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Cliff,
I don't know about the quarts glass, but as long as
you plan to test two pieces of it, why not test both of them at the same
time.
A box ,as you describe it, may not the best fixture
to test in. First of all, it will require a square glass and you'll most
likely be using round lenses in your port holes. Secondly, the flat plates
making up the box will have some flex and tend to deform under pressure, adding
additional bending stress to the glass. A steel or aluminum ring,
with flanges machined on each of the flat sides for O-ring seals, will
be easer to make and will deform uniformly from the stresses of the applied
pressure. One lens could be the bottom and the other lens could be the top,
forming the cavity.
All it would take is a little clamping
pressure, or even a few weights stacked on the top side if it was laid flat,
to start a seal. Once you pressurize the chamber, sealing
force wouldn't be a problem. It's a much simpler fixture then a box
and a more true test with less added stresses.
A simple kids balloon, partly blown up, and places
in between the lenses will tell you if you got a seal or not. If the
balloon is shrinking as your applying pressure, it's not sealed. A
barometer may be even better, but a gauge will require a line through the test
fixture for a reference pressure.
Dan H.
----- Original Message -----
Sent: Friday, June 03, 2005 9:25 AM
Subject: [PSUBS-MAILIST] Portal
Material
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
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