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side view of reduced-symmetry four-fold red-blue dowel-and-fishing-line tensegrity prism

On March 17, 1997, after duplicating the computations for the "skew 3-prismatic system" from the paper mentioned in the previous slide, I went on and tried to duplicate the computations for the "skew 4-prismatic system" from the same paper. Here I was less successful. I was able to come up with a figure with matching member lengths, but it had nowhere near the member forces Motro, et al. had computed. Still it was an interesting figure and worth presenting here. Below is the table of values from the paper augmented by the values I computed. My figures are in bold face. If things were going well, the figures in the "Stress" (Motro et al.) and "Member force" (my values) columns should be proportional. (Note: Motro et al.'s figures follow the European custom of using a comma instead of a decimal point.)

MemberEnd
points
Force
density
Length StressMember
force
1(c) 1 - 2 1 0,901 0,901 t 5.41599
2(c) 2 - 3 1 0,901 0,901 t 2.98493
3(c) 3 - 4 1 0,901 0,901 t 5.41599
4(c) 4 - 1 1 0,901 0,901 t 2.98493
5(c) 2 - 6 1 1,118 1,118 t 4.15001
6(c) 1 - 5 1,5 1,718 2,577 t 5.69853
7(c) 4 - 8 1 1,118 1,118 t 4.15001
8(c) 3 - 7 1,5 1,718 2,577 t 5.69853
9(s) 2 - 5 -1,5 2,516 -3,774 t -9.42666
10(s) 1 - 8 -1 1,5 -1,5 t -4.39231
11(s) 4 - 7 -1,5 2,516 -3,774 t -9.42666
12(s) 3 - 6 -1 1,5 -1,5 t -4.39231
13(c) 5 - 6 ? 1.824 ? 2.73066
14(c) 6 - 7 ? 1.824 ? 1.82388
15(c) 7 - 8 ? 1.824 ? 2.73066
16(c) 8 - 5 ? 1.824 ? 1.82388

On October 27, 2003, I made another attempt to duplicate Motro et al.'s computations. Again I didn't succeed completely, but I think I came much closer. You can see the more-interesting results of that exploration in Skew Four-Prism.


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