Why Britisl and American Design, Differ
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A Canadian Engineer Examines Contemporary Trends in Design and Explains the Fundamental Differences Betiveert the Attitudes of British and American Designers and
ATECHNICAL comparison of British and American goods vehicles requires an appreciation of the various aspects of legislative, geographical and economic conditions which influence the design and construction of these vehicles in the two countries concerned.
It is evident, from the differences in operational circumstances, not the least of which are brought about by legislation, that both .British and American goods vehicles are built to meet exacting conditions, and to fulfil their respective country's road-transport needs with maximum efficiency. Therefore, this review will be confined to a definition of the principal differences and requisites of goods vehicles manufactured in Great Britain and the United States.
Tor purposes Of this article, roadtransport operations in Canada will be grouped with those of the United States. as there is a great similarity between the two.
British Design "Artificial"
It would appear to the writer that the British commercial vehicle is somewhat " artificial " in design—at all events, a substantial compromise — and that British designers are necessarily limited in their activities by Ministry of Transport regulations. This view is, however. tempered with due heed for English roads, topography and economics— factors which, in the main, form the basis for governmental control in the first place. Again, the taxation and cost of motor fuels constitute a handicap to be overcome by the British commercialvehicle designer.
Whilst the American motor engineer must worry about gross vehicle weights in 48 States and nine Canadian provinces, he is relatively free from such problems as minimum tare weights, paring operating and maintenance costs, and "engineered longevity." Produc tion costs are an important element in the American designer's work.
With the lighter mass-produced vehicles, this factor can be a greater obstacle to objective engineering than the legislation of all the 48 States and Canadian provinces. Production costs are not so predominently important to the " heavy " manufacturers, all of whom build excellent vehicles capable of many years of hard work.
All points considered, however, the average American and Canadian fleet operator purchases his equipment on what might be termed in England as an " expendable " basis. Vehicles are operated for three years, until an average maximum of 150,000 miles has been reached. At the end of this period, or when that mikage has accumulated, the. operator regards his equipment as fully depreciated, and trades it in part exchange for new replacements.
This is a widespread prodedure . in both Canada and the United States.
consequently One seldom sees really old commercial vehicles in regular use. It is certainly not incidental that this relatively high rate of turnover in American fleets has kept the initial cost of such equipment down to a competitive figure.
The majority of American states will permit a maximum gross load of 18,000 lb. per single dual-tyred aide. which compares favourably with the legal allowance in England. in Canada, conditions are somewhat different, as the average provincialallowance per single axle amounts to 16,000 lb.
Six-wheelers Further, most Canadian provinces do not recognize the rigid six-wheeler h the same light as the three-axled tractortrailer unit. Whereas most of the provinces will permit a maximum of 40,000 lb. gross load on a three-axled tractor and tandem-axle semi-trailer, the rigid six-wheeler has an average provincial gross rating of 22,000-36,000 lb. In view of its higher tare weight, the six-wheeler finds little application in Canada, except for specialized operations off the road. The Ministry of Transport regulations on the axle-weight distribution, in the case of a four-wheeler, allow the British haulier to carry much bigger loads than are permitted in the average state or province. American and Canadian front-axle ratings are worked out. on a percentage basis, usually about 43 per cent. of the gross vehicle weight.
The articulated combination is greatly favoured by operators in North America for long-distance inter-city haulage. With its long wheelbase between the rear axle of the tractor and the rear axle, or axles, of the semitrailer, the articulated outfit is legally recognized with preferential grossweight allowances.
An operator in Canada or the United States is thereby permitted to carry It tons or 12 tons on a Chevrolet, Dodge, or Ford tractor-truck, which, as a rigid vehicle, would have a manufacturer's rated capacity of, say, 31 tons. The semi-trailer's rear axle will be well within most state and provincial regulations if carrying 6 tons, the remaining 6 tons constituting the load upon the tractor's rear axle.
The discrepancy between the vehicle's normal pay-load of 3i tons. and 6 tons as a tractor, is assumed by the manufacturer in his calculations as a probable overload.
It is in this quarter that we see many American and Canadian hauliers duplicating what is, perforce, a regular practice in England, namely, that of using the lightest possible vehicle for a given load. Further, the condition is aggravated by the fact that overloading is carried out as a matter of course. This is not regarded as a serious offence in either Canada or the United States.
It is interesting to note here that most American states and Canadian provinces stipulate that half-loads be carried dur
in,g the Spring season, when road beds are subjected to severe temperature changes and upheavals.
Nearly all American states and Canadian provinces will allow a 50 m.p.h. speed limit on the open road, this applying equally to private cars and commercial vehicles. Although 50 m.p.h. may be the legal limit in many areas, the North American lorry driver does not always live up to the letter of the law in regard to speeding.
The overall approach to road transport differs so greatly between America and England as to be incomparable. A significant indication of the British operator's views is to be found in British craftsmanship and general engineering—qualities renowned the world over.
Keeping Down Costs Hence, with an inherent appreciation of well-finished machinery, British hauliers have a marked preference for workmanlike vehicles of simple design, built in accordance with the best engineering practice. Another consideration of prime importance to the British user, and one which indirectly follows from the above, is his desire for minimum cost of operation and maintenance, plus a reduced rate of depreciation.
It would appear that certain elements of the British operator's outlook on vehicle design and construction arise not from his own preferences, but, of necessity, from legislation. Matters of weight distribution, unladen weight, fuel consumption, and road speed tend to be far more important to the British haulier than they are to his relatively regulation-free American counterpart.
Britain's Road Traffic Act, 1930, plus a high tax on petrol and oil fuel, has created a type of commercial vehicle, particularly among the lighter capacities, which does not exist in the United States or Canada, Thus, in general summary, the conditions which qualify British goods-vehicle design are conformity with regulations, longevity— perhaps the most important single factor—and low upkeep cost.
On the other hand, the American and Canadian operator, devoid of an appreciation of fine design and finish, has a philosophy which is diametrically opposed to that of the British haulier. In America, the lorry is looked upon primarily as a medium for carrying the heaviest load in as short a time as possible, with the least amount of expenditure and effort.
As a consequence, American manufacturers build vehicles designed for the operator's needs, capable of the maximum amount of usage with the minimum of servicing, and with little or no attention to those engineering niceties which appeal to the British goodsvehicle user
Effects of Speed
Geography and climate have a bearing on commercial-vehicle design. The primary difference here lies in the greater distances which must be covered by American and Canadian vehicles, on inter-city runs, at .speeds approaching those set by private cars. In the final analysis, the variation in the speed limits in the two countries dictates the individual trend of commercial-vehicle design.
As cost of operation is by no means as important to the American operator as it is to the British haulier, American manufacturers build lorries with large engines. American operators had a keener regard for expense until the merits of a bigger engine were realized. The swing towards larger power units started in North America when, in 1937, the United States Bureau of Public Roads said:—
" It is apparent, however, that greater hill-climbing ability is an outstanding need of freight vehicles. This may be obtained by providing greater motive power to move present maximum loads, or by reducing the loads to limits fixed by the ability of present engines. But in either case, it will be necessary, if present annoying and dangerous tises are to. be prevented, that the performance ability of trucks and tractor-trucks shall in some terms be exactly defined by their manufacturers, and that by adequate legal regulation and enforcement, the use of such vehicle shall be kept within defined limits."
This was a governmental move to increase the road speeds of commercial vehicles and to prevent traffic congestion behind such vehicles on hills. Whether operators liked it or not, American commercial vehicles were destined to be equipped with more powerful engines. Rather than sacrifice a reduction in payload to better performance, hauliers accepted bigger engines as a matter of • course, and, with an improved poWerweight ratio, actually made more money by speeding up their schedules to offset the increase in fuel costs.
The British 30 m.p.h. and 20 m.p.h. speed limits, plus a system of taxation on unladen weight, do not promote what the American designer would term a good power-weight ratio, although economical operation is most certainly achieved.
In certain classes the British commercial vehicle may have lighter unladen weight than similar American types, but this may not necessarily be an advantage in the long run. Conversely, the heavier types of American goods vehicle frequently weigh less than Britistk, "heavies."
Whilst the British designer of this class of vehicle strives for longevity— hence the increased weight—the Amen can engineer attempts to reduce weight in an endeavour to keep the gross vehicle rating within the allowances of 48 states and nine provinces. Whereas the British engineer usually prefers a rigid threeor four-axled vehicle for the heaviest loads, the American designer bases his calculations on the truck as a tractor in an articulated combination.
Although the typical British haulier expects design amenities in his lorry, he must also be willing to pay for the increased production costs of such work. The American operator, however, seldom cares how his vehicle is put together, just so long as it will pull 15 per cent. more load than its nominal pay-load rating, be capable of sustained speeds anywhere from 35 m.p.h, to 50 m.p.h., and operate with a reasonable degree of upkeep economy, which means 50,000 miles of hard service between major engine overhauls.
Many medium-capacity and heavy British goods vehicles appear to be built with maximum accessibility and ease of maintenance in mind. Although the average American operator would like this quality in a vehicle, he is not willing to pay the additional expense incurred.
Complaints on this score are numerous and loud, but most American manufacturers would hesitate to drop the current bulbous sheet-metal work and "tinware" in favour of accessibility, if it meant an increase in the selling price. In any case, the American manufacturer of commercial vehicles believes almost as strongly in seasonal models as do his contemporaries, the car producers.
Except in certain areas, and in public service vehicles, the oil engine is still not popular in North America. There are only about 450 oilers in the whole of Canada.
It is granted that the oil engine has superior operating economy, but its use in most American heavy vehicles has not been on that account, but rather on its flat-torque characteristics. Even so, the typical American oil engine develops peak torque at a figure in the neighbourhood of 2,500 r.p.m., as opposed to 2,000 r.p.m. in England.
There is a marked difference between the British lorry cab and the type commonly used by American manufacturers. The American cab is a robustly constructed pressed-steel design, and is fitted out with .the appointments usually associated with the private car.
Extremes of climatic conditions throughout North America demand greater insulation and weatherproofing
of the cab than is the practice in England. As an indication of the standard of driver comfort in the United States and Canada, many a driver on longdistance haulage wilt purchase a car radio at his own expense to brighten what would otherwise be a monotonous occupation. Indeed, lorry drivers will often go'so far as to fit their cabs with cigarette lighters, oversize heaters, and other accessories not normally provided as standard.