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Fig. 340.—Plan View of the Cadillac 1915 Chassis, Showing Location of

Eight Cylinder V Motor and Unit Gear Set.

Chassis Types. Before discussing the points to be inspected and the manner of making repairs when defects are found, it may be well to describe briefly some of the typical chassis constructions in order that the novice repairman may get an idea of the relation of the parts in cars of conventional design. The side and plan views of a National four-cylinder chassis are shown at Fig. 339, all the important components being clearly indicated. This may be considered a good example of high grade car construction in which the power plant and change speed gearing are separate units. As is apparent, the engine may be removed from the frame without disturbing the change speed gearset while the gear box may be taken out without requiring the removal of the engine. The general construction of this chassis is conventional and follows established automobile engineering practice. It has the virtue of having the parts readily accessible so that repairs may be easily made without disturbing other components except those that are to be worked upon.

The plan view at Fig. 340 shows a chassis of recent development produced by the Cadillac Company which is provided with an eight-cylinder V engine having the transmission gearing incorporated as a unit with the engine crankcase. This construction is more accessible than the usual unit power plant is, owing to the design which permits of removing the transmission case from the engine base without disturbing the power plant. In all other respects this chassis follows conventional practice. The important parts are clearly shown and no difficulty should be experienced in identifying them on the actual chassis.

The repairman will be more often called upon to repair motor trucks in the future than he has been in the past on account of the increasing popularity of the heavy duty vehicle. The chassis construction in the main follows the design established in pleasure car practice, excepting for the use of much stronger parts and a tendency to use standard structural steel shapes for frames instead of the special pressed steel side members commonly found in pleasure car service. The average truck chassis will have a pronounced overhang over the front and rear axles in order to obtain a body of sufficient size without upduly increasing the wheel base. Gear

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Fig. 342.—Plan View of Typical Chain Driven Motor Truck Chassis.

driven trucks do not differ materially in construction as far as relation of parts is concerned from pleasure cars of the present-day type. The worm drive and double reduction axles are rapidly gaining favor and the conventional side chain drive construction to which most of the trucks have been built is gradually being displaced by the more modern forms having a live axle instead of the fixed non-rotating member shown at Fig. 342. It will be remembered by those who have had automobile experience, dating a number of years back, that many of the powerful pleasure cars were fitted with side chain driving systems. The power transmission was to a jack shaft which was practically a live rear axle having sprockets at the axle ends instead of wheels, and from that member to the rear wheels, which were revolved on a nonrotatable axle by means of driving chains. The process of taking down a motor truck chassis and the points to inspect for depreciation would not differ materially from that used in repairing a pleasure car assembly. Owing to the use of solid rubber tires, a motor truck is subjected to much more vibration than a pleasure car, and considerable more attention should be given to the running gear parts, as these may become loose much sooner than on the pleasure car, where all of the load is carried by very resilient pneumatic tires.

No treatise on automobile repairing would be complete without showing details of the Ford model T automobile, which is the most widely used motor vehicle in the world. The reader's attention is directed to the very clear sectional view shown at Fig. 343 for an idea of the arrangement of parts on this universally used motor

The various parts are clearly outlined and may be located by following the leader lines to their termination at the arrow point. The other end indicates the name of the component. The plan view at Fig. 344 gives an idea of the appearance when viewed from the top.

Dismantling a Chassis.—The various steps incidental to dismantling a motor car chassis to give all parts a thorough overhauling is shown at Fig. 345. The plan view showing the appearance of the chassis of a Locomobile car at A denotes the appearance after the body and fenders have been removed. It is always ad

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visable to remove the body and the mud guards before any work is done upon the chassis, and in case of an extended overhauling much time can be saved by sending the body and guards to the paint shop while work is being done on the chassis. This is desirable because the finish of the body is much more important than that of the chassis parts, and it takes more time for the painter to do an enduring painting job on the body than on the running gear. The next step is to remove the running boards and running board irons, if these members are fastened to the frame by bolts. If the running board supporting members are riveted to the frame, it is not necessary to remove these unless the frame side member is to be re-enforced. The wheels are removed from the front and rear axles and the frame supported by special jacks. These may be easily made by using substantial cast iron base plates about a foot in diameter in which a piece of two-inch pipe is screwed. A sliding arm of cast iron made with either a cam or gib keylock, or having a strong set screw to keep it in place when it is set at the proper height, is adapted to move up and down the pipe. In some cases holes are drilled through the pipe and a stop pin used through it on which the supporting arm is allowed to rest. These frame supports have the advantage of not 'interfering with the removal of the various chassis components as they support the car weight directly under the frame sides instead of through the medium of the axles and springs as the ordinary lifting jacks do. Four of these stands are used, two on each side of the car.

The appearance of the chassis with the running boards and wheels removed is shown at Fig. 345, B. The next step is to remove the radiator, the steering gear and the change speed gear controlling members. The clutch and brake pedal cross shaft may also be taken from the chassis at this time. This leaves the frame in the condition shown at C, Fig. 345. The next step is to take off the rear axle, including the propeller drive shaft, torque member and radius rods. The chassis then has the appearance as at D. After the removal of the change speed gearing the parts left are shown at E. The dashboard assembly and the engine are next taken off the frame, which leaves the frame as shown at F. At this time only the front axle and rear springs are retained. When all the

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