Making of Sir Robert Matthew's structure
The design of my instrument is an adaptation of the tensegrity structure made by the eminent architect Sir Robert Matthew, following the principles and name invented by Buckminster Fuller. Theoretically, Sir Robert's tensegrity structure could have been built at any size, so it could have been of monumental scale. What would it then have sounded like? How does the tension in a structure like that sound, what would a whole bridge sound like if we could listen to it? The advantage of Sir Robert's model is that the structure has great potential to vibrate, to transmit the energy through its net of strings, provided the construction materials had suitable properties. The original was made from string, the metal part of hanging file folders and meccano.
Prior to building the model I recreated the original using similar materials in order to understand how it works, and devise a strategy for building it.
I wanted to follow Sir Robert's approach in using materials easily available. I chose to work with guitar strings because they are intended for musical purposes, but also because they come in different thicknesses, which would create a richer sound, and also because I could easily find discarded by guitar players. For the solid parts of the model I checked out the sound of different types of metal readily available at home and garden shops. I did find round tubes to be more resistant than other shapes, and chose brass for its sonic qualities, as brass is used in music instruments too. The tubes that I chose are the standard model locomotive steam pipe, because they have a slightly thicker wall than the more commonly available model airplanes ones. To attach the strings I searched for a cheap object that doesn't cut the string, and what I found are PCB mountable wire clamps which have a tiny clamp between the screw and the wire. The first experiment gave me an idea about where to drill the holes in the tubes so that when assembled the strings didn't touch each other and maintain vibration, without dampening the sound.
First I assembled the structure using string.
Then I replaced the string with guitar strings.
The process of assembling the structure was harder than I imagined, and several times it seemed that it was not going end up the way I imagined. Increasing the tension in the strings with the plan I made didn't work. This was because unlike the original I planned to use open connections, with the wire going through several nodes without being restricted, in order for the structure to find its point of stability. This approach generated a never ending process of tuning, each point pushed the next one, creating an inwards rotational movement, towards one direction or the other. This activity was interesting to observe and the sound was not bad. It really helped me understand what forces are at work, where the greatest tension is, what I could do in order to stop it moving, while keeping as many as possible open connections. There are a couple of modifications to the original that allowed me to increase the tension to the desired degree, so that in the present configuration every string has its role, and a similar degree of tension as the others.