Oil Engines and Bodywork Under Review
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ON Saturday, November 7th, two papers were read L./before a conference of the Omnibus Society, at Olympia, during the Commercial Motor Show. The first was that of Mr. G. It. Hutchinson, M.I.Mar.E., entitled "The Heavy-oil Engine for Passenger Vehicles."
The oil engine has now established itself as a sound proposition, technically and economically, for passengervehicle work, said Mr. Hutchinson. The efficiency of this type of unit is materially higher than that of the petrol unit, and fuel-consumption figures over a wide range of road speeds are considerably better with the former type of engine. With the oil engine the torque is superior to that of the equivalent petrol unit.
The author thought that as experience is accumulated, oilongined chassis would probably have one gear fewer than the equivalent petrol-driven machine, and he saw no reason why a straight-eight oil-engined bus should not have a twospeed gearbox.
The' key to the production of an efficient high-speed oil engine is fuel injection and combustion, and absence of smell, noise and, in most eases, vibration are intimately concerned with this twin problem. Mr. Hutchinson next dealt with the technical features of various types and makes of oil engine, and remarked that the chief outward difference lies in the placing of the oil injector. He was critical of some patterns of oil engine, and quoted fuel-consumption figures for various high-speed types. These, he said, vary from 0.385 lb. per b.h.p.-hour to 0.52 lb. per b.h.p.-hour in engines of about the same cylinder dimensions, rating and r.p.m., and are for consumptions at full load or approximately so.
Mr. Hutchinson said that it was a fact of the utmost technical significance that high-speed oil engines giving the best performance in service have shallow, cylindrical combustion chambers formed by a flat cylinder head and a fiat piston crown. The atomizer is located in the centre of the head.
He considered that in a few years' time the open combustion chamber, generally with organized turbulence, and the air-cell systems, would probably represent the majority of designers' ideas on the subject, and he believed that proprietary fuel pumps would, as at present, be widely used.
Looking into the near future, the author foresaw the adoption of oil engines for long-distance coach work, and he anticipated smaller and faster-running engines.
In his opinion, increased power per cubic in, of cylinder volume will be obtained by recourse to supercharging for high-performance coaches. He suggested that a high-duty, supercharged oil engine for coach service might have four inclined valves per cylinder, two being for air inlet arid two for exhaust. One inlet valve of each cylinder could draw in atmospheric air, in the usual way, whilst the second valve could "top up" the cylinder with a charge of high-pressure air from the supercharger.
For long-distance coaches the author favoured straighteight engines equipped with 24-volt starting motors. The engine would be mounted on Silentbloc bushes at three points in the chassis.
When the meeting was thrown open for discussion, Mr.
Regnauld, B.Sc., M.I.E.E., a a expert, raised the question of the wider use of two-stroke oil engines for road vehicles, but Mr. Hutchinson, in replying, said that, in his opinion, the two-stroke cycle was not suitable for small oil units.
Variety in the afternoon's proceedings was provided by Mr. C. E. Lee, C.I.Mar.E., Assoc.Inst.T., M.J.I., who read a paper entitled "Modern Tendencies and Their Influence on Vehicle Design."
The author divided his paper into two parts, the first consisting of an outline of his views on the most suitable spheres of work for double-deck and single-deck passenger vehicles. The double-decker had, he remarked, become generally used on urban routes serving densely populated areas, but, in his opinion, this was mainly -the result of restrictive legislation.
According to recent decisions of the Traffic Commissioners, they appeared to recognize the need for duplicating services at peak periods. This might lead to the adoption of rapidloading single-deckers for local traffic, leaving the night and morning business traffic to limited-stop double-deckers eharging a minimum fare sufficiently high to discourage purely local travellers.
During slack hours the single-decker could operate a frequent-interval service more economically than could the larger type of vehicle, and would be duplicated during rush
hours, thereby absorbinab more staff and probably easing the difficulties of preparing duty schedules.
The author also advocated the employment of doubledeckers on limited-stop routes of about 40 miles, as well as for heavy traffic to the seaside, such as from London to Brighton. Mr. Lee thought that double-deckers would prove useful on long routes, too.
In the second part of his paper the author critically outlined some of the outstanding tendencies in bodywork design, and the position of the entrance in relation to rapid loading was discussed.
Influences which tended towards standardization next came under review. The Road Traffic Act with its reference to type vehicles was, he intimated, a contributing factor, whilst another influence was the existence of various purchasing committees formed by groups of large operators.
Mr. Lee considered that longitudinal seats on coaches were sources of "real and justifiable annoyance" to passengers, and stressed the importance of making all seats to face forwards.
He was dissatisfied with the ventilation of some existing coaches, and advocated the use of a system more on the lines of that employed on seacraft.
Mr. Lee struck a particularly controversial note when he voiced the opinion that sliding roofs would not find widespread acceptance amongst operators. The author was also dissatisfied with many existing arrangements for carrying passengers' luggage, and thought that considerable improvements would have to be made.
In conclusion, he deplored the use of unessential accessories on service buses, although, on coaches, such fittings as blinds, clocks and so on were attractive. He was, however, rather surprised that little attempt had been made to meet the smaller requirements of travellers by providing on coaches slot machines for chocolates and cigarettes.