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I'm
fascinated with solid geometry, geodesic domes,
and space frames. While Buckminster Fuller is
often associated with the geodesic dome, few
know that he is also the creator of a space
frame design called the "octet truss". The word
"octet" is derived from "octahedron" and
"tetrahedron". You see, if you combine
octahedrons and tetrahedrons in a 1:2 ratio, you
get a space filling solid. Thus a framework that
bounds these solids can fill space without gaps.
Fuller was even able to get a
patent on his
design in 1961.
But wait, there's more to the story! Note that the ratio
of tetrahedrons to octahedrons is 1:2. Why is it
specified this way? Fuller was obsessed with
simplifying things, it's possible to simplify
this description even more. If you bisect an
octahedron, you get Johnson solid number one,
the square pyramid. Thus, the "octet" truss can
also be thought of as a space-filling array of
an equal number of tetrahedrons and square
pyramids. Granted, "octet" is a great neologism,
but is there a subtle bias at work here?
Fuller
liked to claim the octet truss was "fully
triangulated" and thus was totally stable in
three dimensions. Indeed, if you look at photos
of some of his original trusses, you always see
the top and bottom surfaces of the array as
forming triangles, or hexagons if you count the
nodes as centers. Actually, within the octet
truss, there is always a plane of squares.
These squares come from the bases of the square
pyramids. Most modern octet trusses orient the
square lattice either at the top or the bottom
of the array. The octet truss, while an
outstanding space frame design, does not really
fulfill Fuller's claim of being "fully
triangulated".
More
fundamentally, Fuller did not invent the "octet"
truss! Credit for that goes to Alexander Graham
Bell! Fuller was honest enough to
acknowledge
this, though.
I'm really not trying to take anything away from
Fuller; to independently discover, then
successfully patent, such a thing is a
significant accomplishment.
With that
historical background in mind, take a look at
the octet truss as art. Here in Seattle we have
a large octet truss array located in front of
Grand and Benedicts, a retail store fixture
outlet, located at
3825 1st Ave S. in Seattle.
On top of
six concrete columns sits a steel octet truss
that seems to be five "layers" high. It appears
to be fabricated from struts and hubs
manufactured by the
Unistrut company. though when I look
through the current Unistrut website I can't
find space frames that utilize this sort of bent
plate hub arrangement. It looks like Unistrut
still makes space frame parts that utilize other
types of hub attachments.
This is all based on information I've
gleaned from an old textbook entitled Space
Structures.
Davies, R.M., ed., Space Structures:
Proceedings of the First International
Conference on Space Structures, Blackwell
Scientific Publications, Oxford, 1967.
Chapter 94
of this book is entitled "The Basic Elements of
the 'Unistrut' Space-Frame", written by S.C.
Hsiao. From the photograph I've included here
from page 1084, we see a close match to the
flange system used at the hub of the
Seattle space frame.
There is no placard at the base of the Grand and
Benedict sculpture to tell us who made it. Perhaps it was simply erected from parts made
by Unistrut, and really has no "artist".
Grand and
Benedict also has a Portland location. When
taking Amtrac down to San Francisco, I quickly
passed a sculpture that looked very much like
the one seen here in Seattle. I would guess this
is the Portland Grand and Benedict location. If
I can find out any more of the "back story" on
this sculpture, I'll post it here. I hope you
enjoy this artwork like I do.
A
similar, if not identical truss system is found
in Seattle at Husky Stadium. Here is a truss
that supports a small roof over the entryway to
the stadium near parking area E-10:
Unlike the Grand and
Benedict truss, which is clearly artistic
sculpture, the Husky stadium truss is fully
functional. The sides and bottom are flat planes
at 90 degrees to each other, but the internal
bracing is triangulated:
Here are close-ups of the flange-nodes:
Screeds and Essays
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