The Modern Motor Car Chassis

Side Elevation of a 20 h.p. Daimler.

Another respect in which engine design has been modified to great advantage is with regard to lubrication. The old haphazard methods have been superseded by systems in which oil is taken in properly regulated quantities to all the bearings. Improved lubrication has done much to make possible the high-speed motor of light weight and great power.

Increases in the number of cylinders above six entail the use of V-type engines. For the earlier developments of such designs, the motor cycle industry was mainly responsible. It is also upon the motor cycle that the two-stroke engine has up to the present been most used on land. This type is also very commonly employed in small marine sets, but so far it has not gained a sure footing as a standardised component of the motor car chassis.

PlanPlan-view of a Clement-Talbot-view of a Clement-Talbot

In one particular feature of motor vehicle design, peculiarly little effective progress has been made since the early days. For the purpose of varying the road speeds corresponding to a given engine speed, sliding gears were from the first employed, but it was generally believed that they would rapidly be superseded by something more mechanically sound from the designer’s standpoint. Epicyclic gears have certainly been used to some extent, while electric, hydraulic, and magnetic forms of transmission have also been tried. Despite every effort, however, the old sliding gear, in improved forms no doubt, still represents standard practice.

As regards transmission to the rear wheels, the roller chains originally fitted have been superseded on all but the heaviest vehicles. Where chains are used at all in the transmission, the silent varieties are generally preferred. Chain transmission has, however, largely given way to the system in which the drive is taken through a propeller shaft and gear to a live back axle. On this axle is situated the differential gear, which allows the engine to propel the rear wheels at different speeds while the vehicle is turning a corner. Previously, the differential was placed on a countershaft. from sprockets on the end of which chains ran to chain wheels attached to the driving wheels of the vehicle, the back axle being a solid rod. In the drive to the rear axle, worm gear, originally pioneered by a British firm, is now frequently used, even on the heaviest industrial vehicles.

In the matter of springing, the principal change has been that which has led to the introduction of cantilever springs, though the old types of semi-elliptical spring is still to a great extent used. The interception of vibration from the road has also been assisted by the introduction of shock absorbers. In ,ihe early cars, the wheels were of wood, but metal wheels are now almost universal, and the wire wheel has gained ground. The great advantages which must attend any facilities for dealing with tyre repairs in the garage rather than on the road have led to the introduction of detachable wheels and detachable rims, which, taken together, may now be regarded as of general application.

In respect of tyres, the chief developments have been those aiming, first, at eliminating trouble due to punctures and bursts; and, secondly, at the prevention of skidding and side-slipping. In the latter connection, we have steel-studded tyres, and also rubber non-skids of various types. Ultimately, the latter is most likely to become general, though the metal-studded tyres has advantages on certain classes of road surface.

With the progress of design in the matter of bodywork, we shall deal later on. At the moment, all that is necessary is to mention that the original influence of the horsed carriage has been gradually superseded by rational design based upon the conditions of use of the motor car, irrespective of those of its predecessor. The changes have been in the direction of simplicity of line and contour, and improved protection from wind and rain. In motor bicycles, development has by degrees led to the use of increased power and the common employment of two cylinders instead of one. Following upon the use of higher powers, the transmission system has been modified, the old twisted belt proving inadequate. The modern belt of V-section is frequently used in conjunction with a chain drive and a two or three-speed gear. Many passenger-carrying devices have been tried in connection with motor cycles. The first was the trailer, which was superseded by the fore-car. This, in turn, gave place to the side-car, which is the most sociable arrangement possible, and has proved far more satisfactory in practice than in theory. The line of demarcation between the motor car and the motor cycle industries has been approached from both sides, and is no longer clearly defined. From the motor car there has been developed the light car of low power, while from the motor cycle has come the cycle-car. It is impossible to say exactly where the cycle-car ends and the light car begins.

In marine motors, attention has been devoted mainly to safety against fire risks, and to the use of heavier and cheaper fuels than petrol.

Any detailed consideration of the design of engines and motor vehicles would be beyond the scope of this book. The foregoing brief sketch is intended merely to be indicative of the fact that the industry has not yet reached a state of finality. For some time to come, the general character of its products must vary from year to year. However, changes are now, as a rule, in matters of detail rather than in matters of general principle. Nevertheless, we have to reckon with the fact that the motor is manufactured for the general public and not by one engineer for the use of another, as is the case with most machinery. The public in this, as in other respects, is always liable to be persuaded by the dictates of fashion, and consequently it is very difficult, if not impossible, for motor car manufacturers ever to reach a point at which they can confidently say that there is no likelihood of the design of their products being modified for several years to come. This tendency towards change in design to meet the fancies of the buyer must necessarily be a source of trouble to those who aim at complete standardisation, with a view to marketing their products at the lowest possible price.