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down on the steering post, while the long arm performs the same function as the steering arm of a worm reduction gear.

Q. Why are the engine control levers usually carried convenient to the steering wheel?

A. The levers used to regulate the time of the ignition and the amount of gas supplied the motor are invariably placed convenient to the steering wheel so the motor speed may be regulated without removing the hand from the wheel rim, except for an instant. In some cases the levers are

placed under the steering wheel and are long enough so they may be moved without removing the hand from the wheel rim. In most cars the construction outlined at Fig. 205 is followed. The spark and throttle levers are carried above the steering wheel and operate on a fixed sector member which remains stationary whether the hand lever is turned or not.

This means that the levers will always retain the same position unless moved by the operator.

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Q. Name two common methods of front axle construction. A. The two general methods of front axle construction are shown at Fig. 206. The form outlined at A is a tubular axle, while that at B is a one-piece forging termed the I beam axle.

Q. How are the various parts of a tubular axle assembled to form a unit?

A. The tubular axle is composed of a number of castings or forgings attached to a steel tube. In the construction shown at Fig. 206-A the steering yokes and spring chairs are separately

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Fig. 206.-Typical Examples of Conventional Front Axle Construction. A-Tubular Axle. B-I Beam Steel Drop Forging.

formed members which are pushed in place on the steel tube forming the axle proper and after being properly located are pinned in place and then brazed to the axle tube.

Q. What is the advantage of the I-beam axle?

A. The I-beam axle is forged in one piece with steering yokes and spring chairs formed integral and there is no possibility of these members becoming loose as sometimes occurs with poorly constructed tubular axles. The I-beam axle is the strongest construc

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Fig. 207.-Front Hub Mounted on Elliot Type

Steering Spindle.

Q. Name two common type of steering knuckles.

A. The two forms of steering knuckles generally used are the Elliot outlined at Fig. 207 and the

Mercedes shown at Fig. 208. In the former, the wheel spindle is attached to a central body member of forged steel that fits in a yoke at the end of the axle and which rotates on a through bolt passing through the axle and wheel spindle boss and forming a bearing for these members as well as holding the assembly together. In the Mercedes type the wheel spindle is attached to a yoke member while the axle is provided with a simple bearing boss, the two parts being held together by a bolt as in the construction previously outlined.

Q.

tages?

What is the "caster" axle construction and its advan

A. Forms of front axles having a peculiar steering spindle construction in which the wheel spindle center line is carried back of

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Fig. 208.-Front Hub Mounted on Mercedes Type Steering Spindle.

that of the axle proper are termed "caster axles" because the wheels tend to trail along and run straight even if the tie bar joining the two wheel spindles should break or become loose. It is contended that this form of axle provides greater safety on account of the wheels tending to travel in a straight path automatically. Other claims of easier steering and longer tire life are also advanced by adherents of this method of construction which is not very widely used.

Q. What types of bearings are generally used in front wheels?

A. Front wheels are invariably mounted on anti-friction bearing of the ball or roller form. The wheel hubs outlined at Figs. 207 and 208 are carried on ball bearings while the wheel spindles of the heavy truck axle depicted at Fig. 202 and that of the touring car axle at Fig. 201 are mounted on taper roller bearings. A full discussion of anti-friction bearings and their advantages is given in Lesson 25.

Q. How are the springs secured to the front axle?

A The springs usually rest on pads or spring chairs, either attached to the axle as in the built-up tubular construction or forged integrally in one-piece axles and are kept from moving out of place by means of U shaped spring clips which straddle the springs and pass through the spring pads or chairs where they are held securely by means of locking nuts. The construction of a spring pad and arrangement of spring clips are clearly outlined at Fig. 202.

LESSON TWENTY-FOUR

WHEELS, RIMS AND TIRES

Q. What types of wheels are used for automobiles?

A. Automobile wheels may be divided into two main classifications, those made of wood and the forms composed entirely of metal. Wooden wheels are generally of the artillery type, while metal wheels may be any one of four different forms. The most common metal wheel construction is the wire spoked form similar in appearance to those used on bicycles and motorcycles. Other forms are composed of two metal discs riveted to the hub at the center portion and together at the rim. There is another method of metal wheel construction patterned after the artillery wooden wheel excepting that it is made up of tubing and channel sections brazed together to form the complete assembly. A form of metal wheel that is receiving some application in heavy vehicle service is composed of a large steel casting, having fewer spokes than the usual artillery wheels. These spokes are cast with flanges or ribs which act as a reinforcement and the wheel is a very substantial member. Q. Describe construction of artillery wheel.

A. The wooden portions of an efficient form of artillery wheel used for pleasure cars are clearly shown at Fig. 209. The spokes, which are made of hickory, are joined together at the central part of the wheel by a series of interlocking mortise and tenon joints. which form a very strong assembly and they are inserted into holes in a wooden felloe at their outer ends. The complete artillery wheel with metal hub and rim in place is shown at Fig. 210, while the two forms outlined at Fig. 211 show clearly the method of holding the lower end of the spoke securely between the main hub casting and the metal flange which acts as a clamping member. The main casting serves as a housing for the bearings on which the wheel revolves.

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