[PSUBS-MAILIST] Mechanical Depth Gauges

[Douglas Suhr via Personal_Submersibles]

A shout-out to Rick Patton for recommending a car headlight
restoration kit for the crazing on the transparent gauge cover... I
bought 3M's headlight kit and it worked perfectly. Their first step
was 500 grit paper, which I skipped for the 800. Then 3000, followed
by a buffing wheel. Clear as it was new... I'm actually pretty
impressed. ~ Doug

On 7/30/18, Rick Patton via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
> I would get some of that stuff they sell at the automotive stores for
> making your headlight lenses clear again after they turn milky ( I was
> really skeptical about that stuff until I tried it but It really worked )
> shine it back clear again then stick a couple of small silaca packs inside
> the housing if there is room for them and see if that works.
> Rick
>
> On Mon, Jul 30, 2018 at 10:15 AM Douglas Suhr via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> 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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>