Racing Car Evolution Part III (Continued): 1926-1927

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With Some Notes on Earlier Racing

By Laurence Pomeroy

This is Laurence Pomeroy’s third contribution to the Evolution of the Racing Car series. The first article was written by Cecil Clutton and covered the period 1895-1908; it appeared in the issue of March, 1942. The next contribution was by Anthony Heal and covered the 1909-16 era (September, 1942). Laurence Pomeroy dealt with the periods 1919-21 and 1922-25 in the October and November issues last year, and he now deals with the years 1926 and 1927, and with the development of the 1.5 litre racing car from 1920-25. The next article will cover 1927-33, and will conclude this valuable and unique concise review of racing car development from the earliest times until the present day, racing from 1934-39 having been covered in an earlier series of articles in “Motor Sport” in 1940 and 1941.—Ed.

In my last article I carried the story of G.P. formula racing up to the end of 1925. At the close of that season the 2-litre cars, which had provided such splendid International competition since 1922, were laid aside, and designers concentrated on the task of producing new models for the 1.5-litre maximum-capacity rule, which was projected for 1926 and 1927. Before I consider in detail the models produced for these two years it will, I think, be of value to deal with 1.5-litre racing which had been seen between the close of World War No. 1 and the end of 1925.

I have not been able to include these in previous articles, except to mention that the first voiturette race was organised in 1920 and was won by three Bugatti cars, which had, in fact, been built in 1914. In 1921 Bugatti again scored a victory on the Brescia circuit, when he averaged 72 m.p.h. in a race that was run shortly after the Italian Grand Prix. It was in this event that the famous “Brescia” model made its first appearance, and although it followed in the main the classic Bugatti lines, it differed from his previous racing cars in that the bore was increased to 69 mm. (the stroke remained at 100 mm.), whilst a built-up crankshaft was employed, with ball-bearing centre main. These engines developed approximately 45 b.h.p. at 4,000 r.p.m., and had a maximum safe limit of perhaps 5,000 r.p.m. This was Bugatti’s last win in a major event for cars of this capacity for four years.

During this period one marque—Talbot-Darracq—dominated the field. This team secured their first win in the voiturette race on the Le Mans circuit in 1921, where Rene Thomas won at 72.1 m.p.h., which compares very favourably with the Bugatti speed of 57.6 m.p.h. in the previous year. Lee Guinness and Segrave finished second and third.

The engines of these cars were in effect 4-cylinder editions of the straight-eight 3-litre S.T.D. (designs which I dealt with in the first part of my article), and they developed about 55 b.h.p. at 5,000 r.p.m., the bore and stroke being 65 x 112 mm., and there being two camshafts operating 16 overhead valves inclined in the cylinder head at 60 degrees to each other. A 3-bearing crankshaft and twin carburetters were provided, and plain bearings were used throughout the engine, whilst the chassis was of orthodox construction, with front wheel brakes.

These models followed up their Continental win by running away with the first 200 Miles Race at Brooklands, in which Segrave was first at 88.2 m.p.h., followed by Guinness and Malcolm Campbell. This, incidentally, was Segrave’s first win in a major event. In the course of this win the Talbot-Darmcqs showed a clear superiority in speed over the Bugattis, the best of which finished fourth.

The year 1922 saw Talbot-Darracq supremacy maintained, with the same cars running completely unchanged. They started by securing first and second places in the 1.5-litre race in the I.O.M., followed by first, second and third places in the French Light Car Cup race at Le Mans, first and third in the J.C.C. 200 Miles Race, and first in the Penya Rhin G.P.

Despite this apparent clean sweep, in point of view of speed they were closely rivalled by the twin o.h.c. Aston-Martin, a design which really consisted of half a 3-litre straight-eight Ballot placed on a crankcase and crankshaft originally designed for a side-valve engine. The bore and stroke were 65 x 112 mm., as on the Ballot, and these cars actually proved superior in speed during the opening laps of the 1922 200 Miles Race, whilst Zborowski was runner-up to Guinness in the Penya Rhin event. It is worth mentioning that these cars were amongst the first to employ alcohol mixture, and were supposed to have derived an additional 1.5 m.p.h. on this account.

In the remote mountains of Sicily Mercedes also started something by running the first supercharged racing cars of European design, but, largely owing to chassis defects, these models did not, in fact, prove so fast, even in the 1.5-litre class, as cars of much more humble origin. However, in 1923 Fiats decided to supercharge a 1.5-litre 4-cylinder car, which once more was really half one of the straight-eight 3-litres which I have discussed at some length in previous notes.

This model made its first appearance in the 200 Miles Race at Brooklands in 1923. Public report of its great speed was sufficient to cause the S.T.D. directors to keep out of the entry lists far this race after they had again won the voiturette race at Le Mans, this time at 71.5 m.p.h. The Fiats speed was certainly no myth, for the two cars, driven by Malcolm Campbell and Salamano, achieved the honour of being the first cars of their capacity to lap Brooklands at over 100 m.p.h., the actual speed being 101.64 m.p.h. Nevertheless, they failed to win, both suffering from engine trouble, and, as a result, victory went to an Alvis, which was nothing more than a highly-tuned edition of the standard “12/50” sports model. This notwithstanding, it achieved the excellent average of 93.29 m.p.h., i.e., 5 m.p.h. faster than the Talbot-Darracqs, which had had pure racing-car lineage. The latter team secured a final triumph with their 65 x 112 mm. engine in the 1923 Penya Rhin race, once again being chased home by Zborowski and his Aston-Martin.

In 1924, as I have previously mentioned, Bertarione left Fiat and joined the S.T.D. combine. His known influence on the Grand Prix cars was equally apparent in the case of the 1.5-litre models. The by now three-year-old Talbot-Darraeqs were abandoned and replaced by a brand new design which was called, simply, the Darracq. It was a scaled-down version of the 2-litre G.P. Sunbeam, but differed slightly in that the bore and stroke were 67 x 105.5 in place of 67 x 94 mm. Mechanically the engines were virtually identical, except, of course, that. the smaller unit had four cylinders and a three-bearing crankshaft. The cars were immediately successful, and gained a superiority which may best be indicated by their 200 Mile Race performance, wherein they finished first, second and third at an average speed of 102.27 m.p.h., i.e., one m.p.h. faster for the full distance than the best Fiat lap of the previous year.

By now other designers were leaning towards supercharging, but neither in 1924 nor in 1925 did anyone contrive to get anywhere near the Darracq performance. Superchargers were fitted to side-valve Anzani engines, also to some specially built Alvis cars which had straight-eight engines and front-wheel drive. A further development was a supercharged 8-valve Aston-Martin, but none of these broke the sequence of Darracq wins which included, in 1925, a race on the Montlhery circuit, where they were first and second, this order being once again repeated in the J.C.C. 200 Miles Race, in which the Outer Circuit was abandoned in favour of a course with artificial corners.

Nevertheless, this year did see a portent of the future in that Bugatti reappeared on the scene with some straight-eight 1.5-litre engines fitted in what was virtually a Type 35 chassis, and having natural aspiration. With these he won the Italian 1.5-litre event at Monza, averaging 86.61 m.p.h. for nearly 500 miles.

Frorn this brief summary of the background to 1926-27 racing it will be seen that the most successful voiturette cars were 4-cylinder editions of 6- or 8-cylinder Grand Prix types of 2- or 3-litres capacity. Supercharging was, by the end of 1925, just as much an established principle in the smaller class as it was on the Grand Prix cars, and although I shall deal in more detail later in this article with technical features, it may be interesting to note that the Darracq engines produced 108 b.h.p. at 5,500 r.p.m., with a boost of about 0.5 atm.

As has been seen from the past articles, manufacturers supported the 2-litre formula in quite a big way right up to the end, and works teams of Alfa-Romeo, Bugatti, Fiat, Delage, Sunbeams and Rolland Pillain, as well as Benz, Schmid and Mercedes, made for exceedingly interesting events.

In 1926 the promise of a 1.5-litre formula was even more satisfactory. Although Alfa-Romeo announced their intention of retiring from the field, most of the other companies were busy preparing, and, in addition, new contenders were to be expected from Alvis and Thomas in this country, O.M. in Italy, and Sima-Violet in France. This being so, the A.C.F. looked forward with a pardonable degree of optimism to the running of the French Grand Prix at Miramas at the end of June. Alas for their hopes! Out of all these possible starters Bugatti alone was ready to race, and he secured a complete walk-over. A unique occasion, one must think, not only because of the absence of other competitors, but because it must have been the only time when Bugatti was ready and the other people weren’t! It was, however, not so much design as construction that was at fault, for much earlier in the year there had been full descriptions of a variety of cars.

Dealing with the new-comers, Alvis had a development of their front-wheel-drive car on the stocks, using eight cylinders of 55 x 77.75 mm., cylinder head and block cast in one, and horizontal valves. This engine was blown by a Roots-type supercharger. The Thomas-Special was another adherent to the straight-eight principle (52 x 88 mm.), and was notable for using leaf springs in the valve gear, whilst the Sima-Violet was a 2-stroke designed and built by a man who had had a great deal of experience with this type in 750 c.c. events. His Grand Prix job was a good deal more ambitious than anything he had previously attempted, and had four horizontally-opposed cylinders of 74 x 84 mm.

Fiat also built a supercharged 2-stroke engine, and although this never appeared in competition, a great deal of work was done on it, and in view of the performance figures which were later published, it is a great pity that it was not able to appear. As it was, however, the main competition (after the French Grand Prix) was between Bugatti, Talbot and Delage.

Bugatti ran supercharged versions of the 1.5-litre cars which he had run in the autumn.of the previous year in the Italian Grand Prix. These had cylinder dimensions of 52 x 88 mm., and, together with the 2.3-litre edition of the same design (60 x 100 mm.) which was run in the Targa Florio, marked the departure of Molsheim from atmospheric-induction, some two years after most of his rivals had taken this step.

The Talbot (it was given this name quite arbitrarily as a member of the S.T.D. group) was a really beautifully designed job. The eight cylinders were made up in two blocks of four, with the characteristic Bertarione welded-up construction. The crankshaft was also made in two pieces and ran on roller bearings throughout, whilst the whole engine was offset from the centre line of the chassis, enabling the driver to be placed really low down on the off side of the car. Thus, the designer took advantage of the regulation which had come into being in 1925, whereby for the first time in motor racing history the mechanic was not carried on the car. The frame was an excellent piece of work, stoutly cross braced and immensely stiff as a beam, being made from a double length of channel, one placed about 6 in. above the other with suitable vertical spacing members, each side member being pressed out as one piece; in other words, it was rather like the Lancia “Lambda” frame on a small scale. The front axle was hollow and in two pieces, with a flanged joint in the centre.

The Delage designed by M. Lory was a direct development from the previous year’s 2-litre cars so far as the engine was concerned. This may not be immediately apparent, as it was a straight-eight and not a V12, as was the original model. Nevertheless, the basic design. concept was very similar, including the use of a single iron casting for the block; as also was the proportion, location and drive of the valves, and the details of the crankshaft and rods. Cylinder dimensions were 57.5 x 75 mm., and the induction arrangements included two superchargers mounted centrally on the near side of the crankcase. They were driven by a pair of gear wheels like those employed on the Monoposto Alfa-Romeo of later time, but the driving gear was mounted on a long shaft which ran forward, inside the crankcase, to pick up with the timing gears on the front end of the engine. Each blower served four cylinders and the engine was set slightly athwart the frame, the transmission line extending this angle so that the crown wheel and pinion were appreciably offset toward the near side of the car. Once again, the purpose was to lower the driver and so reduce the frontal area. A five-speed gearbox was employed, and, unlike the Talbot, the frame was exceedingly light and flexible. One further difference is apparent in the chassis specification, viz., that the Delage brakes were put on through the medium of a friction servo device driven off the rear end of the gearbox, whilst the Talbot had self-servo shoes in the brake drums.

The Delage made its first appearance in the San Sebastian Grand Prix in July, and showed itself vastly superior in speed to the Bugattis, fresh from their French Grand Prix victory. This notwithstanding, Bugatti came home first, as at one time and another all the Delage cars were brought to stop for varying periods of time, due to the roasting action of their exhaust system upon the feet of their unhappy drivers. Owing to the disposition of the superchargers on the near side of the car the exhaust pipe came along the off side, and the offtake pipe of No. 8 cylinder formed a tube of red-hot metal but a few inches from the pedals. The effect, when combined with strong Spanish sun, may well be imagined, and it is certain that this defect cost Delage the race.

The first time the Talbots appeared on the scene was in the first of the only two British Grands Prix which have ever been run by the R.A.C., and the event showed that they were by no means in a fit state to race. On one of them the front axle broke in the first lap, and although Segrave led for 10 laps, and actually made the fastest lap of the day, he eventually went out, probably with valve trouble. The third car also suffered engine trouble before the race was over.

Thus, at this stage it was possible to put Talbot, Delage and Bugatti in an ascending order of reliability and a descending order of speed. Unfortunately, although one might have hoped for a Grand Finale for 1926 with every car at its best in the Italian Grand Prix, this was not to be. Only Bugatti ran, and scored an easy win, thus securing the European Championship.

Dealing with the lesser machines, the Sima-Violet gave some taste of its quality when it ran in the Boulogne Light Car Grand Prix. It showed itself to be slightly slower than one of the works 1,100 c.c. Salmsons, so, although one must give the designer some credit, one can scarcely put the car down as a likely contender for G.P. honours. The Thomas-Special comes into rather a different category, as shown by its hour record at 112.77 m.p.h. Nevertheless, although being able to cover a steady run at this speed, the subsequent record of this car indicates that various defects in the chassis, and the strange valve gear which limited the speed in the gears, were troubles which prevented it from becoming famous in the sphere of road racing.

Thus it was that in 1927 the same competitors who had fought out their triangular duels in 1926 were again fighting amongst themselves. But whereas the Talbot and Bugatti cars ran with comparatively small changes (albeit the Bugattis had larger radiators and superchargers, new engine dimensions of 60 x 66 mm., and were certainly faster than the 1926 Models), Delage incorporated radical “mods.” as a result of his unhappy experiences in the previous year’s events. The cylinder block was turned back to front, as it were, and the exhaust system shifted to the near side of the car, where it was well out of the way. This obviously made it impossible to keep the twin blowers in the centre of the crankcase; they were therefore deleted and a small plate covered up the hole previously made by the drive. A single supercharger was made, using the same rotor forms as previously, and it was therefore of rather abnormal length. It was mounted now at the front of the engine, raised rather high so as to give ample clearance for the front axle and the chassis. The steering connections were stiffened up considerably, and over half a hundredweight; was added to the weight of the car. With these changes the Delage proved quite invincible, and, in fact, for a decade no one was able to produce a more powerful engine of its size, and it stands to this day as a high-water mark of efficiency if one takes blower pressures into account.

The French Grand Prix was run at Montlhery, and with Bugatti a non-starter, it was virtually a straight fight between Talbot and Delage. The latter had new brakes and front axle and stood an excellent chance of winning. In the event only one Delage, the winner, driven by Benoist, was able consistently to keep in front of the Talbots, but the latter suffered from their old unreliability, and eventually Delage gained the hat trick. At this time the S.T.D. combine were in difficulties, and having failed to win the premier event, no further Talbot entries were made in the season’s racing.

In the Spanish Grand Prix, Bugatti started and very nearly won, but a crash by the leading driver let Delage into the lead, chased by another Bugatti into second place. On the fast artificial circuit used at Brooklands for the second British Grand Prix, Delage showed a marked superiority over the Bugatti and won easily, and in the only other event of note, the Italian Grand Prix at Monza, a single Delage was challenged by a Duesenberg and two front-drive Millers. Although the invaders showed turns of speed on occasion, the result was a win for Europe by a very big margin.

The eclipse of the American cars was undoubtedly due to the low efficiency of their brake and transmission systems, and the poor low-speed performance of the centrifugal type of blower. Since their 1921 G.P. win the Americans had, in fact, concentrated entirely on flat-out racing for board and brick tracks, for which purpose their 8-cylinder 1.5-litre cars were no mean performers. In the first year that this size was employed for International racing a Miller averaged 116.58 m.p.h. for 200 miles, and 123.41 m.p.h. over 120 miles. In 1927, at Atlantic City, a Miller front-drive increased the speed for 200 miles to 130.05 m.p.h. Thus there is no doubt that the cars which appeared at Monza were certainly as fast, flat out, as anything on the circuit, and as I have just said, their failure is explicable on other grounds.

At the same time Fiats made their sole appearance with a 1.5-litre car intended for Grand Prix racing. This was in the Milan Grand Prix, and the car was not the 2-stroke which had been previously tested, but a remarkable 12-cylinder model with two crankshafts geared together and a bore and stroke of 50 x 63 mm. This engine developed about 160 h.p., and it put up a lap speed of 96.56 m.p.h. This was over two miles faster than the best speed of the Delage (94.1 m.p.h.), but the latter was not pressed and was running in a long race, whereas the Milan affair was over a short distance only. Both speeds were far below the 2-litre lap record of 104.24 m.p.h., whereas at Montlhery the 1.5-litre Delage was slightly faster than the 2-litre cars.

Delage were, of course, easy winners for the European Championship of 1927, and it must be conceded that the 1.5-litre formula was a failure from a competitive viewpoint. By contrast, it was a brilliant technical success, and the tremendous step forward in the design of 1.5-litre engines from 1922-27 is of extreme interest.

A point which is worthy of particular analysis is the difference between the best specimen of 1924, the Talbot-Darracq, and the 1927 Delage, for both of these cars were supercharged and both used about the same boost pressure.

I have set out in a table the salient facts about these two engines, and a thing that immediately takes the eye is that whereas the gain in m.e.p. in these three years was only 5 per cent., the increase in horse-power-per-litre was over 50 per cent. The reason for the marked superiority of the Delage was its ability to run up to 8,000 r.p.m. and to hold 7,000 r.p.m. for long periods. This ability was derived in part from the use of eight cylinders in place of four, but, even so, the choice of a comparatively high stroke-bore ratio means that the maximum piston speed amounted to as much as 4,500 ft. per minute. This figure was an exceedingly high one, which would have involved severe friction losses if the mechanical lay-out of the engine had not been devised with outstanding skill.

Although there is no reliable data available as to the oil-efficiency of ball and roller bearings, there are certain reasons for suspecting that the extra efficiency derived from using the latter is quite considerable at high rotational and piston velocities. In any event, Lory took no chances in this matter on the Delage, which had ball or roller bearings throughout, with the exception of the oil-pump spindles. Thus, the crankshaft ran on 10 separate roller bearings, with eight roller big-ends. Each camshaft was supported on eight roller bearings, and the drive to both of them involved 14 ball bearings. The blower made up a total of four more roller bearings, and then, just as an incidental, the magneto notches up the score for ball bearings by a further half-score, making a grand total of 62 races of one sort or the other!

When one reckons that, in addition, the engine incorporated 21 gears, 48 valve springs and 32 piston rings, it becomes clear that the Delage company were in no mood to let complications and expense in design or manufacture stand in the way of the best possible results. But all this effort would have been wasted if the design of the blower and cylinder head had not been so arranged that full advantage could be attained from the high engine speed potential.

In point of fact, as a cross-section drawing shows, the lay-out of the cylinder was most excellently arranged. The sides of the casting were left open so that one could be really sure that no sand from the foundry remained in awkward places, whilst the wide angle of valves, and the intelligent disposition of the water spaces, is a model which subsequent designers would have been well advised to follow, but which, unfortunately, they lamentably failed to do.

It is worth noting that the valves were inclined at 100 degrees, and that the inflow value must be quite first-class is shown by the excellent figure of horsepower per square inch of piston area, despite the comparatively low boost and the moderate valve timing, which provides 43 degrees overlap.

Perhaps the most practical illustration of how good this engine is may be found in the fact that it gave in its original form approximately the same power with 7.5 lb./sq. in. boost as the 1935 E.R.A. gave with 13 to 14 lb./sq. in. boost. It is not impossible that with only 15 lb./sq. in. boost the Delage would give nearly 230 h.p., and this would put it on the same plane as the 1939 1.5-litre models of Alfa-Romeo, Maserati and Mercedes-Benz.

Let us now turn back a little to a comparison between the Aston-Martin and the Talbot-Darracq. The power per litre of the latter was nearly twice that of the former, but the engine speed rose by only 20 per cent., and the main gain was derived from a 60 per cent. (I speak in round figures) gain in m.e.p. The source of this benefit is obvious, viz., that the latter engine was supercharged with 7 lb./sq. in. boost pressure, which of itself should suffice to raise the output to over 80 h.p. and the m.e.p. from 106 to 150 lb. per sq. in. What little gain in output that cannot be ascribed directly to blowing can be found in improved inlet arrangements on the later engine, for there is little doubt that the single large inlet valve on the Talbot-Darracq had a substantially better flow-value than the two inlet valves on the Aston-Martin.

In their general lay-out these two cars characterised the change-over between the French and Italian schools of design, and if the Aston-Martin had been supercharged it would certainly have been far from reliable. A cross-section of the engine clearly shows the inadequacy of the head cooling arrangements, whilst the lack of stiffness in the crankshaft and crankcase design generally would have been an insuperable handicap.

There is no doubt that as a 4-cylinder engine the Talbot-Darraeq was a really fine effort, but it is, of course, impossible for an engine with fewer cylinders to compete on equal terms with an engine with a greater number of cylinders on a power-per-litre basis. Thus, the mere fact that Bugatti in 1926 had an 8-cylinder engine gave him an advantage in both power and reliability over any possible 4- or 6-cylinder rival. It is doubtful if this engine of his gave much greater power than the Talbot-Darracq, but the high piston area and comparatively low piston speed gave it outstanding reliability whilst the well-known Bugatti qualities of road-holding and steering enabled the engine output to be used to the fullest extent. The Bugatti was, like all of this series, a three-valve-per-cylinder engine (two inlets and one exhaust), and as the same casting was used irrespective of whether the capacity was of 1.5, 2.0 or 2.3 litres, the smaller size was definitely over-valved, and has much the lowest figure of horse-power per square inch of valve area of any unblown engine. In point of fact, from a mechanical viewpoint the Bugatti could have been supercharged at a much higher pressure, and the horse-power could, I think, have been raised without much difficulty to well over the 150 b.h.p. mark. Owing, however, to the well-known allergy between Bugatti cylinder heads and the cooling fluid, it is very doubtful whether the casting would have remained in one piece very long if this course had been followed; it has always been le Patron’s policy that his racing cars should not break down, even if they are slower than other starters. As a matter of fact, with a single-cam vertically-valved engine Bugatti could not hope to compete in speed with Delage, quite apart from other aspects of the matter, such as his continuance with a 2-seater type of body with the driver mounted above the propeller shaft, and the fact that the car consequently had a comparatively big frontal area.

From a strictly engineering point of view the only possible challenge to the Deluge came from the 8-cylinder Talbot-Darracqs (which were, in fact, just as fast, and could, if they had been taken more seriously, have been made just as reliable, I am sure) and the experimental Fiats. Little has been written of the Italian engines, but the data published indicates some exciting possibilities.

The 2-stroke model had two crankshafts geared together, with six throws on each. There were, therefore, 12 pistons, the combustion space being formed between them. One piston uncovered the inlet and the other the exhaust ports, and with a bore and stroke of 52 x 58 mm. it was possible to run this engine at 6,200 r.p.m., with a piston speed of well under 2,500 ft. per minute. Only 6 lb./sq. in. boost was employed, and despite the inevitably small ports-opening period, a m.e.p. of 122 lb. per sq. in. was realised. This is equivalent, of course, to double the pressure on a 4-stroke engine, so that the exceptionally good output figure of 174 b.h.p. at 6,500 r.p.m. was obtained and 170 b.h.p. at 6,000 r.p.m. The highest m.e.p. equals 320 lb. on a 4-stroke.

The output was held right down the engine scale, 80 b.h.p. being realised at 3,400 r.p.m. One of the designers associated with it has said that no difficulties were experienced with sparking plugs (a common difficulty with designs of this type), but it is fairly evident from some of the suggestions that he makes regarding pistons that these had been a source of much cogitation. The piston uncovering the exhaust ports had an exceedingly hard time, as it had high temperature gas poured right down the side of the piston and over the face of the rings. I do not know what fuel was used, but from the fact that it had a 6.5 to 1 compression ratio, and that the consumption was little over one pint per b.h.p.-hour, I should imagine that the alcohol content was small. Perhaps if a less conservative outlook in this respect had been followed and the alcohol percentage had been raised and the consumption deliberately increased to the 1.5 pints per b.h.p.-hour which is normal with present high power-per-litre engines, this Fiat power unit would really have acquired reliability. As it is, it remains an exceedingly interesting experiment.

Turning now to chassis design, the most obvious development in these two years was the off-setting of the transmission line. This, in turn, was directly inspired by the revision of regulations in 1925, whereby the car was manned by the driver alone. The result can be quickly gauged by an examination of the side elevations of the three typical Grand Prix cars which are illustrated, and which make apparent the relations of frame height, propeller shaft and scuttle height. The net result of all this was to reduce the frontal area of the 1927 Delage to about 9.5 sq. ft. as compared to just under 11 sq. ft. for the Sunbeam of 1924, which may be taken as representative of the 2-litre Grand Prix cars. Lowering of the e.g. improved cornering speeds, whilst the reduction in frontal area just about corresponded with the decrease in horse-power which followed the cutting down of engine capacity from 2-litres to 1.5-litres.

Actually, from measured performances it seems clear that the 1926-27 cars were not quite as fast as their 2-litre predecessors, and if we take 135 m.p.h. for the latter and 130 m.p.h. for the former, we shall not be very far out in our reckoning.

The 2-litre cars had an even better margin in respect of acceleration. Thus, whereas the Delage of this capacity averaged 79.39 m.p.h. and 93.68 m.p.h. for the standing kilometre and mile, respectively, the 8-cylinder Talbot speeds for corresponding distances were 81.55 m.p.h. and 92.33 m.p.h., respectively, this showing up the high speed acceleration, which really counts in racing and which is indicated by the average for that part of the run between the end of the kilometre and the end of the mile. The figures were 132.8 m.p.h. for the 2-litre Delage and 118 m.p.h. for the 1.5-litre Talbot.

An interesting comparison can be made in this matter with the earlier-type E.R.A., which had an average speed of 119 m.p.h. over this distance. But although the smaller cars inevitably paid the penalty of reduced gross power and higher weight-per-litre, the improved engine efficiency did actually result in quite a perceptible reduction in the weight-to-power ratio, which is reflected in the improved average speed over the standing kilometre.

As I have said before, all this, combined with the lower centre of gravity, added up to better performances on slowish circuits, but inability to come up to previous standards on fast courses like Monza.

In suspension and braking systems there is little of interest to record, and it is really true to say that little, if any, progress in these directions was made during the two years under review. In frame design there is no doubt that the 8-cylinder Talbot was far in advance of its time, and it is something of a paradox that the Delage, the most successful 1.5-litre car, had about the weakest frame that can ever have been put into any racing model, particularly as the designer made little use of the crankcase as a means of stiffening the front end.

The winter of 1927 witnessed the close of an epoch in motor racing history. For five years International Grand Prix races had had the support of many leading manufacturers, who had been willing to spend sums of between £50,000 and £100,000 per annum in the construction and operation of entirely special racing cars. Everyone seemed to decide at once that this was excessive, but it had certainly realised magnificent technical results, as the following comparison will show. The 1927 1.5-litre Delage produced 170 b.h.p., which is equal to 112 b.h.p. per litre, 177 lb./sq. in. m.e.p., and 5.3 horse-power per square inch of piston area. The speed of the car was approximately 130 m.p.h. Five years later the Alfa-Romeo Monoposto produced not more than 180 b.h.p. from 2.65 litres, which was equal to 68 horse-power per litre, a m.e.p. of 160 lb./sq. in. and only 4.3 horse-power per square inch of piston area. Thus, at least in so far as engine design is concerned, the decade 1927-37 is one of recession, but this I will now leave for another’s pen to portray.