Orgone Research

Monday, September 25, 2006

Octet Truss

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 this sculpture to tell us who made it, perhaps if 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.


At 3:31 AM, Blogger Thomas Jeal said...

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At 10:55 AM, Anonymous Anonymous said...

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At 11:20 AM, Anonymous Anonymous said...

this page has been really useful! thank you!

At 11:23 AM, Anonymous Anonymous said...

for those that are interested in other cool structures, is a really useful starting point

At 7:27 AM, Blogger Mark Mickunas said...

I very much appreciate this information. I'd read about Bell's experiments. It's next to impossible to "experiment" today. I as yourself, would like to find a ready made source for the hubs. Thank you for any information that you are willing to share. I, Mark Mickunas, am a student at the University of Iowa. email: or 515-274-4370.


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