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Post by SeaRat on Jun 19, 2020 21:31:12 GMT -8
Okay, I've posted this elsewhere here, but here it is again. It is the calculations for the surface area, and therefore the air pressure force, on this exhalation diaphragm in mast attitudes in the water. SCUBA vs Aquamaster001 by John Ratliff, on Flickr Healthways Scuba Exhaust Calcs by John Ratliff, on Flickr Bottom line is that there is almost two ounces of pressure on this diaphragm to close it. Therefore, it doesn't have to seal perfectly, as the water pressure force will close it for you. It's as if you put a two-once lead sinker on that diaphragm. It really is a great design to get around the Cousteau patent. John
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Post by vance on Jun 20, 2020 7:30:15 GMT -8
My piece of old diaphragm is set in the original shape, so it has a big wrinkle right through the middle where it was formed into a dome. Your 2 oz. should press it down on the horn, but I don't think it'd achieve a very good seal.
I checked in with Jeff about his repro exhaust diaphragm a while back, but he wasn't finished with his new mold.
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Post by scubalawyer on Jun 21, 2020 10:49:22 GMT -8
Ok, here is a question for all of you CIH, elasto-polymer bonding folks. I am all for creating a workable HW SCUBA exhaust diaphragm as a replacement for the original, and many of us are seeking that holy grail.
In the meantime, I have an original exhaust diaphragm in remarkably good shape, save for a pin-hole on one of the upper edges. Does anyone see an issue with using neoprene cement to repair that pin-hole so I can get a working HW? First, bonding. The original diaphragm appears to be plastic. I know that neoprene cement bonds well to most plastics. Any issue known? Second, neoprene cement contains toluene and several other nasties to respiratory health. However, once cured, is it still an issue? Showing my ignorance (again) - Mark
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Post by SeaRat on Jun 21, 2020 14:06:23 GMT -8
Ok, here is a question for all of you CIH, elasto-polymer bonding folks. I am all for creating a workable HW SCUBA exhaust diaphragm as a replacement for the original, and many of us are seeking that holy grail. In the meantime, I have an original exhaust diaphragm in remarkably good shape, save for a pin-hole on one of the upper edges. Does anyone see an issue with using neoprene cement to repair that pin-hole so I can get a working HW? First, bonding. The original diaphragm appears to be plastic. I know that neoprene cement bonds well to most plastics. Any issue known? Second, neoprene cement contains toluene and several other nasties to respiratory health. However, once cured, is it still an issue? Showing my ignorance (again) - Mark There is no problem, health-wise, using neoprene cement. Once dry, it is innocuous. Even when still curing, there is very little off-gasing to be concerned about after a few hours. If the neoprene cement doesn't work, a dab of Shoe-Goo will work too. Shoe-Goo is not flexible, like the neoprene cement, so I would try the neoprene cement first. I used to use neoprene cement on small holes in my hoses too, but that was when the solvent was benzene, and not toluene (benzene is a cancer-causing solvent). That was in my younger days, when I didn't know any better too. John
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Post by vance on Jun 21, 2020 16:45:39 GMT -8
Ok, here is a question for all of you CIH, elasto-polymer bonding folks. I am all for creating a workable HW SCUBA exhaust diaphragm as a replacement for the original, and many of us are seeking that holy grail. In the meantime, I have an original exhaust diaphragm in remarkably good shape, save for a pin-hole on one of the upper edges. Does anyone see an issue with using neoprene cement to repair that pin-hole so I can get a working HW? First, bonding. The original diaphragm appears to be plastic. I know that neoprene cement bonds well to most plastics. Any issue known? Second, neoprene cement contains toluene and several other nasties to respiratory health. However, once cured, is it still an issue? Showing my ignorance (again) - Mark Plastic? What do you mean? Isn't it neoprene impregnated cloth? Neoprene cement should work fine for the repair, unless you have some information that suggests otherwise.... I have a couple OEM diaphragms with holes due to the clamp, and I'd repair with a patch + RTV, neoprene cement, etc.
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Post by vance on Jun 21, 2020 16:47:28 GMT -8
My HW main diaphragm cloth, new stainless steel clamp mod seems to be pretty good, so far.
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Post by scubalawyer on Jun 21, 2020 17:14:08 GMT -8
Plastic? What do you mean? Isn't it neoprene impregnated cloth? Neoprene cement should work fine for the repair, unless you have some information that suggests otherwise.... I have a couple OEM diaphragms with holes due to the clamp, and I'd repair with a patch + RTV, neoprene cement, etc. Yup, plastic. Definitely not silicone or neoprene. NAME THE MOVIE:Mr. McGuire: I want to say one word to you. Just one word. Benjamin: Yes, sir. Mr. McGuire: Are you listening? Benjamin: Yes, I am. Mr. McGuire: Plastics.
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Post by Seahuntjerry on Jun 21, 2020 21:38:31 GMT -8
The Graduate
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Post by scubalawyer on Jun 22, 2020 10:11:22 GMT -8
In my continuing efforts to duplicate a HW SCUBA exhaust diaphragm, I took two new (for me) approaches. The first approach had me stretching pantyhose over the exhaust orifice, holding it in place with an o-ring, and mixing a silicone polymer with a shore hardness of about 40. My first attempt failed miserably because the o-ring prevented the silicone from coating the sides far enough down to make a sealing surface against the side of the exhaust portal. However, the finished material was super strong. My second attempt involved me going back to my original mold, using the same silicone mixture, but laying pantyhose material inside the mold. The results were terrific. The new diaphragm is a duplicate of the original and the sides are plenty sturdy to hold the clamp and not tear. Not so fast, however. The added thickness of the pantyhose, while making the nylon impregnated silicone very sturdy, made the diaphragm too thick along the top edge to properly seat down on the metal exhaust flange (lip). The result is that the sides do not extend down far enough for the clamp top secure it. So it is back to the drawing board. Going to try a thinner more sheer nylon next time. Fingers crossed! Mark
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Post by nikeajax on Jun 22, 2020 10:26:04 GMT -8
Mark, try using some cotton gauze like from a first aid kit: it's surprisingly strong: BTW, nice work sir!
JB
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Post by Terry on Jun 22, 2020 11:52:34 GMT -8
Mark, that looks great! I think you're definitely on to something. I'll be keeping tabs on this thread and the progress for sure. Terry
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Post by vance on Jun 22, 2020 16:14:24 GMT -8
Sooo.... This might be stating the obvious, but the OEM HW diaphragm is a coated cloth part. Coated with what? Dunno.
If we want to make a new functional part, we need a formable, covered (with plastic, neoprene, silicone) cloth part. Getting the clamp over a rubber sheet part will make you crazy. Silicone cuts. The diaphragm needs to be pre-formed if you're going to get the clamp over it w/o it squirting off to one side or the other. I've had some success with heat forming.
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Post by SeaRat on Jun 22, 2020 18:26:23 GMT -8
I had thought the original OEM exhaust diaphragm was neoprene-impregnated nylon. I'm about to check mine.
John
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Post by vance on Jun 23, 2020 8:30:25 GMT -8
That does look great, Mark. I hope the thin nylon will work. Here's a pic of the main diaphragm material exhaust diaphragm trimmed and installed with the new clamp. It should work, and it's tough.
I'll get it glued and installed on a working Scuba, and do the leak test.
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Post by vance on Jun 23, 2020 8:40:06 GMT -8
I'm thinking it might be necessary to take a hacksaw and remove the flange from a crusty Scuba can so one can work on it w/o having to deal with the cramped space at the bottom. It is really hard to get material over and under, and getting the clamp on right to make the part.
Also, maybe it could be made into a mold so the sharp rim is retained? Any thoughts on this other than blasting me for even thinking of cutting one up?
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