I have before now been taken to task because, in the course of these articles, I have seemed to some of my readers to harp upon the subject of foreign cars and personalities to the exclusion of the native product. This is an indictment to which I must, in the main, plead guilty, and for two reasons, one of them sound, the other shameful. As to the first, I can fairly claim that as a benevolent legislature in this country has seen to it that the majority of motoring history has been enacted outside it, it is only to be expected that an impartial commentator should have more to say about things Continental than about home affairs. As to the second, I have long, and I must freely admit it, been firmly of the opinion that if one wishes to pose as knowing anything about a subject, then one is very well advised as a writer not to choose subjects about which your readers are likely to know a great deal more than you do!
However, in a recent instalment of these random remarks, I devoted the whole, or very nearly the whole, of an article to discussing the lively and enthralling argument which took place in 1912 between Laurence Pomeroy, the designer of the short-stroke, 90 by 120 mm., 3-litre Vauxhall and Louis Coatalen, the designer of the long-stroke, 80 by 150 mm., 3-litre Sunbeam. For once, at any rate, the article was primarily about British cars; and if at times it wandered off the main point to bring Panhard et Levassor, Sizaire et Naudin, Hispano-Suiza, Peugeot, Delage and a few others into the story, it was only by way of illustration. All the same, such divagations from the main theme were unfortunate, because they resulted in the fall of the editorial guillotine before I had fully said my say about less exotic motor cars.
Laurence Pomeroy, it may be remembered, was, so it seems, right in his advocacy of the short stroke, but right, perhaps, before his time. For all that, he never became more than slightly tinged with the heterodoxy of his age. The 90 by 120 mm., 3-litre “Prince Henry” Vauxhall had a stroke-bore ratio of 1.33 to 1; and when it grew up into the 4-litre “Prince Henry,” the ratio of its 95 by 140 mm. engine, while admittedly higher at 1.55 to 1, was still moderate for the era. One might, perhaps, have expected dimensions of, say, 98 by 130 mm., which would have given the same capacity, to within 50 c.c., and the same stroke-bore ratio, as near as may be, as the 3-litre; but then, ironically enough, a bore of 98 mm. was doubtless considered untidy when the 4-litre “Prince Henry.'” went on the drawing-board in this same year, 1912. At any rate, its designer’s predilections were amply demonstrated, two years later, when it came to building a 4 1/2-litre engine for the 1914 Grand Prix at Lyons: the stroke was left where it was, at 140. mm., and the bore increased to 101 mm. to give the required capacity.
As a result it was, I think, the engine with the biggest bore in the race. The majority of the competitors, Sunbeam, Mercédès, Delage, Th. Schneider, Alda, Nazzaro and Opel, seem to have decided that at all costs they would use a stroke of 160 mm. and found that a bore of 94 mm. was the biggest that they could afford. Peugeot, determined as usual to pursue the long stroke principle à l’outrance, outdid all the others with dimensions of 92 by 169 mm. Only the Fiats, with a bore and stroke of 100 by 143 mm., approximated to the Vauxhall dimensions. But then, Fiat had never taken any interest in voiturette racing; the monsters with which they had last appeared, in the 1912 Grand Prix, had had dimensions of 150 by 200 min., which give the same stroke-bore ratio as that of the contemporary 3-litre Vauxhall.
It is considered, I believe, that the 1914 Grand Prix Vauxhall engine was the most powerful of any employed in the race. But, unfortunately, far too little time was allowed to bring it to concert pitch before the race, in which the very long-stroke Peugeots proved themselves among the fastest of the competing cars, and the moderately long-stroke Mercédès, the most successful. The reputation of Laurence Pomeroy, therefore, derives not from his 1914 Grand Prix racer, but from the two “Prince Henry” models and the “30-98.” And, curiously enough, the “30-98,” as is generally known, was not really designed from scratch at.all, but was rather crudely developed from the 4-litre “Prince Henry.” In order to get more power, the bore was increased to 98 mm., the very figure, as it happens, that we postulated as “correct” for a 4-litre design by Pomeroy; but at the same time the stroke was drawn out to 150 mm. with the result that the ratio remained just over 1.5, to 1. Rather long for Pomeroy, in fact, in its “E ” form; but with the reduction of the stroke to 140 mm. again in the “OE” type we get very close to what may be regarded as the apotheosis of the Pomeroy Style. Vauxhall, in his era, may have been unlucky in the big races, but unquestionably the “30-98” became one of the most famous, if not, indeed, the most famous, sports car that this country has ever produced.
And what of the long-stroke exponent? Well, curiously enough, the fruits of Sunbeam’s victories in the Coupe de l’Auto and the 1914 Tourist Trophy were gathered not by Sunbeam but by W. O. Bentley. The R.A.C., rather inconveniently, had fixed the capacity limit for this 1914 Tourist Trophy at the odd figure of 3,310 c.c.; but the untidiness of the limit can hardly have worried Messrs. Bentley and Bentley when they decided to enter for it a 2-litre D.F.P. MM. Doriot, Flandrin et Parant, its constructors, had not themselves taken much interest in racing, although I imagine that. Doriot himself was the man who had driven one of the 3 1/2 h.p. Peugeots in Paris-Rouen in 1894, was fourth in a similar car in Paris-Bordeaux-Paris the following year, and continued to race Peugeots until the end of the century. Some forty years ago, he and his partners were already building a voiturette with an 1,843-c.c. 4-cylinder engine of 70 by 120 mm. bore and stroke; twenty years later, they were still building an engine with the same dimensions! But in the meantime, if they did not themselves take part in racing, they were not slow to study the lessons of the long-stroke era; and in 1913, wanting rather more power for a “sporting” edition of their car, they increased the stroke to 130 mm. This produced a stroke-bore ratio almost exactly equal to that of the 3-litre Sunbeam, and, rather inconveniently, like the 1914 T.T. regulations, a capacity of 2,001 c.c.
In the hands of W. O. Bentley, one of these cars (always affectionately referred to as “the little D.F.P.”) succeeded in finishing the race in creditable manner; but during the wartime interregnum which followed, ideas of bigger and better things were forming in the mind of its driver. In 1919 they began to take concrete shape, and before the year was out, the first 3-litre Bentley was on the road. For its engine dimensions, its designer chose just those of the Coupe de l’Auto Sunbeam; and, like Sunbeams, he had borrowed from Peugeot and its other Continental exponents the idea of the overhead camshaft, although, as was long the case even with Bugatti, for example, he was content with one instead of two. The 3-litre Bentley, in fact, was a production edition of a pre-1914 racing car; only if there was any logic in history, it ought to have been built not by Bentley but by Sunbeam.
In any event, it was extraordinarily successful. It would be hard to say whether it or the “30-98” won, in its own class, the greater réclame. Obviously, they were never directly comparable because they were in two completely different categories, as far as engine size was concerned. And when the 4 1/2-litre Bentley was produced for the Grand Prix d’Endurance in 1927, the “30-98” was about to go out of production.
But as soon as the 4 1/2-litre is considered, certain significant facts immediately spring to mind. In the first place, like the 4,210-c.c. “OE” type “30-98,” it was not, strictly speaking, a 4 1/2-litre at all, the capacity of its 100 by 140 mm. engine coming out at 4,387-c.c. And secondly, it is immediately noticeable that in order to produce a larger engine, the designer had not only, naturally enough, increased the bore, but had actually reduced the stroke as compared with that of his 1919 design. The stroke-bore ratio of the 3-litre was 1.86 to 1; dimensions of 90 by 170 mm. for the larger engine would only have raised it in the second place of decimals, and would have given a capacity of 4,304-c.c.; an increase in the bore to 91 mm. would have given, on both counts, almost exactly the right answer.
Of course, it must not be forgotten that two years previously Bentley had produced the 100 by 140 mm. 6-cylinder, and the choice of these dimensions for the big four may have been dictated by considerations of manufacturing convenience. But where the price of his product is not an all-important sales factor, I should hardly have thought that this was a point to which a designer was likely to give undue weight. And it must be remembered that, whatever was its subsequent history, the Six was originally introduced as a chassis suitable for the conveyance of luxurious limousines. For sports models, the long-stroke engine had, in 1919, been regarded as an almost essential feature; and a car primarily intended for the Le Mans race was obviously designed from the first as a sports model. It might, of course, be argued that, taking into account the top-hamper represented by overhead valves and camshafts, 150 mm. was considered the actual maximum stroke which could conveniently be accommodated by anyone except Peugeot. But this is no explanation of why it was reduced; its combination with a bore of 96 or 97 mm. would have given approximately the capacity required, without inflicting such a violent onslaught on the ratio. No, after consideration of all the relevant facts as I can see them, I can only come to the conclusion that the supersession of the 3-litre Bentley by the 4 1/2-litre twenty years ago marked the end of the long-stroke era, which had been inaugurated exactly twenty years before. After fifteen years, Pomeroy’s arguments of 1912 were finally vindicated.
I do not know on what basis these dimensions of 100 by 140 mm. were chosen by Bentley in 1925 for the 6-cylinder, or in 1927 for the 4 1/2-litre. But it is rather entertaining, even if, perhaps, it is in no way instructive, to take a rearward glance at their previous history. The first 4-cylinder racing Panhard et Levassor, the 8-h.p. of 1896, had had a bore of 80 mm. and a stroke, moderate by the standards of 1907 to 1927, of 120 mm., giving a ratio of 1.5 to 1. It was succeeded in 1899, first by the 12-h.p., 90 by 130 mm. (1.44 to 1) and then by the 16-h.p., 100 by 140 mm. engine. It was with this 16-h.p. model that Réné de Knyff won the Tour de France, averaging 30 m.p.h. for 1,350 miles, and it represented, in many ways, the apotheosis of the racing Panhard. It was the last model which relied solely on tube ignition, and it was the last year in which Panhard held undisputed sway over all competitors: the big race of 1900 was won by Levegh on a Mors.
Thereafter, attention was increasingly focused on the big-bore engine, and before the limited-bore regulation had reversed the trend, a stroke-bore ratio of 1.4 to 1 had come to look enormous. When observers inspected with interest at the end of 1906 the first Spanish car ever to be shown at the Paris Salon, in the shape of the Hispano-Suiza, they found two 4-cylinder models, one of 100 by 120 mm. and the other of 130 by 140 mm. bore and stroke, with a couple of “Square” 6-cylinders with dimensions of 115 by 115 mm. and 130 by 130 mm., respectively. (One of the more eminent contributors to this journal, when confronted with a photograph of one of the first of the smaller of the 4-cylinder models to arrive in this country, in 1907, immediately identified it as the then property of his great-uncle; but most reprehensibly, in my opinion, he is no longer cognisant of its whereabouts.) By 1910, in deference to the lessons learnt in voiturette racing, the stroke of this model had become elongated to 150 mm., and in this shape, I believe, its manufacture continued at Barcelona until about 1922 or 1923. In its 1907 form, at any rate, it had cylinders cast in pairs and a T-head, while, according to a contemporary description, “semi-elliptical springs are fitted to the rear axle, but the rear of the spring is attached to each frame member by means of a half semi-elliptical spring, which takes the place of the usual spring-horn” — a form of words which I commend to the Editor if he wants both some padding and a description for the 3/4-elliptics on his own “Alfonso.” It also had 4 speeds, with direct drive on third, use of top, I am informed, being frowned upon by my colleague’s great-uncle.
At any rate, when Marc Birkigt came to design his famous 37-h.p. 6-cylinder model in 1919 he must have used this engine to some extent as a basis, because he employed the same bore but retracted the stroke a trifle to 140 mm. At the time when the long-stroke 3-litre Bentley was being designed, Birkigt, it would seem, was already veering away from the long-stroke. As a result, his 1919 engine had the same dimensions as the 6-cylinder Bentley of 1925, and a direct comparison between the performances of the two cars would be highly interesting.
By the time that the 6-cylinder Bentley was produced, however, Birkigt had already travelled further along the road towards the short-stroke engine. In 1923, with a view to getting increased power from the 37-h.p. engine, he produced a small number of the genuine “Monza” engines, with the bore increased to 102 mm. and the stroke restored to the 150 mm. of the old 4-cylinder. But this engine was never produced in series, and the super-Hispano, which had first appeared in 1921, and which was marketed a year or two later, proved to be the 45-h.p. “Boulogne” model, 110 by 140 mm. bore and stroke. In 1930 Bentley replied with the 8-litre; once more, I should be much obliged if someone could supply me with comparative data of the performances of the two cars. As for Marc Birkigt, he was busy rummaging among his 6-cylinder designs of 1906; and in 1931 there appeared the 12-cylinder Hispano with a “Square” engine of 100 by 100 mm. bore and stroke. It seems to me as though instead of puzzling our heads over octane values, as recently suggested in these columns, it is about time that we resuscitated the limited-bore regulation!