[PSUBS-MAILIST] Mechanical Depth Gauges

Tue Jul 31 13:48:28 EDT 2018

Thanks Alec!

On 7/31/18, Alec Smyth via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
> 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.
>>>>>>> _______________________________________________
>>>>>>> Personal_Submersibles mailing list
>>>>>>> Personal_Submersibles at psubs.org
>>>>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> _______________________________________________
>>>>>> Personal_Submersibles mailing list
>>>>>> Personal_Submersibles at psubs.org
>>>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>>>
>>>>>
>>>> _______________________________________________
>>>> Personal_Submersibles mailing list
>>>> Personal_Submersibles at psubs.org
>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>
>>>
>> _______________________________________________
>> Personal_Submersibles mailing list
>> Personal_Submersibles at psubs.org
>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>