Member Descriptions [name, end point names, weight (if in objective function), second power of length (if a constraint), member category, Obj/Con/Exc (put in objective function, use as a constraint or exclude from computations), flags] For assembly purposes, only the name and end point names are of interest. The other information may be of interest after A Practical Guide to Tensegrity Design has been consulted. # strut <Member> struta1 p3' p1 -1.0 sqr(3.0) 1 Obj * <Member> struta2 p5' p3 -1.0 sqr(3.0) 1 Obj * <Member> struta3 p1' p5 -1.0 sqr(3.0) 1 Obj * <Member> strutb1 p4' p2 -1.0 sqr(3.0) 9 Obj * <Member> strutb2 p6' p4 -1.0 sqr(3.0) 9 Obj * <Member> strutb3 p2' p6 -1.0 sqr(3.0) 9 Obj * # interlayer tendon <Member> xlta1 p1' p1 1.0 sqr(2.60841859702260) 3 Con * <Member> xltb1 p2' p2 1.0 sqr(3.20436408549826) 3 Con * <Member> xlta2 p3' p3 1.0 sqr(2.78065654253971) 3 Con * <Member> xltb2 p4' p4 1.0 sqr(2.60841859702260) 3 Con * <Member> xlta3 p5' p5 1.0 sqr(3.20436408549826) 3 Con * <Member> xltb3 p6' p6 1.0 sqr(2.78065654253971) 3 Con * # end tendons <Member> end1 p2 p1 1.0 1.0 2 Con * <Member> end2 p3 p2 1.0 1.0 2 Con * <Member> end3 p4 p3 1.0 1.0 2 Con * <Member> end4 p5 p4 1.0 1.0 2 Con * <Member> end5 p6 p5 1.0 1.0 2 Con * <Member> end6 p1 p6 1.0 1.0 2 Con * <Member> enda1' p3' p1' 1.0 3.0 4 Con * <Member> endb1' p4' p2' 1.0 3.0 4 Con * <Member> enda2' p5' p3' 1.0 3.0 4 Con * <Member> endb2' p6' p4' 1.0 3.0 4 Con * <Member> enda3' p1' p5' 1.0 3.0 4 Con * <Member> endb3' p2' p6' 1.0 3.0 4 Con *
In-Situ Member Lengths These are the lengths of the members when they are in place and prestress is applied. The strut lengths are from pin insertion point to pin insertion point, as are the tendon lengths. The values are in model units. struta1: 2.0659 struta2: 4.14682 struta3: 3.70568 strutb1: 3.70568 strutb2: 2.0659 strutb3: 4.14682 xlta1: 2.60842 xltb1: 3.20436 xlta2: 2.78066 xltb2: 2.60842 xlta3: 3.20436 xltb3: 2.78066 end1: 1 end2: 1 end3: 1 end4: 1 end5: 1 end6: 1 enda1': 1.73205 endb1': 1.73205 enda2': 1.73205 endb2': 1.73205 enda3': 1.73205 endb3': 1.73205
Relative Member Force Magnitudes These values are useful for developing an assembly strategy for the structure. The tighter tendons are much easier to tie in place early on, while the looser tendons can be left to the last. This information is also used to adjust tendon lengths since the measured length of a tendon will be shorter for a highly-stressed tendon with the same in-situ length as a tendon which is not so stressed. If you think the relative member forces are somewhat correlated with the member lengths, you are right. struta1: -2.06590 struta2: -4.14682 struta3: -3.70568 strutb1: -3.70568 strutb2: -2.0659 strutb3: -4.14682 xlta1: 2.60842 xltb1: 3.20436 xlta2: 2.78066 xltb2: 2.60842 xlta3: 3.20436 xltb3: 2.78066 end1: 1.73205 end2: 1.73205 end3: 1.73205 end4: 1.73205 end5: 1.73205 end6: 1.73205 enda1': 1 endb1': 1 enda2': 1 endb2': 1 enda3': 1 endb3': 1
Construction Lengths (in inches, sixteenths and thirty-seconds) The construction length of a tendon is less than the in-situ length since when the tendon is measured off it isn't under any prestress force. The construction length for the strut represents the length of the 3/16-inch-diameter wooden dowel. The tendons were made of 12-lb.-test braided nylon fishing line. In this case, the attachment point at the hubs was a simple metal pin stuck into the end of the strut, so no member-length adjustments were necessary. Prestress forces are assumed not to affect strut lengths. Elongation of Tendon of Unit Cross Section Under Force of Average Magnitude (fraction)> .02 Length Scale Factor> 9/5 (scaled for a total length of 9 inches) Strut and Tendon Hub Adjustments - s;t> 0 0 struta1: 3 11 1 struta2: 7 7 1 struta3: 6 10 1 strutb1: 6 10 1 strutb2: 3 11 1 strutb3: 7 7 1 xlta1: 4 9 0 xltb1: 5 9 0 xlta2: 4 14 0 xltb2: 4 9 0 xlta3: 5 9 0 xltb3: 4 14 0 end1: 1 12 1 end2: 1 12 1 end3: 1 12 1 end4: 1 12 1 end5: 1 12 1 end6: 1 12 1 enda1': 3 1 1 endb1': 3 1 1 enda2': 3 1 1 endb2': 3 1 1 enda3': 3 1 1 endb3': 3 1 1
Wishbone Tensegrity with Point Labels
structure file: tprism/x6prism8c.rc variable file: tprism/x6prism8c.dat digit list: src/standard.dls |
CONTACT: Bob Burkhardt Tensegrity Solutions Box 426164 Cambridge, MA 02142-0021 USA e-mail: bobwb@juno.com |