- Historic Sites
Ten Innovations That Made History
The nuts-and-bolts perspective on how cars have shaped our lives
November 1996 | Volume 47, Issue 7
Four-wheel hydraulic brakes made driving safer, and by reducing the physical effort required, they allowed Detroit’s leaden behemoths of the 1950s and 1960s to be driven by sixteen-year-old girls. Moreover, efficient and reliable stopping lets Americans complain seriously that a speed limit of seventy-five miles per hour is too constricting. The eternal American obsession with speed has thus been able to continue its seamless progression from horses to steamboats to railroads to automobiles.
Horse-drawn carriages did not have much padding, but fortunately old Dobbin couldn’t pull hard enough to give riders too big a jolt. When cars started scorching at twenty miles per hour over rutted country lanes, though, the shaking was intolerable. Improvements came on many fronts: paving materials, shock absorbers, independent suspension. The biggest change occurred where the rubber meets the road.
Bicycle-style pneumatic tires did a fair job of cushioning early autos but were increasingly inadequate as the vehicles got faster and heavier. They were only about four inches wide and required around sixty pounds of pressure, which did not provide much give. As the car industry grew, tire makers developed new recipes for rubber and learned to incorporate belts of cord fabric. In 1923 Harvey S. Firestone used these advances in his balloon tire, which was six inches wide and required only about thirty pounds of pressure. It was an instant hit. Just as important as the smooth ride and easier steering, low-pressure balloon tires blew out much less often. Spares were banished from the fender or running board to the trunk, and the days when fixing flats was a routine part of an auto excursion were gone forever.
“Any customer can have a car painted any color he wants so long as it is black.” Unlike most pithy quotes attributed to famous men, Henry Ford actually said this, and his reason, as usual, was based on speeding up production: Black lacquer dried the fastest. That was important, because as car sales exploded during the 1910s and 1920s, painting became an ever-bigger bottleneck. The moving assembly line could build a car in a few hours, but applying varnish and waiting for it to dry took at least a week, and often much longer. One manufacturer observed that without a solution, “it would have been necessary to put a roof over the entire state of Michigan to get storage space great enough.”
In the early 1920s Du Pont chemists devised a paint based on pyroxylin (similar to guncotton, an explosive with which the company had much experience). It dried fast —too fast in early tests, when a spray would turn to powder before hitting the car. In late 1923 General Motors introduced Duco lacquer on its Oakland line, and the pale “True Blue” finish was an instant hit. Suddenly painting times were measured in hours instead of weeks, and the last vestige of craftsmanship had been banished from large-scale domestic car manufacture. By 1935 heat lamps had made drying a five-minute step.
Early cars were built like the carriages they replaced, with a wood-and-sheet-metal body, usually open to the elements, bolted onto a sturdy chassis. After World War I, auto design threw off the yoke of tradition, and by the late 1920s most cars had enclosed bodies made completely of steel except for the roof. The improvements in welding and metallurgy that had made all-steel construction possible suggested a further step: merging the chassis and body into a single unit. The 1934 Chrysler Airflow had such a unitary body; it was so strong that as a promotional stunt one was pushed over a 110-foot cliff and then driven away under its own power. But the Airflow’s many other innovations made it too revolutionary for Depression car buyers. It was the industry’s most notorious flop until the Edsel.
The 1940 Nash 600 series revived the concept, but war soon intervened. For many years after, the unibody’s advantages—lightness, ruggedness, safety, more interior room —were considered less important than the styling possibilities the old system allowed. Besides, American makers were reluctant to scrap their entire system of designing and building cars. Not until the oil crisis of the 1970s did unibody construction become generally accepted, its adoption allowing the American car industry to escape its postwar decline and start building nimble, reliable vehicles that could compete with the growing flood of imports.
Automobile engines run best at several thousand revolutions per minute, which must be geared down to drive the wheels. Changing speeds and road conditions call for different gear ratios, so shifting is required. In early cars this was done by sliding the appropriate gears in and out of place. The procedure was far from easy, especially the dreaded double declutching; if you didn’t do it right, your gears would be stripped. The Model T had a planetary transmission that was much simpler, but it could accommodate just two forward gears.