|
Cliff, Quartz windows are how it all
started. Otis Barton’s bathysphere of the 1930s had flat quartz windows 8
inches in diameter and 3 inches thick, supported by a 1 inch flange. The windows
withstood depth all right. I’m not sure what the calculated burst depth
was, or even if it was calculated at all, but the bathysphere went to about
3,000 feet and came back. Barton made a batch of 5 windows, but 3 of them broke
during installation or testing. After the sub had sat indoors at a museum for 4
years between 1930 and 1934, the two surviving windows were found to have
degraded and failed testing at only 900 psi. All of this is from William Beebe’s
wonderful book, “Half Mile Down”. In summary the material did work,
yet seems to have been quite unforgiving. Most importantly there isn’t
any literature that I’m aware of for design and calculation of quarta
windows. If you get hold of Stachiw’s “Handbook of Acrylics”
you’ll get an idea how much testing is needed to determine that sort of
information. Given the wealth of data on acrylic, it’s the choice on
virtually every sub. Cheers,
-----Original Message----- OK, enough of the love-fest :)!! Glad everyone agrees on the importance of the
site and that it should be used for it’s intended purpose. I acually have a technical question: I am planning to test some quartz glass I
would like to use for portals. I have
access to a diver decompression chamber and can take the test assembly to many
hundreds of feet in depth. I need to
know from some of you M,E.’s if I build a box to mount the windows on and
make it small enough to go into the decomp chamber (probably 18 inches square),
would that be sufficient to duplicating the inside and outside pressures of a
larger vessel (like the sub)? I realize
that the smaller test box would have a much greater crush strength than a
larger vessel, however, I simply want to know if the glass will withstand the
pressure / temperature changes and expect to build the box overly strong so
that there is nearly no movement or reaction on it’s part. I will have at least two windows of varying
thickness mounted on the test box with a pressure gauge on the inside and
visible through the window to make sure the inside is still at ambient pressure
when the chamber is ramping up. The
reason I want to do this is that I am familiar with this glass in some high
temperature scientific furnace applications and I know it is very resistant to
scratching, easy to clean, greatly resists warping / bending and can withstand
sudden changes in temperature (will not crack).
I suspect that a 8” x ½” thick portal made from this glass
would withstand some serious pressures.
Worst case depth I’m targeting (emergency only) would be 300
feet. Normal useful depth would be 125
feet. I am hoping it will easily
withstand pressures at a depth of 750 feet.
As far as thermal stresses, outside of the decomp chamber, I am planning
to place a electric heater inside the test box and heat the entire assembly to
about 200 degrees F. After letting it
“soak” at that temperature for at least 30 minutes, I will hose it
down with ice-cold water, simply to ensure that there is no chance for
cracking. That should more than ensure
that a hot sub sitting in the sun for many days will not have the portals crack
when it is launched into cold water.
Sealing material will be Buna-N O-rings.
Suggestions? Comments? Thanks, as always, for your input. Cliff The contents of this e-mail are intended for the named addressee only. It contains information that may be confidential. Unless you are the named addressee or an authorized designee, you may not copy or use it, or disclose it to anyone else. If you received it in error please notify us immediately and then destroy it. |