|
Post by SeaRat on Mar 12, 2017 12:21:21 GMT -8
So, in this head down position, and when the membrane is not sealing the exhaust horn, the regulator will freeflow? Couldn't this be negated by further lever adjustment? JB Two things here, yes, this leakage of air in a normal diving position could be negated by further lever adjustmet, but at a cost of breathing effort. Get the cracking effort up over one inch of water pressure, and it won't free-flow, or leak air. But the cost is in the performance of the regulator, especially at low tank pressure. Now, for your question about the head-down position, no the lever adjustment would not seal the exhaust diaphragm as the internal case pressure is sensed at the diaphragm. If the diaphragm's center is above the exhaust diaphragm, the exhaust diaphragm will be at less than ambient pressure, and will not seal. John
|
|
|
Post by vance on Mar 12, 2017 18:14:51 GMT -8
So, to re-state:
In the first case, head down, with a flexible membrane, the seal on the exhaust horn is NOT made and the reg will NOT freeflow. With a hard cover, the horn would NOT be sealed and would NOT freeflow. This is because the superior air pressure inside the can is lost in this head down position and the air and water pressures are then equal? If so, then the loss of the superior pressure is due to the changed relationship of the exhaust port placement relative to the demand diaphragm in this upside down orientation?
In the second case, horizontal or head up, with a flexible membrane, the seal IS made and the reg will NOT freeflow. However, with the hard cover, the seal is NOT made and the reg WILL freeflow. And this is because, moving from head down into the horizontal or head up position, the air pressure returns to being greater than the ambient water pressure that the exhaust hose is subjected to, due to the lack of seal over the exhaust horn's end?
Is either scenario changed given the presence or absence of a duckbill?
You say, "However, if you were to provide a hard cover to the exhaust rather than the normal exhaust diaphragm, that differential in pressure would be "felt" by the regulator, as this exhaust hose is now exposed. To the ambient pressure." (This is in the horizontal/head up position.)
So, the exposure of the exhaust hose to ambient water pressure that you mention is the tiny amount of water allowed into the exhaust horn (without the membrane's seal) and surround the duckbill?
I've put my questions into italics. John, could you please address each of them? I think we're missing each other's meaning at these points.
Thanks for your patience and for sharing your wealth of knowledge.
|
|
|
Post by vance on Mar 12, 2017 18:17:36 GMT -8
Sorry, slow reply so some questions are answered. But, please restate in order of my above italicized questions, please!
|
|
|
Post by SeaRat on Mar 12, 2017 20:46:17 GMT -8
So, to re-state: In the first case, head down, with a flexible membrane, the seal on the exhaust horn is NOT made and the reg will NOT freeflow. With a hard cover, the horn would NOT be sealed and would NOT freeflow. This is because the superior air pressure inside the can is lost in this head down position and the air and water pressures are then equal? If so, then the loss of the superior pressure is due to the changed relationship of the exhaust port placement relative to the demand diaphragm in this upside down orientation?
That is correct; because of the orientation of the regulator, whereby the exhaust diaphragm is below the center of the main diaphragm, there will be no overpressuring of the air inside the regulator box. The exhaust diaphragm will not seal, and air will bubble out of the exhaust tube as it fills with water. Exhalation clears the water out. Even with a duckbill in the exhaust tube, there will be some small amount of water inside it too, but outside the duckbill.In the second case, horizontal or head up, with a flexible membrane, the seal IS made and the reg will NOT freeflow. However, with the hard cover, the seal is NOT made and the reg WILL freeflow. And this is because, moving from head down into the horizontal or head up position, the air pressure returns to being greater than the ambient water pressure that the exhaust hose is subjected to, due to the lack of seal over the exhaust horn's end? Is either scenario changed given the presence or absence of a duckbill? Almost correct. What happens is that the pressure at the main, inhalation diaphragm which moves the demand levers is higher by about an inch of water pressure than the area of the exhaust diaphragm/exhalation horn. If the exhaust diaphragm is in place, it will seal the exhaust tube. But if the exhaust diaphragm is replaced by a rigid plate, then the area outside that rigid plate, where the exhaust duckbill (now in a primary role) is seated will be one inch above the main diaphragm, and if the regulator is fine-tuned to have a cracking effort of about half an inch of water pressure, it will leak. You say, "However, if you were to provide a hard cover to the exhaust rather than the normal exhaust diaphragm, that differential in pressure would be "felt" by the regulator, as this exhaust hose is now exposed. To the ambient pressure." (This is in the horizontal/head up position.) Correct. The "feel" happens through the main demand diaphragm, which is then an inch below the exhaust hose. (See the further explanation immediately above.)So, the exposure of the exhaust hose to ambient water pressure that you mention is the tiny amount of water allowed into the exhaust horn (without the membrane's seal) and surround the duckbill?
I've put my questions into italics. John, could you please address each of them? I think we're missing each other's meaning at these points. Thanks for your patience and for sharing your wealth of knowledge. Phil, no, not quite. The amount of water that gets into the hose makes no difference in this scenario. The only difference that matters now is the "head" of water pressure caused by the one-inch difference (maybe more) in vertical location between the bottom of the diaphragm and the top of the exhalation hose in the water column. I hope this clears things up a bit.
I may, if I get the time, do this demo in a bathtub to show what is happening.
John
|
|
|
Post by vance on Mar 13, 2017 8:19:22 GMT -8
Thanks, John. Things are much clearer to me now.
I would do the bathtub experiment, but don't have a suitable tub. I am going to pool test as soon as the pool is uncovered and heated. The problem with these kind of explanations is that level of knowledge the explainer has might be far beyond the listener's. The explainer assumes some knowledge in the listener about the subject and begins the explanation at too sophisticated a level. Then, when you're done, they ask something like, "What's air pressure?"
|
|
|
Post by nikeajax on Mar 13, 2017 8:38:09 GMT -8
John, thank you for that helpful explanation The thing I see is that the original duckbill had inferior sealing characteristics due to the wire clip used to secure it. I could see that without the flexible membrane used to hold back the water pressure, it will seep past through the inner bore of the air horn because the clip isn't making a absolute perfect seal. I think, and this is only my opinion, that if a properly designed duckbill is glued in, thus creating a superior seal between it and the air horn, the flexible diaphragm is no longer needed because water pressure will hold the end of the duckbill closed... JB
|
|
|
Post by nikeajax on Mar 13, 2017 8:51:01 GMT -8
Please remember, that duckbill was made to get around the Aqualung Lung patents, so securing it that way was their only option: I'm sure that if they folded it over the end of the air horn, that Frenchman with the big nose would have been all over them like stink on poo JB
|
|
|
Post by vance on Mar 13, 2017 10:32:24 GMT -8
This will be tested shortly. As I mentioned somewhere above, I am making a new mold which will produce a longer duckbill that can be folded over the end of the horn. It will have a bit of sheer nylon molded into it at the point where it will fold. Hopefully, the fabric will stretch enough to get the duckbill off the form. I'm just waiting for the varnish to dry. Which it REFUSES to do because of the cooolness and humidity!
|
|
|
Post by nikeajax on Mar 13, 2017 10:46:20 GMT -8
Come on over to the East Bay, we had 82-degrees yesterd'y!
I've been thinking about what I said: the original DB leaks because the force going into the seal is wedge-shaped, which is used in cutting and... OK Wikipedia will explain it better than me:
A wedge is a triangular shaped tool, and is a portable inclined plane, and one of the six classical simple machines. It can be used to separate two objects or portions of an object, lift up an object, or hold an object in place. It functions by converting a force applied to its blunt end into forces perpendicular (normal) to its inclined surfaces. The mechanical advantage of a wedge is given by the ratio of the length of its slope to its width.Although a short wedge with a wide angle may do a job faster, it requires more force than a long wedge with a narrow angle.
JB
EDIT: The reverse of this is why the the original USD Calypso is a low-pressure regulator: it's second stage valve seat is flat, and all modern regs have a sharp edge on their valve seat...
|
|
|
Post by nikeajax on Mar 13, 2017 12:04:43 GMT -8
Phil, may I recommend using a bit of soapy water to get the DB on/over the air horn? Like, as I'm sure you're aware being an old car guy, when they put windshields in...
Just a thought!
JB
|
|
|
Post by vance on Mar 13, 2017 12:15:22 GMT -8
Yup. It will need some lube. It will probably fold over easily, but slipping the hose over it will take some doing, without wrecking the DB and/or distorting it in the tube. They will have to be installed before the membrane in order to get them in right. I'm concerned the silicone will cut at the fold.....
|
|
|
Post by tomcatpc on Mar 13, 2017 13:08:30 GMT -8
I wonder how many Diver around the World are attempting to figure out ways to make Healthways SCUBA regs more "diveable"? Guessing this lot right here and that is it maybe? Mark
|
|
|
Post by nikeajax on Mar 13, 2017 13:49:53 GMT -8
Mark, this is exactly why I love HW gear so much: it's not "plug and play"... I've said it once and I'll keep saying it; I get more satisfaction from figuring out how to make something work than I do from off-the-shelf gear. I enjoy learning from my mistakes, and teaching others about, "The way I do it..." or having jousting-matches with someone like John so that I learn from them.
Like when we were little, everyone wanted to be Speed Racer, who races the car: not me, I want to be Sparky, the guy who makes the Mach-Five work!
JB
|
|
|
Post by SeaRat on Mar 13, 2017 14:36:33 GMT -8
John, thank you for that helpful explanation The thing I see is that the original duckbill had inferior sealing characteristics due to the wire clip used to secure it. I could see that without the flexible membrane used to hold back the water pressure, it will seep past through the inner bore of the air horn because the clip isn't making a absolute perfect seal. I think, and this is only my opinion, that if a properly designed duckbill is glued in, thus creating a superior seal between it and the air horn, the flexible diaphragm is no longer needed because water pressure will hold the end of the duckbill closed... JB JB, Here's a quote from Emile Gagnan/Jacques Cousteau's original patent: This is the point I'm trying to make. It is not the duckbill that was patented, but the position of the duckbill below the diaphragm. If you bring the duckbill higher than the diaphragm, it will leak air (not water into the hose). John
|
|
|
Post by nikeajax on Mar 13, 2017 15:03:03 GMT -8
John, you didn't have to do that, but you did; and things like this are why I'm so loyal to this site only. We take our time on this site and don't simply say, "Because I said so, that's why...", or, "Don't worry about it, just slap this thing in and ya ain't gotta think about nuthin' no more..." I want to think, I want a challenge, and I like going out of my way to help people JB
|
|