Notes on the Parabolic Zigzag-Strut Tensegrity Dome
Spencer Hunter, 2003
This document, unaltered, is in the public domain.

Public domain pictures of my self-deployable 2v parabolic zigzag-strut
tensegrity dome model can be found under "Parabolic Domes" or
"Zigzag-Strut Tensegrities" at:

http://www.u.arizona.edu/~shunter/cads.html

...or one level up from this document.

Inventory of parts:

72 soda straw struts
42 elastic tensioning tendons (hair-ties)
84 paper-roll connectors
204 cotton packaging twine tendons (My second model will contain all
the extra tendons needed to stabilize the perimeter prisms.  An
alternative to achieving this is to cross-brace the perimeter prisms
and use only 144 twine tendons.  Cross-bracing would increase the
weight of the structure because of the 24 extra struts involved, and
perhaps improve the strength, but it shouldn't affect
self-deployability.)
Not one bit of glue or adhesive!

The jigs, on the other hand, consist of 24 inter-tied triangular
prisms of 72 index cards made from four templates, 24 newspaper loops
to hold the perimeter struts in place, and lots of adhesive tape.
Although the templates could have been derived graphically, I decided
to use a hand calculator to determine distance values and angles.
Because of the parabolic geometry, the templates are irregular
trapezoids with differing diagonal measurements.  Spherical geometry
(as in geodesic domes) would yield easier-to-calculate regular
symmetrical trapezoids and quarter the strut-length variation of this
dome.

The model took over a month to build, with about an hour and a half
spent each day on it.  Hopefully, its big brother can be
mass-produced, and the eventual end user will need only to cut a
ribbon and the dome will self-deploy within seconds.  Stand back!