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Master Diver
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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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Master Diver
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Joined: Thu Apr 08, 2010 11:25 am
First Name: Mark
Location: Laguna Beach, CA

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
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