Rudolf Laban was a dancer, choreographer and movement theorist (https://www.theatrefolk.com/blog/the-eight-efforts-laban-movement/). One of Laban’s most enduring contributions to dance is his notation – this notation acts as a way of recording movement and communicating dance, much like a musical score communicates between a composer and a musician.
One part of this notation indicates how the dancer should move in space – is your body extended up and back and right, or low and forward and left? Other parts of the notation include the part of the body that is moving, how long the movement goes on for and the dynamic qualities of the movement (https://en.wikipedia.org/wiki/Labanotation).
Much as cellist might practice their scales to help learn the position of their hands, a dancer needs to increase their ability to sense where their body is in space – they must hone their proprioception. Sportspeople do this all the time – when I trampolined we talked about the angle of kickout in terms of time (“a twelve o’clock kickout” means someone exits a shape directly towards the ceiling) and we would hone this by aiming for some position, then feeding back via our coach or a video to do better next time.
Improving your proprioception is made much easier when you have immediate feedback. Fortunately, the positions considered in Laban dance, the points you aim for, which are the corners of three planes that pass through you as you stand, coincide with the vertices of an icosahedron. If you stand in the center of an icosahedron and point to its vertices, you are pointing towards the positions shown in Laban notation, and will be better able to use the notation, and other aspects of the theory, to improve your dancing.
Laban dance teachers and students have been dancing inside icosahedrons as a training tool since the creation of the theory, but their complex nature has meant these icosahedrons tend to be permanent, expensive fixtures – not a lightweight training tools that can be taken to beginners classes, which is where they are likely to have the greatest value. So there is a need for laban dance teachers to be able to carry icosahedrons to lessons, erect the icosahedron, use it during their lesson, deconstruct it and carry them away again.
The icosahedron seems like quite a complex shape to produce – but why? It is completely repetitive and platonic, once you have one rod design, one node design and a way to fit them together, the problem is solved. All the thought must go into the creation of the joints if a ‘rod and node’ solution is pursued. It is also possible to move the complexity around the model – using a tensegrity form to absorb the nodes into the rods and flexible tension members, using a series of face pieces that join at the edges. These alternative approaches were explored – with really interesting and unconservative results. Sadly, perhaps, none were good enough to displace an improved ‘node and rod’ approach, which shares much with what has gone before.
The complexity of the nodes can be largely eliminated by using a magnetic connection – it provides many benefits in this application: it snaps into positon so can be attached without need for precision or force, it cannot transmit enough force to allow damage to the rest of the structure, it can be connected and disconnected without wear or damage and allows extreme geometric simplicity – easing manufacture. The drawbacks of a magnetic connection: low strength, especially little moment capacity, and absolutely no ductility. All of these forthcomings can be designed around by choosing strong magnets and making sure the nodes are built accurately to avoid moments at the connections. A design of embedded magnets in wooden spheres, with embedded magnets in wooden rods was chosen. The extra magnet in each sphere is for holding extra training ribbons in position.
A full set of drawing and manufacturing instructions to follow.
Deconstructing the icosahedron by removing a node. Image: Charlie Cornish of Expedition