ATM Got Glass?

[Anthony Stillman <atmer@flash.net>]

Ever since I read Richard Albrecht's "The Design of Telescope Structures -
I" published in the January 1989 issue of S&T, or rather took a close look
at the Material Properties table on page 98, I've wondered why glass hasn't
been used in the construction of telescope structures.

Glass is ten percent lighter than aluminum, has the same elastic modulus
and, a much smaller coefficient of thermal expansion.  Yea sure it breaks,
but come on, everything breaks.  I've often eyed long, discarded florescent
tubes and thought, ummmm  struts.  Of course there's the bit about the
phosphorus and mercury inside which, given the break thing, makes them a
little less appealing.

This brings me to the point.  While waking the yard of my favorite junk
store I came across two large radiant heaters.  Each had four elements, two
of which were broken.  The elements appeared to be made of glass (I'm
guessing fused silica) and contained a coiled wire heating element.  Well,
for a song, they are now sitting in the garage partially disassembled.  The
struts (uh, I mean tubes) are 16 mm in diameter with 2 mm walls and are
64.6 cm long.  They are not clear, but rather have a white translucent
fibrous appearance.  The fibers run the length of the tubes.  I've written
Fostoria Ind., the maker, and asked for specifics but, I've got to expect
this is going to be a dead end.  Hence my query.  Anyone know anything
about this material?

Naturally I've thought of a half dozen other uses for the rods, especially
if they turn out to be silica, but my iconoclasm still favors struts.


Anthony