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Datasheet for Variation on Emmerich's 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
 struta  po2' pi1  -1.0      0.0      1 Obj CalcClear *
 strutb  pi1' po2  -1.0      0.0      1 Obj CalcClear *

# interlayer tendons
 xlta    pi1' po1   0.0      sqr(2.0) 3 Con CalcClear *
 xltb    pi1  po1'  0.0      sqr(2.0) 3 Con CalcClear *

# end tendons
 end     pi2  pi1   0.0      1.0      2 Con CalcClear *
 end'    pi2' pi1'  0.0      1.0      4 Con CalcClear *
 endx    pi1  po2   0.0      1.0      2 Con CalcClear *
 endx'   po2' pi1'  0.0      1.0      4 Con CalcClear *


        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.
        The values are in model units.

   struta:      2.64575    strutb:      2.64575      xlta:            2
     xltb:            2       end:            1      end':            1
     endx:            1     endx':            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.

   struta:     -2.64575    strutb:     -2.64575      xlta:            2
     xltb:            2       end:            2      end':            2
     endx:            1     endx':            1


        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.
        The tendons were made of braided nylon fishing line.
        Prestress forces were assumed not to affect strut lengths.

        Elongation of Tendon of Unit Cross Section
        Under Force of Average Magnitude (fraction)> .02
        Length Scale Factor> 170/2.64575
        Strut and Tendon Hub Adjustments - s;t> 6.0 3.5
        (The 6.0 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.)

   struta: 158 0    strutb: 158 0      xlta: 118 1      xltb: 118 1
      end:  56 0      end':  56 0      endx:  56 1     endx':  56 1


pedagogic view of variation on Emmerich's prism
View of Variation on Emmerich's Prism
with Point Labels

 

structure file:  tprism/x3eaprism2.rc
 variable file:  tprism/x3eaprism2.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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