1/ PAILLIONTH BEDFORD TRUCK, Noise problems insoluble?
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24Th MARCH 1869
On Monday the Minister of Technology, Mr. Anthony Wedgwood Benn, drove the one-and-halfmillionth Bedford truck from the production line of the Vauxhall Motors Dunstable factory. With over 60 per cent of Bedford production exported in the 12 months up to February this year, it was appropriate that the Bedford—a 16-ton-gross KM model— should have been a left-hand drive chassis. It will be exhibited at the Turin Show next month and then at other exhibitions before going into service. Standing just ahead of the driver's mirrors is Mr. David Hegland, chairman and managing director of Vauxhall Motors Ltd. At a lunch to celebrate the occasion, Mr. Berm paid tribute to the motor industry—"a key industry in our present, and our
future". • Turbocharging will tend to reduce noise and smoke, particularly if lower compression ratios can be used, but other design trends will have the opposite effect. The engine designer will be fighting a battle with regard to noise that he has little chance of winning. An answer will have to be found to the problem, at present insoluble, of total engine enclosure with sound-deadening material.
Mr. C. H. Bradbury, managing director, Simms Group Research and Development Ltd., made these comments in a paper, "Smoke and noise control for commercial vehicles" that he read at a meeting of the Institute of Road Transport Engineers at the Royal Society of Arts centre in London last week.
Earlier Mr. Bradbury said that bigger or faster engines would be built to cater for the higher outputs needed to meet minimum power requirements and that the diesel was firmly entrenched as the principal power source for road vehicles for some years to come. Later, however, he forecast that the gas turbine would increase its penetration into the truck field and might be the -major propulsion unitin five to 10 years time.
Dealing with the use of fuel additives as a means of reducing diesel smoke, Mr. Bradbury asked why, in view of the favourable claims made for smoke depressants, they were not universally employed. Unless or until there was relevant legislation neither the oil companies nor the operators would tolerate the price increase of d per gallon that it would involve. No operator would employ an additive to obtain a cleaner exhaust when by existing standards he had no need to do so.
Mr. Bradbury listed a number of valid claims the conflicting nature of which indicated the engine designer's difficulties in attempting to cope with the noise problem. He said it was rightly stated that for a given power a heavier engine was quieter than one of light construction and also that a low-speed engine operated at a lower noise level than its high-speed counterpart. Designers acknowledged that unsupported flat surfaces should be avoided and that cast covers were better than covers of sheet metal.
Valve gear covers, he said, should be irregular in shape and injectors should be located under the covers. The fuel pump should be mounted on a well-supported part of the crankcase to ensure rigidity and gear trains should be short and compact. Sharp edges on connecting rods, main-bearing supports and so on should be reduced to a minimum to reduce windage noise in the crankcase, and radiator fans should be designed to give minimum blade resonance. The fuel-pump train should be independent of the valve gear.
To incorporate all these features in an engine would be uneconomic. But engine designers were alive to the problems and there was evidence of this in some of the more recent engines developed for road transport.