MERCEDES BENZ 300SL and 300SLR. Few manufacturers supported motor racing more wholeheartedly than M

However, two disappointing performances in Argentina against more modern Ferraris persuaded them that the blown V12s' racing days were done, and their role thereafter became that of demonstrators.

Yet the Mercedes will to race was strong, and while resolving to resume Grand Prix racing with the new Formula 1 in 1954, they turned meantime to sports car racing—"just opening a little window on the motor racing scene", as technical director Fritz Nallinger said almost apologetically. The decision was made a week before Jaguar's magnificent 1951 win at Le Mans with the XK120C developed from production parts. The moral was obvious, and designer Uhlenhaut turned to his own Type 300, "flagship" of the Mercedes line. This was a luxury six-cylinder saloon with tubular chassis, swing rear axles and an 85 x 88mm, 2,996cc engine delivering a velvety 115bhp at 4,600rpm on low compression and low octane fuel. Yet it propelled the 3,7001b 300 at close on 100mph, and from its 7-bearing crank-shaft to the unusual aluminium slant head and single overhead camshaft operating staggered parallel valves, this engine promised well. A 300S version with high-compres-sion triple-carburettor, 150bhp engine and shorter wheelbase appeared at the 1951 Paris Salon, making only mild impact amongst more exotic cars, but the subsequent 300SL or Sport Leicht descendant, was to jolt the motor sporting world severely. Type 300 coil spring independent front suspension and rear swing axles were both united with an ingenious new multi-tube welded space frame, notably light yet rigid. Cloaking the entire structure was a superbly clean and effective aero dynamic coupe body, in which the frame side rails were left undisturbed by using specially formed doors, hinged downwards from the centre of the roof —the famous Mercedes gullwing treat-ment which ensured maximum frame rigidity while complying with FIA regulations, albeit demanding extra agility from the driver. Further enterprise featured in the engine installation.

Now giving 171bhp at 5,200rpm with triple downdraught Solex carburettors, the unit was slanted at 50 degrees from horizontal to provide a low bonnet line, and equipped with dry sump lubrication. Simple nose treat-ment with an oval GP-like grille and modest overall height kept frontal area impressively low, and quick-release pressed-steel wheels with alloy rims, and wide-drum two-leading-shoe brakes were employed, the dry weight with the 300's heavy cast-iron engine and gear-box coming out at slightly over 1,9001b. Doubts were cast on the efficacy of the rear swing axles for high speed work, with their tendency to "tuck under" when cornering fast, while the engine output was below that of several rivals. Reliance, however, was placed in superior aerodynamics and team know-how. There remained, moreover, that intangible "moral ascendancy" possessed by Mercedes-Benz with its unique racing reputation. The fact that "Mercs were back" put their rivals on edge in their very first race, Italy's famous Mille Miglia. Three sleek silver 300SLs ran; one finished second, one fourth and one crashed, a single 2.7 litre 12-cylinder Ferrari on its home ground denying them first place. Yet their speed and near-victory paid off handsomely in subsequent races. At Berne in Switzer-land their presence caused the favourite in his factory-loaned 41 litre Ferrari to break his transmission on the start line —and Mercedes-Benz finished 1-2-3.

At Le Mans reports of their prodigious speeds in the Mille Miglia "panicked" Jaguars into revising the XK120C cooling and streamlining, precipitating their early retirement. With Aston Martin and Ferrari also out, only an older 41 litre Talbot stood between the 300SLs and victory; then it broke a connecting rod one hour before the finish, probably through the fatigue of driver Levegh, who was trying to complete the entire 24 hours himself—and Mercedes sailed home 1-2 to a prestigious victory. At Niirburgring before the home crowd four 300SLs with coupe tops removed sat in formation behind a fleet Gordini, waiting for it to break—then moved in to a 1-2-3-4 demonstration win. Their last race was much tougher —the five-day, 1923-mile Pan-American Road Race in Mexico, with Ferrari, Talbot, Lancia, Gordini and Porsche all present. The Mercedes outpaced some, outlasted others, and despite a buzzard through one screen at 135mph, a dog through another radiator at 125mph, and flying treads at over 150mph, they came through to another 1-2 victory. The factory 300SL team raced no more after 1952, but the car was put into limited production as a high-performance road model. This was unveiled early in 1954, more refined, more handsome, and with an important engine innovation—Bosch direct fuel injection in place of carburettors. Com-plex to build, it was costly to buy, but demand by connoisseurs was unexpect-edly high, and a total of 3,250 300SLs were produced between 1954 and 1962 —"gullwing" coupes up to 1956, and open roadsters with normal side doors thereafter. New low-pivot swing axles were introduced in 1957 to improve handling, and disc brakes featured in 1961-62. That sophisticated slant six engine gave 219bhp at 5,800rpm and a maximum speed of over 150mph, com-pelling respect, both from the driver and

certainly from his opponents in com-petition.

Many major European rallies and race class wins fell to this brilliant car, rated today as one of the "peak" classic sports cars of the 1950s. Specification-300SL Engine: 6 cylinders in line, angled at 50'; 85 x 88mm, 2,996cc; ohc operating 2 valves per cylinder; triple Solex downdraught carburettors; magneto ignition (Bosch coil ignition on production models); 7-bearing crankshaft; 171bhp at 5,200rpm (219bhp at 5,800rpm on production models). Transmission: Single dry-plate clutch; 4-speed all-synchromesh gearbox in unit with engine; open propellor shaft; hypoid-bevel final drive. Chassis: Welded tubular space frame; independent front suspension by coil springs and wishbones; swing rear axles with coil springs; telescopic hydraulic dampers all round; hydraulic drum brakes to 1960 (servo-assistance on production models); disc brakes, 1961-62. Dimensions: Wheelbase, 7ft 104in; front track, Oft 61-in (4ft 7in from 1957); rear track, 4ft 9in; approx. dry weight, 1,9201b (competition car); 2,5601b (production car).

The 300SLR If the Mercedes-Benz 300SL seemed complex in design, what of the 300SLR with its eight cylinders, 10-bearing crankshaft, desmodromic valves, fuel injection, inboard front and rear brakes and, in two races, an air brake as well? Yet it was probably the easier car to develop to race-worthiness, since it derived directly from the WI96 Formula 1 Grand Prix single-seater, using basic-ally the same engine enlarged to 3 litres, the same transmission and suspension, and broadly the same space frame. Thus development of the basic design had virtually been completed in 1954 by the W196 when winning four Grands Prix, and only sheer lack of time postponed the 300SLR's appearance until 1955. Whereas the 2+ litre Fl engine measured 76 x 68.8mm, the 300SLR had a larger bore and stroke, making it "square" at 78 x 78mm (2,982cc). The straight-8 unit was built up in two blocks of four cylinders, with the timing gear train in the centre, as on the pre-war Alfa Romeos. While making up the new cylinder blocks, Mercedes departed from their traditional sheet steel fabrica-tions and had them cast in aluminium alloy. The bores were then chromium-plated to a depth of 0.008in and finished by honing, this process proving very. durable. Other variations included a different firing order, wider valve angles, improved porting and provision of the generator and starter motor essential to sports-racing cars.

The rest of the engine specification sounds alarmingly complicated, as indeed it was, save to the ultra-efficient Daimler-Benz organisation with its ruth-less philosophy of adopting the right solution irrespective of cost and com-plexity, backed by the resources and reputation for doing it. Twin overhead camshafts operated two valves per cylinder, but in place of return springs these were opened and closed by a posi-tive desmodromic system of cams and rockers. Bosch direct fuel injection, demanding a high-precision fuel pump, was employed, and the built-up crank-shaft ran in 10 roller bearings, with a power take-off from the centre to a sub-shaft, and thence via propellor shaft to a ZF five-speed gearbox in unit with the final drive. Peak engine output on alcohol was a thought-provoking 340bhp at 7,700rpm, and revs could safely be taken up to 8,000; race output on less potent fuels varied between 276 and 300bhp accord-ing to the course. The power unit was slanted even further on the 300SLR, at 33 degrees from horizontal, and the low-nosed full-width bodywork, made in Electron alloy with left-hand drive, inherited much from the older 300SL, although a planned coupe was never raced. Longitudinal torsion bars served front and rear as the suspension medium, and the rear swing axles were located by two curved arms pivoted below the differential casing to provide a low roll centre. The wheelbase and track were identical with those of the longer wheel-base Formula 1 car, and big self—adjusting brakes with wide turbo-fmned drums were mounted inboard to reduce unsprung weight. The air brake, a large hydraulically-controlled flap over the tail, first tried three years earlier on a 300SL, proved very effective at Le Mans and in Sweden, not only in retardation from high speeds, but also in imparting a useful downforce on the car when cornering, thereby inadvertently antici-pating the modern "wing". The main object was to save the drum brakes in long, fast races, at a time when discs were available only to British cars. Windows were cut for rearward vision, and the flap was operated by the driver through a lever on the scuttle. But for malign circumstance, the 300SLR's record of success would almost certainly have been higher than in fact it was. Mercedes-Benz' aim was to contest the 1955 World Sports Car Championship, and this they won in glorious fashion despite missing the two opening rounds. Availing themselves of the finest driving talent, including Fangio, Moss and Peter Collins, they finished first and second in the Mille Miglia, first, second and third in the TT at Dundrod, and first, second and fourth in the Targa Florio, the latter contested at short notice in a final bid for the Championship title. The cars also won the Eifel GP at Niirburgring and the Swedish GP, but their greatest victory could well have been at Le Mans where, instead, they became the unfortunate instrument of fate in the world's worst motor racing disaster. In a sporting gesture, Mercedes invited Pierre Levegh, the driver who lost the 1952 Le Mans race to the 300SLs during the 23rd hour, to drive one of the 300SLRs in the 1955 race. It was the ill-starred Frenchman who con-tacted a slewing Austin-Healey when passing at around 150mph, his car hitting

Top : Moss and navigator Jenkinson on the starting ramp, about to set off on their record-shattering Mille Miglia victory with the 300SLR in 1955 Above : Peter Collins was recruited to co-drive with Stirling Moss in the 1955 Targa Florio Opposite, top : Stirling Moss's 300SLR, bearing honoured wounds, winning the 1955 Dundrod TT a bank and disintegrating, parts flying into the packed enclosure opposite the pits. Levegh and 81 spectators were killed, and Daimler-Benz withdrew their remaining cars while they were holding first and •third positions. At the close of 1955, having proved their supremacy both in Formula 1 and sports car racing by winning both Championships, Mercedes-Benz some-what precipitately announced their total withdrawal from racing. They said "for several years", but the awe-inspiring silver cars from Unterturkheim have not raced since.