[PSUBS-MAILIST] Mechanical Depth Gauges

[Douglas Suhr via Personal_Submersibles]

Ah, I think you're right Jon... because the gauge plate would not be
pressured anyway, huh. Never thought of that.

No there was no gasket or anything, so I guess any moisture in the
viewing portion of the gauge would just come from moisture inside the
hull of the sub.

And thank you for the pressures... not a huge difference but I suppose
at deep depths it could work out to be somewhat of an error.

I wonder how Alec printed such a nice looking label(?). ~ Doug

On 7/30/18, Jon Wallace via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
> Fresh water: .433psi per footSalt water: .445 psi per foot
> If there was no gasket sealing the acrylic/glass cover and bezel then it's
> likely condensation caused the wrinkling of the label.
> Jon
>
>       From: Douglas Suhr via Personal_Submersibles
> <personal_submersibles at psubs.org>
>  To: Personal Submersibles General Discussion
> <personal_submersibles at psubs.org>
>  Sent: Monday, July 30, 2018 1:16 PM
>  Subject: [PSUBS-MAILIST] Mechanical Depth Gauges
>
> All, as you may've been aware, in late 2015 I purchased Snoopy (a
> K-250) from Alec Smyth. Regrettably I have been quite neglectful of
> performing much upkeep on the sub, save for keeping the batteries
> topped off. My schedule is finally allowing me to spend some real time
> working on the sub and getting to know the specifics of each system.
>
> As you can imagine, I've been bugging Alec with a question here and
> there, but thought with this topic I should start a discussion here on
> the list for the benefit of anyone else who might have questions /
> curiosities about mechanical depth gauges.
>
> Snoopy's depth gauge is nice and large (about 5" in diameter) so it's
> easy to read. Alec created a nice label for the gauge face which reads
> from 0 to 300 (in feet) with the last fifty feet being marked in red
> to indicate 'too deep.'
>
> Problem is, when I looked at the depth gauge the other day, I noticed
> that the transparent cover plate on the gauge looked to be quite
> opaque (to the point where I couldn't quite read the numbers or count
> the hash marks). I assumed that there was some moisture trapped in the
> gauge, causing the obscuration. I decided to remove the gauge from the
> sub and open it up to let it dry out.
>
> After removing the gauge from the sub, I unscrewed three small screws
> around the bezel and popped off the transparent cover plate. It was
> only then that I realized the opaqueness was not caused by moisture
> but a distortion in the clear plastic. The distortion (like super fine
> scratches) appears to be on the outside of the cover, as though it was
> cleaned by something that started to melt the plastic or was left out
> in the sun too long. I don't think either of these explanations make
> sense, but I'm puzzled as to what might have caused it. I might try to
> buff / polish the plastic, or perhaps just replace it with glass.
>
> I think it's a good idea to stick a dive computer in viewing range of
> a viewport for a depth reading, but I like the idea of having a
> mechanical gauge in the sub as well. A couple of questions that come
> to mind: what is the pressure variation between salt water and fresh
> water? Also, although I didn't find moisture in the gauge, The label
> on the face is wrinkled a bit as though it has seen moisture. Although
> water should never actually reach the gauge, I can see how moisture
> from the inlet tube could find its way up into the gauge body. Should
> I be concerned about drying it out somehow after a dive (especially in
> salt water)? If so, how should I go about it? ~ Doug S.
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