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Post by duckbill on Jun 24, 2021 14:13:45 GMT -8
Also, I'm a bit surprised that stacking j valves would give a reserve of each added together. I'd have to think through it, but it seems that the maximum reserve possible would be that yielded by the weakest link, meaning the highest reserve. In other words, a 300 psi reserve on a 500 psi reserve manifold would give a maximum reserve that the 500 psi reserve alone gives, and the 300 psi reserve just giving an additional step warning at 300 PSI. Or am I missing something? If I read the process right, based on what I've seen out of my Sherwood J-valve, the manifold J is withholding 500 psi on that one tank... so really, the first 500 psi will come off of one tank (I base this off of the fact my J valve will read 300 psi "low" until I pull the rod). So once the non reserve tank is at 1300, the reserve side is at 1800 and starts sharing the load (just staying 500 psi higher). When the pressure reaching the Regulator is at 300, the reserve side tank is at 800 and non-reserve side is at 300. Regulator J-valve gets pulled, and you keep breathing that 300 both tanks (full dual tank 300 psi reserve). In theory, you breathe that down to empty (as felt by the regulator) and you are at 0 on the non-reserve side, but still 500 on the reserve side. Pull the manifold reserve, and the tanks equalize at a 250 psi reserve. I think. Respectfully, James Makes sense. Thank you.
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Post by snark3 on Jun 24, 2021 14:25:04 GMT -8
Here's my thoughts on this subject. Lets say we're diving with twin 50's 3000psi. We'll draw off both tanks equally until we get to 500 psi, now if we're using say a Conshelf 14 with no reserve we'll continue breathing off the right (non reserve) tank until it's empty. We pull the reserve and we have 250 psi in each tank. If we take the same scenario with a Calypso J we'll breathe off both tanks equally until we get to the same 500 psi at which time the reserve on the left tank will stop allowing air to pass, air will be supplied from the right tank until we get to 300 psi on THAT TANK, at which time the reserve mechanism on the Calypso J will stop air from the right tank only (the 500psi reserve on the left tank is still holding). If we pull the reserve on the Calypso, we'll continue just like the Conshelf. If we pull the reserve on the left tank the tanks will equalize at 400psi, we continue breathing until we hit the 300 psi then we must pull the reserve on the Calypso.
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Post by james1979 on Jun 24, 2021 14:52:19 GMT -8
Here's my thoughts on this subject. Lets say we're diving with twin 50's 3000psi. We'll draw off both tanks equally until we get to 500 psi, now if we're using say a Conshelf 14 with no reserve we'll continue breathing off the right (non reserve) tank until it's empty. We pull the reserve and we have 250 psi in each tank. If we take the same scenario with a Calypso J we'll breathe off both tanks equally until we get to the same 500 psi at which time the reserve on the left tank will stop allowing air to pass, air will be supplied from the right tank until we get to 300 psi on THAT TANK, at which time the reserve mechanism on the Calypso J will stop air from the right tank only (the 500psi reserve on the left tank is still holding). If we pull the reserve on the Calypso, we'll continue just like the Conshelf. If we pull the reserve on the left tank the tanks will equalize at 400psi, we continue breathing until we hit the 300 psi then we must pull the reserve on the Calypso. The only reason I disagree, is that the guts of the J-valve have no input from ambient pressure. The "poppet," as it were of the J-valve is reacting to differential pressure when in the "Dive" position... manifold (or regulator) pressure on one side, and interior of the tank pressure on the other. The spring in the J mechanism determines the differential pressure needed to push open the poppet.... and the 500 PSID (PSI Differential) doesn't know or care if its 0 to 500, or 2000 to 2500. Hence why a well sealing J-valve will show a jump in pressure when you pull the rod (or, if the rod was pulled, resetting it to dive will make taking a few breaths look like a closed valve on the pressure gauge). Sounds like what we really need is for SeaRat to do a controlled test for us! Respectfully, James
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Post by SeaRat on Jun 24, 2021 15:24:29 GMT -8
Guys, working through these kinds of problems is what keeps us young, in mind at least. Keep it up.
James, I may be able to do a test of this, as I just used my twin 40s with a solid J-valve manifold. I used it down to about 500 psig on Tuesday during a dive and a swimmer assist I did after the dive. I was diving my Trieste II regulator, with a MR-12 octopus and a Scubapro SPG/Compass/Depth Gauge counsel. That set is now sitting in my garage with 500 psig in it. I'll see what I can do.
John
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Post by snark3 on Jun 25, 2021 9:39:26 GMT -8
Here's my thoughts on this subject. Lets say we're diving with twin 50's 3000psi. We'll draw off both tanks equally until we get to 500 psi, now if we're using say a Conshelf 14 with no reserve we'll continue breathing off the right (non reserve) tank until it's empty. We pull the reserve and we have 250 psi in each tank. If we take the same scenario with a Calypso J we'll breathe off both tanks equally until we get to the same 500 psi at which time the reserve on the left tank will stop allowing air to pass, air will be supplied from the right tank until we get to 300 psi on THAT TANK, at which time the reserve mechanism on the Calypso J will stop air from the right tank only (the 500psi reserve on the left tank is still holding). If we pull the reserve on the Calypso, we'll continue just like the Conshelf. If we pull the reserve on the left tank the tanks will equalize at 400psi, we continue breathing until we hit the 300 psi then we must pull the reserve on the Calypso. The only reason I disagree, is that the guts of the J-valve have no input from ambient pressure. The "poppet," as it were of the J-valve is reacting to differential pressure when in the "Dive" position... manifold (or regulator) pressure on one side, and interior of the tank pressure on the other. The spring in the J mechanism determines the differential pressure needed to push open the poppet.... and the 500 PSID (PSI Differential) doesn't know or care if its 0 to 500, or 2000 to 2500. Hence why a well sealing J-valve will show a jump in pressure when you pull the rod (or, if the rod was pulled, resetting it to dive will make taking a few breaths look like a closed valve on the pressure gauge). Sounds like what we really need is for SeaRat to do a controlled test for us! Respectfully, James James I may not have conveyed my thoughts clearly here. I agree with you 100% the J valve is a mechanical device and doesn't care about ambient pressure. I was trying to compare a regulator without a "J" built in (scenario 1) to a regulator with a "J" built in (scenario 2). In "scenario 2" there are 2 "J" valves working.
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Post by james1979 on Jun 25, 2021 12:05:53 GMT -8
snark3,
The disconnect I have with your scenarios revolves on the function of the manifold mounted J-valve. The reason I brought up ambient and PSID was to illustrate that a J-valve (as I understand them... I have been known to be wrong!) doesn't work by being open until it reaches it's design pressure, rather they work by maintaining design pressure as a differential. So your initial scenario of only drawing from the right tank when pressure isn't right (if I'm right, lol). Rather, when John starts at 1800 psi on both tanks, it only draws from the right tank initially (haven't reached the 500 PSI differential for the J to let air out of the left tank). Once the right tank gets down to 1300, he starts drawing from both, with that 500 PSID staying constant (Right side 1300, left 1800. R 1200, L 1700, etc), until he reaches R300/L800. At that point, the manifold is only experiencing 300... the J is still "closing" when below 500 PSID. If he then pulls the regulators J valve, he regains access to the last 300 PSI that the manifold is experiencing... at which point the tank pressures would be R300/l800.... R200/L700... all the way to R0/L500. At that point he pulls the manifold J, opening it so the tanks equalize and 250 PSI is available from both tanks.
The difference in the manifold J maintaining PSID of 500 versus just withholding the last 500 comes into play with your last sentence where you said pulling the manifold J instead of the Calypso J would have them equalize at 400. Rather, at that point the 2 tanks are at 300/800 and would equalize at 550. Interestingly, that would have John's second warning be at 300 PSI on both tanks, rather than the 250 that they both equalize to if you do the Calypso first.
I'm not trying to argue, just trying to clarify my thoughts... So if I'm wrong they can be accurately shot down!
And thank you for the discourse, and making me think deeper on this!
Respectfully,
James
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Post by snark3 on Jun 25, 2021 14:23:15 GMT -8
snark3, The disconnect I have with your scenarios revolves on the function of the manifold mounted J-valve. The reason I brought up ambient and PSID was to illustrate that a J-valve (as I understand them... I have been known to be wrong!) doesn't work by being open until it reaches it's design pressure, rather they work by maintaining design pressure as a differential. So your initial scenario of only drawing from the right tank when pressure isn't right (if I'm right, lol). Rather, when John starts at 1800 psi on both tanks, it only draws from the right tank initially (haven't reached the 500 PSI differential for the J to let air out of the left tank). Once the right tank gets down to 1300, he starts drawing from both, with that 500 PSID staying constant (Right side 1300, left 1800. R 1200, L 1700, etc), until he reaches R300/L800. At that point, the manifold is only experiencing 300... the J is still "closing" when below 500 PSID. If he then pulls the regulators J valve, he regains access to the last 300 PSI that the manifold is experiencing... at which point the tank pressures would be R300/l800.... R200/L700... all the way to R0/L500. At that point he pulls the manifold J, opening it so the tanks equalize and 250 PSI is available from both tanks. The difference in the manifold J maintaining PSID of 500 versus just withholding the last 500 comes into play with your last sentence where you said pulling the manifold J instead of the Calypso J would have them equalize at 400. Rather, at that point the 2 tanks are at 300/800 and would equalize at 550. Interestingly, that would have John's second warning be at 300 PSI on both tanks, rather than the 250 that they both equalize to if you do the Calypso first. I'm not trying to argue, just trying to clarify my thoughts... So if I'm wrong they can be accurately shot down! And thank you for the discourse, and making me think deeper on this! Respectfully, James James- I'm not trying to have an argument either, hopefully just a discussion. I can certainly (and have) learned from many on this forum. I may be wrong on this but my understanding of the operation of the "J" valve is that when it's set in the Dive mode the pressure in the cylinder overrides the spring trying to make the ball shut off air in the tank, When the cylinder pressure gets low enough that it can no longer override the spring, the air is in effect shut off. When the rod is pulled to reserve a cam rotates and allows the spring to retract further, releasing the tension on the spring and allowing air to flow again. Again I may be wrong but thats my understanding of it.
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Post by SeaRat on Jun 25, 2021 17:42:53 GMT -8
I just went through a preliminary test of my J-valve regulators. I have two Calypso-J regulators, a Scubair J, and a Sportsways Sport Diver with a "J" reserve built in. I put them on a single 72 with a Sherwood J-valve which was at just below the 300 psig, and the Sherwood J-valve when activated completely stopped the air flow. But the two Calypso-J regulators did not! The Healthways Scubair-J also did not seem affected by the low tank pressure. The Sportsways Sport Diver (tilt valve) stopped the air flow cold when the resever lever was up, but it doesn't fit onto the USD solid monifold J-valve; its J-lever interferes with it being mounted. I took the Calypso-J down below 200 psig, and it started restricting the air flow. So I'm not sure about my planned evaluation of the "stacked" J-valves. More later...
John
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Post by luis on Jun 25, 2021 19:40:58 GMT -8
I haven’t had time to read all of this, but I just wanted to add a bit of information. Not all reserve valves (“J” valves) are created equal, in tank valves or regulators. And even if they were equal there are variations on how tight they seal. Many were never intended to be completely tight.
Some reserve valves create a constant pressure differential just like James describe. Just like James describe some reserve have a very good seal and the pressure gauge jumps up by a fairly constant quantity when the level is activated.
But many reserves were never intended to have such a tight seal and some seal better than others. Some reserves like the Scubapro DCAR valve just have a metal to metal restrictor and never intended to have a perfect seal. You can normally tell in some of these reserves because a pressure gauge needle will move when you inhale. Most of the time you may not even notice the needle move with high tank pressure, but it becomes pronounced as the pressure gets lower. I have heard divers think that a small leak is a malfunction, but in many cases it is not. We sold many J valves in the 70’s and it was very common with brand new valves to see the pressure gauge move slowly back up between breaths. The restriction worked just fine as a low air indicator when the diver inhaled. The amount of leaking tends to change a lot with pressure. Some will even seal at low pressure, but leak so much at high pressure that you barely see the needle move and you are reading full tank pressure.
Note: In the 70’s, I have had to explain to more than one customer that the pressure gauge needle moving between breaths was normal. And yes, the shop owner had verified this with some of the manufacturers.
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Post by SeaRat on Jun 27, 2021 16:51:51 GMT -8
Okay, it's over 107 degrees outside, so with my boredom I decided to see what the heck is wrong with my Calpyso-J regulators. I have a Calypso-J that is just a first stage, and I took it apart on the J-valve side to see what it looked like. It had the J-valve spring, but no ball. The regulator that I used above had a ball, but no spring. I have not used these regulators in diving for a long, long time. I had them apart to check the piston function, etc. but never looked at the J-valve side of them. I have one more to look at, so I'll report back later. However, it appears that each one of these has a compromised J-valve. That's why I was getting nepharious readings when I tested them on the single tank.
More later, but it looks like I may be able to make one work. It also appears that there is a small screw in the middle that could change the setting on the J-valve. Anyone have any ideas about this?
John
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Post by luis on Jun 27, 2021 18:58:18 GMT -8
Hi John, I recommend that you download the 1971 Aqua Lung repair manual from VDH. I will post some pictures of the different Calypso J tomorrow. It is a bit late. In case you are not aware of it, there were two totally different J reserve mechanism that were contemporary to the Calypso III. There was the Calypso J 1048-00 (page 32 of the repair manual) and Calypso J 1070-00 (also 1051-45, page 58 of the manual. From the outside, both of these look very similar. The second one had a spring and ball detente on the lever. The first one did not. The reserve was more of a cam. There was a third Calypso J that was contemporary to the Calypso IV. You can tell this one apart easily since it has the same multi-port swivel with LP ports as the Calypso IV. If I recall correctly the reserve mechanism in this particular Calypso IV is very similar (if not the same) as the one with he cam. This one is not included in the 1971 repair manual, but I do have diagram somewhere. None of the reserve mechanism had any intentional means of adjusting the reserve.
Added a link below to a thread in ScubaBoard with the diagrams. It is not as easy to add the pictures here. www.scubaboard.com/community/threads/usd-calypso-j-rebuild.609748/
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Post by SeaRat on Jun 27, 2021 22:21:44 GMT -8
Thanks Luis,
I’m pretty sure I already have that publication, having downloaded it some years ago from VDH. But today I didn’t even go upstairs to look. It was still in the 80s with AC up there. So I simply took two of my three Calypso-J first stages apart to look.
John
Nope, I only downloaded the Aqualung Repair Manual for the DA Aquamaster. I'll have to get the one for the Calypso regulators now. Thanks Luis.
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Post by surflung on Jun 28, 2021 8:12:16 GMT -8
DivAir Reserve is Different...- SwimJim and I were diving our DivAir regulators last weekend and the DivAirs have a unique approach to the reserve function. Instead of the typical over pressure style valve, the DivAir reserve limits the travel of the diaphragm. With the reserve lever up, you can only suck the diaphragm down so far. When the air tank pressure gets low enough, the diaphragm won't go low enough to give air. You pull the reserve lever down, and it lets the diaphragm go lower to release the lower pressure air until empty. - One drawback we discovered is that we can't fit a DivAir to a twin tank manifold. The reserve lever gets in the way. So, we had to dive our DivAir regs on single tanks!
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Post by scubalawyer on Jun 28, 2021 20:55:50 GMT -8
Eb, great write-up on your vintage dive weekend! Did you know that Bill Arpin designed the DivAir to work on double tanks/double manifold too? The L-shaped bracket that holds the lever is designed to be rotated 90 degrees to position the lever vertical to fit between twin tanks. You just have to reposition the screws holding the bracket into the pre-drilled alternate holes beneath the bracket. My 2psi.
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Post by SeaRat on Jun 29, 2021 10:25:07 GMT -8
I am starting to get a better idea of the Calypso-J design. Here's the parts diagram. Screen Shot 2021-06-29 at 11.21.36 AM by John Ratliff, on Flickr Note that there is no ball or spring under the part #36, which has the J design internally. John
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