[PSUBS-MAILIST] Mechanical Depth Gauges

Tue Jul 31 11:53:00 EDT 2018

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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20180731/b95bfc05/attachment-0001.html>