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Pegaso quizzed by Leyland

5th March 1971, Page 29
5th March 1971
Page 29
Page 29, 5th March 1971 — Pegaso quizzed by Leyland
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Which of the following most accurately describes the problem?

• Could some means be found to supplement the power provided by a turbo-charger at low speeds to ease the transmission problem? Could the gasoline engine be revived for use in heavier commercial vehicles? Is there a future for steam engines and for engines running on LPG or natural gas, for hydrostatic and electric drives, for independent front suspension and for multiple trailers and guided systems?

Dr A. Fogg, deputy managing director and director of engineering of British Leyland, put these questions to Dr Ing, Carlos M. Carreras, chief engineer and director of the design department of Empresa Nacional de Autocamiones Sa (Pegaso) and president of Fisita 1969 /71, at an I.Mech.E. meeting in Coventry on Tuesday.

Dr Fogg said that turbo-charging could reduce engine noise level by 3 dBa. The Stirling engine was quiet and its use would reduce pollution. He asked Dr Carreras to "persuade Europe" to refrain from being' hysterical about pollution problems, notably the oxides of nitrogen problem.

Replying, Dr Carreras said that the development of the steam engine was possible on anti-pollution grounds but it would be difficult to develop a unit to match diesel and gasoline engines in performance. Electric transmission, too, was a possibility but would increase fuel consumption.

In his paper on the design of heavy commercial vehicles, Dr Carreras said diesels of 450 bhp would be required in order to cater for future power-to-weight requirements on the Continent.

A normally-aspirated engine of this power would have a capacity of 22.5 litres; that of a slightly turbo-charged engine would be 19 litres while with a strongly turbo-charged engine it could be reduced to 14.5 litres. A turbo-charged/charge-cooled diesel of 13 litres could be developed to produce this output. The naturally-aspirated engine would have to be a V10 or V12 unit weighing around 1300kg. Turbo-charging favoured the use of six-cylinder in-line engines although the 19-litre unit could be a V8 or VIO and could weigh 1200kg. The weights of the 14.5 litre and 13 litre (in-line engines) would be 1150kg and 1100kg respectively.

Turbo-charging was likely to come down in cost and its use enabled a wide range of ratings to be obtained from the same basic engine; and a turbo-charged unit had installation advantages over a V engine. Moreover, smoke emission was reduced and rated performance obtained at higher altitudes. As Volvo had shown experimentally, the compression ratio could be reduced to 12.5 to 1 if starting troubles were overcome. It would be possible to operate at a bmep of 185 psi at maximum torque with a peak pressure of 1550 psi. But a turbo-charged engine had to be built for turbo-charging.

The Wankel rotary engine, he said, was unlikely to prove suitable for trucks in the near future.

Mr C. M. Pemberton, of Chrysler UK, commented that fitting the braking system horizontally to make use of half of the foundation brake gear in the event of failure of one section of the system, could have advantages. The stability of artics on roundabouts and S-bends should be improved, but this would not be possible unless radical changes were made to the fifth-wheel. Front-wheel disc brakes were successful but, at the rear, dirt caused excessive pad wear.

Dr Dennis, of Girling, said disc brakes needed more space than drums. The introduction of wheels with 22-in. rims would enable the efficiency of both disc and drum brakes to be increased.

Mr D. K. Roberts, of AEC, said that a minimum speed limit of 50 kph (35 mph) would apply on motorways in South Africa as from April 1, so on gradients of 5 per cent a power-to-weight ratio of 16 bhp /ton would be required.


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