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Vintagediver
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Re: Question on reproduction silicone diaphragms

Wed Jun 24, 2020 7:42 pm

This is the form I'm referring to; it's made from 1-1/4" dowel rod glued together. As can be seen it he picture both pieces of rod had to be trimmed about 3/16" to provide the right length. Today I managed to fill the indentations where the two pieces join at the center with Bondo, got it all sanded down nice and smooth and my old original diaphragm fits perfectly. In fact right now I have a piece of inner tube material fitted over this form and held in place with a zip tie. I've taken a heat gun to it and now I'm going to let it set for awhile and see how this turns out,
HW diaphragm mold 1.jpg
HW diaphragm mold 1.jpg
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ScubaLawyer
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First Name: Mark
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Re: Question on reproduction silicone diaphragms

Wed Jun 24, 2020 9:24 pm

antique diver wrote:
Wed Jun 24, 2020 7:26 pm
Great job! I'm glad you kept after it instead of giving up.
I ran into problems with the one I made, and seems to be at least in part due to the #10 hardness of the silicone mix I used. It is way too soft to hold its position. Looks like I will need to find a way to thicken it or order some heavier stock.

What did you use to modify the hardness? I don't know much about this stuff since I didn't purchase it. It is some left-over from Jerry M's stash, and surprisingly cures properly. It's just too soft for this application, and it turned out way too soft for the Trieste diaphragm I was attempting.
PlatSil® Part H Hardener with Platsil Gel 25 A and B in a 1-1-1 ratio which gives a shore hardness of about 40. Platsil#10 is way too soft for the HW exhaust diaphragm. Mark
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

Faster
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Re: Question on reproduction silicone diaphragms

Tue Nov 03, 2020 11:15 am

Bumping this thread for an update from Mark.

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ScubaLawyer
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Re: Question on reproduction silicone diaphragms

Wed Nov 04, 2020 4:14 pm

Faster wrote:
Tue Nov 03, 2020 11:15 am
Bumping this thread for an update from Mark.
I used the above-listed formula but ultimately used it to impregnate nylon for a more solid product. I did one exhaust diaphragm for me that works fine but it is too much of a PITA to make more (plus I'm not 100% confident the clamp won't crush the silicone over time). Much greater strides have been made by James who came up with a 3D-printed cap that goes over rubber sheeting and clamps down. I've put my project on the back burner for now. Mark
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

Vancetp
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First Name: Phillip
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Re: Question on reproduction silicone diaphragms

Thu Nov 05, 2020 5:42 pm

A big part of the problem with a replacement diaphragm, whether attempting a cast "reproduction" or using sheet material is the clamp. The original wire clamp can cut or fray the diaphragm, and is not very good at creating a seal. The original style diaphragm was glued on with a black goo sealer.

The 3D rim and sheet material seems to be the best solution to a working diaphragm, but it is nowhere like the OEM diaphragm. I made a new style flat stainless steel clamp which seems to eliminate pinching and cutting. It features a bit of band on one end that extends under the opposite end. This eliminates the opening at the screw bosses which can pinch and puncture the sheet material. The clamp works much better on OEM diaphragms, as well.

ImageIMG_5426 by Vancetp, on Flickr

Faster
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Re: Question on reproduction silicone diaphragms

Thu Dec 17, 2020 7:31 pm

All suggestions welcomed.

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Bryan
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Re: Question on reproduction silicone diaphragms

Sun Dec 27, 2020 9:42 am

In the past when I've put duckbills in Trademark era regulators I used waxed nylon lacing cord. I used a tensioning knot and the wax lets the knot slide easily and gets really tight. I've never tried it in a Healthways regulator but I don't see any reason it wouldn't work.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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antique diver
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Re: Question on reproduction silicone diaphragms

Fri Jan 01, 2021 10:12 am

Bryan wrote:
Sun Dec 27, 2020 9:42 am
In the past when I've put duckbills in Trademark era regulators I used waxed nylon lacing cord. I used a tensioning knot and the wax lets the knot slide easily and gets really tight. I've never tried it in a Healthways regulator but I don't see any reason it wouldn't work.
Waxed cord and line is underrated stuff that I find many uses for, including as above. Properly wrapped and tied it seems to last and hold forever. I used thin flat waxed line of unknown material to whip the ends of my 3/8" twisted nylon anchor line some 50 years ago, and it's still holding up well.
The older I get the better I was.

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