Motor Vehicles

means of self-propelled railless transportation.

History As early as the Middle Ages attempts were made to build carriages that would move on the power of the wind and by the muscular force of the people sitting in them. In 1752 a self-taught Russian mechanic, the peasant Leontii Shamshurenkov, constructed a vehicle that was rather accomplished for his time. His “self-driven carriage” was set in motion by the force of two people. In 1784–91 the Russian inventor I. P. Kulibin worked on versions of three- and four-wheel “pedal vehicles.” His “pedal vehicle” was the first to employ such motor vehicle elements as the gearbox, steering mechanism, brakes, and roller bearings. With the advent of the steam engine in the second half of the 18th century, the construction of self-propelled vehicles progressed rapidly. In 1769–70 steam cars were built by J. Cugnot in France and a few years later by W. Murdock and R. Trevithick in England. Steam vehicles became somewhat popular in the 19th century—for instance, the steam carriages of G. Gurney and W. Hancock (England) and A. Bollée, A. de Dion, and L. Serpollet (France). In the 1830’s there were attempts to establish regular passenger runs in steam carriages. In Russia there were many interesting projects for the use of steam carriages. In 1837 the inventor and entrepreneur V. Gur’ev proposed to build a network of wooden (timber) roads for regular runs of steam tractors with wheeled trailers (carts) in the summer and sledge trailers in the winter. At the end of the 19th century there were experiments to construct electric cars with storage battery power supplies. These cars acquired a certain popularity. In 1899 the Russian engineer I. V. Romanov designed an original electric cab and electric bus. The development of motor vehicle construction was greatly influenced by the invention of the differential (1828, by O. Pecqueur of France), the pneumatic tire (1845, by R. Thompson of England), steerable front wheels on journals (1816, by G. Langensperger of Germany), independent wheel suspension (1878, by A. Bollée of France), and so on.

The extensive use of motor vehicles as a means of transportation began with the advent of the high-speed internal combustion engine. In 1862, J. E. Lenoir of France made an unsuccessful attempt to install his gas engine in a motor vehicle. In 1885, G. Daimler of Germany built a motorcycle operating on a gasoline engine, and in 1886 his countryman C. Benz took out a patent for a three-wheel motor vehicle with the same 0.75 hp engine design. The following years saw the beginning of the industrial production of motor vehicles. In the 1890’s the first Panhard-Levassor and DeDion-Bouton motor vehicles appeared in France; in 1892, Henry Ford built his first automobile in the USA and in 1903 began to produce them on an industrial basis. One of the first Russian motor vehicles was the Russo-Balt of 1908. The first Soviet motor vehicle, the AMO-F15, came out in 1924. In 1932 the USSR began to produce the GAZ-A and GAZ-AA in quantity.

Since 1894 motor races, which have played a great role in the development of motor-vehicle construction and distribution, have been held regularly. Whereas the average speed in the first race was 24 km/hr, five years later it had already reached 70 km/hr; in 1904 it was 100 km/hr; and in 1907, 114 km/hr. In 1968 the world speed record was 966.753 km/hr in a car with a gas turbine engine and 658.667 km/hr in one with a piston engine.

Motor vehicle classification According to the purposes for which they are intended, motor vehicles are divided into transport, special, and racing vehicles. Transport vehicles serve for the transportation of freight and passengers. Special motor vehicles have permanently mounted equipment or installations and are employed for various purposes (for instance, fire engine and public utilities vehicles, mobile shops, truck-mounted cranes, and the like). Racing cars are designed for sport contests, including setting speed records (record-race cars).

Transport motor vehicles are in turn divided into passenger cars, trucks, and buses. Passenger cars seat from two to eight people. They come with closed (sedan and limousine), open (phaeton), and convertible (cabriolet) bodies. Trucks are equipped with bodies for transporting freight and have a carrying capacity ranging from 0.25 ton to 100 tons. Trucks without a body or with a small body intended for ballast are designed for handling trailer systems. Called motor-tractors, they are truck-tractors (semitrailers or full truck-trailers). Motor vehicles or tractors together with the trailer system (trailer, semitrailer, pole trailer, heavy truck trailer) form a motor-vehicle trailer train. Buses, which have bodies capable of carrying more than eight persons, are subdivided into city, suburban, intercity (tourist), local service, and other types.

According to their roadability, motor vehicles are divided into road, off-road (quarries), and increased and high roadability vehicles (cross-country vehicles). Road vehicles are designed for driving on the general network of high ways. Off-road vehicles having larger overall dimensions and greater axial loads may be used only on special roads, such as those in quarries. Motor vehicles with increased and high roadability are intended for work in difficult road and roadless conditions. Most vehicles of these types have all-wheel drive (that is, they have a drive for each wheel). Besides those on wheels, there also exist the following types of high roadability vehicles: convertible vehicles with interchangeable tracks or wheels; half-trucks having both tracks and wheels; snowmobiles running on broad tracks or spiral conveyors; motor vehicles on pneumatic roller tires; amphibious motor vehicles, which are wheeled vehicles with watertight bodies and a supplementary screw propeller; air-cushion motor vehicles driven by a tractor propeller or by the reaction of a rearward-directed jet of air from a compressor; and striding motor vehicles that advance by means of shuffling skis. The roadability of ordinary road vehicles can be substantially improved through the use of wide section, highly adhesive ribbed tires on the rear driving wheels.

Motor vehicle construction A motor vehicle consists of a power plant, transmission, chassis, steering gears, electrical equipment, a body for transporting passengers or freight, and a cab (for trucks).

According to engine type, motor vehicles are differentiated as steam vehicles (not in use); gasoline vehicles, with an internal combustion engine operating on motor vehicle gasoline (majority of passenger cars and light and medium trucks); diesel vehicles, with an internal combustion engine operating on diesel fuel (primarily heavy trucks and mul-tiseat buses); bottled gas-driven vehicles, with an internal combustion gas engine operating on compressed or condensed gas fuels stored in cylinders that are mounted on the vehicles (in use only in regions with cheap gas fuel); gas-producing vehicles, with internal combustion engines operating on gas obtained from solid fuel (wood, coal, peat, and various briquettes) in gas generators mounted on the vehicles (in wide use during the Great Patriotic War as a result of a shortage of liquid fuels); gas turbine vehicles, with a gas turbine (as yet not in use but holding promise for future use in heavy, off-road trucks and rapid intercity buses); and electric vehicles, with an engine operating on storage batteries (because of their small range and great weight, these are now used in small numbers, primarily as light city trucks, but they hold promise for the future to be used as cars and trucks when industry will have developed large-capacity lightweight batteries).

The transmission transmits the torque from the engine to the running assembly of a vehicle (wheels, tracks, etc.). A transmission may be mechanical, electromechanical, and hydromechanical. Most widely used is the mechanical transmission, ordinarily consisting of a clutch, which is a coupling device that allows the instant disengagement and smooth engagement of the engine, and of the following transmission mechanisms: a gearbox, a multiple gear reducer that allows for wide variation in the torque at the driving wheels (tractive force) and for driving in reverse; a Cardan drive, shafts with joints that transmit the torque from the gearbox to the axle drive even when the shafts change angles in relation to each other; an axle drive, a gear reducer that constantly raises the torque transmitted from the gearbox to the driving wheels; a differential, a mechanism that distributes the torque from the axle drive among the driving wheels, as a result of which they rotate with different angular speeds on curves and bumps in the road; and half shafts that transmit the torque to the driving wheels.

The axle drives, formerly a pair of bevel spur gears (in trucks two pairs, spur and bevel gears), are now of the spiral or hypoid gear type. Where the engine is arranged transversely, the axle drives are spur gears. Some high roadability motor vehicles or high-tonnage trucks have divided axle drives in the form of a central bevel reducing gear and final (wheel) reduction gears (a pair of spur gears with inner or outer gearing and a planetary reduction gear).

Most promising for the future are infinitely variable transmissions that make driving considerably easier, improve the comfort of the ride, and increase the roadability of the vehicle. These transmissions are frequently called automatic transmissions, since their gear ratios change automatically by means of a device that automatically controls the gearbox or through the combined action of the torque converter and the automatic control device. In wide use are hydromechanical (hydraulic torque converter and variable mechanical gearbox), fluid drive (hydropump and hydromotors), and electromechanical (generator, electrical motors, and mechanical reducing gears) transmissions. Hydromechanical transmissions are most frequently employed in luxury passenger cars and in large urban buses; electromechanical transmissions are used in extra-heavy trucks.

The running gear of a vehicle consists of the frame, suspension, axles, and wheels. The frame serves as the supporting structure for the body, cabin, engine, gearbox, and other mechanisms and assemblies. In most passenger cars and buses the frame has been supplanted by the body, which in this case constitutes its own sturdy and rigid supporting system. The motor vehicle suspension provides a resilient linking of the frame or supporting body with the axles. It transmits the forces acting on the wheels to the frame (body), softens the shock load, and gives the desired character to the rocking, thus ensuring the requisite driving smoothness and stability of the moving vehicle. For a long time motor vehicles used leaf-spring suspension; later, coil springs, torsion bars, and pneumatic or hydropnuematic elements also began to be used as resilient components. Shock absorbers (ordinarily hydraulic lever and telescoping types) are introduced into the suspension system for swift suppression of rocking, and lateral stabilizers are used for lessening the tilt on curves. In wide use is independent wheel suspension, in which each wheel is suspended independently from the frame, so that a change in the position of one wheel does not give rise to a shift in another.

Most motor vehicles have disk wheels consisting of a disk and rim with a tube or tubeless pneumatic tire attached to a hub that is mounted on the axle; heavy trucks and large buses have also diskless wheels with the rim attached directly to the hub.

The control mechanism of a motor vehicle includes the steering and brake systems. The steering system serves for changing directions. This is effected by turning the front wheels, together with the journals on which they are mounted, by means of the steering mechanism (worm, screw, crank, or rack-and-pinion drives) that is linked by the steering shaft to the steering wheel and by the drive system to the journals of the front wheels. To make steering easier, the steering gear is provided with hydraulic, pneumatic, or hy-dropneumatic boosters. In the USSR and other countries with right-hand traffic the steering wheel is on the left side of the car, and vice versa. This improves road visibility, which is especially important when passing another vehicle.

The steering mechanism should provide good maneuverability of the vehicle without side skidding of the steer-able wheels on curves and with a minimal effort at the steering wheel. It ought also to ensure the stabilization of the wheels in straight-line driving. Driving ease is brought about by the appropriate gear ratio of the steering mechanism and steering gear (the power gear ratio is in the range of 100–300). The gear ratio of the steering mechanism is often variable. The steering gear simultaneously turns the steerable wheels at different angles and allows them to roll without side sliding. The stabilization of the steerable wheels—that is, their ability to maintain the position they hold in straight-line driving and automatically to return to that position when the steering wheel is released—is achieved by means of the transverse and longitudinal incline of the pivots of the stub axles. To increase the maneuverability of a vehicle, especially of a vehicle with increased roadability, all wheels (of two-axle vehicles) or the wheels of the two front axles (of four-axle vehicles) are made steerable. It is for that purpose that the wheels of pole trailers or semitrailers in a motor-vehicle trailer train are made steer-able. The brake system serves for slowing down the movement and for complete stoppage (foot brake) and also for keeping the vehicle in place (parking hand brake). The foot brake acts on all wheels. Each wheel has a drum or disk braking gear that operates by means of hydraulic, pneumatic, or pneumohydraulic drives. In the brake mechanisms, brake shoes with friction lining press during braking against the wheel brake drum or disk. Passenger cars and light trucks have a hydraulic brake drive that is often equipped with a vacuum or pneumatic booster. Other vehicles mostly have pneumatic controls using compressed air from a compressor that is activated by the engine. The parking brake ordinarily acts only on the driving wheels (directly or through the transmission).

To increase the reliability of the brakes, use is made of separate brake controls from the single pedal to the front and rear wheels or of dual controls to the rear wheels. Large buses and heavy trucks increasingly employ accessory decelerator brakes in which the braking momentum is often created by the engine as a result of shutting down the exhaust manifold and cutting off of the fuel supply. Also in use are decelerator brakes with electrical or hydraulic braking gear that is independent of the motor and acts directly on the transmission of the vehicle.

The electrical equipment of a motor vehicle consists of the sources of the current (storage batteries and motor-driven generator) and of several user groups. Electricity is required for the operation of the ignition system and for starting the motor and also for the internal and external lighting equipment and for the light and sound signal system. The system of external lighting and signaling includes headlights with a low and high beam (the light parameters of the headlights are chosen to ensure visibility of 100–150 meters of the road ahead when driving at high speeds and to ensure safe travel on a comparatively narrow road without blinding the drivers of the oncoming vehicles); white or yellow lights (fender lamps) showing the frontal outline of the vehicle when driving without headlights during the dark hours over well-lit streets and roads; red tail lights showing the rear outline of the vehicle; turn signals (blinker lights located at the front and rear and sometimes also at the sides of the vehicle); and stop lights for signaling braking. In addition, fog lamps, marker lights, and reflectors and also special lit-up signs (for motor-vehicle trailer trains, taxis, and so on) may be installed. In some countries blinking red tail lights are used to signal that a vehicle is standing on the road.

Many factors enter into the evaluation of the degree of perfection of a motor vehicle’s construction. Construction compactness is determined by the efficient use of the size and weight for meeting the requisite load or passenger capacity of the vehicle and minimal expenditures of materials for its manufacture. Performance is measured by the rate of acceleration, the dynamic stability in direct drive, the maximum speed, and the drawbar pull (for motor-vehicle trailer trains). Fuel economy is related to the fuel consumption for a given transportation assignment (trucks and buses) or for a one-kilometer run (passenger cars). Roadability considers the geometric parameters of the chassis and body (road clearance, angles of overhang, radii of longitudinal and transverse passage), the tractive and drag characteristics, and the unit ground pressure. Convenience of use covers the degree of load safety in transit, the ease of loading and unloading, and the comfort with which passengers are transported (dimensions of the seats and aisles, height of the steps, width of the doors, softness of the suspension, heating, ventilation, and so on). Driving ease is determined by the degree of effort and number of motions required of the driver, the maneuverability of the vehicle, the starting ease, the fuel distance, and so on. Driving safety includes the dynamic driving stability, braking reliability and braking distance, road visibility, the efficiency of the lighting and signaling, and the like. Also evaluated are accessibility for maintenance and repair work, the frequency and labor-consumption of the maintenance and repair work and the ease of access to the components and assemblies when checking, adjusting, or repairing them; and durability and reliability, including the lifetime, the runs between repairs, repair needs, the stability of operations, the rate of breakdowns, freedom from defects, and so on.

The perfection of the construction of motor vehicles foresees the maximum automation of the operations of the assemblies, mechanisms, and systems and also of the driving. Vehicles have been built that can travel an assigned route without a driver or with minimal intervention on his part. In designing new models of vehicles, great consideration is given to the matter of increasing their general reliability and decreasing to a minimum the maintenance requirements. Vehicles designed for the future have no assemblies that require adjustments or periodic lubrication (they employ antifriction materials and permanent lubrication); the oil (in the motor and transmission) may be changed at great intervals (30,000–50,000 km).

The USSR has designed and is regularly improving a long-range series of motor vehicle types meant to completely satisfy the demands of the national economy and population for vehicles of various designations and various load and passenger capacities. This series anticipates an efficient and economically justified quantity of basic models with a large number of modifications based on a broad design standardization of the units, assemblies, and parts. Thus is assured reliable and efficient operation of vehicles under various climatic and road conditions requiring a minimum of expenditures for their maintenance and repair.