[PSUBS-MAILIST] Mechanical Depth Gauges

Tue Jul 31 13:46:41 EDT 2018

Just friction - pull it off with your fingertips, it shouldn’t need any tool.

Sent from my iPhone

> On Jul 31, 2018, at 1:31 PM, Douglas Suhr via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Nothing complicated to you Alec, but remember that sometimes I have
> trouble dressing myself in the morning! Thankfully, with the graphic
> you shared I won't have to worry about spacing, etc. No chance you
> recall how to remove the needle(?). It looks like a friction fit, but
> I don't want to force it off either (might bend it).
> 
> On 7/31/18, Alec Smyth via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>> Hi Doug,
>> 
>> Yes, it was in psi. All I did was calculate how many psi corresponded to
>> the max depth I wanted to show (300 fsw), note where that fell on the face
>> of the instrument, and subdivide the included angle into equal segments
>> when I drew the new face plate. Nothing complicated.
>> 
>> 
>> Best,
>> Alec
>> 
>> On Tue, Jul 31, 2018 at 11:21 AM, Douglas Suhr via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>> 
>>> Alan - Thanks for the info on these computer programs... perhaps it is
>>> something that I will look into. You're right that between all of us
>>> psubbers (and especially Jon / Cliff) I could probably figure it out.
>>> 
>>> Alec - thanks for the gauge graphic! Here's another question for you:
>>> When you bought this gauge, I'm guessing that it was intended to read
>>> PSI? When you designed that label, how did you go about getting the
>>> spacing of the feet numbers correct? ~ Doug
>>> 
>>> On 7/30/18, Alec Smyth via Personal_Submersibles
>>> <personal_submersibles at psubs.org> wrote:
>>>> Hi Doug! I looked on my laptop and sure enough found a simple 2D CAD
>>>> file
>>>> called "Depth gauge faceplate." So here you go, I'll paste a screen
>>>> shot
>>>> below so you can print it. It's black and white, and the red was I
>>>> think
>>>> just done with a marker over the hatch pattern. Looking at this, the
>>> "250"
>>>> is not quite straight, but when printed at the scale of the instrument
>>>> I
>>>> don't recall noticing it. So... just try printing this a few times
>>>> until
>>>> you get the scale right, then cut out with scissors and then paste
>>>> right
>>>> onto the instrument. That's all there is to it.
>>>> 
>>>> Concerning the question about whether the instrument sees water, here's
>>> an
>>>> explanation for everyone else. The pressure gauge is in the CT, high in
>>> the
>>>> boat, but the line that feeds it pressure comes into the hull at close
>>>> to
>>>> the lowest point. It is open to the sea, and as you dive the air in the
>>>> line will of course compress. It will not, however, ever compress
>>>> enough
>>>> that the sea water actually reaches the instrument. The gauge measures
>>> the
>>>> difference between inlet pressure and ambient, so the instrument case
>>>> is
>>>> not sealed or it would establish a reference pressure. There is an
>>> opening
>>>> in the case in order to equalize pressure, and as I recall a little
>>> filter
>>>> element intended to keep dust out but let air through. It will let in
>>> cabin
>>>> humidity too, which in places like the keys probably means you'll print
>>>> a
>>>> new paper face-plate from time to time.
>>>> 
>>>> Best,
>>>> Alec
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Mon, Jul 30, 2018 at 2:36 PM, Douglas Suhr via Personal_Submersibles
>>>> <
>>>> personal_submersibles at psubs.org> wrote:
>>>> 
>>>>> 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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>>>>>> Personal_Submersibles at psubs.org
>>>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>>> 
>>>>>> 
>>>>>> 
>>>>> _______________________________________________
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>>>>> 
>>>> 
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>> 
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