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Datasheet for
Two-fold Prism Girdled by Four-fold Prism


Copyright © 2004 by Bob Burkhardt

        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.

# struts
<Member> sa    pa' pa  -1.00    0.0   1 Obj CalcClear Inelastic *
<Member> sb    pb' pb  -1.00    0.0   1 Obj CalcClear Inelastic *
<Member> s1    p1' p2  -1.01998    0.0   9 Obj CalcClear Inelastic *
<Member> s2    p2' p3  -1.01998    0.0   9 Obj CalcClear Inelastic *
<Member> s3    p3' p4  -1.01998    0.0   9 Obj CalcClear Inelastic *
<Member> s4    p4' p1  -1.01998    0.0   9 Obj CalcClear Inelastic *

# tendons
<Member> tab'  pa' pb'   3.0      sqr(1.0) 2 Con *
<Member> ta1'  pa' p1'   3.0      sqr(1.0) 2 Con *
<Member> ta2'  pa' p2'   3.0      sqr(1.0) 2 Con *
<Member> tb3'  pb' p3'   3.0      sqr(1.0) 2 Con *
<Member> tb4'  pb' p4'   3.0      sqr(1.0) 2 Con *
<Member> t1    p1' p1    3.0      sqr(1.0) 2 Con *
<Member> t2    p2' p2    3.0      sqr(1.0) 2 Con *
<Member> t3    p3' p3    3.0      sqr(1.0) 2 Con *
<Member> t4    p4' p4    3.0      sqr(1.0) 2 Con *
<Member> ta1   pa  p1    3.0      sqr(1.0) 2 Con *
<Member> tb2   pb  p2    3.0      sqr(1.0) 2 Con *
<Member> tb3   pb  p3    3.0      sqr(1.0) 2 Con *
<Member> ta4   pa  p4    3.0      sqr(1.0) 2 Con *
<Member> tab   pa  pb    3.0      sqr(1.0) 2 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
        screw-eye center to screw-eye center, as are the tendon lengths.
        These values are in model units.

       sa:      2.08845        sb:      2.08845        s1:      2.08846
       s2:      2.08846        s3:      2.08846        s4:      2.08846
     tab':            1      ta1':            1      ta2':            1
     tb3':            1      tb4':            1        t1:            1
       t2:            1        t3:            1        t4:            1
      ta1:            1       tb2:            1       tb3:            1
      ta4:            1       tab:            1


        Relative Member Prestress 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.

       sa:     -2.08845        sb:     -2.08845        s1:     -2.13019
       s2:     -2.13019        s3:     -2.13019        s4:     -2.13019
     tab':      1.71887      ta1':      2.01762      ta2':      1.52751
     tb3':      2.01762      tb4':      1.52751        t1:      1.96191
       t2:      2.48823        t3:      1.96191        t4:      2.48823
      ta1:      2.01762       tb2:      1.52751       tb3:      2.01762
      ta4:      1.52751       tab:      1.71887


        Construction Lengths (in millimeters and halves)
        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 5/16-inch-diameter wooden dowel.
        Braided nylon fishing line was used for the tendons.
        Prestress forces are assumed to affect tendon lengths and
        not strut lengths.

        Elongation of Tendon of Unit Cross Section
        Under Force of Average Magnitude (fraction)> 0.02
        Length Scale Factor> 292/2.08846
        Strut and Tendon Hub Adjustments - s;t> 5.0 3.5
        (The 5.0 mm adjustment for the strut is the amount
         the screw-eye center extends from the dowel.  The 3.5 mm
	 adjustment for the tendon is half the outer diameter of the
         screw eye.)

       sa: 282 0        sb: 282 0        s1: 282 0        s2: 282 0
       s3: 282 0        s4: 282 0      tab': 130 1      ta1': 130 0
     ta2': 130 1      tb3': 130 0      tb4': 130 1        t1: 130 0
       t2: 129 1        t3: 130 0        t4: 129 1       ta1: 130 0
      tb2: 130 1       tb3: 130 0       ta4: 130 1       tab: 130 1

ray trace of two-fold prism girdled by four-fold prism
Two-fold Prism Girdled by Four-fold Prism
with Point Labels
(NB: The colors are reversed here as compared with the assembled model.)

structure file:  tprism/x2girdle4.rc
variable file:   tprism/x2girdle4.dat
digit list:      src/mm.dls

CONTACT:

Bob Burkhardt
Tensegrity Solutions
Box 426164
Cambridge, MA 02142-0021
USA

e-mail: bobwb@juno.com

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