drado
Pro Diver
Posts: 186
|
Post by drado on Jul 11, 2011 22:07:12 GMT -8
John, I was reading the NEDU 9-59 report on the old vs the new design of exhaust horn and flapper valve wherein the conclusion was that the newer one only met the Navy specifications after modifications were made: Did they elucidate what exact modifications were made?
|
|
|
Post by elmerfudd on Jul 12, 2011 16:52:33 GMT -8
Well, I dove a RAM with a DBE yesterday. Sad to say, I was diving with a new diver and we were hunting crabs and I didn't pay the slightest attention to the exhalation. I guess the fact that I never noticed it however must mean that exhaling through a DBE doesn't totally suck.
Today I rigged up a makeshift magnahelic using a piece of clear tubing with water in it taped to a piece of PVC pipe alongside a ruler.
I submerged a DAAM with a duckbill and a RAM with a DBE in my sink and measured them side by side. Resistance was identical so far as I could tell using my rather crude measuring equipment. Both were around 1.75-2" under sustained exhalation with an initial spike as high as 3" with hard exhalation. The depth of the horn was approximately 2" deep, which accounts for the rather significant effort.
Next I tried to rate them subjectively as to which one seemed to breathe harder and watched the flow of bubbles out of the can to see if I could see any difference and honestly, I couldn't see or feel any.
|
|
|
Post by SeaRat on Jul 12, 2011 17:40:25 GMT -8
John, I was reading the NEDU 9-59 report on the old vs the new design of exhaust horn and flapper valve wherein the conclusion was that the newer one only met the Navy specifications after modifications were made: John Did they elucidate what exact modifications were made? Drado, They did not say, and it seems likely that they did nothing until after the US Navy tests of the Non-Magnetic DA Aquamasters, where the EDU apparently worked closely with USD to develop a better-performing material for the duckbill. In doing so, they probably made it more flexible and therefore better able to handle heavier exertions. If you look closely at the Mistral report, it shows that they preferred the older bottom box to the newer design with the duckbill inside. The older had the duckbill on the outside of the tube (see the photos of the tests to see the difference). Elmer, I don't think we can really tell much of a difference in most of our diving. The EDU tests these exertion rates at depth, under high rates of exertion. They also do not take into account the regulator positioning. For instance, I know that my Healthways regulators (2nd and 3rd generation) breathe with more resistance than the USD regs, but because in most of my diving the regulator is quite a bit above my lungs, that differential seems almost to suck air out of my lungs. So the small difference between a mushroom valve and a duckbill will not be felt much unless the exertion is high and the diver is pretty deep. It is also very difficult to measure with a water manometer on the surface for the same reasons.
|
|
|
Post by SeaRat on Jul 12, 2011 22:13:39 GMT -8
Well, I kinda messed up that above post. I don't appear to be able to edit it either, so you'll just have to look to see where I put my comments. Hint--they are above the last sentence, which should be the end of the quote. Oh well, time for bed.
John
|
|
drado
Pro Diver
Posts: 186
|
Post by drado on Jul 13, 2011 3:45:01 GMT -8
Hahaha! I had to do a double-take, but there it is Thanks! I really appreciate all the info and links that you provide. Always an interesting read.
|
|
|
Post by JES on Jul 13, 2011 4:11:36 GMT -8
Well, I kinda messed up that above post. I don't appear to be able to edit it either, so you'll just have to look to see where I put my comments. Hint--they are above the last sentence, which should be the end of the quote. Oh well, time for bed. John John, I was able to modify your post to correct this for you. Cheers, JES
|
|
|
Post by SeaRat on Jul 17, 2011 19:37:38 GMT -8
JES,
Thank you. I appreciate that correction as it makes the post a lot more readable.
All,
This evening I made a different post on the Instruction area, and feel it is appropriate here too: [/B], U.S. Divers Co., 3323 West Warner Ave., Santa Ana, CA, Catalog No. 7804-00, USA, 4th Printing November 1965, copyright 1962, page 29.
John[/Quote] We have been talking a lot about rather minute exhalation resistance differences between the mushroom valve and the duckbill valve. We need to consider that this difference is probably dwarfed by the actual positioning of the regulator. I took my Healthways SCUBA Gold Label into the water last weekend with both mushroom valves removed from the mouthpiece, leaving only the mouthpiece baffle in place. Well, it still had enough blow-by that I aborted the dive (inhalation air going out the exhalation valve on the box when I was inhaling, even with the baffle plate in the mouthpiece. So I have not put the exhalation mushroom (a silicone Healthways valve reproduction) back into the mouthpiece. What I have done is to take one of these mouthpieces and carved out the whole wagon wheel, leaving a smooth surface. That remains on the inhalation side, but the regulator has a very strong venturi, and needs the extra resistance in the exhalation side to keep from having blow-by. The little bit of increased exhalation resistance is more than made up for by the regulator position higher than my lungs.
John
|
|