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Re: New ideas
I think it's called a "pre-crushed" or "pre-buckled" cylinder. U of Hawaii
made an acrylic one to form the core of a walk-through aquarium about 20
years ago.
-----Original Message-----
From: John Brownlee <jonnie@chronic.lpl.arizona.edu>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Wednesday, February 24, 1999 9:55 AM
Subject: Re: New ideas
> I just finished reading in the book 'Hydrodynamically Loaded
>Structures' which describes an interesting hull design. The whole hull
>looks like it's accordion folded, with hemi-heads on each end. Turns out
>in testing that it's actually comparable in strength to a comparable
>cyllinder IF MADE WITHIN TIGHT TOLERANCES. That's an important disclaimer,
>remember that different geometries tolerate (or in most cases don't
>tolerate) deviations from perfect volumes of revolution in very different
>ways. The cross-section of the "cyllindrical" wall looks like this:
>
>
> /~~\ /~~\
> / /\ \ / /\ \
> / / \ \ / / \ \
> \ \/ / \ \
> \__/ \ \
>
> I mean, the damned thing looks like it would fold up along the
>revolution axis like a piece of collapsible Tupperware! But, all the
>finite element models and pressure tests showed that it held up if it's
>made exactly right. Bizarre-O.
> Now, to read most of your minds and answer your concerns, this is
>not necessarily a great idea, what it is supposed to illustrate is that
>sometimes math and physics join together to confound common sense in
>engineering. However, and this is the REAL point, unless you have amazing
>manufacturing skills, your common sense should always over-ride such
>counter-intuitive ideas. Often such elegant and beautiful juxtapositions
>of opposing forces (such as the accordion fold hull above) are intolerant
>of imperfections which real-world structures are going to have.
> So unorthodox ideas need to always be approached with caution,
>because chances are someone else already had them and didn't do it for a
>good reason. That's a long way to come to get that out. Sheesh!
>
> Back to wood, it's been done before rather sucessfully. That means
>that it is possible to create a viewport that handles the cycling fine. In
>fact, if I remember my reading right, there's a lot of good qualities
>attributed to plywood, ease of manufacture not the least among them. Just
>be prepared to have to re-create in wood the solutions people with steel
>subs had solved for them in the 50's, like viewports and penetrations.
>
>
> John
>
>John Brownlee
>Lunar and Planetary Lab
>University of Arizona
>jonnie @ lpl . arizona . edu
>
>