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Post by SeaRat on Nov 22, 2019 16:30:09 GMT -8
Phil, I have been curious for years about whether there was a significant Venturi on the tilt valve second stage of the Duel Air? I know that most of the tilt valve second stages on a single hose regulator have none, but what about the Duel Air? It seems to suggest that there was one. How does it breathe? John It appears to be quite strong, and the regulator breathes easily. I wondered about this too. The single jet hole is quite large and points right down the pipe pretty close to the intake horn. Air escapes from the valve "arm" slot toward the can center, as well, but the air blast from the jet is considerable. Thanks, Phil, That is very interesting. I know that the Hydro Twin has a very nice Venturi too. Now, you Duel Air does have the overpressure relief valve (OPRV) attached, correct? That may also need to be cleaned up and made to work correctly. Since I think there is only one LP outlet, you may also need a splitter to use it well, but be sure that the OPRV is in place too. John
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Post by vance on Nov 22, 2019 17:51:03 GMT -8
Actually, there are two LP ports and one HP port. One LP port is for the OPRV, but, as you know, if you use a downstream second stage it's all good. These are very interesting regs and very unusual. I'm not a big fan of the tilt valve conceptually, but in practice, they might be very effective. I haven't dived it yet, but I expect it to be a good performer.
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Post by tomcatpc on Nov 22, 2019 17:57:48 GMT -8
Way off topic.. I love the New England Divers logo, and think it would look great on a yellow T-Shirt! Back to the real topic... Mark
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Post by nikeajax on Nov 22, 2019 18:09:54 GMT -8
Actually, there are two LP ports and one HP port. One LP port is for the OPRV, but, as you know, if you use a downstream second stage it's all good. These are very interesting regs and very unusual. I'm not a big fan of the tilt valve conceptually, but in practice, they might be very effective. I haven't dived it yet, but I expect it to be a good performer. Phil, this really doesn't surprise me: so does this have the same valve body as HydroTwin? JB
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Post by vance on Nov 22, 2019 18:24:02 GMT -8
I'm pretty sure it does. The HT II is different. The Navy, II, and III are like the DualAir/HydroTwin. The HT II balanced has a different HP seat holder, IP adjuster, and HP soft seat with the long shaft. There's other stuff I'm not listing, as well. Robert's Bible will have info on some variations and different first stages, but isn't current up to the latest iterations.
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Post by nikeajax on Nov 22, 2019 19:02:24 GMT -8
Could you get us an image of the label please? So from your first image it looks like the same idea for the second stage used on the HT's: that hex-nut dingus slips over it: is this correct? It's a really brilliant bit of engineering, so bloody simple! JB
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Post by vance on Nov 22, 2019 21:14:19 GMT -8
Yes, this keeps the second stage lever in alignment w/o pins or other schemes. I think it's the same kind of cylinder inside a nut as the HT II. I'd have to take my Ht II apart to absolutely confirm, but I think its the same deal. Notice the HT II (and maybe others) have 4 screws holding the first stage to the can. The DualAir has 3.
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Post by vance on Nov 22, 2019 21:28:35 GMT -8
So, as I reread JB's question about whether this is the same first stage body as the HydroTwin, I began to consider a couple of things. This is essentially the same, but it does not have a second stage seat in the first stage body. The DualAir has a spring seat in the first stage over the LP orifice, but the hard seat is upside down from downstream regs and is contained in the second stage nut/sleeve.
Most likely, this cannot be easily converted to an HT type second stage. I don't think I would consider doing so in any case, but as an intellectual exercise.....
I haven't dug deeply in to the first stage LP orifice, but it might be removable and replaced with a seat. I don't think so. Thinking on it, the spring seat might be shaped into a taper to make an LP seat if it doesn't come out....
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Post by vance on Nov 23, 2019 11:35:29 GMT -8
Phil, First, congratulations on this acquisition. That's quite a find! Second, your question. I looked up in Basic Scuba, and the part number for the tilt valve in the Sport Diver single hose regulator is 400-8, while the part number for the tilt valve in the Duel Air is 1325-5. So I doubt that they are actually the same. In this book, he states for trouble shooting the Duel Air: 'Hope this helps. john I'm guessing the part #s are only different because the DualAir seat is bent to shape. I can't see any difference between them other than the bent wire arm. I was going to say "the bends", but that'd be bad form describing scuba equipment!
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Post by nikeajax on Nov 23, 2019 12:11:40 GMT -8
Phil, please remember, this is a low-IP regulator 95-110 PSIG: just thought I'd remind you just in case!
JB
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Post by snark3 on Nov 23, 2019 14:49:23 GMT -8
Phil you mentioned the DualAir has 3 screws holding the can to the body while the Hydrotwin 2 has 4. My NED/Hydrotwin I has 3 also.
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Post by vance on Nov 23, 2019 15:08:11 GMT -8
Phil, please remember, this is a low-IP regulator 95-110 PSIG: just thought I'd remind you just in case! JB When the valve was leaking, and I checked the IP which was cranked up to 155 psig, I momentarily thought, "AhHa! There's the problem". But then remembered, "DUH! Upstream!" Higher IP is going to close the valve even harder, not push it open. Next thing I have to do on the reg is adjust the OPRV to blow at 160 or so.
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Post by vance on Nov 23, 2019 15:11:52 GMT -8
Phil you mentioned the DualAir has 3 screws holding the can to the body while the Hydrotwin 2 has 4. My NED/Hydrotwin I has 3 also. I guess they added the 4th screw when the HT II came out. You can see the 3 screws on my reg in the first pic on pg1, and the 4 screws on the pic JB posted.
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Post by SeaRat on Nov 23, 2019 17:15:41 GMT -8
Phil,
According to Fred Roberts in Basic Scuba, the Master Diver has an interstage pressure set at plus or minus 110 psig. But the Master Diver had a balanced diaphragm first stage and tilt valve second stage, so the tank pressure did not make any difference. For the Duel Air, which has an unbalanced first stage, I would use 110 psig as the pressure at 500 psig for the tank pressure. It will therefore be less at full pressure, and 110 psig would be the pressure at the end of the dive.
Fred Roberts, on page 133 of Basic Scuba, also talk about adjusting the overpressure relief valve (OPRV) in the Healthways regulators. It's under the "SCUBA-STAR" troubleshooting guide. Here's what it states:
Note that the discussion of high than normal interstage pressure from Fred pertains only to unbalance piston regulators, which have higher interstage pressure as the cylinger goes higher.
With the Duel Air, these procuders should also apply, but do the adjustment to the OPRV at 200 psig cylinder pressure when the interstage pressure is highest.
John
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Post by vance on Nov 24, 2019 17:41:28 GMT -8
200 psig oprv release. That's what I'll set it to, kew.
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