BUILDING FOR SPEED

Evening Post, Volume CXIX, Issue 128, 1 June 1935, Page 30

BUILDING FOR SPEED

ENGINEERING PROGRESS

THE LIGHT GERMAN RACERS

The "Automobile Engineer" remarks that from the year 1898, when the fastest land speed by a petrol vehicle was in the neighbourhood of forty miles an hour, until the year 1926, when the record stood at about 170 miles per hour, the increase in speed from one land-speed record attempt to the next followed a tolerably stable curve. Any engineer, < studying the past figures and constructing a graph from them, would have hazarded a guess that a land speed of 200 miles an hour ought to be achieved by approximately 1945. Actually, the graph steepened in the year 1927, when the record made a sudden leap of nearly 40 miles per hour, and passed the round double century, which precedent;

suggested could only be attained after another twenty years of painstaking research. But the year 1927 was in no sense epoch-making so far as general engineering and the history of the internal-combustion engine are concerned. No sensational discovery in power outputs was made. Still less was it suddenly found that all theories about wind resistance had been mis- • taken. The actual explanation of the surprise of 1927 was very much simpler. Sir Malcolm Campbell merely took an enormous engine which had been evolved for racing seaplanes, put it in a chassis larger than any motor-car had ever employed before, covered it with a streamlined, low-resistance shell, and the sudden leap in the graph of record speeds followed automatically. The subsequent smashing of the 1927 record, which added nearly seventy miles an hour to an already sensational' speed, was due to further ' experience with the same equipment. The chassis had been still further improved little by litle, so that there was less tendency to wheelslip, less resistance to the air, and the brakes could stop it within the space available at Daytona; Simultaneously, the special racing tires had been rendered capable of lasting ten miles at speeds which would have disintegrated the ' tires used in 1927; and the great seaplane engine had been tuned to furnish a fractionally greater horsepower. Dealing with the question, a writer in the "Manchester Guardian" says:— ''Nobody, and least of all no Englishman,: would ever say a word to deprecate Sir Malcolm's immense, courageous, and enviable achievements or those of the technicians associated with the various firms that manufactured his car. But in the whole history of his onslaughts upon this coveted record there.is not one outstanding technical discovery, either in respect of streamlining or .of extracting phenomenal power from engines of a given cubical capacity. 'Technically, a deeper interest actually attaches to the recent speed achievements of two German cars, feats which are still unrecognised by the man in the street. The Blue Bird has an engine of 36J-Htre capacity and weighs five tons. While it can undoubtedly travel at 300 miles an hour, supposing a safe track for the purpose can be discovered, and it is booked' to attempt that speed on a ten-mile stretch in Utah at its next essay, it is technically less remarkable and less interesting than two comparatively small German cars. Not long ago a four-litre Mercedes racing car clocked a speed of just under 198 miles per hour, on a straight road. At a level rate of engineering progress this speed was not due till 1945. If a motor-car of touring dimensions with an engine of normal size has antedated such a feat by nearly twenty years, some real progress is indicated. Nobody in Britain is as yet permitted to know how the Mercedes engineers have accelerated the normal increase in efficiency. "Even more marvellous is another German racing car which early this year on an Italian Auto-Strada missed 200 miles per hour by as small a fraction as .89 miles per hour, and will undoubtedly touch 200 miles per hour before we are much older. The engine of this Auto-Union car is oneseventh the size of the Blue Bird's engine, and the complete car weighs 15cwt as compared with Blue Bird's five tons. "Here is real progress and real engineering genius. In the first place the weight of the car has been scientifically reduced to a figure normally associated with small touring vehicles. In the second place, a five-litre engine (of the sixteen-cylinder type with two banks of cylinders arranged V fashion at an angle of 45 degrees) has been mounted at the rear of the chassis. The speed possibilities of an ultra-high power-to-weight ratio have been understood for years; but in practice they have not previously been exploited on this scale because the wheelspin associated with such designs is usually terrific and well calculated to destroy any tire, most of all the thin-skinned tires which alone can resist the enormous centrifugal forces generated in their casings at very high speeds. But the Autc-Uriion is. comparatively immune from wheelspin, thanks, to a special form of rear suspension under which each rear wheel is separately sprung. A casual glance at the naked chassis reveals that all the important mechanism is mounted at the stern. The front two-thirds of the chassis serves merely as a sort of extension to carry the 1 driven the jadiatefc *ind- .the steering

gear; it consists of little more than a couple of narrowly-spaced side-tubes, braced by sturdy tubular cross-mem-bers. The light streamlined shell is built to weigh next to nothing, and in no sense stiffens up the car as a whole."