Three struts up in the air. This is what a tensegrity is all about. I think I've made over one hundred tensegrities, but this one is still my favourite. It's simplicity makes it magic. It is the most simple tensegrity one can imagine. The basic brick of all tensegrities, with that unique tensegrity characteristic: the twist.
It may not seem difficult to invent (or is it discover?) this tensegrity. Nevertheless, as far as we know, it is not invented by the Ancient Greeks, the Romans or any other old civilization. In fact, it's history is very young. This 3-strut prism was probably first made either by a Lithuanian artist Karl Ioganson around 1920 or by a Fuller student at the University of North Carolina in the early 1950's named Ted Pope. But both Karl's and Ted's contribution towards the development of the tensegrity stops here. In fact we are not even sure they actually build this basic tensegrity. The real start of tensegrity was in a basement somewhere in Pendleton, Oregon in the autumn of 1948, where a young student called Kenneth Snelson experimented with thread, wire, clay, metal from tin cans, cardboard, etc... Or maybe it started a little earlier, when Snelson attended a summer course in North Carolina at Black Mountain College and got "electrified" by a charismatic visionary designer, architect and inventor named Richard Buckminster Fuller..
This site is full of information about tensegrities, but a great deal of the experience is in practice. If you want to get some understanding to the meaning of a tensegrity, it should be wise to turn off the computer once in a while, and do some practice. A good start would be for instance the following experiment: saw three sticks equal in length, drill a screw in each end of each stick, take some rope and try to make your own 3-strut prism... ..and by the time you are back at this site you realize that it is not that simple..
This basic tensegrity, with many names such as "3-strut T-prism", "simplex", "elementary equilibrium", "3 struts, 9 tendons", "twist element", "3 struts single layer ", "(3,9;2,1)", shows what a tensegrity really is. But what is it? Since the existance of the tensegrity there have been many discussions of what it is and what it is not. From a technical point there is a wide range of opinions varying from "purists" like Kenneth Snelson himself to people with a broader, less critical, mind, who think a bicycle wheel, a balloon and a spider web also belong to the family of tensegrities. These many discussions have led to nearly as many definitions of a tensegrity.
Apart from these technical discussions there are people who are so impressed by the characteristiscs or the qualities of a tensegrity that they want to have a part of it one way or another. For instance there is someone called Carlos Castaneda who teaches "tensegrity" and his definition is: "Tensegrity is the name given to the modern version of the magical passes: positions and movements of body and breath that were dreamt and stalked by men and women seers who lived in Mexico in ancient times."
Another person called Timothy Wilken speaks about "Ortegrity", a word he made up from Organisation and Tensegrity, as a system based on synergic principles for organizing two or more humans. Where a continuous pull of "decision" is balanced by the discontinuous push of "action". In his mind tensegrity is the pattern that results when push and pull have a win-win relationship with each other.
Personally, I received a question from a certain Linda who wanted to use one of my tensegrities as a logo for her business. She has a life coaching business for women in which she emphasizes the importance of achieving balance in life.
Espessially the "technicians" or the "purists" among us may laugh about this, or even get a little angry, but I think it comes with the charme of a tensegrity itself. People don't like to refer to a few struts and strings, but in this case they do because a tensegrity shows that the total is much more than it's individual parts. And that is just one of its characteristics.
In fact, the charme of tensegrity is that it shows a lot of qualities we encouter in our lives: Indeed the most catchy one is probably that the total is more than the sum of the individual parts but there is more. For instance, tensegrity is full of the "daily" push-and-pull we experience in our lives, especially when we want to get something done. But more subtal, it is delicate and strong at the same time and the reverse of "the total is more than the sum.." means that the structure needs every strut and every string. No one can fail, because when one strut bends, or one string breaks, the structure will collapse..
History & Description
There is one person who is everywhere in describing tensegrity. His name is Buckminster Fuller, also well-known as "Bucky" and he even invented the word TENSEGRITY by the contraction of TENSIONAL INTEGRITY. In his book Synergeticshe gives the following definition: "Tensegrity describes a structural relationship principle in which structural shape is guaranteed by the finitely closed, comprehensively continuous, tensional behaviours of the system and not by the discontinuous and exclusively local compressional behaviors." Quite a mouthful, but he also could say it in a different way, like: "...compression elements in a sea of tension..."
This man expected a lot, if not everything, of the tensegrity principle. He saw tensegrities wherever he looked, which is illustrated by the following text, also in his book Synergetics: "All structures, properly understood, from the solar system to the atom, are tensegrity structures. Universe is omnitensional integrity." And in a letter to Robert Burkhardt: "I simply found that the Universe is compressionally discontinuous and only tensionally continuous. The structural integrity of Universe is tensional as Kepler discovered. I gave this phenomena the name "tensegrity". For him, it was not strange he "preached" tensegrity the way he did. Already in 1932 Bucky famously philosophized: "Don't fight forces. Use them!", which is exactly what a tensegrity is all about, so he must have been delighted when Snelson showed him the first tensegrity in 1949. After 17 years this was the structure that showed that the fundamental phenomena tension and compression were not opposites, but complements that could always be found together and never found apart.
In general one could say that the longer the definition, the more accurate and precise the description and the less fascinating. Bucky spoke of "compression elements in a sea of tension" which gives a clear picture. In my opinion Rene Motro gives a good definition:"Tensegrity system is a system in a stable self-equilibrated state comprising a discontinuous set of compressed components inside a continuum of tensioned components." But one that anticipated best on my imagination came from a Dutch article from Chris Heunen en Dick van Leijenhorstand sounded like "De touwtjes houden het hele bouwsel bijeen en de houtjes uit elkaar." Which is something like "A tensegrity is a set of strings that keep the construction together and the sticks apart."
With the picture below, I hope to demonstrate that tensegrities can be quite strong. But this doesn't mean that it's practical value has developed very easily or very fast. Robert E. Skelton, a professor of mechanical and aerospace engineering, expressed himself in an article in the Science Daily, april 2006 with the following strong words for both history and future of the tensegrity: "Tensegrity, as a concept, has been around for more than 50 years, but until now we have lacked the mathematics needed to make it an engineering tool.. ..There are lots of ways to put sticks and strings together that give you nothing but a useless pile. However, our new computational tools enable us to design an airplane wing structure that can extend and retract like a bird's wing."
Just in case you want a little help making your first tensegrity: Try three struts of 30 cm each and nine tendons of 20,4 cm each. Good luck!
..some "strange struts"..:
.. and a few three strut tensegrities knit together..