I.A.E. It is a legitimate criticism of many motor-racing
a many lectures to say that the lecturers are preaching to the converted. All the more credit, therefore, to Laurence Pomeroy, for delivering a dissertation on the lessons from motor racing to the London graduates of the I.A.E., an audience of young men who may have a big influence on the future of British racing.
Before getting down to his subject in earnest, Mr. Pomeroy made it clear that he did not intend to discuss the thorny subject of whether racg lessons were applicable to production cars, or why manufacturers of excellent racing cars sometimes built such terrible tourers. He intended to concentrate on the direct lessons learned from racing, and often forgotten again all too quickly—a fact not imassociated with designers failing to share with others, through the technical Press, the secrets of their successes or failures.
Contrary to the belief of some folk, racing engineers are not possessed of any secret powers. Although they may sometimes obtain surprising results, theory and practice usually agree closely: victory going to the car which is technically superior to its rivals.
In the years preceding the present war, the lecturer suggested that the most valuable developments had concerned chassis design, despite which it is still possible to build a car which is too light. German cars built to the 3-litre formula., weighing about 2,900 lb. on the starting line and with 440 b.h.p. available, were as fast on road circuits as the ‘750 kilogram” cars for which the corresponding figures were 2,500 lb. and 600 b.h.p. Apparently, in the present state of knowledge, the German engineers regard one ton as the ideal unladen weight of a racing car.
With moderate power outputs, the much-maligned swing-axle system of independent rear suspension was satisfactory. With more than about 300 b.h.p., however, it becomes necessary to brace the system with fore-and-aft radius arms, which steer the wheels slightly as the springs deflect and make the car difficult to handle. The De Dion system, used eventually by both Mercedes and Auto-Union, proved very satisfactory.
Modern practice was to use chassis frames of tubular section, either normal circular tubes or oval tubes fabricated from two halves being employed. Brakes were invariably of the hydraulic variety, using two (or more) leading shoes, welded-up steel brake shoes being employed in preference to the lightalloy variety.
Engine design has developed much less during recent years than has chassis design, the one real innovation being the two-stage Roots supercharger. The single Roots blower is small, reliable even at a speed of 20,000 r.p.m., and mechanically efficient, but it is an inefficient pump for high-pressure rises. Vane blowers are much better as pumps, but they need lubrication, and oil lowers the rating of any fuel. The two-stage Roots blower manages to combine the advantages of both types, and when it was fitted to the Auto-Union the blower power consumption fell from 190 h.p. to 120 h.p. for the same 18-1b. boost pressure.
An interesting point is that all the most efficient racing engines make wide use of roller beatings. Accurate figures concerning the gain in power output obtained in this way are hard to come by, but it seems that it is probably in the region of 10 per cent., and apparently the German cars did not require any bearing replacements during the racing season.
Although pump petrols improved enormously between wars, racing fuels showed no corresponding progress. Alcohol is still generally used, sometimes with small amounts of acetone and water also. Mr. Pomeroy concluded the lecture by showing a number of drawings from the Motor, many of them awful examples of how not to design a racing car. Be told how replacement of the beautiful (to look at) induction system of a tnonoposto Alfa-Romeo by one giving evenly-spaced suction impulses gave a 2 m.p.h. increase in lap speed and lowered the boost pressure from 9 lb. to 3 lb./sq. in. But, instancing the single camshaft Bugattis with their almost uncooled cylinder heads and with flat surfaces everywhere (oven on the crankshaft I), he pointed out that
a bad design well made can be much more effective than a technically-sounder layout which cannot be made satisfactorily. The engine, which was described as ” a sort of racing gas-engine,” had best remain nameless.
From the discussion which followed the lecture, it was evident that the audience (unusually numerous for such a meetin*) fully appreciated Mr. Pomeroy’s talk, and the meeting eventually had to be terminated by the chairman at quite a late hour. All were not familiar with the subject, as witness a query concerning the possible results of supercharging the 3-litre Ricardo-Vauxhall, but there was no doubt of the interest which had been aroused.
A considerable amount of interesting information came to light during the discussion, particularly concerning the modifications made to the 1+-litre Delage at the time of its come-back. It appears that engine modifications comprised little beyond an increase in compression ratio, together with restoration of the valve Wiling to Delage settings which did not correspond to the marks on the timing gears. For the rest, weight reductions, hydraulic brakes, and wider-spaced front springs accounted for most of the extra speed—these and the addition of a first-class driver, as Joe Craig remarked.—J. L.