automobile, self-propelled vehicle used for travel on land. The term is commonly applied to a four-wheeled vehicle designed to carry two to six passengers and a limited amount of cargo, as contrasted with a truck truck, automotive vehicle designed primarily for the transportation of goods. A truck is constructed on the general lines of the automobile but uses larger and heavier parts. It may be powered by a gasoline internal-combustion engine or a diesel engine.
..... Click the link for more information. , which is designed primarily for the transportation of goods and is constructed with larger and heavier parts, or a bus bus [Lat. omnibus=for all], large public conveyance. A horse-drawn urban omnibus was introduced in Paris in 1662 by Blaise Pascal and his associates, but it remained in operation for only a few years. The omnibus reappeared c.
..... Click the link for more information. (or omnibus or coach), which is a large public conveyance designed to carry a large number of passengers and sometimes additionally small amounts of cargo. For operation and technical features of automobiles, differential differential, in the automobile, a set of gears used on the driving (usually rear) axle. The two wheels on the driving axle must be interconnected in order to receive their energy from the same source, the driving shaft; at the same time they must be free to revolve
..... Click the link for more information. ; fuel injection fuel injection, system in an internal-combustion engine that delivers fuel or a fuel-air mixture to the cylinders by means of pressure from a pump. It was originally used in diesel engines because of diesel fuel's greater viscosity and the need to overcome the high
..... Click the link for more information. ; ignition ignition, apparatus for igniting a combustible mixture. The German engineer Nikolaus A. Otto, in his first gas engine, used flame ignition; another method was heating a metal tube to incandescence.
..... Click the link for more information. ; internal-combustion engine internal-combustion engine, one in which combustion of the fuel takes place in a confined space, producing expanding gases that are used directly to provide mechanical power.
..... Click the link for more information. ; lubrication lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid, semisolid, or solid—that permits free action of
..... Click the link for more information. ; muffler muffler, in automobiles, device designed to reduce the noise from the exhaust of an internal-combustion engine. When the exhaust gases from an internal-combustion engine are released directly into the atmosphere, they create a loud noise, caused by the passage of the
..... Click the link for more information. ; odometer odometer (ōdŏm`ĭtər)
..... Click the link for more information. ; shock absorber shock absorber, device for reducing the effect of a sudden shock by the dissipation of the shock's energy. On an automobile, springs and shock absorbers are mounted between the wheels and the frame.
..... Click the link for more information. ; speedometer speedometer, instrument that indicates speed. A cable from an automotive speedometer is attached to the rear of the transmission of an automobile; the cable turns at a rate proportional to the speed of the car.
..... Click the link for more information. ; steering system steering system, in automobiles, steering wheel, gears, linkages, and other components used to control the direction of a vehicle's motion. Because of friction between the front tires and the road, especially in parking, effort is required to turn the steering wheel.
..... Click the link for more information. ; suspension suspension, in automobiles, system of springs used to suspend the frame, body, engine, and power train above the wheels. Its principal purpose is to lessen the jarring of the automobile that is caused by irregularities in the roads traveled.
..... Click the link for more information. ; tachometer tachometer (tăkŏm`ətər)
..... Click the link for more information. ; tire tire, device made of rubber and fabric and attached to the outer rim of a vehicle wheel. Solid rubber tires were in limited use before 1850; they are still used in some special applications, e.g., for industrial trucks in factories.
..... Click the link for more information. ; transmission manual transmissions, and consist of a system of interlocking gearwheels. These wheels are arranged so that by operating a lever the driver can choose one of several ratios of speed between the input shaft and the output shaft.
..... Click the link for more information. .

Automobile Propulsion Systems

Reciprocating Internal-Combustion Engines

The modern automobile is usually driven by a water-cooled, piston-type internal-combustion engine, mounted in the front of the vehicle; its power may be transmitted either to the front wheels, to the rear wheels, or to all four wheels. Some automobiles use air-cooled engines, but these are generally less efficient than the liquid-cooled type. In some models the engine is carried just forward of the rear wheels; this arrangement, while wasteful of space, has the advantage of better weight distribution. Although passenger vehicles are usually gasoline fueled, diesel engines diesel engine, type of internal-combustion engine invented by the German engineer Rudolf Diesel and patented by him in 1892. Although his engine was designed to use coal dust as fuel, the diesel engine now burns low-cost fuel oil.
..... Click the link for more information. (which burn a heavier petroleum oil) are employed both for heavy vehicles, such as trucks and buses, and for a small number of family sedans. Both diesel and gasoline engines generally employ a four-stroke cycle.

The Wankel Engine

For some years, it was hoped that the Wankel engine, a rotary internal-combustion engine developed by Felix Wankel of Germany in 1954, might provide an alternative to the reciprocating internal-combustion engine because of its low exhaust emissions and feasibility for mass production. In this engine a three-sided rotor revolves within an epithrochoidal drum (combustion chamber) in which the free space contracts or expands as the rotor turns. Fuel is inhaled, compressed, and fired by the ignition system. The expanding gas turns the rotor and the spent gas is expelled. The Wankel engine has no valves, pistons, connecting rods, reciprocating parts, or crankshaft. It develops a high horsepower per cubic inch and per pound of engine weight, and it is essentially vibrationless, but its fuel consumption is higher than that of the conventional piston engine.

Alternative Fuels and Engines

Internal-combustion engines consume relatively high amounts of petroleum, and contribute heavily to air pollution; therefore, other types of fuels and nonconventional engines are being studied and developed. An alternative-fuel vehicle (AFV) is a dedicated flexible-fuel vehicle (one with a common fuel tank designed to run on varying blends of unleaded gasoline with either ethanol or methanol) or a dual-fuel vehicle (one designed to run on a combination of an alternative fuel and a conventional fuel) operating on at least one alternative fuel. An advanced-technology vehicle (ATV) combines a new engine, power train, and drive train system to significantly improve fuel economy. It is estimated that more than a half million alternative-fuel vehicles were in use in the United States in 2002; 50% of these operate on liquefied petroleum gas liquefied petroleum gas or LPG, mixture of gases, chiefly propane and butane, produced commercially from petroleum and stored under pressure to keep it in a liquid state.
..... Click the link for more information. (LPG, or propane propane, CH₃CH₂CH₃, colorless, gaseous alkane . It is readily liquefied by compression and cooling. It melts at −189.9°C; and boils at −42.2°C;.
..... Click the link for more information. ) and almost 25% use compressed natural gas Liquefied natural gas, or LNG, is natural gas that has been pressurized and cooled so as to liquefy it for convenience in shipping and storage. The boiling point of natural gas is extremely low, and only in the 1970s did cryogenic technology (see low-temperature physics ) advance
..... Click the link for more information. (CNG).

The ideal alternative-fuel engine would burn fuel much more cleanly than conventional gasoline-powered internal-combustion engines and yet still be able to use the existing fuel infrastructure (i.e., gas stations). Compressed natural gas, propane, hydrogen, and alcohol-based substances (gasohol gasohol, a gasoline extender made from a mixture of gasoline (90%) and ethanol (10%; often obtained by fermenting agricultural crops or crop wastes) or gasoline (97%) and methanol , or wood alcohol (3%).
..... Click the link for more information. , ethanol ethanol (ĕth`ənōl') or ethyl alcohol, CH₃CH₂
..... Click the link for more information. , methanol methanol, methyl alcohol, or wood alcohol, CH₃OH, a colorless, flammable liquid that is miscible with water in all proportions. Methanol is a monohydric alcohol . It melts at −97.
..... Click the link for more information. , and other "neat" alcohols) all have their proponents. However, although these fuels burn somewhat cleaner than gasoline, the use of all of them involves trade-offs. For example, because they take up more space per mile driven, these alternatives require larger fuel capacities or shorter distances between refueling stops. In addition, conventional automobiles may require extensive modifications to use alternative fuels; for example, to use gasohol containing more than 17% ethanol, the spark plugs, engine timing, and seals of an automobile must be modified; since 1998, however, many U.S. automobiles have been manufactured with equipment that enables them to run on E85, a mixture of 85% ethanol and 15% gasoline. Grain-derived fuels, such as ethanol, are a popular concept because they do not deplete the world's oil reserves; in various locations, "biodiesel" test cars have run on fuel similar to sunflower-seed oil. Similarly, dual-fuel (gasoline-diesel and gasoline-propane) and water-fuel-emulsion cars are being tested.

Alternative propulsion systems are also being studied. Steam engines, which were once more common than gasoline engines, are being experimented with now because they give off fewer noxious emissions; they are, however, less efficient than internal-combustion engines. Battery-powered electric engines, previously used mainly for local delivery vehicles, can now be used in automobiles capable of highway speeds, but they are restricted to relatively short trips because of limitations on the storage batteries that power the motors.

Some engineers worry that widespread adoption of electric cars might actually generate more air pollution, because additional electric power plants would be needed to recharge their batteries. Therefore, design and research work has also intensified on solar batteries, but they are generally not yet powerful enough to power such vehicles. The most promising technology for electric engines is the fuel cell fuel cell, electric cell in which the chemical energy from the oxidation of a gas fuel is converted directly to electrical energy in a continuous process (see oxidation and reduction ).
..... Click the link for more information. , but fuel cells currently are too expensive for practical applications.

Hybrid vehicles, or hybrid electric vehicles (HEVs), are powered by two or more energy sources, one of which is electricity, to produce a high-miles-per-gallon, low-emission drive. There are two types of HEVs, series and parallel. In a series hybrid, all of the vehicle power is provided from one source. For example, an electric motor drives the vehicle from the battery pack and the internal combustion engine powers a generator that charges the battery. In a parallel hybrid, power is delivered through both paths, both the electric motor and the internal combustion engine powering the vehicle. Thus, the electric motor may help power the vehicle while idling and during acceleration. The internal combustion engine takes over while cruising, powering the drive train and recharging the electric motor's battery. Some hybrids can operate in electric-only mode. Automobiles with gasoline-electric hybrid engines first appeared on the consumer market in 1999; unhampered by the AFV's limitations, sales of these vehicles increased steadily at the beginning of the 21st cent.

Automobiles and the Environment

Pollutants derived from automobile operation have begun to pose environmental problems of considerable magnitude. It has been calculated, for example, that 70% of the carbon monoxide, 45% of the nitrogen oxides, and 34% of the hydrocarbon pollution in the United States can be traced directly to automobile exhausts (see air pollution air pollution, contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health.
..... Click the link for more information. ). In addition, rubber (which wears away from tires), motor oil, brake fluid, and other substances accumulate on roadways and are washed into streams, with effects nearly as serious as those of untreated sewage. A problem also exists in disposing of the automobiles themselves when they are no longer operable.

In an effort to improve the situation, the U.S. government has enacted regulations on the use of the constituents of automobile exhaust gas that are known to cause air pollution. These constituents fall roughly into three categories: hydrocarbons that pass through the engine unburned and escape from the crankcase; carbon monoxide, also a product of incomplete combustion; and nitrogen oxides, which are formed when nitrogen and oxygen are in contact at high temperatures. Besides their own toxic character, hydrocarbons and nitrogen oxides undergo reactions in the presence of sunlight to form noxious smog smog (smŏg) [smoke+fog], dense, visible air pollution . Smog is commonly of two types.
..... Click the link for more information. . Carbon monoxide and hydrocarbons are rather easily controlled by the use of high combustion temperatures, leaner fuel mixtures, and lower compression ratios in engines. Unfortunately, the conditions that produce minimum emission of hydrocarbons tend to raise emission of nitrogen oxides. To some extent this difficulty is solved by adding recycled exhaust gas to the fuel mixture, thus avoiding the oversupply of oxygen that favors formation of nitrogen oxides.

The introduction of catalytic converters in the exhaust system has provided a technique for safely burning off hydrocarbon and carbon-monoxide emissions. The fragility of the catalysts used in these systems required the elimination of lead compounds previously used in gasoline to prevent engine knock. California, which has the most stringent air-pollution laws in the United States, requires further special compounding of gasoline to control emissions, and several states have mandated that ethanol be mixed with gasoline; as with the elimination of lead, measures taken to control air pollution have a negative impact on fuel efficiency.

Automotive Safety

Fatalities due to automobile accidents have stimulated improvements in automotive safety design. The first innovation involves creating a heavy cage around the occupants of the automobile, while the front and rear of the car are constructed of lighter materials designed to absorb impact forces. The second safety system uses seat belts to hold occupants in place. This was largely ineffective until states in the United States began passing laws requiring seat belt use. The third system is the air bag; within a few hundredths of a second after a special sensor detects a collision, an air bag in the steering wheel or dashboard inflates to prevent direct human impact with the wheel, dashboard, or windshield (newer vehicles sometimes include side air bags, to protect occupants from side collisions). Other advances in vehicle safety include the keyless ignition, which makes it impossible for a driver to start a car while under the influence of alcohol (over half of all vehicle fatalities involve at least one driver who has used alcohol) and antilock braking systems, which prevent an automobile's wheels from locking during braking.

Development of the Automobile

The automobile has a long history. The French engineer Nicolas Joseph Cugnot built the first self-propelled vehicle (Paris, 1789), a heavy, three-wheeled, steam-driven carriage with a boiler that projected in front; its speed was c.3 mph (5 kph). In 1801 the British engineer Richard Trevithick also built a three-wheeled, steam-driven car; the engine drove the rear wheels. Development of the automobile was retarded for decades by over-regulation: speed was limited to 4 mph (6.4 kph) and until 1896 a person was required to walk in front of a self-propelled vehicle, carrying a red flag by day and a red lantern by night. The Stanley brothers of Massachusetts, the most well-known American manufacturers of steam-driven autos, produced their Stanley Steamers from 1897 until after World War I.

The development of the automobile was accelerated by the introduction of the internal-combustion engine. Probably the first vehicle of this type was the three-wheeled car built in 1885 by the engineer Karl Benz in Germany. Another German engineer, Gottlieb Daimler, built an improved internal-combustion engine c.1885. The Panhard car, introduced in France by the Daimler company in 1894, had many features of the modern car. In the United States, internal-combustion cars of the horseless buggy type were manufactured in the 1890s by Charles Duryea and J. Frank Duryea, Elwood Haynes, Henry Ford, Ransom E. Olds, and Alexander Winton. Many of the early engines had only one cylinder, with a chain-and-sprocket drive on wooden carriage wheels. The cars generally were open, accommodated two passengers, and were steered by a lever.

The free growth of the automobile industry in the early 20th cent. was threatened by the American inventor George Selden's patent, issued in 1895. Several early manufacturers licensed by Selden formed an association in 1903 and took over the patent in 1907. Henry Ford, the leader of a group of independent manufacturers who refused to acknowledge the patent, was engaged in litigation with Selden and the association from 1903 until 1911, when the U.S. Circuit Court of Appeals ruled that the patent, although valid, covered only the two-cycle engine; most cars, including Ford's, used a four-cycle engine. The mass production of automobiles that followed, and the later creation of highways linking cities to suburbs and region to region, transformed American landscape and society.

Bibliography

See D. L. Lewis and L. Goldstein, The Automobile and American Culture (1983); J. J. Flink, The Automobile Age (1988); B. Olsen and J. Cabadas, The American Auto Factory (2002); P. Wollen (ed.) and J. Kerr (ed.), Autopia: Cars and Culture (2003).

automobile

Four-wheeled automotive vehicle designed for passenger transportation and commonly propelled by an internal-combustion engine using a volatile fuel. The modern automobile consists of about 14,000 parts and comprises several structural and mechanical systems. These include the steel body, containing the passenger and storage space, which sits on the chassis, or steel frame; the internal-combustion gasoline engine, which powers the car by means of a transmission; the steering and braking systems, which control the car's motion; and the electrical system, which includes a battery, alternator, and other devices. Subsystems involve fuel, exhaust, lubrication, cooling, suspension, and tires. Though experimental vehicles were built as early as the 18th century, not until the 1880s did Gottlieb Daimler and Karl Benz in Germany begin separately to manufacture cars commercially. In the U.S., James and William Packard and Ransom Olds were among the first auto manufacturers, and by 1898 there were 50 U.S. manufacturers. Some early cars operated by steam engine, such as those made from c. 1902 by Francis E. Stanley and Freelan O. Stanley. The internal-combustion engine was used by Henry Ford when he introduced the Model T in 1908; Ford would soon revolutionize the industry with his use of the assembly line. In the 1930s European manufacturers began to make small, affordable cars such as the Volkswagen. In the 1950s and '60s U.S. automakers produced larger, more luxurious cars with more automatic features. In the 1970s and '80s Japanese manufacturers exported their small, reliable, fuel-efficient cars worldwide, and their increasing popularity spurred U.S. automakers to produce similar models. Sport-utility vehicles (SUVs) and minivans, with their greater cargo and passenger capacities, became highly popular in the U.S. during the 1990s and led to a resurgence in sales of domestic vehicles. By the start of the 21st century, China had surpassed all European nations to become the third largest automobile market behind the U.S. and Japan. See also axle; brake; bus; carburetor; electric automobile; fuel injection; motorcycle; truck.

See automotive systems.