R. Buckminster Fuller called "vector equilibrium" (VE) a set of 12 vectors in the space defined by the center and the 12 vertices of a cuboctahedron (it is the only spatial configuration in which the length the polyhedral edges is equal to that of the radial distance from its center of gravity to any vertex); the angles between each vector and its four "neighbors" are all 60° and the vectors are opposite by pairs. The VE is obviously related to the CCP (cubic close packing of spheres).
"Jitterbug" is the name given by Fuller to a transformation of the VE stickmodel in which the 12 vertices move symmetrically. The jitterbug transforms smoothly a cuboctahedron into a regular octahedron with an intermediate icosahedral shape; thus it appears as a unifying motion between 4fold (octahedral) and 5fold (icosahedral) polyhedral symmetries. 


animation 



Around the animated jitterbug are the four remarkable positions: cuboctahedron, octahedron, icosahedron and the less known dodecahedron.
The distance of the triangles from the center is given by e×Sqrt[2/3]×Cos[a] where e is the edge's length and a the angle of the rotation.
The values of a for the four positions are respectively 0°, 60°, around 22.24° and around 37.76° (Robert W. Gray, more in the references).
references: 
• A Fuller Explanation (chapter 11) by Amy C. Edmondson
• "Jitterbug defines polyhedra" and "The Jitterbug Motion": web pages by Robert W. Gray • jitterbug applet by Bob Burkhardt  jitterbug animations by Adrian Rossiter 
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