From: Charles J Knight (c.knight_at_juno.com)
Date: 03/05/00
Date: Sun, 5 Mar 2000 15:02:06 -0800 Subject: Re: ball connection Message-ID: <20000305.150236.-211671.1.c.knight@juno.com> From: Charles J Knight <c.knight_at_juno.com>
> > An idea. Could the design be modified slightly (no ball end,
> perhaps?)
> > to
> > make its low tech manufacture a bit easier? No need for me to
> turn
> > strut ends on a lathe, for example. Could, for example, a simple
> groove
> > near the end of the strut, produce a similar "locking" effect?
>
> Actually, a groove was my first design, but it doesn't allow
>
> for full range of motion on the hub.
Yeah, I've played with a few ideas, and a ball (or "football" shaped
end) works the best. The socket design can be made several ways,
but the hemispherical cutout in your design works very well.
> In order to get the full range of this biaxial motion, you
> really need a ball-and-socket sort of connection, or some sort of
> difficult-to-manufacture and prone-to-breakage, complicated
> double-hinged swivel / gimbal arrangement. (Not only hard to
> manufacture, but hard to type! ;^) )
I've tried making a few of these too -- MUCH more difficult to make,
lots more parts, moving articulated joints that can wear out, etc.
> > Your design is nearly perfect for mass manufacture, with
> sophisticated
> > equipment. But it's lacking just a bit, for easy prototyping in a
> Thanks. That was my intent (to make it easy to mass-produce,
I could tell. What kinds of strength are required for these units?
Since
domes redistribute stresses so effectively, would the hubs need to be
particularly strong?
Let me suggest a few modifications... Unless the strength of steel is
actually required, an injection molded plastic piece could work for the
connectors. PVC plumbing connectors are common and
cheap -- injection molding can reproduce parts like your connector
with great ease, and by the billions if necessary.
Think of how many PVC fittings are made -- my local Home Depot
probably has nearly 1/4 million units of various fittings, in stock, if
you add together all the fittings for all the various sizes of plumbing
and conduit pipe.
They're definitely manufacturable on the scale we require, and very
cheaply. PVC is not an ideal material since it degrades in UV, but
there is a UV stabilized formula, as well as hundreds of other polymers
from which to choose.
> not to make it hard for hobbyists.) Too often, I think that much of
> housing technology hasn't really advanced because there is so very
> much craft involved in building. Especially in domes.
Probably true -- though the ability to model things at home is highly
desirable. :-) Can't fault me for trying...
> This design, by design, is intended for domes. A variety of
> domes, but specifically domes. It won't work in square houses, but
> should work perfectly for what it's designed.
Yes, and with a simple "connection" at the center of the hub, it could
easily act as the verteces for a hypar unit. The dome framework could
hold a "tent" rigid. I think Bucky did a design similar to this. Rigid
hypar
panels, something like Temcor's domes, could also be mass
manufactured and attach to the same points.
> > Hmmm...wonder if standard dowels, inserted into wooden beads,
> > would work for a strut's ball end?
>
> Now you're on to it! That's exactly my intention. There are
> already pre-milled metal balls used in certain types of furniture
> construction. I know a few architects who work with these to design
> furniture that's modular and extensible. It's all rectilinear-based,
Yeah...pipe is extremely common, and most composite materials
are best manufactured as rod or pipe extrusions. This could easily
work for our purposes.
> we also have cut to whatever specific lengths are needed. Then you
> just screw the ball onto the end, and viola!, instant strut.
Making a ball that can screw on will require either very precise casting
(doable with injection molding equipment, ala PVC fittings) or for metal,
it will require tapping the balls, and cutting threads in the pipe.
A simpler design might be to use something akin to a set-screw, to
hold the struts into the ball ends. That way the struts could be cut
on site, if necessary, with no finishing necessary. It could also use
local materials, even tree branches, whittled down to the right diameter.
This might make repairs easier, in case a strut bends or breaks.
Even assuming an intent towards pre-fab, why not build in some
flexibility?
> maker (or 7 of them), a hub-maker (or 7 of them), an aerogel-panel
Is aerogel producible on site? Much like foam, it might be simpler to
ship the materials to the site, and "foam" it in.
Since you're talking about making the struts on site, the panels may not
be a "standard" size. Being able to "fill in" between the struts might
be
a useful feature.
> maker (or 7 of them), and octet-truss floor makers (or 7 of them).
I remember a folded "strip of steel" octet design from one of Bucky's
books, which could easily produce the floor units. Simple enough.
> A 4-frequency geodesic sphere will have the following
> component parts (provided my calculations are correct! :-) ):
> Hub part counts are based on my hub design at
> http://reality.sculptors.com/~salsbury/House/
A question -- why a 4 frequency? Here's why I ask. Most of the world
is familiar with soccer balls -- truncated icosahedra. This, if
triangulated,
*is* a 3F dome. Going with a familiar geometry might assist people in
actually erecting these home shells. It also requires fewer parts,
though
the final structures cannot be quite as large without becoming unwieldy.
> Remember also that those numbers are per-year, and that
> we're
> looking at 40-year sustained order loads, just to deal with today's
> homeless issues.
Another question. Most homeless people are not in a position to purchase
a home kit, despite our good intentions. How will these be funded?
I wonder if an "advertising" model, something like Juno and NetZero,
would
allow for genuinely free houses?
I'd like to think a group like Habitat could make these available, but
they've
proven themselves to be anti-dome.
-- Chuck Knight
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