhaust diaphragm to seal it shut.

And here is a diagram which illustrates the differences in the location of the exhausts between the original Healthways SCUBA and the USD Mistral/Aquamaster exhaust:


Note that this drawing assumes a 3/4 inch difference between the demand and exhaust diaphragms, but I just measured it at approximately one inch of difference.
John

[vance]

Yes, I understand that the original diaphragm is optimal, and the original diaphragm with the duckbill a little less. This is the direction I'm going: a suitable replacement diaphragm, and a replacement duckbill.

What I may not understand is how the duckbill is located "an inch of water pressure over the center of the (demand?) diaphragm" when it practically touches the exhaust diaphragm. So, exhalation is exhausted from the same position as it does with a diaphragm?

However, the original diaphragms are often missing, broken, too stiff, and replacements are not available. My concern with a replacement membrane is that the material has to be pretty thin and flexible to overcome the EXTRA distance between it and the end of the exhaust horn. The OEM diaphragm is made so that the center is depressed toward the horn. This leads me to assume that the manufacturer had difficulty with the exhaust seal and had to reduce the distance by building in a depression. Things like that are not done without a reason.

I am concerned about the safety of a thin flexible membrane such as your glove material (as you have suggested yourself). If this was to fail, the consequences would be disastrous.

I am going to try a sheet of 1/32" silicone rubber, a piece of light racing tube rubber, a piece of swimcap, and anything else I can think of as a diaphragm with and without the duckbill. And I'll try out the mushroom adapter without the duckbill. I expect it to be awkward, unnecessary, and just a bit silly looking. I also expect it to be a failure. But I'm undaunted!

I am waiting for the weather to get a bit warmer, though. Sea trials are upcoming!