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Design and distortion
Page 35
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CHANGES in vehicle or power unit design result from a variety of pressure-s. Most important and most relentless is the competitive spur, usually compounded of customer demand and the knowledge of what rivals are doing or planning. It is this sort of pressure which has, for instance, inspired such purpose-built vehicles as the insulated, heated and refrigerated types featured in this special issue.
Sometimes an engineering change stems more from a manufacturer's own initiative than from any overt customer demand. But even this sort of progress usually reflects a foreseen demand.
An excellent example is the gas turbine for trucks— which Leyland, for one, is now publicly committed to producing. Is there great demand for it? No, not yet. But the LMC believes the demand will come.
When it does, the fruits of US gas-turbine research by Chrysler, Ford and General Motors are likely to be made available to sister companies in Britain. The rapid build-up of demand will come when social pressures for quieter vehicles confront the economic (and, ironically, social) demands for higher-performance trucks to carry yet greater loads.
Road diesels in the 300/500 b.h.p. class are likely to present daunting problems of noise suppression. The turbine avoids this, is lighter and more compact and could perhaps meet these very big c.i. engines on price; now engineers will hustle to ensure comparable fuel economy, reliability and acceptable throttle responsiveness.
A third source of design innovation is unfamiliar but could become significant as the pace of progress increases: the change enforced by world shortages. For instance, last week in CM a staff writer forecast the eventual switch to electric propulsion when natural fuel sources (oil, coal, gas) run out.
All these changes are either desirable of inevitable. But there is another sort: that dictated by arbitrary legislation unconnected with true economic or engineering pressures.
For years the RAC-horsepower-rating system encouraged long-stroke engines in cars (and thus light vans). When the car-tax system was changed, designers went in for the more ideal short-stroke engines. And do you remember the 3-ton dividing line for commercial speed limits? That was responsible for some unsatisfactorily lightened chassis.
Now we are faced with another arbitrary division5 tons unladen—this time to suit a largely political purpose. Despite the safeguards implicit in the type approval, this must exert a pressure for change which is outside the mainstream of engineering progress: in a phrase—design distortion. Yet another reason for resisting Mrs. Castle's quantity licensing plans.