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Annular Dodecahedron

Annular Dodecahedron
Side 3 version

Type	Category:Dodecahedron

Rods	1350 ×
Spheres	700 ×
Author	--Karl Horton 11:34, 29 October 2007 (UTC)

A Geomag classic: pentagonal torii stitched together into a dodecahedron.

1 Steric Interference
2 Counting
3 Building Instructions
4 More Pictures
5 Related Links

Steric Interference Edit

There is a technical problem with this construction: all of the rods along the red edges of the outer dodecahedron are too crowded: they cannot all remain with full contact on the 1/2" spheres. Nontheless, after the model is complete there is no tendency for the joints to slip.

Counting Edit

Each module has 105 center rods, and 15 edge rods. So, there are 12*105 + 30*3 = 1350 rods in total.

Each module has 40 balls: 25 center, 10 edge and 5 vertex. So there are 12*25 + 30*10 + 20*5 = 700 balls.

The model weighs 27lb (12.4kg) but can, with care, be moved.

Rod to Ball ratio: 2:1

Building Instructions Edit

Build a Pentagonal Torus module: it is helpful to build an extra module out of a different color and leave it nearby, because its really easy to get lost whilst building.
Build another torus
Strip the edge of one torus to join the two together
Rest the linked modules on the hinge, and erect scaffolding poles to support the modules at the right angle.
Now, resist the temptation to proceed onwards with modules. Instead, learn how to build the diamond-shaped tube in-place on the model. Use a contrasting color for the true edges of the dodecahedron to keep yourself orientated.
It helps to use pentagonal panels to stabilise the build.
Let the structure grow at first like a bowl, then like a dome. Keep the build balanced and keep evolving the model with an eye to the symmetry.