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Engine Performance Offers Scope for Economy

2nd May 1952, Page 32
2nd May 1952
Page 32
Page 32, 2nd May 1952 — Engine Performance Offers Scope for Economy
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Which of the following most accurately describes the problem?

THE most fruitful source of investigation into the problem of increasing the efficiency of vehicles is the economics of engine performance. Whereas the overall efficiency of a good mechanical transmission is as high as 93 per cent., ,leaving little room for improvement, the thermal efficiency of a good direct-injection oil engine is 37 per cent., and for some petrol engines as low as 23 per cent.

Mr. G. Waring, A.M.1.Mech.E., research engineer of Leyland Motors, Ltd., and Mr. F. W. Margetts, A.M.I.Mech.E., productiml manager of the Leyland research dtsion, made these observations in a paper, "Factors Affecting the Economic Operation of Commercial Vehicles," read to the north-west division of the Institution of Mechanical Engineers, last week.

Much had been done to secure engine economy by extending the overhaul periods up to 200,000 miles, they said.

Power and Weight It was contended that 5-6 b.h.p. per ton would be acceptable for a heavy goods vehicle, whilst for a bus 9-10 b.h.p. per ton would be reasonable in Britain. Using these figures as the basis, a 44-seat single-decker would require 30 b.h.p. for the passengers and 2i times this amount (75 b.h.p.) to move the unladen vehicle.

Every effort should, therefore, be made to reduce the unladen weight, because for every ton, saved, engine power could be reduced by 10 b.h.p. This saving in power, roughly translated into fuel consumption, represented an economy of 1 m.p.g.

Manufacturers had already done much to extend the overhaul periods of chassis units. The use of rubber bushes in shackle pins provided a probable mileage of 250.000 before replacement. Hard chromium-plated kingpins and sleeves embodying automatic lubrication would cover this distance without attention, and it was then necessary only to rotate the components through 90 degrees to duplicate this mileage.

Stress was laid upon

the desirability. of

examining lubrication records for all major chassis units at intervals of at least three days to ensure that undue amounts of lubricant were not being consumed. Extensive tests carried out to determine the effect upon fuel consumption of the number of stops per mile made by a bus showed • that five to seven stops per mile increased consumption by 7 per cent.

Siting Bus Stops

It was suggested that city bus stops should be placed on the departure sides of traffic-light controls at intersections, thus avoiding stops whenever the lights favoured an approaching vehicle.

The choice of gear ratios was also important.. It was desirable that a bus should be able to restart easily in second gear on slight gradients when half laden. ••••\ The 35-gallon fuel tank usually fitted on modern vehicles was seldom emptied below the one-third mark. A 10-gallon reduction in capacity was suggesjed. This would save about 100 lb. of load.

On all services, particularly on circular routes, with an overall running time of 30 minutes or less, singledeckers should be used in preference to double-deckers. Not only were they lighter, -but there was less chance of fares being uncollected. Body weight could be reduced by revising seat design and using thinnersection pillars and panels. Lighter glass could also be fitted. A saving of 600 lb. was possible by the adoption of such means.

GLASS PLASTICS CONVENTION A GLASS-RESIN plastics convention, ft said to be the first to be held in Britain, is to be staged at Ashborne Hill, Leamington, on May 13-14. The purpose is objective •discussion of the manufacture, application and future of these new structural materials. It is being organized by Fibreglass, Ltd.


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