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Email from Doug Milliken

Date: 12/1/2003 10:12 PM

Hi Bob,

I think I've managed to subscribe to the listserv...will see if this appears back in my inbox...

I recommend the jig method for anyone interested in quick-n-dirty model building. It saves a lot of time measuring out lengths of string. We used this at a "Tensigrity Party" in my dorm room, not long after I went to a Bucky lecture in Boston. This was back in the mid-1970s, might be some holes in my memory...

The struts were square rods (made in campus wood shop) with thin slots in the ends. Button thread was tied to one end of a strut, then the thread was run from one strut to the next, tie-ing off when required. With the struts held by the jig it was easy to tense everything up (and adjust for symmetry) before removing the cardboard solid inside. I think we made models that were the "doubles" of a cube and trapezoid, but I don't remember what some of the other people at the party made.

Anyway, thanks for your reply. I might take a crack at one of your beautiful structures one of these days!

-- Doug Milliken

On Mon, 1 Dec 2003, Bob Burkhardt wrote:

> Ref:
> Hi Doug,
> I've got my struts all ready to go.  I've never used a jig to assemble a
> tensegrity, and for these linear sorts of tensegrity I think it's even
> less necessary.  I've compared assembling a tensegrity to knitting
> although I've never knitted myself, just watched others.  My
> plan is to assemble one stage at a time.  I'll start by tying a
> hexagonal ring of "tS" and "TS" tendons uniting six struts, three struts
> going one way and three struts going the other way.  Then at one of the
> opposite ends I'll tie another ring which will introduce another three
> struts.  Then I'll have the framework for one tensegrity prism which
> I'll first tie the "guy" tendons for and then the "tT" tendons.  Then I
> can just continue at either end of that prism, tieing up new prisms
> stage by stage until I wrap around the whole torus.  The asymmetry of
> the prisms will mean I have to take a little care in making sure I
> choose the right lengths for each "guy" and "tT" tendon, maybe marking
> the struts somehow with point labels so I don't get them confused, but
> other than that I think it's pretty straight forward though I always
> find assembling a tensegrity a pretty challenging intellectual exercise.
> This strategy is based on my experience assembling the arch which
> has the same topology for most of the stages (see
> I'm going to use braided nylon fishing line and 3/8" dowels (cut to
> 230mm lengths) with
> picture-framing screw eyes in either end.  If I run into a tight tendon,
> I'll tie it using a temporary wire first and then tie in the nylon
> tendon.  I try to keep things easy though by tying in the tight tendons
> first when they will be slacker and tying in the looser tendons last
> (see the table of relative member forces for who's tight and who's loose).
> I've computed "Construction Lengths" and added them to the datasheet.
> These are member lengths I compute taking into account the actual scale
> of the structure, the hub dimensions and the tightness of each tendon.
> The accommodation of the hub dimensions is somewhat ad hoc, but nylon is
> forgiving enough it does alright.
> Bob
> On Sun, 30 Nov 2003 18:21:20 -0500 (EST) Doug Milliken
> writes:

>> Bob & Dick,
>> Great work!!  (I caught the post on bit.listserv.geodesic )
>> Now, tell us how to jig the struts, so we can try to make one of
>> these.  I remember making simple tensigrities easy to assemble by,
>> for example, attaching the struts to the sides of a cube, then
>> stringing
>> them up, and finally removing the cube from the middle.
>> Any bright suggestions?  Maybe use a real Christmas wreath and poke
>> the struts through the branches, removing the pine branches at
>> the end...
>> -- Doug Milliken (not posting due to SWEN problems)
>> On 28 Nov 2003, Dick Fischbeck wrote:

>> > Subject:    Zig-Zag Tensegrity Torus Datasheet
>> >
>> > Ref:
>> >
>> > Just in time for the holiday season!  The tensegrity torus!
>> >
>> > Scroll down to the bottom for pictures.
>> > Wouldn't it make a great holiday wreath?  I also designed a smaller
>> > eight-stage (24 struts)
>> > version which the clearances are kind of tighter on.  This version
>> > has ten stages (30 struts).
>> >
>> > Bob

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