Datasheet for Aspension Tower II

Copyright © 2007 and 2008 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> struta     pa2' pa1  -1.0      sqr(0.75)  1 Con *
<Member> strutb     pb2' pb1  -1.0      sqr(0.75)  1 Con *
<Member> strutc     pc2' pc1  -1.0      sqr(0.75)  1 Con *

# interlayer tendons
<Member> xltc       pc1' pc1   1.0      0.5   3 Obj *
<Member> xltb1      pb1  pc1   1.0      sqr(0.178)   3 Con *
<Member> xltb2      pb1' pc1   1.0      sqr(0.37)   3 Con *
<Member> xlta1      pa1  pb1   1.0      sqr(0.178)   3 Con *
<Member> xlta2      pa1' pb1   1.0      sqr(0.37)   3 Con *

# end tendons
<Member> basea      pa2  pa1   1.0      0.5   2 Con *
<Member> enda'      pa2' pa1'  1.0      0.125 4 Con *
<Member> endb'      pb2' pb1'  1.0      0.125 4 Con *
<Member> endc'      pc2' pc1'  1.0      0.125 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.

   struta:         0.75    strutb:         0.75    strutc:         0.75
     xltc:      0.52349     xltb1:        0.178     xltb2:         0.37
    xlta1:        0.178     xlta2:         0.37     basea:     0.707107
    enda':     0.353553     endb':     0.353553     endc':     0.353553
    baseb:     0.706905     basec:     0.706576

        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.

   struta:     -1.23205    strutb:    -0.756595    strutc:        -0.75
     xltc:      0.52349     xltb1:     0.482199     xltb2:     0.594721
    xlta1:     0.785004     xlta2:     0.968612     basea:     0.542416
    enda':     0.785501     endb':     0.482123     endc':     0.407942

        Average tendon force magnitude: 0.619112

        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> 200/0.75
        Strut and Tendon Hub Adjustments - s;t> 0 0

   struta: 200 0    strutb: 200 0    strutc: 200 0      xltc: 137 1
    xltb1:  46 1     xltb2:  97 0     xlta1:  46 1     xlta2:  95 1
    basea: 185 1     enda':  92 0     endb':  93 0     endc':  93 0

pedagogic view of second version of aspension tower
Aspension Tower II with Point Labels

structure file:  marcus/x3l3marcusa.rc
 variable file:  marcus/x3l3marcusa.dat
    digit list:  src/mm.dls


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


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