Sorting Out the Specialised Sports Cars
With Some Notes on the Trend of Amateur Design
Last month we drew attention in the Editorial to the extremely healthy state of the Sport from the aspect of amateur-built sports cars.
In an attempt to clarify the salient points in the design of such cars we give a table (see pages 340-341) covering sixteen different cars which are seen in current sports-car racing. In referring to these cars as of amateur design we imply no criticism of their constructors, far from it; we use this term to differentiate between the sports cars of the small constructors and the accepted manufacturers.
The former have grown out of a desire on the part of keen enthusiasts to possess and race vehicles which really do "go" and hold the road, and it is significant that the better of such cars have begun seriously to challenge such manufacturers' sports/racing cars as the D-type Jaguar, Aston Martin DB3S, Austin-Healey 100S, and Frazer-Nash in British circuit races.
Indeed, the British Motor Industry should look to its laurels. In the 1,100-c.c. class it has nothing comparable to the Cooper Climax and Lotus. The once-virile 1 1/2-litre category is again the undisputed preserve of the larger-engined Lotus and Connaught cars. In the 2-litre class the Lister-Bristol has no manufacturers' counterpart and, at all events on a wet course, the R.G.S. Atalanta "sees off" cars like works Jaguars and Aston Martins in spite of having an engine which literally has never had an overhaul since it was purchased and which pokes out under 200 h.p., the car's acceleration and performance thus reflecting the efficiency of its chassis and body design.
Jaguar has so ably upheld British prestige in the past that we shall expect great things from the latest of Bill Lyons' cars at Le Mans, where it is to be hoped that the fortunes of that genuine enthusiast, David Brown, will improve, for since entering racing his Aston Martins have had a rather dismal record. It seems that M.G. will re-enter sports-car racing at Le Mans, probably with 1 1/2-litre cars having new inclined-valve cylinder heads and all-enveloping bodies, and Frazer-Nash and Bristol will enter cars. Otherwise, it is from the small-production specialised sports models that we derive interest in sports-car racing, at club race meetings up and down the country.
To qualify the specifications given in the accompanying table let it be said that the design details on such cars change frequently as improvements are incorporated, and experiments made, but the data published was reasonably accurate at the time it was compiled. Figures for tyre size, axle ratios and brake-drum size can be approximate only, changes being possible here to suit changing conditions and circuits, while for b.h.p. and weight figures we have had to rely on the estimates of constructors; the weight figures, in particular, are approximate, some being for cars "wet," others "dry" (i.e., sans fuel, oil and possibly water), while because the smaller concerns seldom possess a dynamometer horse-power figures are often "guesstimation."
On the whole, however, we think the information to be gleaned is definitely worth while.
The outstanding factor is the employment by these small builders of the very best Continental design practice. Thus, of the sixteen cars described, only three, the Elva, J.A.G. and Leonard, use a rigid back axle and these are in the smaller-capacity classes.
Every single one of these cars has a tubular chassis frame — here the problem-child of nomenclature again rears its ugly head and "space frame" is best understood as implying a frame with more than two parallel tubes (the "ladder" frame), because a true spaceframe has every tube in tension or compression and, in fact, there are not very many frames of which this is so. Dick Shattock refers to the frame of his R.G.S.-Atalanta as a multi-tube frame for this very good reason but where builders call theirs space-frames we have followed suit.
In 1955 no surprise is occasioned that all the sports cars with which we are dealing have independent front suspension, but manufacturers who still cling to the old-fashioned rigid back axle should note how the amateur builder, unless very cramped for finance, has discarded this troublesome component, using some form of independent rear suspension unless, as in the case of the Beart-Rodger, Buckler, Connaught, H.W.M., Lister and Lotus; a de Dion rear-end is employed. There is obvious understanding of the need to have large-area, well-cooled brakes even on these comparatively lightweight cars and following the lead amongst manufacturers taken by Jaguar, Austin-Healey and now Aston Martin in the use of disc brakes, Cooper Cars, Ltd., have this type of retardation on the Mark II Cooper-Jaguar, as has the Lotus-Bristol, and Lister have been trying them on the 1955 Lister-Bristols. The employment of inboard drums at the back to reduce unsprung weight to a minimum and so exploit independent suspension of the back wheels to its full advantage is seen in the Lister-Bristol, Lotus Mark IX and X, and R.G.S.-Atalanta, and the little Revis, with its solitary inboard drum.
Perusal of the columns of the table devoted to engines and gearboxes proves that here most amateur constructors are sadly hampered, although the fortunate procure Bristol or Jaguar power units if entering the 2-litre and upwards classes and for the 1 1/2-litre and under brigade some excellent progress is being made in the development of former bread-and-milk engines.
While on this subject I must hasten to correct the false impression that the 1,100c.c. Coventry-Climax type FWA engine is virtually a marine unit. This impression may have arisen because one of these engines was exhibited in the Motor Boat section at the last Earls Court Motor Show, but the makers, Coventry-Climax Engines Ltd. of Whittington Road Works, Coventry, inform us that they have never made a marine petrol engine and that the type FWA was designed as a sports/racing car unit. They are justifiably proud that it produces some 75 b.h.p. at 6,200 r.p.m. for a weight of 208 lb. complete with starter and dynamo. They have no intention, contrary to rumours of offering a 1 1/2-litre version of this engine, but hope to have "something interesting to offer for 1956" — perhaps a twin o.h.c. 1 1/2-litre unit? By the way, Moss retired the Beart-Rodger Climax at Goodwood on Easter Monday because the throttle-linkage came adrift, not because its engine blew-up.
How much good chassis design and especially a proper understanding of aerodynamics pays is illustrated by a speed increase of about 25 m.p.h., from 113 to about 140 m.p.h. achieved from the R.G.S.-Atalanta without any alteration to its aforesaid rather "cooking" Jaguar power plant.
For this reason all-enveloping are universal, and the Monkey Stable are using coupés to combat driver-fatigue in the longer races that are their main interest. The stage has certainly been reached when air-tunnel research should pay big dividend, and real live aerodynamicists must be employed in body-shape research, as Lotus and Connaught have done.
The glass-fibre body construction pioneered by R.G.S. has, we see, spread to Kieft, J.A.C. and Lester.
Torsion bar suspension is not popular, being confined to Connaught and R.C.S.-Atalanta. probably because torsion bars are less easy to anchor than coil springs. The latter are the most popular form of suspension medium, but the dear old "cart-spring," in transverse location, as borrowed for this class of car by Cooper from the Fiat Topolino front-suspension layout, has not by any means gone out of the picture.
Far from being outclassed, these brave new "backyard builders" can give points to the Industry. Only when it comes to our three outstanding manufacturers sports/racing cars do we find affinity. For example, the 3-litre 180 b.h.p. Aston Martin DB3S has a tubular ladder-type 7 ft. 3 in. wheelbase frame, de Dion Dion rear-end, trailing-arm torsion-bar independent suspension all round and special Girling brakes with Alfin bi-metallic drums, disc brakes having been used experimentally. Then the D-type Jaguar possesses a 3 1/2-litre 250 b.h.p. engine in a 7 ft. 6 in. wheelbase stressed alloy space frame, torsion bar and wishbone i.f.s., trailing arm torsion bar suspension of (however) a rigid back axle, specially located, and Dunlop disc brakes. The Austin-Healey 100S develops 132 b.h.p. from a 2.6-litre four-cylinder engine and its specification embraces a 7 ft. 6 in. wheelbase frame mainly of 3-in, square steel tubing, coil-spring unequal-length wishbone i.f.s., Dunlop disc brakes and a rigid back axle located by a Panhard rod and sprung on 1/2-elliptic leaf-springs which is outmoded in the backyards.
Needless to say, these three care have all-enveloping bodies, the D-type Jaguar having a faired headrest for the driver which incorporates a single fin.
Frazer-Nash use an 8-ft. wheelbase ladder-type tubular frame, de Dion rear end with torsion-bar and A-bracket suspension, coil-spring or transverse-leaf-spring wishbone i.f.s., rack-and-pinion steering, and all-enveloping or exposed-wheel two-seater or coupé body to choice for their faster models, which to date have used a Bristol engine from which 145 b.h.p. is probably realised in the works car.
The performance of the specialised products in competition with those of the big factories is truly praiseworthy. In this year's British Empire Trophy Race, a 2-litre Lister-Bristol won outright (a Cooper-Bristol did so in 1954) and this car and the new 1 1/2-litre Connaught (further details on page 313) vanquished Parnell's disc-braked new 2 1/2-litre Aston Martin in the final, while the R.G.S.-Atalanta set the fastest race-average speed, quicker in the rain than Duncan Hamilton's D-type Jaguar. At Castle Combe a driver new to the R.G.S.-Atalanta, after a poor start, came home second in the big sports-car category to a C-type Jaguar, while at the Easter Goodwood Meeting the Lister-Bristol beat a Frazer-Nash Le Mans Replica in the sports-car event, and at Charterhall the Lister-Bristol beat Austin-Healey 100S and Jaguar XK120C.
So far as sports-car racing on British circuits is concerned I look to these specialised, in some cases "one-off" cars to provide the main interest in the four months that remain of the 1955 season. We have not seen everything yet for some of the 1955 models, such as Connaught and Lister-Bristol, are not, at the time of writing, developed to quite the same extent as the 1954 cars. Incidentally, can I now make a plea for abolition of "Le Mans" starts for short races? Such a start is excellent for the real Le Mans race, where no one settles down for a lap or so and the huge crowds like to see their drivers on parade. But it is exasperating to spectators at short races when promising duels between closely-matched rival makes fail to materialise because the cars concerned have started from opposite ends of a long line of parked vehicles and maybe one driver is a bad sprinter or trips over the gear-lever and so loses the race before his engine starts. In "production sports-car races," where proper doors and efficient starters are part of the game, a Le Mans start is perhaps permissible. But please, not for drivers of the less-sedate sports cars, in brief races. — W. B.