# Zome Geometry

## Hands-on Learning with Zome Models

### George W. Hart   and  Henri Picciotto

Key Curriculum Press, 2001

This page contains a list of corrections to the first printing.  Most of these are corrected in the second printing.  If you find any errors not listed here, please let me know.

### Strut Lengths

When the book was written, the three lengths available of each color strut were referred to as 1, 2, and 3 in the book.  A few years later, Zometool stopped making the size 3 and introduced a new shorter lengths (reduced by the golden ratio from what used to be the shortest length).  So a strut of size 3 in a newer kit is the same length as a strut of size 2 in the book.  And a strut of size 2 in a newer kit is the same length as a strut of size 1 in the book.  So the diagram on page 265 is not labeled correctly for newer kits  and the measurements in Section 7.2 are off by one strut.  Also, with the new, shorter length 3, the big domes in Chapter 18 will not be so big as the image on p. 147 suggests.

### Chapter 21. The Fourth Dimension

Exploration 21D, the 600-cell, stops too soon in error.  On the triacontahedron's rhombi, add r1s and y2s as the slanting edges of 30 rhombic pyramids, i.e., 60 tetrahera.  Then connect their peaks using 60 b2s (that outline an icosidodecahedron) to complete 60 tetrahedra around the 5-fold axes and 20 over the 3-fold axes. (Vin de Silva, Nov. 2001)

• p. 231, typo, 12.3 Q1 a, truncated tetrahedron has three 2-fold axes.
• p. 235, typo, Expl. 13C, denominator 1- tau squared beta should be 1- tan squared beta.
• p. 237, A better answer for Challenge 15.1 is a b2-y1-y1 triangle, with area 0.25 b1^2.  (Bob Mead, Jan 2002)
• p. 241, typo, Expl. 16G should refer to Activity 21.4 (not 21.3).
• p. 241, A better answer for Challenge 17.1 is a low slanted triangular prism built on a b2-y1-y1 triangle, using either four b1s or four y1s for the side edges. The height is the same in either case, and the volume is approximately 0.0773 b1^3.  (Bob Mead, Jan 2002)

### Index and Table of Parts Needed

• 120-cell: The parts count should say "120 r1 and 120 r2", not "180 r1 and 180 r2". (Casey Mann, Nov 2002)
• 31-zone zonohedron: The parts count is for a hemispherical dome; double it if you want to make the entire ball (which would have to be suspended, as one face can't support the whole weight).  (Kevin Perkins, Jan 2001)
• 600 Cell: 120 b2, 120 y2, 72 r1, 72 r2, 75 balls, for the complete model described above.  (Vin de Silva, Nov. 2001)
• compound of 3 cubes: The parts count should say "12 b3", not "12 b2".  (Kevin Perkins, Jan 2001)
• comound of icosidodecahedron and rhombic triacontahedron: Should say "120 b2, 60 r1, 60 r3". (Dave Keenan, Nov. 2001)
• truncated cuboctohedron: 24 bx, 48 gbx, 48 balls. (Kevin Perkins, Jan 2001)