Little Chance for Oilers in U.S.A.

18th March 1955, Page 89

18th March 1955

Page 89

Page 89, 18th March 1955 — Little Chance for Oilers in U.S.A.

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Growing Popularity of Cab-over-engine Types of Heavy-duty Lorry : High-horsepower Units Running on Petrol or Liquid Gas

VIOST engines in heavy-duty cornalmercial vehicles in the United States will continue to use petrol with octane ratings of 88-90 Research and liquid petroleum gas. That was the view given by Mr. Robert Cass, assistant president, The White Motor Co., in a lecture which he delivered in London, last Friday, to members of the Automobile Division of the Institution of Mechanical Engineers.

The use of oil engines, he said, was quite small and there seemed little prospect of this position changing. It was generally accepted that unless a vehicle ran 75,000-80,000 miles a year, the use of an oil engine was not justified on economic grounds.

During the past few years there had been a drop from 17.5 per cent. to 7.6 per cent, in the use of oil engines. One explanation was the advantage which the petrol engine of high output had in weight.

In 1954, domestic sales of oil engines in the United States dropped about 38 per cent, below the 1951 figure. The present trend in oil-engine design was towards units of 165-170 b.h.p., and the turbo-charger was, for the first time, making its bid in the commercialvehicle field.

Loop-scavenged Types

Another development was in the direction of the loop-scavenged oil engine which was new to the U.S.A. The extended use of the oil engine, however, would have to await changes other than in fuel economy.

The background against which the heavy-duty lorry was pictured by Mr. Cass was one of continuous runs from San Francisco to Chicago, a distance of 2,300 miles, during which mountain ranges hundreds of miles deep had to be traversed. Mountain passes rose to 13,000 ft.. the temperature at one end being 70F. and at the other 30-40° below zero F.

There were many operations in which a speed of 70 m.p.h. was considered to be practicable in long-distance haulage and vehicles must be capable of meeting those conditions. Their gross weights were up to 35 tons. In some areas the call was for lower speeds with a gross vehicle weight of about 44 tons.

The most significant trend in chassis design during the past four or five years was the cab-over-engine type. The cab could be tilted forward to give access to the engine, permitting the largest engines—those of 200 b.h.p.—to be used.

A vehicle designed to make pallet loading possible had its frame members dropped between the axles. Its principal advantages were a reduction in labour costs, increase in storage capacity within the plant and a reduction in damage to containers, as well as to the goods. In the case of bottled goods of all kinds, as much as 85 per cent, less man-hours were required to load and unload.

Mr. Cass stressed the difficulties which had to be met in complying with the law in the various States. Quoting a typical example, he said that vehicle combinations in respect of length alone would differ legally by as much as 20 ft. as between one State and another.

Front-axle Loading

For instance, in the eastern and middle western area of the United States, where heavy loading on the front axle without relation to wheelbase was permitted, a 35 per ccnt, increase in front-axle loading became possible with a low-bed vehicle. Because a 45-ft. length limit was general, it was also possible to pull a larger container behind or mount a longer body on the chassis.

In the western part of the United States, the length limit was 60 ft. for a tractor-trailer combination. In those States the front axle must be located as far forward as practicable to comply with the law.

As examples of space-saving, Mr. Cass referred to a vehicle in which the depth of the cab was exactly the length of the engine, the radiator being mounted at the rear of the cab on the right-hand side. Tests had indicated a marked improvement in cooling with this arrangement. The saving in length was 7 in.

The ultimate in space-saving had been obtained with an underfloorengined vehicle, "the only vehicle of its type in the United States with a 200 b.h.p. oil engine mounted under the frame immediately rear of the cab, with a dimension of 48 in. from the back of the cab to the front bumper."

The use of carburetted engines in heavy-duty trucks fell into two classes —those using petrol and those running on liquid petroleum gases. The range available was from 120 b.h.p. to 200 b.h.p., with a few of 300 b.h.p. Today, engine components, such as pistons, valves, piston rings and bearings, were good for amazingly high mileages without needing attention. particularly since the advent of Zero-Lash tappets, valve rotators, ni-resist insert pistons and tri-metal bearings. Great strides had been made in reducing fuel consumption, and the largest engines commonly had a consumption rate of 0.5 lb. of fuel per b.h.p.

Fuel injection now had distinct possibilities and, if successful, the margin between the oil engine and the petrol Unit would be much narrower. The price of the equipment had retarded the use of petrol-injection systems, but this could be rapidly changed by new pump developments.

One of the most interesting phases had been the use of liquid petroleum gases in petrol-type engines. A saving of 5-7 cents per U.S. gallon, as compared with other fuels, encouraged the conversion of existing engines, and many thousands of heavy-duty vehicles were running on liquid petroleum gases.

Lack of deposits from the fuel and automatically balanced fuel distribution were other arguments in favour of their use, and mileages in excess of 200,000 Without major repairs were not uncommon.

Gas turbines for road vehicles represented a trend that could not be ignored. Although such a unit could not, at present, compete with a piston engine in respect of fuel consumption. a reduction in internal pressure losses. a rise in operating temperatures and the use of the heat exchanger, would enable some big strides to be made in improving its economy.

Although automatic transmissions were found extensively in private cars. the semi-automatic and fully automatic adaptations for commercial vehicles had not been in use long enough to establish any important operating background. The type of gearbox which had been most widely used was a five-speed unit with either a direct or overdrive top ratio.

Two-speed Axle Favoured

In the medium heavy-duty range24 tons gross—the two-speed axle, in conjunction with a five-speed gearbox. had taken a firm hold. The two-speed axle was much cheaper in the United States than the planetary types of auxiliary gearbox which had been developed in Britain.

The number of heavy-duty vehicles employing power-assisted steering was small, but Mr. Cass thought it would be only a matter of time before its use became more general.

Developments were proceeding with air suspension systems in which the compressor on the vehicle was responsible for maintaining the air supply. In view of the growing demands made on the compressor, some units now fitted were of 12 cu. ft. per min. capacity.

Light alloys occupied a relatively small place in heavy-duty vehicle

design. It was considered that aluminium had disadvantages where the component, such as a rear-axle casing, had to be designed for stiffness and rigidity. It was generally said that an operator in the U.S.A. would pay a dollar per pound weight saved, but a more realistic figure. said Mr. Cass. was 70 cents per pound weight.