Today, some technologies we don't see when we first
look. The University of Houston's College of
Engineering presents this series about the machines
that make our civilization run, and the people
whose ingenuity created them.
A laser or a VCR is an
invention that's right out in the open where we can
see it. We admire such devices and their inventors.
But have you ever thought how much ingenuity is
hidden from view -- how much ingenuity we don't
even realize is there?
For example, were you aware that gear teeth are far
more than just wedges protruding from a wheel --
that their shapes have been mathematically formed
so that smooth, almost-flat surfaces push against
one another without any sliding? Gears are designed
so the back of each tooth very nearly stays in
contact with the mating tooth. That way the gear
can be reversed without backlash. Some very complex
human ingenuity has been used to avoid the sharp
edges, sliding motion, and backlash that wear gears
Or consider the huge twelve-foot-long Swiss
alpenhorn. I hadn't realized until a French horn
player pointed it out, that it's the same
instrument as the French
horn you see in modern orchestras. Some
ingenious musician realized it was possible to roll
that length of tubing into a compact coil without
It's unlikely that you know what a complex
mathematical shape an ordinary highway curve is if
you weren't trained as a civil engineer. Those
curves are far from simple arcs of a circle.
They're made from two pieces of Archimedean
spirals. One piece starts out straight, goes to
maximum curvature, then the second piece unwinds
back to straight again. Highways are made that way
because you can't to turn your steering wheel all
at once, nor would you want to. Furthermore, the
highway is banked from flat to a maximum angle and
back to flat again. Like gear teeth, highway curves
have very complex three-dimensional shapes.
The simple paper clip
doesn't need much explaining on the face of it. We
can all see how it works. But few of us have
thought through the design problem that it solves.
A paper clip must be easy to apply and remove. In
fact, its use should be nearly self-evident. It
shouldn't tear the paper. It shouldn't lose its
grip with time or leave rust stains. It has to be
Put all that together and you face a formidable
design challenge. The paper clips that you and I
use are a compromise solution which inventors still
struggle to improve upon.
The examples go on. No one thought of those little
yellow Post-It notes when
a 3-M company engineer accidentally mixed up a
batch of glue that refused to solidify. The stuff
kicked around for months before another person saw
what could be done with it.
We don't have to build the Brooklyn Bridge or
invent the radio to change the world. The vast
array of commonplace things that we handle every
day summons up stunning displays of ingenuity.
Anonymous genius rides all the anonymous parts of
our anonymous machines, and it cries out the joyful
"I am" of countless creative people.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
For the matter of highway design, see, e.g., Davis,
R. E., and Foote, F. S., Surveying Theory and
Practice (Third ed.). New York: McGraw-Hill Book
Co., 1940, Sections 526 through 528, Spiral Curves.
Gear design is treated in any mechanical
engineering design text. See, e.g., Shigley, J. E.,
and Uicker, J. J., Theory of Machines and
Mechanisms. New York: McGraw-Hill Book Co.,
1980, Chapter 7, Spur Gears.
Petroski, H., The Evolution of Artifacts.
American Scientist, Vol. 80,
September/October 1992, pp. 416-420. (for the
history of the paper clip)
Nayak, P. R., and Ketteringham, J. M.,
Breakthroughs: How the Vision and Drive of
Innovators in Sixteen Companies Created Commercial
Breakthroughs that Swept the World. New York:
Rawson Associates, 1986. Chapter 3 deals with the
invention of Post-It notes.
This is a revised version of Episode 49.
The Engines of Our Ingenuity is
Copyright © 1988-1998 by John H.
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