On a summer day in 1904 a young man by the name of William Brush
helped bring about the modem automobile suspension system. Driving his
brother Alanson's Crestmobile, Brush was rolling along too fast for the
unpaved roads of the day and went into a curve at 30 mph. The car's right
front wheel skittered onto the dirt shoulder and whammed into a deep rut.
Almost at once, the wheel started shimmy violently. The undulations of the
jarred right front elliptic leaf spring had sent shock waves across the solid
I-beam axle to the left side of the vehicle. This set the entire front of the
car to vibrating furiously. Brush was caught unawares and lost control. The
car crashed through a barbedwire fence, hit a ditch and overturned in a
cow pasture.
Several hours later young William 'fessed up to Alanson, whose demeanor
switched from stern to thoughtful, since he was trying to design a better
car. That car, dubbed the Brush Two-Seat Runabout, finally appeared in
1906. It featured a revolutionary suspension system that incorporated two
innovations never before assembled together: front coil springs and devices
at each wheel that dampened spring bounce -- shock absorbers -- mounted
on a flexible hickory axle.
Some European car makers had tried coil springs, with Gottlieb Daimler in
Germany being the leading exponent. However, most manufacturers stood
fast with leaf springs: They were less costly, and by simply adding leaves
or changing the shape from full elliptic to three-quarter or half elliptic, the
spring could be made to support varying weights.
Leaf springs in one form or another have been used since the Romans
suspended a two-wheeled vehicle called a Pilentum on elastic
wooden poles. The first steel spring put on a vehicle was a single flat plate
installed on carriages by the French in the 18th century.
The venerable leaf spring, which some manufacturers still use in rear
suspensions today, was invented by Obadiah Elliot of London in 1804. He
simply piled one steel plate on top of another, pinned them together and
shackled each end to a carriage.
The coil spring is not a spring chicken, either. The first patent for such a
spring (British patent No. 792) was issued to R. Tredwell in 1763. The
main advantage of coil springs was that they did not have to be spread
apart and lubricated periodically to keep them from squeaking, as leaf
springs did.
Henry Ford's 1908 Model T Ford featured old-fashioned leaf springs with a
novel twist -- he used only one spring at each axle, mounted transversely,
instead of one at each wheel. Ford's adaptation of high-strength vanadium
steel from a French racing car allowed him to save weight and cut costs in
many areas of the Model T without compromising its durability.
With the exception of a car here and there, independent coil spring front
suspension remained in limbo for 25 years after the introduction of the
Brush Runabout. Then suddenly in 1934, General Motors, Chrysler,
Hudson and others reintroduced coil spring front suspension, this time with
each wheel sprung independently. In that year, most cars started using
hydraulic shock absorbers and balloon (low-pressure) tires. Coupling a
solid front axle with shock absorbers and these tires really aggravated front
end shimmy. Suspending each wheel individually lessened the effects of
spring bounce.
Not all cars used coil springs at first. Some had independently suspended
leaf springs. But soon after World War II, all manufacturers switched to
coil springs for the front wheels.
Buick became the first U.S. manufacturer to use back-end coil springs in
1938. Manufacturers have switched back and forth from model to model
between leaf and coil springs since then. Generally, large, heavy cars are
equipped with leaf springs, while small light cars have coil
springs.
Independent rear suspension became popular on the rough, twisty roads of
Europe because it can offer improved ride and handling. The cheapest
method is the swing axle, for which early VWs were infamous. The
differential is bolted to the frame, with constant-velocity joints on each
side. However, as the wheels bounce over bumps, the tire camber and rear
track change radically, causing some handling quirks. In extreme
maneuvers, an outside wheel can actually tuck under the car, causing it to
flip.
Axles with joints at both ends do a better job of keeping the wheels upright
in a turn, and an amazing variety of control arms have been used to meet
this end. Trailing arms, once popular, sometimes allowed trailing throttle
oversteer -- lift your foot off the gas pedal in a turn and the rear wheels
shift slightly, throwing the car into a skid. Modern designs use up to six
control links at each wheel to prevent such erratic behavior as bump steer
and trailing throttle oversteer.
Air suspension, which Lincoln ballyhooed for some models in 1984 was
introduced in 1909 by the Cowey Motor Works of Great Britain. It did not
work well because it leaked.
The first practical air suspension was developed by Firestone in 1933 for
an experimental car called the Stout-Scarab. This was a rear-engined
vehicle that used four rubberized bellows in place of conventional springs.
Air was supplied by small compressors attached to each bellow. As you
might imagine, the air bag suspension was an expensive setup -- still is, in
fact.
The first automobile to use torsion bar suspension was the 1921 Leyland.
Most of the credit for the wide acceptance of torsion bars in Europe goes
to Dr. Ferdinand Porsche who made it standard on most of his cars,
beginning with the 1933 Volkswagen prototypes. By 1954, 21 makes of
European cars were equipped with torsion bars.
By contrast, in America, only Chrysler went the torsion bar route on its
large-sized cars. Despite its excellent ride qualities, high cost has limited its
acceptance in this country.
A renowned British surgeon, who had been knighted by Queen Victoria,
was convinced of a direct relationship between sound health and driving a
car. Dr. William Thomson's observations were made in a 1901 edition of
the Journal of Medicine:
"I have found my drives to improve my general health," Sir Thomas stated.
"The jolting which occurs when a motor car is driven at fair speed
conduces to healthy agitation that acts on the liver. This aids the peristaltic
movements of the bowels and promotes the performance of their
functions."
Manufacturers of cars either did not read Sir Thomas's report or did not
care for his views, because soon afterward they began using shock
absorbers to suppress vehicular jolting.
Since early motor cars were limited to much the same speed as carriages,
leaf springs for them could be made of the right proportion to provide
relatively jolt-free rides. As roads were improved and speeds shot up, a
1909 edition of Automobile Engineering noted:
"When springs are made sufficiently stiff to carry the load properly over
the small inequalities of ordinary roads, they are too stiff to respond readily
to the larger bumps. The result is a shock, or jounce, to the passengers.
When the springs are made lighter and more flexible in order to minimize
the larger shocks, the smaller ones have too large an influence, thus
keeping the [car] body and its passengers in motion all the time. These two
contradictory conditions have created the field for the shock
absorber."
The first recorded use of a crude shock absorber is the invention by one A.
Gimmig in 1897. He attached rubber blocks to the top of each leaf spring.
When the suspension was compressed sufficiently, the rubber bumpers hit
bolts that were attached to the frame. Rubber bump stops are still used in
many modern suspensions, but their effect on ride control is
minimal.
The first true shock absorbers ware fitted to a racing bicycle in 1898 by a
Frenchman named J. M. M. Truffault. The front fork was suspended on
springs, and incorporated a friction device that kept the bike from
oscillating constantly. In 1899, an American automobile enthusiast named
Edward V. Hartford saw one of Truffault's bikes win a marathon race at
Versailles. Hartford immediately recognized the automotive potential of the
friction device.
Hartford and Truffault got together and by the next year Hartford had
outfitted an Oldsmobile with a variation of Truffault's device. This first
automobile shock absorber consisted of a pari of levers that were hinged
together with a pad of rubber placed at the pivot point. One of the lever
arms was attached to the frame, while the other was bolted to the leaf
spring.
A bolt placed at the hinge point could be tightened or loosened to increase
or decrease the friction, providing a stiffer or softer ride. The Truffault-
hartford unit was, therefore, not only the first automotive shock absorber,
but also the first adjustable shock.
Hartford brought the car to America, where he opened his own plant, the
Hartford Suspension Co., in Jersey City, New Jersey. His first big contract
came from Alanson P. Brush, who installed shock absorbers along with
front col springs on the 1906 Brush Runabout. The ride given by the car
was called "magnificent" in a critique written by Hugh Dolnar for Cycle
and Automobile Trade Journal.
From then on shock absorber designs came fast and furious. Among
them:
The Nissan Maxima for 1985 sold in Japan had electronically controlled
shocks that automatically provided a soft, medium, or firm ride depending
upon road conditions, speed, and driving style. A sonar unit under the
bumper monitored the road surface, while other sensors checked speed,
acceleration, steering angle, and brake use.
Data were fed to a central processing unit that decided if you were driving
gently or aggressively, then activated shafts in the shock absorbers that
altered the size of fluid passages.
The Lotus Active Suspension System does away with springs and shock
absorbers altogether. Eighteen motion sensing transducers send data to four
computer-controlled hydraulic rams. The system distinguishes roll, dive,
jounce, and bump. Valves in the rams adjust the ride accordingly. These
valves can change position as much as 250 times per second.
The Lotus system has the uncanny ability to keep a car level in a tight turn
or even bank it toward the inside of the turn, rather than leaning to the
outside as other cars do.
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