Tensegrity, tensional integrity or floating compression, is a structural principle based on the use of isolated components in compression inside a net of continuous tension, in such a way that the compressed members (usually bars or struts) do not touch each other and the pre stressed tensioned members (usually cables or tendons) delineate the system spatially.
Clients - Tata Institute of Fundamental Research, International Center for Theoretical Sciences.
Brief - Use the concept of tensegrity to create interactive pieces of exhibits for The Mathematics of Planet Earth exhibition to take place in Visvesvaraya Industrial and Technological Museum, Bangalore.
The Exhibit - Using Tension and its load bearing capabilities to create forms such as pieces of furniture that can take human weight. Used simple low cost materials to create a DIY method for building Tensegrity furniture
Materials used - Neem wood , wood pegs and Poly Propelene rope Method - I begin with this basic triangular form where in one end of each strut passes through a length of rope from another strut. This was done for one end of each of the three struts. Then a rope is passed along all three extended edges and a single pull point is used to make the structure rise upwards and form a three dimensional tensegrity. This gave me a form that was relatively flexible upon human weight(due to the flexibility of poly propelene rope). And would sort of compress and give a spring like feel, good for seating purposes. The wooden struts wood never touch each other, even with added weight.
Method - I begin with this basic triangular form where in one end of each strut passes through a length of rope from another strut. This done for one end of each of the three struts. Then a rope is passed along all three extendeded edges and a single pull point is used to make the structure rise upwards and form a three dimensional tensegrity.
This gave me a form that was relatively flexible upon human weight(due to the flexibility of poly propelene rope). And would sort of compress and give a spring like feel, good for seating purposes. The wooden struts wood never touch each other, even with added weight.
Wooden pegs hold the rope in place and prevent it from sliding. The rope passes through a V hole in the wooden strut and the peg is inserted perpendicular to the V hole.
Metal cable and wood to test structural strength with other materials
Used a simple rachet mechanism by twirling a large screw, with one end of the metal cable attached to it, mounted on an L rod to create the required tension, which was otherwise difficult.
The result was a very solid tensegrity, almost like a rock, with no scope of flex or movement(due to the metal cable). Ideal for a table or podium.
Comfort and Ergonomics
Using fabric with pockets to create a dismantle able tensegrity stool which is comfortable. A triangular piece of canvas with pockets at each vertex that slips onto the ends of each strut. a length of rope is passed along the perimeter inside the fabric for durability. The upper triangle formed by the rope(in the structure) is kept at a distance under the seat as it tends to bite into the thigh due to its high tension. This leads to a very comfortable seat while keeping the tensegrity.
Using fabric with pockets to create a dismantle able tensegrity stool which is comfortable. A triangular piece of canvas with pockets at each vertex that slips onto the ends of each strut. a length of rope is passed along the perimeter inside the fabric for durability. The upper triangle formed by the rope(in the structure) is kept at a distance under the seat as it tends to bite into the thigh due to its high tension. This leads to a very comfortable seat while keeping the tensegrity.
A Pentagonal stool - A Tensegrity stool with 5 struts using the same method
This gave me a stool with an even larger springback due to the larger number of rope and struts, and hence, a larger overall flex, making it highly comfortable to sit on.
At the exhibition.
Roddam Narasimha seated on the pentagonal tensegrity stool at the exhibition.
Featured in Wikispaces - Tensegrity
A Special Thanks to Sudipto and Nandini, our facilitators incharge, for their help and valuable inputs.