Copyright © 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. # struts <Member> s1 c1 p1 -1.00 sqr(330) 1 Con * <Member> s2 c1 p2 -1.00 sqr(330) 1 Con * <Member> s3 c2 p3 -1.00 sqr(330) 1 Con * <Member> s4 c2 p4 -1.00 sqr(330) 1 Con * # tendons <Member> t1-2 p1 p2 1.00 sqr(498.5297) 3 Con * <Member> t1-3 p1 p3 1.00 sqr(498.5297) 2 Con * <Member> t1-4 p1 p4 1.00 sqr(498.5297) 2 Con * <Member> t2-3 p2 p3 1.00 sqr(498.5297) 2 Con * <Member> t2-4 p2 p4 1.00 sqr(498.5297) 2 Con * <Member> t3-4 p3 p4 1.00 sqr(498.5297) 3 Con * <Member> tc c1 c2 1.00 sqr(80) 3 Obj *In-Situ Member LengthsThese 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. s1: 330 s2: 330 s3: 330 s4: 330 t1-2: 498.53 t1-3: 498.53 t1-4: 498.53 t2-3: 498.53 t2-4: 498.53 t3-4: 498.53 tc: 80Relative Member Force MagnitudesThese 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. s1: -61.0385 s2: -61.0385 s3: -61.0385 s4: -61.0385 t1-2: 17.8211 t1-3: 28.2843 t1-4: 28.2843 t2-3: 28.2843 t2-4: 28.2843 t3-4: 17.8211 tc: 80 Average tendon force magnitude: 32.6827Construction Lengths (in mm 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 a member represents the distance between the locations where it departs from the hub. The struts were cut from 3/4-inch diameter hardwood dowel. The tendons were made of 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. For the tc member, a double hook was used that kept the screw-eye centers 80 mm apart. stress-strain chart: v04oct_d/wellingtn.ssc Average Tendon Force Magnitude (chart units)> 15 Length Scale Factor> 1 Strut and Tendon Hub Adjustments - s;t> 13 8 (subtract 2*(13 mm) off strut lengths to get dowel lengths; subtract 2*(8 mm) off tendon lengths to get hub-adjusted in-situ tendon lengths) s1: 304 0 s2: 304 0 s3: 304 0 s4: 304 0 t1-2: 460 1 t1-3: 451 0 t1-4: 451 0 t2-3: 451 0 t2-4: 451 0 t3-4: 460 1 tc: 80 0

Tensegrity Tetrahedron Point Labels

structure file: tetra/tetra3.rc variable file: tetra/tetra3.dat |

CONTACT:

Bob Burkhardt

Tensegrity Solutions

Box 426164

Cambridge, MA 02142-0021

USA

e-mail: bobwb@juno.com