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Datasheet for Perspective Prism


Copyright © 2007 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.

<Member> 01(c) pt01 pt02  0.0 sqr(0.261008730199888) 2 Con *
<Member> 02(c) pt02 pt03  0.0 sqr(0.301915332950701) 2 Con *
<Member> 03(c) pt03 pt04  0.0 sqr(0.383095246542990) 2 Con *
<Member> 04(c) pt04 pt05  0.0 sqr(0.464146377838545) 2 Con *
<Member> 05(c) pt05 pt06  0.0 sqr(0.464146377838546) 2 Con *
<Member> 06(c) pt06 pt07  0.0 sqr(0.383095246542990) 2 Con *
<Member> 07(c) pt07 pt08  0.0 sqr(0.301915332950701) 2 Con *
<Member> 08(c) pt08 pt01  0.0 sqr(0.261008730199888) 2 Con *
<Member> 09(c) pt01 pt09  1.0 sqr(0.689891161160713) 3 Obj *
<Member> 10(c) pt02 pt10  1.0 sqr(0.665510875807512) 3 Con *
<Member> 11(c) pt03 pt11  1.0 sqr(0.739256300739300) 3 Con *
<Member> 12(c) pt04 pt12  1.0 sqr(0.908039523981026) 3 Con *
<Member> 13(c) pt05 pt13  1.0 sqr(1.09882495341673)  3 Con *
<Member> 14(c) pt06 pt14  1.0 sqr(1.14981051589702)  3 Con *
<Member> 15(c) pt07 pt15  1.0 sqr(1.01049024008915)  3 Con *
<Member> 16(c) pt08 pt16  1.0 sqr(0.813398015083213) 3 Con *
<Member> 17(s) pt01 pt16 -1.0 sqr(0.930211225870888) 1 Con *
<Member> 18(s) pt02 pt09 -1.0 sqr(0.849854394375223) 1 Con *
<Member> 19(s) pt03 pt10 -1.0 sqr(0.877233805489365) 1 Con *
<Member> 20(s) pt04 pt11 -1.0 sqr(1.00302205041128)  1 Con *
<Member> 21(s) pt05 pt12 -1.0 sqr(1.15285087051696)  1 Con *
<Member> 22(s) pt06 pt13 -1.0 sqr(1.21931486941198)  1 Con *
<Member> 23(s) pt07 pt14 -1.0 sqr(1.19871926268034)  1 Con *
<Member> 24(s) pt08 pt15 -1.0 sqr(1.08313829018149)  1 Con *
<Member> 25(c) pt09 pt10  0.0 sqr(0.276112253335532) 2 Con *
<Member> 26(c) pt10 pt11  0.0 sqr(0.256060301692048) 2 Con *
<Member> 27(c) pt11 pt12  0.0 sqr(0.276112253335532) 2 Con *
<Member> 28(c) pt12 pt13  0.0 sqr(0.338385830283023) 2 Con *
<Member> 29(c) pt13 pt14  0.0 sqr(0.428933030260907) 2 Con *
<Member> 30(c) pt14 pt15  0.0 sqr(0.477402187936063) 2 Con *
<Member> 31(c) pt15 pt16  0.0 sqr(0.428933030260908) 2 Con *
<Member> 32(c) pt16 pt09  0.0 sqr(0.338385830283022) 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 pin insertion
        point to pin insertion point, as are the tendon lengths.
        The values are in model units.

    01(c):     0.261009     02(c):     0.301915     03(c):     0.383095
    04(c):     0.464146     05(c):     0.464146     06(c):     0.383095
    07(c):     0.301915     08(c):     0.261009     09(c):     0.689891
    10(c):     0.665511     11(c):     0.739256     12(c):      0.90804
    13(c):      1.09882     14(c):      1.14981     15(c):      1.01049
    16(c):     0.813398     17(s):     0.930211     18(s):     0.849854
    19(s):     0.877234     20(s):      1.00302     21(s):      1.15285
    22(s):      1.21931     23(s):      1.19872     24(s):      1.08314
    25(c):     0.276112     26(c):      0.25606     27(c):     0.276112
    28(c):     0.338386     29(c):     0.428933     30(c):     0.477402
    31(c):     0.428933     32(c):     0.338386


        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.

    01(c):     0.373147     02(c):     0.325355     03(c):     0.257914
    04(c):     0.210412     05(c):     0.210412     06(c):     0.257914
    07(c):     0.325355     08(c):     0.373147     09(c):     0.689891
    10(c):     0.714551     11(c):     0.644801     12(c):     0.526374
    13(c):     0.433788     14(c):     0.413674     15(c):     0.472738
    16(c):      0.58702     17(s):    -0.723498     18(s):    -0.788567
    19(s):    -0.765149     20(s):    -0.672798     21(s):    -0.585149
    22(s):    -0.549745     23(s):    -0.560797     24(s):    -0.623763
    25(c):     0.353997     26(c):     0.379874     27(c):     0.353997
    28(c):     0.291607     29(c):     0.229412     30(c):      0.20375
    31(c):     0.229412     32(c):     0.291607

        Average tendon force magnitude: 0.381256


        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 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> 125
        Strut and Tendon Hub Adjustments - s;t> 0 0
 
    01(c):  32 0     02(c):  37 0     03(c):  47 0     04(c):  57 1
    05(c):  57 1     06(c):  47 0     07(c):  37 0     08(c):  32 0
    09(c):  83 0     10(c):  80 0     11(c):  89 1     12(c): 110 1
    13(c): 134 1     14(c): 140 1     15(c): 123 1     16(c):  98 1
    17(s): 116 1     18(s): 106 0     19(s): 109 1     20(s): 125 1
    21(s): 144 0     22(s): 152 1     23(s): 150 0     24(s): 135 1
    25(c):  34 0     26(c):  31 1     27(c):  34 0     28(c):  41 1
    29(c):  53 0     30(c):  59 0     31(c):  53 0     32(c):  41 1


        Material Quantities (in millimeters)
        Estimates of the total amount of material required to build
        the structure.  The adjustment in this case includes "waste":
        for the strut, the amount lost when sawing the strut from a
        length of dowel (1 mm from each end); for the tendons, the amount
        of extra needed to successfully tie the tendon (20 mm extra at
        each end).

        Elongation of Tendon of Unit Cross Section
        Under Force of Average Magnitude (fraction)> .02
        Length Scale Factor> 125
        Strut and Tendon Adjustments - s;t> -1 -20

                    Cross
         Type     Section    Quantity Count

            2           1     1325.31    16
            3           1     1170.98     8
            1           1     1055.29     8
        Strts                 1055.29     8
        Tndns                 2496.29    24


pedagogic view of perspective prism
Perspective Prism with Point Labels

structure file:  sk8prsm/stage6.rc
 variable file:  sk8prsm/stage6.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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