OP
Chez7222
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That'd would be great, my oldest son is planning on doing the same. If he's done I was trying to get my wife and youngest out there too.
DA Mistral Project
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Chris,
Concerning the duckbill eliminator, my tests indicate that no mushroom valve will equal a duckbill. But I did the evaluation using water as a fluid, not air and did not make any measurements on breathing resistance. Also, I have not specifically evaluated the Duckbill Eliminator. Here are two photos of my evaluations:
Note that the Healthways Scuba Deluxe has the mushroom valve, while the duckbill was from the original box for the USD Overpressure Breathing regulator. Note also the backup of water in the Healthways verses the USD duckbill which let the water flow through. This simply shows the fluid dynamics of the two systems. The backup occurs because the fluid (air or water) must take a 90 degree turn to exit through the mushroom, and then must lift the mushroom too. Anytime the fluid flow (from ventilation equations) must turn, there is an efficiency loss. According to my reference (ACGIH Industrial Ventilation, 26th Edition, ACGIH, Copyright 2007, "Duct Design Data Elbow Losses"), the eitered 90 degree turn has a elbow loss coefficient of 1.2. A stamped smooth 90 degree turn has a loss coefficient of 0.12 to 0.71, depending upon the radius/duct diameter ratio. But the duckbill allows almost straight-through exit, and so would be even lower.
Now, there are many advantages for a duckbill eliminator (mushroom valve). Once you have it, you probably will never need to replace it. I have 50 year-old Healthways mushroom valves which still function. Also, this may be very academic as there is a 6 inch or more suction on the exhaust hose measured from the center of the lungs. I have used my Healthways with the mushroom valve, and noted no problems with the exhaust resistance. But if you are taking the regulator on a very deep dive, or a hard-working dive at moderate depth, the duckbill will probably out-perform the mushroom valve.
SeaRat
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Paladin
Contributor
Since you guys were over on my "J-valve rod" thread, I'm going hijack this thread for a moment for a special announcement:
Yesterday, I received a pull rod that fits my double 72s perfectly. Earlier this week, I ordered a pin spanner and replacement mushroom valves for my Duckbill Eliminator from Vintage Double Hose. I received the items I ordered but, included in the package was a mint J-valve pull rod! Many thanks to Bryan at VDH for his generosity and thoughtfulness. Just another example of the type of service and customer support that makes Vintage Double Hose such an important part of the vintage diving community.
I talked to Bryan this morning by phone to thank him and he said he had seen my thread on the VDH forum about trying to find one. He had that one laying around so he added it to my shipment. How's that for customer service, huh?
Thanks again Bryan!
This hijack is now over. We now return you to your regularly scheduled thread.
Yesterday, I received a pull rod that fits my double 72s perfectly. Earlier this week, I ordered a pin spanner and replacement mushroom valves for my Duckbill Eliminator from Vintage Double Hose. I received the items I ordered but, included in the package was a mint J-valve pull rod! Many thanks to Bryan at VDH for his generosity and thoughtfulness. Just another example of the type of service and customer support that makes Vintage Double Hose such an important part of the vintage diving community.
I talked to Bryan this morning by phone to thank him and he said he had seen my thread on the VDH forum about trying to find one. He had that one laying around so he added it to my shipment. How's that for customer service, huh?
Thanks again Bryan!
This hijack is now over. We now return you to your regularly scheduled thread.
OP
Chez7222
Registered
Pretty awesome that guy is
@ John, makes perfect sense when given a visual, all of my rebuilds have duckbill eliminators. I am rebuilding an Aquamaster that a lady gave me for $free.99 at a LDS in Fernandina. I took the long yoke off of an old USD first stage an I'm having a lip machined to fit the Aquamaster to facilitate the use of a banjo. I will install a duckbill so that I dive both under the same conditions. I like to see how they both dive...
@ John, makes perfect sense when given a visual, all of my rebuilds have duckbill eliminators. I am rebuilding an Aquamaster that a lady gave me for $free.99 at a LDS in Fernandina. I took the long yoke off of an old USD first stage an I'm having a lip machined to fit the Aquamaster to facilitate the use of a banjo. I will install a duckbill so that I dive both under the same conditions. I like to see how they both dive...
John,
I should have sent you a private message the first time you posted this "test". I left it alone at VSS because I didn’t see much harm due to the limited audience over there, but I apologies for not correcting this earlier.
You “test” is extremely flawed.
I realize that you are trying to learn about fluid dynamics, but some of the stuff you post are not well researched.
The first flaw is that you are using water to simulate air. Water is a fluid that is over 800 times denser than air. Please do not try to justify by saying that it is a worst case test. It is not.
By using water your Reynolds number is over two orders of magnitude larger than air.
If you have a good knowledge of fluid dynamics modeling and simulation it is possible to scale test done with different fluid densities, but to be valid the Reynolds number needs to in the same order of magnitude. In one of my labs in college I manipulated fluid densities to cover a large range of Reynolds numbers for some fluid drag testing we were doing.
That is the reason why I am capable of doing regulator test on the surface and I am able to scale and do fairly good predictions of performance when the air density is 4 or 6 times denser (99 to 165 feet of depth). The Reynolds number is within the same order of magnitude (not over 800 times higher). I have been working with fluid dynamic for over 30 years.
To make your test much worst you are using an open flow to represent a closed flow system (basically a piping/ hose system). They are totally different systems. The flow inside a hose can be analyzed and it is described by Bernoulli’s equation, Open flow is not. For open flow you would have to apply impulse-momentum fluid equations. And there is not direct correlation between Bernoulli’s equation and the impulse-momentum equations.
One of the big differences between close flow and open flow is that close flow is primarily driven by pressure versus your “experiment is driven by fluid momentum”. The drag coefficient for an elbow that you are quoting, does not apply, at all, to open flow.
You can do a lot of searches on the internet and find a lot of information of what I am talking about. But if you are really interested maybe you need to take some courses in fluid dynamics. Getting pieces of information here and there just puts you in a position as described by the old saying of “having just enough information to be dangerous”.
The “test” that you are doing is very visual. It is the kind of stuff that someone in the marketing department of a corporation would try to pass as scientific, but it is not supported by any science. It really irritates me when I see someone in a marketing department do that. I realize that you are not in marketing and are not trying to mislead anyone.
I apologize if am being harsh, but I have a lot of respect for your background (and a lot of other people do too), but IMHO you should be careful on some of the stuff you post. I realize this is the internet, but I am sure you do not want to pass wrong information.
Note: the duckbill eliminator does have an extremely efficient mushroom valve, but to create the design to fit in the horn it did required to have a slight flow area reduction in the tube. This was a minor design trade-off that has been tested to be insignificant. The testing has been done using proper instrumentation in a control environment. I should add that this Duckbill Eliminator is not my design, but I was involved in the testing of it.
By the way, I spent a little bit of time down in Panama City and I got some nice “cooks tour” of NEDU, the dive depot, and the dive school. I had a nice chance to talk to some of the dive equipment researchers and engineers.
As expected a lot of the work they do is with rebreathers.
One of the discussions I had was specifically about the work of breathing and the mouthpiece valves. I got to see some nice detail drawings of the mushroom valves and some of the associated data.
Rebreathers require the lowest possible breathing resistance on the hose loop. They do not have the aerodynamic advantage of any venturi flow or any other pneumatic assist provided by the compressed air on a cylinder. That is why rebreathers normally use larger hoses and the most streamlined hose loop.
All rebreathers use mushroom valves as one way valves (both military and commercial). The valves used on rebreathers are absolutely the lowest possible flow resistance valves that can be designed by one, and they are mushroom valves.
If there was any performance value to using flutter valve/ duckbills in rebreathers, they would be used. They are not.
This information is common knowledge among rebreather’s manufacturers; none of it is sensitive (and definitely not classified in any form).
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Luis,
Actually, I welcome your comments on this. What I was trying to do in this "evaluation" (which is probably not the word I should have used, maybe "demonstration" would have been better), was to show visually why the U.S. Navy reports came back so negative on different types of valves. Here is the old-style top can for the USD regulators (in this case, a Broxton DA Aqualung--their first commercially-available regulator, and my favorite exhaust).
The "newer" duckbill valve that USD put together on the Mistral did not fair well either (in the 1958 evalutation):
But worse still were the evaluations on the Dacor Dial-a-Breath regulator, which employed a double-diaphragm with a mushroom valve in the diaphragm. My demonstration of this regulator looks like this:
The U.S. Navy Experimental Diving unit's graphs of this Dacor Dial-a-Breath regulator were even worse:
The "competitive regulator" up in this graph is probably the USD DA Aquamaster.
I was pretty careful not to say that I had evaluated the Duckbill Eliminator. I spoke generally about mushroom valves in the cans of double hose regulators. I have four that I have dived, the Dial-a-Breath, the Sportsways Hydro-Twin, the Nemrod Snark III and several Healthways Scuba Deluxe or Gold Label regulators. I also pointed out that there essentially is a vacuum of about 6-8 inches between the center of the chest and even a well-placed double hose regulator when in many diving positions (swimming horizontally). I further stated that there are advantages to the Duckbill Eliminator too. So I think I covered it with reasonable objectivity. I do not present this as a scientific demonstration, as there are no actual measurements of exhalation resistance in that presentation--just visual demonstration. And, you are entirely valid in showing that the visual demonstration has limitations.
But at the same time, I find it interesting that the U.S. Navy Experimental Diving Unit never "passed" a double hose regulator and published the results with a mushroom valve exhaust design, in spite of the fact that I know they have used the Nemrod Snark III and now the Aqualung Mentor. Both of those latter regulators have mushroom valve exhausts. Early single hose regulators did not fair well either in these tests, specifically the Healthways Scubair, Scubair 300, and USD early Calypso (which we in the USAF ignored--the tests--and procured as they worked much better than double hose regulators for parascuba jumps). I think the Snark III has perhaps the best design for a mushroom valve exhaust on a two-hose regulator that I have used, and my Scubapro AIR-1 is the best single hose design exhaust I have used.
If you have any information on these regulators tests (Snark III and Aqualung Mentor), I would be interested in seeing them. Also if you have test information on the Duckbill Eliminator, that also would be interesting. But as I said above, I think this is mainly academic, as "there is a 6 inch or more suction on the exhaust hose measured from the center of the lungs" which seems almost to suck air out of the lungs in a horizontal position.
SeaRat
---------- Post added February 22nd, 2013 at 05:59 PM ----------
Luis,
Actually, I welcome your comments on this. What I was trying to do in this "evaluation" (which is probably not the word I should have used, maybe "demonstration" would have been better), was to show visually why the U.S. Navy reports came back so negative on different types of valves. The "newer" duckbill valve that USD put together on the Mistral did not fair well either:
But worse still were the evaluations on the Dacor Dial-a-Breath regulator, which employed a double-diaphragm with a mushroom valve in the diaphragm. My demonstration of this regulator looks like this:
The U.S. Navy Experimental Diving unit's graphs of this Dacor Dial-a-Breath regulator were even worse:
I was pretty careful not to say that I had evaluated the Duckbill Eliminator. I spoke generally about mushroom valves in the cans of double hose regulators. I have three that I have dived, the Dial-a-Breath, the Sportsways Hydro-Twin and several Healthways Scuba Deluxe or Gold Label regulators. I also pointed out that there essentially is a vacuum of about 6-8 inches between the center of the chest and even a well-placed double hose regulator when in many diving positions (swimming horizontally). I also pointed out that there are advantages to the Duckbill Eliminator too. So I think I covered it with reasonable objectivity. I do not present this as a scientific demonstration, as there are no actual measurements of exhalation resistance in that presentation--just visual demonstration. And, you are entirely valid in showing that the visual demonstration has limitations.
But at the same time, I find it interesting that the U.S. Navy Experimental Diving Unit never "passed" a double hose regulator and published the results with a mushroom valve exhaust design, in spite of the fact that I know they have used the Nemrod Snark III and now the Aqualung Mentor. Both of those latter regulators have mushroom valve exhausts. I think the Snark III has perhaps the best design for a mushroom valve exhaust that I have used.
If you have any information on these regulators' tests (Snark III and Aqualung Mentor), I would be interested in seeing them. Also if you have test information on the Duckbill Eliminator, that also would be interesting. But as I said above, I think this is mainly academic, as "here is a 6 inch or more suction on the exhaust hose measured from the center of the lungs" which seems almost to suck air out of the lungs in a horizontal position.
SeaRat
Actually, I welcome your comments on this. What I was trying to do in this "evaluation" (which is probably not the word I should have used, maybe "demonstration" would have been better), was to show visually why the U.S. Navy reports came back so negative on different types of valves. Here is the old-style top can for the USD regulators (in this case, a Broxton DA Aqualung--their first commercially-available regulator, and my favorite exhaust).
The "newer" duckbill valve that USD put together on the Mistral did not fair well either (in the 1958 evalutation):
But worse still were the evaluations on the Dacor Dial-a-Breath regulator, which employed a double-diaphragm with a mushroom valve in the diaphragm. My demonstration of this regulator looks like this:
The U.S. Navy Experimental Diving unit's graphs of this Dacor Dial-a-Breath regulator were even worse:
The "competitive regulator" up in this graph is probably the USD DA Aquamaster.
I was pretty careful not to say that I had evaluated the Duckbill Eliminator. I spoke generally about mushroom valves in the cans of double hose regulators. I have four that I have dived, the Dial-a-Breath, the Sportsways Hydro-Twin, the Nemrod Snark III and several Healthways Scuba Deluxe or Gold Label regulators. I also pointed out that there essentially is a vacuum of about 6-8 inches between the center of the chest and even a well-placed double hose regulator when in many diving positions (swimming horizontally). I further stated that there are advantages to the Duckbill Eliminator too. So I think I covered it with reasonable objectivity. I do not present this as a scientific demonstration, as there are no actual measurements of exhalation resistance in that presentation--just visual demonstration. And, you are entirely valid in showing that the visual demonstration has limitations.
But at the same time, I find it interesting that the U.S. Navy Experimental Diving Unit never "passed" a double hose regulator and published the results with a mushroom valve exhaust design, in spite of the fact that I know they have used the Nemrod Snark III and now the Aqualung Mentor. Both of those latter regulators have mushroom valve exhausts. Early single hose regulators did not fair well either in these tests, specifically the Healthways Scubair, Scubair 300, and USD early Calypso (which we in the USAF ignored--the tests--and procured as they worked much better than double hose regulators for parascuba jumps). I think the Snark III has perhaps the best design for a mushroom valve exhaust on a two-hose regulator that I have used, and my Scubapro AIR-1 is the best single hose design exhaust I have used.
If you have any information on these regulators tests (Snark III and Aqualung Mentor), I would be interested in seeing them. Also if you have test information on the Duckbill Eliminator, that also would be interesting. But as I said above, I think this is mainly academic, as "there is a 6 inch or more suction on the exhaust hose measured from the center of the lungs" which seems almost to suck air out of the lungs in a horizontal position.
SeaRat
---------- Post added February 22nd, 2013 at 05:59 PM ----------
Luis,
Actually, I welcome your comments on this. What I was trying to do in this "evaluation" (which is probably not the word I should have used, maybe "demonstration" would have been better), was to show visually why the U.S. Navy reports came back so negative on different types of valves. The "newer" duckbill valve that USD put together on the Mistral did not fair well either:
But worse still were the evaluations on the Dacor Dial-a-Breath regulator, which employed a double-diaphragm with a mushroom valve in the diaphragm. My demonstration of this regulator looks like this:
The U.S. Navy Experimental Diving unit's graphs of this Dacor Dial-a-Breath regulator were even worse:
I was pretty careful not to say that I had evaluated the Duckbill Eliminator. I spoke generally about mushroom valves in the cans of double hose regulators. I have three that I have dived, the Dial-a-Breath, the Sportsways Hydro-Twin and several Healthways Scuba Deluxe or Gold Label regulators. I also pointed out that there essentially is a vacuum of about 6-8 inches between the center of the chest and even a well-placed double hose regulator when in many diving positions (swimming horizontally). I also pointed out that there are advantages to the Duckbill Eliminator too. So I think I covered it with reasonable objectivity. I do not present this as a scientific demonstration, as there are no actual measurements of exhalation resistance in that presentation--just visual demonstration. And, you are entirely valid in showing that the visual demonstration has limitations.
But at the same time, I find it interesting that the U.S. Navy Experimental Diving Unit never "passed" a double hose regulator and published the results with a mushroom valve exhaust design, in spite of the fact that I know they have used the Nemrod Snark III and now the Aqualung Mentor. Both of those latter regulators have mushroom valve exhausts. I think the Snark III has perhaps the best design for a mushroom valve exhaust that I have used.
If you have any information on these regulators' tests (Snark III and Aqualung Mentor), I would be interested in seeing them. Also if you have test information on the Duckbill Eliminator, that also would be interesting. But as I said above, I think this is mainly academic, as "here is a 6 inch or more suction on the exhaust hose measured from the center of the lungs" which seems almost to suck air out of the lungs in a horizontal position.
SeaRat
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All that aside, in actual use, in the water, even at maximum sport diver depths, I simply notice no real difference between the duckbill and the DBRV in terms of exhaust effort. What I do notice is that I no longer having rotting duckbills stuck in my can and keeping me from cinching my hose clamp down or inverting or gluing themselves to the diaphragm or any other similar most annoying behaviors.
N
N
Hi John,
I just have a real issue with this statement below. You had no data (or very limited) to make that conclusion and the statement is incorrect. Your “general statements” about the mushroom valves is what is not correct.
I also have an issue with this statement.
I would not say that the visual demonstration “has limitations”; it is actually, totally misleading because it has no physical relation to the enclosed gas flow.
You are still showing pictures of water impacting the inside of the horn, like if it had any value. It has no scientific or physical resemblance to the actual flow. Again, this is what a salesman/ marketing would do and I find this type of visual manipulation of reality to be very inappropriate. I realize that you are not doing it intentionally as a salesman, but it is very misleading.
I realize that you did not make any comments about the Duckbill Eliminator, but you were making very general statements about mushroom valves with very little data, and mostly basing it in an extremely flawed demonstration. Your only data seems to be from very old poorly designed exhaust systems.
The Navy Experimental Diving Unit (NEDU) did not “pass” any of the old single hose regulators either because all their exhausts were poorly designed back then. Now-a-days most single hose regulators will pass all NEDU breathing tests and many others (including the European standards). And they all use mushroom valves for exhaust.
On a separate subject, I realize that there is a lot of old literature that uses the center of the lungs as critical point, but my theory that is not was partially verified during my visit to the Navy Experimental Diving Unit. Let me just say that the test probes on the breathing simulator test dummies is not located at the lungs.
I just have a real issue with this statement below. You had no data (or very limited) to make that conclusion and the statement is incorrect. Your “general statements” about the mushroom valves is what is not correct.
I also have an issue with this statement.
I would not say that the visual demonstration “has limitations”; it is actually, totally misleading because it has no physical relation to the enclosed gas flow.
You are still showing pictures of water impacting the inside of the horn, like if it had any value. It has no scientific or physical resemblance to the actual flow. Again, this is what a salesman/ marketing would do and I find this type of visual manipulation of reality to be very inappropriate. I realize that you are not doing it intentionally as a salesman, but it is very misleading.
I realize that you did not make any comments about the Duckbill Eliminator, but you were making very general statements about mushroom valves with very little data, and mostly basing it in an extremely flawed demonstration. Your only data seems to be from very old poorly designed exhaust systems.
The Navy Experimental Diving Unit (NEDU) did not “pass” any of the old single hose regulators either because all their exhausts were poorly designed back then. Now-a-days most single hose regulators will pass all NEDU breathing tests and many others (including the European standards). And they all use mushroom valves for exhaust.
On a separate subject, I realize that there is a lot of old literature that uses the center of the lungs as critical point, but my theory that is not was partially verified during my visit to the Navy Experimental Diving Unit. Let me just say that the test probes on the breathing simulator test dummies is not located at the lungs.
Lewis,
My "data" was from the NEDU--their tests. I was trying to see why their tests came out the way that they did. If my demonstrations are misleading, then why do they correspond to the graphs in the NEDU tests of these regulators? Concerning mushroom valves verses duckbill valves, I was specifically talking about double hose regulators' valves in the bottom box. I had a Healthways Gold Label in the 1980s which I put a double mushroom valve into (by drilling appropriate holes) and that improved that particular regulator in my experience (again, no data, just subjecting breathing in river water), much as the Dacor Olympic regulators with the double mushrooms improved the Dacor second stage performance. The Olympic second stage passed NEDU tests...whereas the Dacor R-4 did not pass. So these demonstrations originated with my trying to determine why these regulators either passed or did not pass the NEDU tests.
Apparently the key to the mushroom valves passing on single hose regulators was that they increased their size while also increasing the flexibility of the valve themselves with the use of silicone. While I have not seen the Duckbill Eliminator, I figured that these same principals had been used in its design. I agree with Nemrod, that there are many advantages to the Duckbill Eliminator. I'm just saying that the original design did pretty well too.
Lewis, could you explain this statement a bit more. It is of interest to me because it is primary in my way of thinking about regulator placement and work of breathing.
SeaRat
PS--I just went onto the VDH site, and looked closely at the Duckbill Eliminator. I then compared it with the Healthways Scuba Deluxe mushroom exhaust chamber (a metal enclosure into which an exhaust has been stamped). The stamping is not at the end, but is 5/8 inch up from the bottom edge, and is 1 inch in diameter with a three-rib "wagon wheel" style attachment. This means that the water flow would hit the bottom and back up; however with the Duckbill Eliminator there is no "bottom," only out the valve. I suspect if the Duckbill Eliminator were put to the same demonstration, water would flow right through without obstruction.
Lewis, you are saying this is not a valid "test." Perhaps not, but it let me understand the difference in flow between the exhaust designs I wanted to better understand; yes they are old, vintage even, but that's what I'm interested in.
My "data" was from the NEDU--their tests. I was trying to see why their tests came out the way that they did. If my demonstrations are misleading, then why do they correspond to the graphs in the NEDU tests of these regulators? Concerning mushroom valves verses duckbill valves, I was specifically talking about double hose regulators' valves in the bottom box. I had a Healthways Gold Label in the 1980s which I put a double mushroom valve into (by drilling appropriate holes) and that improved that particular regulator in my experience (again, no data, just subjecting breathing in river water), much as the Dacor Olympic regulators with the double mushrooms improved the Dacor second stage performance. The Olympic second stage passed NEDU tests...whereas the Dacor R-4 did not pass. So these demonstrations originated with my trying to determine why these regulators either passed or did not pass the NEDU tests.
Apparently the key to the mushroom valves passing on single hose regulators was that they increased their size while also increasing the flexibility of the valve themselves with the use of silicone. While I have not seen the Duckbill Eliminator, I figured that these same principals had been used in its design. I agree with Nemrod, that there are many advantages to the Duckbill Eliminator. I'm just saying that the original design did pretty well too.
Lewis H:
Lewis, could you explain this statement a bit more. It is of interest to me because it is primary in my way of thinking about regulator placement and work of breathing.
SeaRat
PS--I just went onto the VDH site, and looked closely at the Duckbill Eliminator. I then compared it with the Healthways Scuba Deluxe mushroom exhaust chamber (a metal enclosure into which an exhaust has been stamped). The stamping is not at the end, but is 5/8 inch up from the bottom edge, and is 1 inch in diameter with a three-rib "wagon wheel" style attachment. This means that the water flow would hit the bottom and back up; however with the Duckbill Eliminator there is no "bottom," only out the valve. I suspect if the Duckbill Eliminator were put to the same demonstration, water would flow right through without obstruction.
Lewis, you are saying this is not a valid "test." Perhaps not, but it let me understand the difference in flow between the exhaust designs I wanted to better understand; yes they are old, vintage even, but that's what I'm interested in.
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Paladin
Contributor
I honestly cannot tell any difference in exhalation effort between the old duckbill and the new DBE. I like the DBE because it's in a nice, neat little package that tucks up against the can, out of the way.
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