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Second Tensegrity Obelisk Construction Data
(Six-Layer Version)


Copyright © 1999, 2005 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> strut0305 pt03A pt05c 0.0 sqr(2.5) 1 Con CalcClear Inelastic *
<Member> strut0406 pt04A pt06a 0.0 sqr(2.5) 1 Con CalcClear Inelastic *
<Member> strut0507 pt05A pt07c 0.0 sqr(2.5) 1 Con CalcClear Inelastic *
<Member> strut0608 pt06A pt08a 0.0 sqr(2.5) 1 Con CalcClear Inelastic *
<Member> strut0709 pt07A pt09c 0.0 sqr(2.5) 1 Con CalcClear Inelastic *
<Member> strut0810 pt08A pt10a 0.0 sqr(2.5) 1 Con CalcClear Inelastic *

<Member> baset  pt03A pt03B 0.0 sqr(1.5) 10 Exc *
<Member> apext  pt10a pt10b 0.0 sqr(1.0) 10 Con *

<Member> guy0   pt03A pt04A 0.26 0.0      3 Obj *
<Member> guy3   pt03A pt05b 0.46 0.0      3 Obj *
<Member> guy4   pt04A pt06b 0.37 0.0      3 Obj *
<Member> guy5   pt05A pt07b 0.40 0.0      3 Obj *
<Member> guy6   pt06A pt08b 0.50 0.0      3 Obj *
<Member> guy7   pt07A pt09b 0.45 0.0      3 Obj *
<Member> guy8   pt08A pt10b 0.70 0.0      3 Obj *

<Member> xtr5   pt05a pt05A 0.36 0.0      7 Obj *
<Member> xtr6   pt06a pt06A 0.36 0.0      7 Obj *
<Member> xtr7   pt07a pt07A 0.36 0.0      7 Obj *
<Member> xtr8   pt08a pt08A 0.36 0.0      7 Obj *

<Member> TL0304   pt03A pt04B 0.55 0.0      4 Obj *
<Member> TS0405   pt04A pt05a 1.45 0.0      2 Obj *
<Member> TL0405   pt04A pt05B 0.55 sqr(1.60584) 4 Con *
<Member> tS0405   pt04A pt05b 1.45 0.0      2 Obj *
<Member> TS0506   pt05A pt06a 1.45 sqr(.984101) 2 Con *
<Member> TL0506   pt05A pt06B 0.55 0.0      4 Obj *
<Member> tS0506   pt05A pt06b 1.45 0.0      2 Obj *
<Member> tL0506   pt05a pt06a 0.55 0.0      4 Obj *
<Member> TS0607   pt06A pt07a 1.45 0.0      2 Obj *
<Member> TL0607   pt06A pt07A 0.55 0.0      4 Obj *
<Member> tS0607   pt06A pt07b 1.45 0.0      2 Obj *
<Member> tL0607   pt06a pt07b 0.55 0.0      4 Obj *
<Member> TS0708   pt07A pt08a 1.45 0.0      2 Obj *
<Member> TL0708   pt07A pt08B 0.55 0.0      4 Obj *
<Member> tS0708   pt07A pt08b 1.45 0.0      2 Obj *
<Member> tL0708   pt07a pt08a 0.55 0.0      4 Obj *
<Member> TS0809   pt08A pt09b 1.45 0.0      2 Obj *
<Member> tS0809   pt08A pt09a 1.45 0.0      2 Obj *
<Member> tL0809   pt08c pt09a 0.55 0.0      4 Obj *
<Member> tL0910   pt09a pt10a 0.55 0.0      4 Obj *


        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
        hub center to hub center, as are the tendon lengths.
        These values are in model units.

strut0305:          2.5 strut0406:          2.5 strut0507:          2.5
strut0608:          2.5 strut0709:          2.5 strut0810:          2.5
    baset:      1.51987     apext:            1      guy0:      1.33158
     guy3:      2.01281      guy4:      2.18526      guy5:      2.08293
     guy6:       2.1659      guy7:      2.22818      guy8:      2.24252
     xtr5:       0.8186      xtr6:     0.708883      xtr7:     0.719252
     xtr8:     0.805133    TL0304:      1.66303    TS0405:      1.04135
   TL0405:      1.60584    tS0405:     0.956123    TS0506:     0.984101
   TL0506:      1.60423    tS0506:      1.02919    tL0506:      1.66715
   TS0607:     0.994281    TL0607:      1.60176    tS0607:      1.03325
   tL0607:      1.61019    TS0708:      1.01978    TL0708:      1.68087
   tS0708:     0.984525    tL0708:       1.6565    TS0809:       0.9407
   tS0809:     0.907978    tL0809:      1.65306    tL0910:      1.72719


        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.

strut0305:     -2.43384 strut0406:      -2.4833 strut0507:     -3.14895
strut0608:      -3.3746 strut0709:     -3.31851 strut0810:     -2.70319
    apext:     0.506916      guy0:     0.346211      guy3:     0.925894
     guy4:     0.808545      guy5:     0.833171      guy6:      1.08295
     guy7:      1.00268      guy8:      1.56976      xtr5:     0.294696
     xtr6:     0.255198      xtr7:     0.258931      xtr8:     0.289848
   TL0304:     0.914668    TS0405:      1.50996    TL0405:     0.288695
   tS0405:      1.38638    TS0506:     0.947462    TL0506:     0.882328
   tS0506:      1.49233    tL0506:     0.916934    TS0607:      1.44171
   TL0607:     0.880968    tS0607:      1.49822    tL0607:     0.885604
   TS0708:      1.47868    TL0708:      0.92448    tS0708:      1.42756
   tL0708:     0.911076    TS0809:      1.36402    tS0809:      1.31657
   tL0809:      0.90918    tL0910:     0.949954

        Average tendon force magnitude: 0.953174


        Construction Lengths (in inches, 16ths and 32nds)
        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 a member
        represents the distance between the locations where it
        departs from the hub.  The struts were cut from
        1-inch by 1-inch hardwood garden stakes.  The tendon material
        was single strands of twisted #18 nylon twine.  Its behavior
        under stress is highly non-linear, so a look-up table
        was used to compute strains.  Prestress forces were assumed
        to affect tendon lengths and not strut lengths.

        Average Tendon Force Magnitude (chart units)> 20
        Length Scale Factor> 42/2.5
        Strut and Tendon Hub Adjustments> 0 0.5
        (adjust the tendon lengths by subtracting a half inch from
         both ends)

strut0305: 42  0 0 strut0406: 42  0 0 strut0507: 42  0 0 strut0608: 42  0 0 
strut0709: 42  0 0 strut0810: 42  0 0     apext: 14 14 1      guy0: 20  7 1 
     guy3: 30  1 0      guy4: 33  0 0      guy5: 31  5 1      guy6: 32  2 1 
     guy7: 33  3 1      guy8: 32  8 0      xtr5: 12  4 1      xtr6: 10  8 1 
     xtr7: 10 11 1      xtr8: 12  1 0    TL0304: 24 11 1    TS0405: 14 10 1 
   TL0405: 25  0 1    tS0405: 13  7 1    TS0506: 14  3 1    TL0506: 23 13 1 
   tS0506: 14  8 0    tL0506: 24 12 1    TS0607: 14  0 0    TL0607: 23 13 0 
   tS0607: 14  8 1    tL0607: 23 15 0    TS0708: 14  5 1    TL0708: 24 15 1 
   tS0708: 13 14 0    tL0708: 24 10 0    TS0809: 13  4 0    tS0809: 12 12 1 
   tL0809: 24  9 0    tL0910: 25 10 0 

        Base chord length = (1.51987/2.5)*42" = 25.5338" = 25 8 1


        Material Quantities
        This provides an estimate of how much material will
        be needed to assemble the structure, in this case
        inches of garden stake and inches of nylon twine.
        The lengths must be adjusted to take into account the
        fact that the strut extends past the hub and some length
        of tendon is required to tie it to the strut.
        The Quantity value given for each Type does not take
        into account the Cross Section value.  The total
        Quantity given across from Tndns does.

        Length Scale Factor> 42/2.5 
        Strut and Tendon Adjustments> 0 (-6)

                    Cross
         Type     Section    Quantity Count

            1           1         756    18
           10           1     81.5565     3
            3           1     888.924    21
            7           1     287.309    12
            4           1     1097.36    30
            2           1     767.801    30
        Strts                     756    18
        Tndns                 3122.95    96
side view of the second tensegrity obelisk another side view of the second tensegrity obelisk
Two Views of the Tensegrity Obelisk
(VRML Model)

Schematic for the Second Tensegrity Obelisk
Schematic for the Second Tensegrity Obelisk

          structure file:  obelisk2/stage3.rc
           variable file:  obelisk2/stage3.dat
stress-strain chart file:  v04oct_d/wellingtn.ssc
         digit list file:  src/standard.dls

CONTACT:

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

e-mail: bobwb@juno.com

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