BODY
BODY
The body of an automobile is categorized according to the number of doors, the arrangement of seats, and the roof structure. Their roofs are conventionally supported by pillars on each side of the body in recent times, there are convertible models with retractable fabric tops that rely on the pillar at the side of the windshield for upper body strength, as convertible mechanisms and glass areas are essentially nonstructural. The glass areas have been increased for improved visibility and for aesthetic reasons. New designs are usually programmed on three- to six-year cycles with generally minor refinements appearing during the cycle.
Redesigning was a tough job in the past, when as much as four years of planning and new tool purchasing was needed for a completely new design. Computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques may now be used to reduce this time requirement by 50 percent or more.
Sheet steel is generally used to make automotive bodies. Elements are added to the alloy to improve its ability to be formed into deeper depressions without wrinkling or tearing in manufacturing presses. Steel is used because of its general availability, low cost, and good workability. Other materials for certain other materials are also used. Other materials, such as aluminum, fiberglass, and carbon fiber reinforced plastic are used because of their special properties.
For more toughness and resistance to brittle deformation, Polyamide, polyester, polystyrene, polypropylene, and ethylene plastics have been formulated. Tooling for plastic components generally costs less and requires less time to develop than that for steel components.
Painting and priming processes are used to protect bodies from corrosive elements and to maintain their strength and appearance. Bodies are first dipped in cleaning baths to remove oil and other foreign matter and then they go through a succession of dip and spray cycles. Enamel and acrylic lacquer are both in common use.
Electrodeposition of the sprayed paint, a process in which the paint spray is given an electrostatic charge and then attracted to the surface by a high voltage, helps assure that an even coat is applied and that hard-to-reach areas are covered. To speed up the drying process in the factories, ovens with conveyer lines are used. In those body areas that are more susceptible to corrode, galvanized steel with a protective zinc coating and corrosion-resistant stainless steel are used.
Redesigning was a tough job in the past, when as much as four years of planning and new tool purchasing was needed for a completely new design. Computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques may now be used to reduce this time requirement by 50 percent or more.
Sheet steel is generally used to make automotive bodies. Elements are added to the alloy to improve its ability to be formed into deeper depressions without wrinkling or tearing in manufacturing presses. Steel is used because of its general availability, low cost, and good workability. Other materials for certain other materials are also used. Other materials, such as aluminum, fiberglass, and carbon fiber reinforced plastic are used because of their special properties.
For more toughness and resistance to brittle deformation, Polyamide, polyester, polystyrene, polypropylene, and ethylene plastics have been formulated. Tooling for plastic components generally costs less and requires less time to develop than that for steel components.
Painting and priming processes are used to protect bodies from corrosive elements and to maintain their strength and appearance. Bodies are first dipped in cleaning baths to remove oil and other foreign matter and then they go through a succession of dip and spray cycles. Enamel and acrylic lacquer are both in common use.
Electrodeposition of the sprayed paint, a process in which the paint spray is given an electrostatic charge and then attracted to the surface by a high voltage, helps assure that an even coat is applied and that hard-to-reach areas are covered. To speed up the drying process in the factories, ovens with conveyer lines are used. In those body areas that are more susceptible to corrode, galvanized steel with a protective zinc coating and corrosion-resistant stainless steel are used.
The chassis forms the main structure of the modern automobile. A large number of designs in pressed-steel frame form a skeleton on which the engine, wheels, axle assemblies, transmission, steering mechanism, brakes, and suspension members are mounted. During the manufacturing process the body is flexibly bolted to the chasis.
This combination of the body and frame performs a variety of functions. It absorbs the reactions from the movements of the engine and axle, receives the reaction forces of the wheels in acceleration and braking, absorbs aerodynamic wind forces and road shocks through the suspension, and absorbs the major energy of impact in the event of an accident.
There has been a gradual shift in modern small car designs. There has been a trend toward combining the chasis frame and the body into a single structural element. In this grouping, the steel body shell is reinforced with braces that make it rigid enough to resist the forces that are applied to it. To achieve better noise-isolation characteristics, separate frames are used for other cars. The presence of heavier-gauge steel components in modern separate frame designs also tends to limit intrusion in accidents.
This combination of the body and frame performs a variety of functions. It absorbs the reactions from the movements of the engine and axle, receives the reaction forces of the wheels in acceleration and braking, absorbs aerodynamic wind forces and road shocks through the suspension, and absorbs the major energy of impact in the event of an accident.
There has been a gradual shift in modern small car designs. There has been a trend toward combining the chasis frame and the body into a single structural element. In this grouping, the steel body shell is reinforced with braces that make it rigid enough to resist the forces that are applied to it. To achieve better noise-isolation characteristics, separate frames are used for other cars. The presence of heavier-gauge steel components in modern separate frame designs also tends to limit intrusion in accidents.
Fuel combustion takes place in a confined space, and produces expanding gases that are used to provide mechanical power. The four-stroke reciprocating engine that is used in automobiles is the most common internal-combustion engine. In this mechanism, mechanical power is supplied by a piston that is fitted inside a cylinder. On a downstroke of the piston, the first stroke, fuel that has been mixed with air (by fuel injection or using a carburetor) enters the cylinder through an intake valve; the piston moves up to compress the mixture at the second stroke. At ignition, the third stroke, a spark from a spark plug ignites the mixture, forcing the piston down; in the exhaust stroke, an exhaust valve opens to vent the burned gas as the piston moves up. The piston is connected to a crankshaft by means of a rod. The reciprocating (up and down) movements of the piston rotate the crankshaft, which is connected by gearing to the drive wheels of the automobile. The ignition spark is provided by an electrical system whose power comes from a battery. This also supplies power to the starting system, which is a small electric motor that turns the crankshaft until the engine takes over. Water circulating around the cylinders cool the engine, and lubrication occurs motor oil that is driven around the moving engine parts by an oil pump. Small vehicles like lawn mowers and motorcycles use the two-stroke engine, which combines intake and compression in the first stroke and power and exhaust in the second.
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