Ball and chain are the form and
substance of this very cool sculpture, which I call Ball and Chain. It is a
6-inch diameter ball made of chain mail, and quite amazing, if I do say
so myself. The material
is nylon, robotically fabricated on a rapid prototyping machine by
selective laser
sintering.
Individual rings and links are polyhedral tori that are free to move,
as you can
see
from this close-up rendering of the design.
In this close-up photo, you can see the
chain mesh came out well, though near the limits of what this SLS
machine can accurately produce. Also notice one ring near the
center has only five links while all the others have six. Twelve such
5-fold rings are distributed around the ball on the 5-fold axes.
If all the rings and links were free to
move, it would collapse like an empty sack. So I fused together
some rings and links, shown in blue above, arranged like the edges of a
dodecahedron. Their solidity determines the overall form.
This leaves
twelve circular regions, shown in red,
arranged like the faces of a dodecahedron, where the links are free to
move. There is one 5-fold link in the center of each red region.
You can see how gravity pulls down the
free sections in the top hemisphere, while the rigid portions maintain
the overall form. As you slowly rotate it, whichever circles are on top
will hang inwards to be
concave, while the bottom ones will hang outwards to be convex. So the
top
always looks dimpled and the bottom always looks spherical, no matter
how you turn it.
All together, there are 920 rings with six links and 12 special rings
with five links. Plus there are 2790 links which each connect two
rings. The detailed pattern is chiral, based on the (7,4) Goldberg
polyhedron.
Here is a high
res image to show more detail.
