> Square-corner bellows (yes, exactly what you're talking about) are folded
> just like the accordian-pleated file folders you get at stationery stores.
> At least mine are. A physical specimen is as close as the nearest
> secretary.
Sure enough! I even had one of these in my office. VERY Interesting
THANKS!
> Square-corner bellows are not quadradially symmetrical -- they are
> biradially symmetrical. The "sides" are different from the "top & bottom".
> The "extra material" is all put into two sides (or edges, if you prefer),
> while the truncated-corner bellows seems to distribute it in the bevel.
Not sure what you mean by the "sides being different from the top &
bottom"? In the "truncated" bellows the fold peaks in one side are the
valleys in the adjacent side. For the square-corner bellows the peaks and
valleys match up in adjacent sides. This is what was preventing me from
getting the square corner in my experiments.
> Now for the conjecture: I'm no origami expert, but it looks like the
> "tube" you begin with may be the same for square and truncated, but the
> folds are different.
Yep! Looks like the actual layout is the same. Whether you get square or
truncated corners depends on how you go about making the folds. If you
match peaks to peaks and valleys to valleys in adjacent folds you get
square corners. You get truncated corners by matching peaks to valleys in
adjoining corners. Looks to me like the truncated corner bellows is
simpler to fold since you don't need the extra little "pucker" in each
corner. I'm also wondering if the "truncated" corner isn't a bit more
efficient when it comes to folding? I'm counting four layers of material
in the truncated fold corner versus six for the square corner. It looks
like you'd get a flatter fold with the truncated design. I might have to
make one of each just to see how this works out.
Thanks again!
- Wayde
(wallen@boulder.nist.gov)