Today, we build a chair for a front-porch America.
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 few years ago I picked up a
fifty-dollar kit -- a large box of precut redwood
boards and brass fittings. When I assembled it, I had
a glider-style love-seat. The motion of a glider seat
is very comfortable. And for a good reason. It has to
do with your semicircular canals!
Any time you turn your head while your body is moving
in a curved path, you activate something called a
Coriolis force in the fluid of your inner ear. That
force moves the fluid in a deceptive way. It sends a
wrong signal to your brain. It makes you think you
aren't moving the way your eyes say you are.
The result is motion sickness. If you suffer motion
sickness, the worst thing you can do is to turn your
head in a lurching car or plane. That's also true in
a swing -- on the playground or on your front porch.
I'm very bad that way. Who doesn't love to be in
motion; but even rocking chairs bother me.
Now Margaret Culbertson writes about porch gliders.
They use a simple but subtle mechanism to avoid
curved motion. The seat hangs in a frame. The front
and back swing from different points. The seat stays
nearly level as it moves to and fro.
The word glider fits. The seat really does seem to
glide. The motion is nearly straight, and it doesn't
bother your stomach. Besides, you can move it around
like any other piece of furniture. It isn't nailed to
the ceiling or tied to a tree branch.
Culbertson finds the first precursor to the glider in
an 1898 Ladies Home Journal. From then
until 1925 inventors varied the theme and used names
like "Couch Hammock," and "Swinging Davenport." This
was, after all, America's front-porch era.
By the late '20s, the glider found its present form.
In 1925 an inventor also found the right word to
describe it. When he called his version the "Glide
Hammock," he added the word glider to our vocabulary.
Some very fancy gliders appeared in the 1930s. Frank
Lloyd Wright used them. You could even buy a hideaway
bed in glider form. Then something changed in
America.
We moved off our porches. We became a peripatetic
people -- no longer facing outward toward our
neighbors. Our lives take us far from our homes and
our TV and air conditioning take us indoors. We are
no longer a front-porch people.
So I look for my wife in the early morning. I find
her drinking coffee in that wooden glider. But now
it's in the back yard -- away from the
overstimulation that drives us all to privacy. In the
glider, she can turn her head this way and that in
perfect comfort. But she turns to see robins and
roses, cats and chameleons -- instead of neighbors
and passers-by.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Culbertson, M., E-Z Glider, Cite, Spring,
1992, pp. 30-32.
I don't have a citation for the mechanisms of motion
sickness. Colleagues in the Wenner-Gren Aeronautical
Laboratory at the University of Kentucky told me
about that during the late 1960s. Working under
contract with NASA, they studied motion sickness
among primates in large centrifuges. They explained
to me how the Coriolis force worked in the inner ear.
Photo by Margaret
Culbertson
A typical porch glider
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
