Engineering News
Page 16
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Encapsulation 1990
THE CONSENSUS among European vehicle manufacturers is that engine encapsulation will be the only way to meet the drive-by noise limits of the late 1980's. This was made clear at an I Mech E conference on vehicle noise and vibration last week (see previous page).
Peter Fietz, head of DaimlerBenz's noise legislation department for lorries and buses at Stuttgart, said that the effect of the revisions to the noise testing procedure, which are defined in the EEC directive 81/334, was to lower the limit by 2-5 dB (A). A further reduction in the limit is expected to be implemented by 1988, and certainly not later than 1990. "This means complete encapsulation will be necessary by then," said Mr Fietz.
Kit Mitchell, head of vehicle engineering at the Transport and Road Research Laboratory, who presented a paper on the UK's QHV 90 project, agreed that at least some encapsulation will be necessary. "It is likely that even with a quiet engine and auxiliaries, and an effective exhaust silencer, some shielding of the complete power plant will be needed to achieve the desired levels of quietness," he said.
He, and the manufacturers participating in the QHV 90 project namely Bedford, Cummins, ERF, Foden, Ford, Gardner, Leyland, Perkins and Rolls-Royce (Perkins Shrewsbury), have recognised the maintenance problems which shielding can cause. "The vehicle manufacturers hope that on the vehicles built as part of the QHV 90 project, noth ing more complex than tunnel enclosures will be needed," said Dr Mitchell.
QHV 90 (Quiet Heavy Vehicle) is a E10m, 5-year project funded jointly by the UK Government and vehicle and engine manufacturers. It will include research on heavy goods vehicle noise and the development and testing of prototypes of quiet vehicles, engines and systems components.
The current EEC noise limit for a goods vehicle over 12 tonnes gvw and with power rating over 200hp is 88 dB (A). The EEC Commission proposal is that by October 1, 1989, all goods vehicles over 3.5 gvw should be below the 84 dB (A) limit.