In some types of motor cars and in very many motor trucks the steering linkage is ar ranged crosswise of the vehicle, which arrange ment is modified in several ways and can have the advantage, if the front vehicle springs must be of high camber, that the steering action is then less influenced by oscillations of these springs than when the steering rod runs length wise.
Fifth-wheel steering, as standardized for vehicles drawn by animals, is scarcely ever used for motor vehicles of any class, excepting only a few, mostly electric, in which a fore carriage containing the whole power mechanism forms a separate unit coupled to the rest of the vehicle.
The typical system of brakes for motor cars consists of service brakes operated by a pedal and emergency brakes operated by a lever at the right side of the driver's seat. The lever can be locked in any position given it by means of a pawl acting against a notched quadrant secured to the car frame, and the emergency brakes can therefore be used to hold a car on a hill unattended. Linked rods, in cluding an enualizer bar (shown in Fig. 2), transmit movements of brake pedal and lever, separately, to brakes acting on drums secured to the driving wheels. Usually (Fig. 27) the service brakes are brake shoes (faced with friction fabric) which are forced by the turn ing of a cam against the inside of the drum, and the emergency brakes are steel bands lined with special brake-surfacing material, which are contracted by a similar cam action against the outside of the drum. To permit the cooling of the drum, the latter is in some cases widened and the emergency brakes are made like the service brakes and act side by side with them, both sets on the inside of the drums. In many European cars and some American ones, the service brake is single and is mounted upon the transmission as in Fig. 13, usually upon the gear shaft just behind the gearbox and in front of the universal joint connecting with the drive shaft. In connection with this con struction, the emergency brakes are expansion brakes in the rear wheel drums. The use of brakes on all four wheels is practised on a few makes of cars in England and occasionally on a racing car, the systems used in each case being described in the larger textbooks on automobile construction. Hydraulic brakes are used for some heavy motor trucks, largely with a view to the operation of such vehicles on long declivities. For motor cars, hydraulic,
pneumatic and electric brakes are in a state of development. Patented systems exist for utilizing the engine as a brake by omitting fuel-charging and ignition and making the pis tons work against air charges in the cylinders. But these have not been widely adopted, per haps mainly for not being subject to finely graduated control of the braking effect.
Wheels.— The wheels of motor cars are either wood wheels or wire wheels, the wood wheel being a development of ordinary vehicle wheels and the wire wheel of bicycle wheels, and in either case the hub is adapted to be mounted on ball bearings or roller bearings, and the rim is arranged to receive a pneumatic rubber tire. For construction details of wheels, wheel bearings, wheel rims (now usually readily dismountable and called °demountable rims," a corruption of French demontable), and pneumatic tires, see WHEELS; BALL BEARINGS; ROLLER BEARINGS; RUBBER TIRES.
Motor Car Bodies.— The technical develop ment and construction of carriage bodies has undergone radical changes in its adaptation to the automobile and to mass-manufacturing methods. Wood, steel and aluminum are all largely used for the framework and panels of the bodies, with a growing preference for sheet metal work. The painting which was at first a laborious and time-consuming art is turned more and more into spraying and dipping proc esses followed by rapid artificial drying by hot air, taking place while the bodies are carried on conveyor belts from one end of a long build ing to another, and the atmosphere in the build ing is carefully filtered to exclude dust. Fend ers and engine hoods are often made as special ties at outside factories.
A general view of mechanism and arrange ment of an elaborately designed motor car of the °touring cat" class is given in Fig. 28.
Motor Wagons.— The chassis of motor wagons are frequently almost identical with chassis made for motor cars of the same manu facture. But large numbers are especially de signed for delivery of merchandise and express wagon work, and in many of these chassis power transmission is of the chain-drive type, the vehicle springs are less flexible than for motor cars of comparable size, and wheels are larger and are shod with solid rubber instead of pneumatic tires. For technical details, see SPROCKETS; SPROCKET CHAINS; SILENT CHAINS.