Scuba Exhaust Diaphragm

[vance]

Having just sent 2 exhaust diaphragm kits to SeaRat, I thought I'd put a little tutorial up so people could see what they're about and how to install them. I've done several so far, and found there's an easy (er) way to make the clamps and to install the kit.

This post will be about installing a pre-made kit. I'll post another thread (or add it here, later) about making the clamps. Clamp making is a very good skill to have since you can make hose clamps and lots of others with this method.

The kit consists of a James 3D printed flange rim, a piece of theraband sheet rubber, and a VTP designed stainless steel flange clamp. The original wire clamp HW made will not work with the 3D rim, and can fail if used with alternative sheet rubber diaphragms. It can pinch and tear the diaphragm, causing water intrusion into the intake side of the regulator. 

[vance]

I will edit this post with photos. I have a Scuba I'm working on today, and have made several band clamps this afternoon.

[scubalawyer]

I'll be interested in seeing the process. This just showed up at the house today from a friend in Nevada of all places. I have not seen a green label Scuba before.

[vance]

I think that's just age. I have seen green looking labels before.

[vance]

Procedure:

Cut a rectangle of the theraband so it will generously cover the Scuba flange and leave about 1/2" excess all around.

Lay the rubber over the flange and press the 3D rim (w/o the clamp) over the flange and rubber sheet. Press the rim onto the flange. You might need to do this a few times. When satisfied the sheet is stretched evenly over the flange (no folds or sags), leave it in place for a day or so. Longer would be better, maybe.

When ready, lift the rim off the sheet rubber. The sheet should have taken a set. You can see the oval of the flange.

Trim the diaphragm to leave 3/8" or so around the flange.

Push the loosened clamp over the 3Drim (get the clamp as loose as possible and centered in the groove). Lay the rubber sheet on the flange in position, and press the rim/clamp assembly onto the flange. Do it over until you get a smooth surface and a uniform excess all around.

Here is a trimmed and formed diaphragm:

Lay it over the flange:

Loosely place the diaphragm rim (with the clamp already in place) over the flange:

Squidge it around over the diaphragm and flange until it looks like it will capture the rubber sheet correctly with a fairly even overlap on all sides, then press it in place. Repeat until correct. No bunches, sags, or whatnot allowed.

Make sure the short protruding section of the clamp that fits under the nut is in the rim groove and tighten:

[vance]

Check for leaks by taping up the exhaust holes and hanging the box by a hose clamped to the exhaust horn. Then fill the hose with water. Leave for a while. If you get a leak, tighten the clamp a bit. The clamp should not need to be super tight!