BEHAVIOR
They wipe back and forth to swish the rain and snow off a viewing
quadrant so you can see the road ahead. Their melodic “wipe wipe
wipe” can lull you to sleep.
HABITAT
Wipers rest (park) at the base of the windshield, like a faithful dog resting at your feet.
HOW IT WORKS
Wipers are powered by an electric motor that turns a worm gear. A worm gear is a spiral of a raised edge wrapped around a metal cylinder, much like a metal screw. Worm gears are fundamentally different from other gears in several ways. They can radically increase the turning power, or torque, which is useful in applications such as windshield wipers where torque is need to push the long wiper across the windshield.
Also, worm gears can change the direction of rotation. In the windshield wiper the worm gear changes the direction of the motor shaft’s rotation 90 degrees. The worm gear drives a second gear which is connected
to a cam or crank. The cam or crank converts the rotary motion of the motor into the back-and-forth motion of the wipers. Hand-operated rubber wipers were introduced in 1917 by the company that later became Trico, which is today the largest maker of windshield wipers. After World War I, the company introduced wipers powered not by electric motors, but by the vacuum pressure created in the intake manifold of the engine. This arrangement meant that the speed of the wipers was tied directly to the speed of the engine.
Electric motor wipers were introduced in 1926. Wipers for rear windows were added in 1959. Intermittent wipers were invented by engineer Robert Kearns (later sparking a series of lengthy patent infringement suits) and were introduced in 1969 on Ford’s model Mercury.
INTERESTING FACTS
Windshield wipers were invented before windshields were common in cars. In their early years, cars were a fair weather mode of transportation and had no use for wipers. Mary Anderson invented a simple wiper
for streetcar windows in 1903. Anderson lived most of her life in Birmingham, Alabama. But on a trip to New York she noticed how hard it was for a trolley driver to see through the windshield during a rainstorm, and this experience prompted her to invent the wiper. Wipers for headlights were added by Saab in 1970. Now rain-sensing wipers have appeared on luxury cars.
All rights reserved
Published by Chicago Review Press, Incorporated
814 North Franklin Street
Chicago, Illinois 60610
ISBN: 978-1-55652-812-5
Printed in the United States of America
5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Sobey, Edwin J. C., 1948–
A field guide to automotive technology / Ed Sobey.
p. cm.
Includes index.
ISBN 978-1-55652-812-5
1. Automobiles—Popular works. 2. Mechanics—Popular works. I. Title.
TL146.5.S63 2008
629.2—dc22
2008046620
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