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Datasheet for 3v Pars Tetra Tensegrity


Copyright © 2009 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> s01.07        p01     p07     0.00   sqr(4.0925)      1 Con *
<Member> s02.08        p02     p08     0.00   sqr(4.0925)      1 Con *
<Member> s03.09        p03     p09     0.00   sqr(4.0925)      1 Con *
<Member> s04.10        p04     p10     0.00   sqr(4.0925)      1 Con *
<Member> s05.11        p05     p11     0.00   sqr(4.0925)      1 Con *
<Member> s06.12        p06     p12     0.00   sqr(4.0925)      1 Con *
<Member> s01.10.04.07a p01.10a p04.07b 0.00   sqr(4.0925)      9 Con *
<Member> s01.10.04.07b p01.10b p04.07a 0.00   sqr(4.0925)      9 Con *
<Member> s02.11.05.08a p02.11a p05.08b 0.00   sqr(4.0925)      9 Con *
<Member> s02.11.05.08b p02.11b p05.08a 0.00   sqr(4.0925)      9 Con *
<Member> s03.12.06.09a p03.12a p06.09b 0.00   sqr(4.0925)      9 Con *
<Member> s03.12.06.09b p03.12b p06.09a 0.00   sqr(4.0925)      9 Con *
# triangle tendons
<Member> t01.03   p01   p03    0.00   1.00       2 Con *
<Member> t02.01   p02   p01    0.00   1.00       2 Con *
<Member> t03.02   p03   p02    0.00   1.00       2 Con *
<Member> t04.09   p04   p09    0.00   1.00       2 Con *
<Member> t05.07   p05   p07    0.00   1.00       2 Con *
<Member> t06.08   p06   p08    0.00   1.00       2 Con *
<Member> t07.12   p07   p12    0.00   1.00       2 Con *
<Member> t08.10   p08   p10    0.00   1.00       2 Con *
<Member> t09.11   p09   p11    0.00   1.00       2 Con *
<Member> t10.06   p10   p06    0.00   1.00       2 Con *
<Member> t11.04   p11   p04    0.00   1.00       2 Con *
<Member> t12.05   p12   p05    0.00   1.00       2 Con *
# zig-zag tendons
<Member> z01.10a  p01     p01.10a    1.00   1.00       3 Con *
<Member> z01.10b  p01.10a p01.10b    1.00   0.00       3 Obj *
<Member> z01.10c  p01.10b p10        1.00   1.00       3 Con *
<Member> z02.11a  p02     p02.11a    1.00   1.00       3 Con *
<Member> z02.11b  p02.11a p02.11b    1.00   0.00       3 Obj *
<Member> z02.11c  p02.11b p11        1.00   1.00       3 Con *
<Member> z03.12a  p03     p03.12a    1.00   1.00       3 Con *
<Member> z03.12b  p03.12a p03.12b    1.00   0.00       3 Obj *
<Member> z03.12c  p03.12b p12        1.00   1.00       3 Con *
<Member> z04.07a  p04     p04.07a    1.00   1.00       3 Con *
<Member> z04.07b  p04.07a p04.07b    1.00   0.00       3 Obj *
<Member> z04.07c  p04.07b p07        1.00   1.00       3 Con *
<Member> z05.08a  p05     p05.08a    1.00   1.00       3 Con *
<Member> z05.08b  p05.08a p05.08b    1.00   0.00       3 Obj *
<Member> z05.08c  p05.08b p08        1.00   1.00       3 Con *
<Member> z06.09a  p06     p06.09a    1.00   1.00       3 Con *
<Member> z06.09b  p06.09a p06.09b    1.00   0.00       3 Obj *
<Member> z06.09c  p06.09b p09        1.00   1.00       3 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.

s01.07:         4.0925  s02.08:         4.0925  s03.09:         4.0925 
s04.10:         4.0925  s05.11:         4.0925  s06.12:         4.0925 
s01.10.04.07a:  4.0925  s01.10.04.07b:  4.0925  s02.11.05.08a:  4.0925 
s02.11.05.08b:  4.0925  s03.12.06.09a:  4.0925  s03.12.06.09b:  4.0925 
t01.03:         1       t02.01:         1       t03.02:         1 
t04.09:         1       t05.07:         1       t06.08:         1 
t07.12:         1       t08.10:         1       t09.11:         1 
t10.06:         1       t11.04:         1       t12.05:         1 
z01.10a:        1      z01.10b:         1.00001 z01.10c:        1 
z02.11a:        1      z02.11b:         1.00001 z02.11c:        1 
z03.12a:        1      z03.12b:         1.00001 z03.12c:        1 
z04.07a:        1      z04.07b:         1.00001 z04.07c:        1 
z05.08a:        1      z05.08b:         1.00001 z05.08c:        1 
z06.09a:        1      z06.09b:         1.00001 z06.09c:        1 

        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.

s01.07:        -0.768474 s02.08:        -0.768474 s03.09:        -0.768474 
s04.10:        -0.768474 s05.11:        -0.768474 s06.12:        -0.768474 
s01.10.04.07a: -0.294165 s01.10.04.07b: -0.294165 s02.11.05.08a: -0.294165 
s02.11.05.08b: -0.294165 s03.12.06.09a: -0.294165 s03.12.06.09b: -0.294165 
t01.03:         0.674415 t02.01:         0.674415 t03.02:         0.674415 
t04.09:         0.674415 t05.07:         0.674415 t06.08:         0.674415 
t07.12:         0.674415 t08.10:         0.674415 t09.11:         0.674415 
t10.06:         0.674415 t11.04:         0.674415 t12.05:         0.674415 
z01.10a:        1.00001  z01.10b:        1.00001  z01.10c:        1.00001 
z02.11a:        1.00001  z02.11b:        1.00001  z02.11c:        1.00001 
z03.12a:        1.00001  z03.12b:        1.00001  z03.12c:        1.00001 
z04.07a:        1.00001  z04.07b:        1.00001  z04.07c:        1.00001 
z05.08a:        1.00001  z05.08b:        1.00001  z05.08c:        1.00001 
z06.09a:        1.00001  z06.09b:        1.00001  z06.09c:        1.00001 

	Average tendon force magnitude: 0.869769

        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> 200/4.0925
        Strut and Tendon Hub Adjustments - s;t> 0 0

        At the level of accuracy here, it turns out all the struts have
        the same length, as do all the tendons.

        strut  200 0
        tendon  48 0

        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 (50 mm extra at
        each end).

        Elongation of Tendon of Unit Cross Section
        Under Force of Average Magnitude (fraction)> .02
        Length Scale Factor> 200/4.0925
        Strut and Tendon Adjustments - s;t> -1, -50

	            Cross
	 Type     Section    Quantity Count

	    1           1        1212     6
	    9           1        1212     6
	    2           1     1759.16    12
	    3           1     2619.43    18
	Strts                    2424    12
	Tndns                 4378.58    30


pedagogic view of 3v Pars Tensegrity Tetrahedron
3v Pars T-Tetra with Point Labels

structure file:  v2tetra/pars/pzzttnox1.rc
 variable file:  v2tetra/pars/pzzttnox1.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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