Construction

From: mike regan (make-r_at_webtv.net)
Date: 09/29/98


From: make-r_at_webtv.net (mike regan)
Date: Tue, 29 Sep 1998 10:27:30 -0700 (PDT)
Subject: Construction
Message-ID: <5950-36111882-2367@mailtod-161.iap.bryant.webtv.net>

I have built several domes, both here and in Bellingham, Wa, both
geodesic, and some of my own design, using conventional materials,
2x6's, plywood, drywall,etc. I and my wife are living in the last one, a
"twelv-a-gon" of 34' diameter, with one large room on the top floor,
skylights, dormers, etc.
Recently started another one, and have been handling rebar for the
foundation. 16', 5/8th inch rebar would not be hard to hold onto while
someone welded the ends. Actually, the easiest way is to make triangles
first, then place them in position while other, single struts are
connected to them.
   The idea I was describing in my last e-mail of having a triacon
"wrapping around" an alternate is to get trianulated depth, through the
surface of the dome, where struts would connect to each other at hubs to
make, in effect, trusses. When this is draped inside and out with wire
mesh, and all is filled with accretion , the result is incredbly strong:
The accreted material is able to sustain high compression, and the
steel, boh mesh and rebar will sustain tension. Underwater, a
hemisphere will experience uniform, omnidirectional compression, so the
steel is just a formfor the accretion (think of concrete) to hang onto
while it's being put in place.
The same forces apply from gravity on an earth-based dome: uniform
compression. Look at the Pantheon in Rome: 300', all concrete, no
rebar, and lasting 2000 years.
The triacon is so-named after the tracontahedron, a thirty-sided
polyhedron whose faces are diamod-shaped. the icosa corners meet at the
pointy corners of the diamonds, and icosa struts run end-to end down
the diamonds. Now, "bulge-out' the triacontahedron so that the obtuse
corners lie on the same sphere as the others, and add a strut from
obtuse to obtuse corner. You have here a two-frequency triacon. Take
any alternate-breakdown geodesic, double the frequency, and make a
triacon of this freq to "wrap around" the original alternate. There
will be three times the number of struts, and the lengths will be
approximately that of the alternate, divided by "root-3".
      Wieght: I designed this as a twelve-freq alt, "wrapped " by a
twenty-four freq triacon. The alternate would be made with 16' pieces
of 5/8th rebar, and the triacon out of 91/3' pieces of half-inch.
Half-inch wieghs .668 lbs/ft, and 5/8th wieghs 1.43lbs/ft.
There are 2198 struts in the alternate hemisphere, which, times tree,
minus two-and one-half times sixty (to eliminate the excess around the
equator) gives 6594-150=6444 triacon struts.
alt: 35168 linear ft 50,290lbs
triacon: 6444x.9.333x.668=40,175lbs
Total wieght, less humans, is 90,464 lbs.
divide by sixty for the wieght at each corner of the equator, and you
have 1507 lbs for each float.divide that by 63.25 (pounds per cu ft of
water) and you have rquired displacement of 23 cu ft per float. Make
the floats out of styrofoam and wood, 20'x16'x1'. and you have about
fifteen times the foatation needed.
Lash two extra-large floats, at opposite corners, do the "inversion"
using polypro ropes, and boats at a distance, pulling out only half the
floats. BE CAREFUL the hemisphere may come back up under the half not
removed. Oh, I forgot to calculate the wieght of the wiremesh.
After partial accretion, float it a bit, and build the other hemisphere
on it. then, rotate again and accrete to desired thickness and wieght.
The bottom half should be thicker than the top (leave the top
translucent)
Spheres can be connected by simple "hinge-joints" to accommodate the
uppings and downings of wave action (or sea-swells) Hinge axis
horizontal. There should not be any shifting between and among spheres,
so ball-and-socket will not be necessary



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