|
It isn't the most high tech device, but I'm sure it works better than most. The buoyancy indication is a great thing to have. I'm going to build one! David Bartsch > Date: Fri, 12 Mar 2010 13:34:33 +0100 > Subject: [PSUBS-MAILIST] Papenberg Depth Gauge #5 > From: laland@artematrix.org > To: personal_submersibles@psubs.org > > This all started by Michael asking me 'how do I make one at home?'. Such a > question required (my assumption) something else than a set of drawings > and a few tips on how to machine the parts. > > It was my intention - should my fragmented inputs spur any interest for > the instrument - that we all, collectively, could come up with something > useful for the PSUBS website in the end (as a result of a final rewriting > of my own fragments by including other people's opinions, questions, > proposals, advice, comments, etc., etc.). > > I believe that we could get some very interesting web site material using > this approach. But it requires that the originator of a topic take the > responsibility upon himself to do the final editing (re-writing), then > issue this draft for comments prior to have a document of "instructional" > format officially published on the PSUBS website. > > ** For what its worth, I found the posts up until #4, to be > ** lacking enough detail to comment on. > ** It probably would have been better if you started with the > ** overall sketch and then showed the details in subsequent posts. > > I'll try to introduce my next topic in a more inspirational manner, and > also be very clear (up front) on why I think it would be useful for other > people, and not only myself. > > ** The unit you are describing is very similar to what we call a > ** "water level" in the States. > > I agree that the Papenberger could be misinterpreted to be nothing more > than a "water level". > > However, it's far from it! > > It is a very precise depth gauge used at shallow depths. Together with > it's operational companion, the trim indicator, this unity (see attached > image) provides you with an excellent tool that you can use to bring your > boat to a perfect diving trim. Besides, it will even tell you how close > you are at neutral buoyancy as soon as you dive. > > ** It is the curvature of the water surface within this thin tube > ** that gives an early indication of direction the boat will travel. > > I could not say it any better than what David just did [in the above > quote], but I would still recommend everyone to check up the fourteen text > lines and two images available at Wikipedia on the same subject, ref > http://en.wikipedia.org/wiki/Meniscus > > ** internal PSI rating of the glass tube and where do you find that > information. > > I would simply determine its pressure rating by performing realistic bench > tests. > > And I would probably use an "unbreakable" plexiglass instead of glass > tubing to avoid splinters all over the place should the gauge burst open > due to excessive depth with the instrument open to sea (ignore to shut > down the sea cock valve). Maybe even furnish the assembly with a small > rupture disk at the very top of the air chamber, this to prevent any view > glass bursting at all. > > ** Also, is the depth indication (graduations) as shown by the water > ** column linear, or does it vary as the air bubble is compressed? > > As Frank just pointed out, the variations will gradually get smaller as > the pressure increases. > > To avoid a lot of tedious, repetitive calculations, I made a program that > generate a table required to make a proper graduated (non-linear) depth > scale. The same software is also a great help to determine the optimal > volume (length of scale versus air-cushion volume) for a final design of > such an instrument. > > Finally, please note, that the attached image can be found in full size, > at my ftp server, ref > ftp://ftp.artematrix.org/instrumentation/papenberg_and_trimmzeiger/S302.jpg > > Best regards, > Jens Laland > > > > > > > > > > > > > > > > > Hotmail is redefining busy with tools for the New Busy. Get more from your inbox. Sign up now. |