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Factors Affecting Design
Page 127
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THE design of the average goods vehicle depends upon three main factors. First, the class or classes of loads to be carried; secondly, the economic ..
factor ; thirdly, existing legislation. It often happens, however, that the latter two are, to a considerable extent, influenced each by the other, whilst the first cannot really be considered as altogether apart from the second.
Dealing with the loads carried, it is fairly obvious that there should be some distinction between the vehicle built for arduous duty, such as that involved in the carrying of dead-weight loads of a low value-to-bulk ratio and often operating under difficult conditions as, for example, in quarries, on building sites, etc., and another vehicle of the same load capacity but requireJ for service on smooth roads, often carrying valuable' freight and running at a higher average speed.
From the point of view of economy, the initial outlay must not be too great, maintenance will have to be kept within reasonable limits and the running costs must not be excessive.
Weighing-up the Economic Factor.
In considering the economic factor, capacity is, of course, of the uhkost significance, but this, again, is bound up with the matter of loads to be carried and the districts in which the vehicle is to be operated. In congested areas, where the routes are not very hilly and where man ceuvrability is important, the small-engined machine of the motor-horse type is capable of dealing with heavy, loads with a degree of economy which, in the light of the experience of former years, appears almost incredible.
Of the -three influences, however, that exerted by legislation is, perhaps, the most important. By it, the overall sizes and weights of carrying media are con-. trolled, partly by the fixing of certain limits and partly as a result of taxation. The latter is not altogether beneficial and has, in some respects, influenced design in a manner altogether at variance with the intentions of the legislators. Human nature being what it is, vehicle buyers and operators naturally endeavour to obtain the most for their money and try to avoid the employment of means which will result in burdening them with high overhead costs.
There are two ways in which the duty on a vehicle may be kept low. First, there is the all-round lightening of the chassis and bodywork, and this is fostered by the almost universal adoption of the pneumatic tyre ; then
comes the spreading of the load over a large number of wheels, as is particularly the case when the ordinary trailer or articulated trailer is employed. Neither type has been viewed very favourably in the past in official circles, yet officialdom has almost compelled their employment, and their value is being recognized in the new Road Traffic Bill, as is indicated by the raising of the limits of speed, particularly for the articulated, vehicle, which is suffering considerable disability a's a result of the limit of 16 m.p.h.
The legislative encouragement given to the pneumatic tyre has certainly had a most beneficial influence and has, perhaps, done more than anything else to stifle .the Complaints as to the damage to property, noise, etc., which were prevalent when the solid tyre was the y'ogue.
The Influence of Taxation.
In considering taxation, we must not forget its influence upon the design and type of power units. It is quite probable that if the taxation on petrol had, years ago, been as heavy as it is to-day, the steam wagon and battery-electric would not only have retained, but have strengthened their positions ; but with the arrival of the oil engine as an alternative power unit affording great economic advantages, the hopes for these types cannot be considered so promising as might otherwise have been the case. The steam wagon, in particular, may, however, yet regain some of its former popularity, and even make forward strides if given the necessary enconrag,:.ment, presenting, as it does, the unquestionably important advantage of consuming a home-produced fuel.
It is quite probable that the compression-ignition oil engine, because of its high efficiency, would have developed even if petrol had not been so burdenedwith taxation, but the process would certainly have occupied a much longer period.
Despite the fact that much criticism can be levelled at legal restrictions, they have undoubtedly assisted in the promotion of safety-at least, so far.,as the design of what may be termed the standard type CA vehicle is concerned. One has only to study some examples of foreign design with their excessive overhang and most unequal distribution of axle loads, to realize what might have happened in this country had there been no restrictions in respect of such points as these, and we are fortunately not blessed with the class of legislator who introduces demands for restrictions purposely designed to bring work and profit to particular commercial enterprises.