1954 - 1955
The Mercedes-Benz W 196 R designed for the 1954 season met all the demands of the new Grand Prix formula decreed by the sport's governing body, the CSI (Commission Sportive Internationale): a capacity of 750 cc with or 2500 cc without supercharger, free choice of gas mixture, a racing distance of 300 kilometres or a minimum of three hours. The streamlined version was completed first because the Reims race kicking off the season permitted very high speeds. After that there was also a version with exposed wheels.
Fritz Nallinger was in charge of the project as a whole, ably assisted by Rudolf Uhlenhaut, Chief Engineer of the racing department since 1 September 1936, and after the war also head of the Car Testing department, who influenced the development decisively. Uhlenhaut headed a team of engineers including Hans Scherenberg, Ludwig Kraus, Manfred Lorscheidt, Hans Gassmann, and Karl-Heinz Göschel, as well as further top-level staff of the company. And although, yet again, in the case of the W 196 R, the whole was much more than the sum of its parts, every component is worth mentioning: cutting-edge technology in terms of its era, in spite of the fact that, in some cases, there had been precedents in the history of motor sports.
This silver masterpiece, of which 14 units including a prototype were built, drove its competitors to despair in the following two years. Its original streamlined body was both expedient and visually appealing. From the German Grand Prix on the Nürburgring in early August 1954 onward, however, an open-wheel (monoposto) version also formed part of the line-up. Its tubular space frame was light and sturdy, its suspension with torsion bars and a new single-joint swing axle at the rear as well as the giant, turbo-cooled, and at first centrally arranged Duplex drum brakes were unconventionally good. The eight-cylinder in-line engine with direct injection and desmodromic valve control (1954: 256 hp (188 kW) at 8260 rpm, 1955: 290 hp (213 kW) at 8500 rpm) was installed into the space frame at an angle of 53 degrees to the right to lower the centre of gravity and reduce the frontal area. What's more, meticulous preparations for each individual race harked back to the glorious 1930s while at the same time anticipating the modern Formula One approach. But there was something else as well: so as to have the best cars in the world raced by the best drivers, racing manager Alfred Neubauer hired the – initially reluctant – superstar Juan Manuel Fangio, plus the up-and-coming Stirling Moss in 1955 – a virtually invincible pairing.
Two versions: monoposto car and streamliner
The two versions of the W 196 R were interchangeable quite effortlessly. Chassis number ten, for instance, glittering with former glory in its brand-new aluminium body one day, was entered with open wheels in the 1955 Argentinean Grand Prix (driven by Hans Herrmann, Karl Kling and Moss to fourth place) and the Dutch Grand Prix (with Moss at the wheel, finishing as runner-up), and fully streamlined again performed tests in Monza. Which of them was used depended upon the peculiarities of the circuit, the strategy chosen and the likes and dislikes of the respective driver.
The W 196 R featured a swing axle with low pivot point instead of the customary De Dion layout – a configuration explained by Uhlenhaut with its better behaviour under acceleration. An almost perfect balance was achieved by positioning heavy elements in the extremities of the W 196 R, the water and oil coolers right at the front, the tanks holding petrol and oil in the tail. In 1955 the front drum brakes were relocated into the wheels on some cars, while three wheelbase lengths were available: 2150 millimetres, 2210 millimetres, and 2350 millimetres. The shortest was ideally suited for the tight round-the-houses circuit in Monaco, at the same time it had an ambience of stocky purposefulness. But it did not, of course, prevent the disaster that struck the silver cars on that 22nd day of May: Hans Herrmann suffered a severe accident during a practice session, Fangio had to retire from the race with a broken propeller shaft, and both Moss and replacement driver André Simon in the third Silver Arrow with engine damage.
The engine as a high-precision machine
As usual, before a fully-fledged eight-cylinder engine gave its first roar on the test rig, a single-cylinder test unit with 310 cc and four valves had to go through its paces. This solution uncovered a deficiency the Silver Arrows' racing engines had already struggled with in the 1930s, namely valve-gear problems when exceeding 8000 rpm and above all fragile springs. Going home after work in a streetcar in the evening of 20 May 1952, suburban commuter Hans Gassmann came up with the answer, presenting it the next morning. Cam lobes and rocker arms would control both the opening and closing of the valves so that one could make do without springs. The advantages of that concept were obvious: higher revs, more safety, greater power. As it also permitted to employ larger and heavier valves, the engineers opted for two valves per cylinder.
The injection pump, developed together with Bosch and not unlike the ones used in diesel engines, consisted of a casing with eight cylinders which fed the gas straight into the combustion chambers at a pressure of 100 kilograms per cubic centimetre. The eight-cylinder in-line configuration was inspired by the famous 18/100 hp Grand Prix car of 1914 in that the cylinders (two groups of four, with central power take-off) were firmly connected to a base plate, though bolted to an aluminium casing separate from the valve gear housing and surrounded by a welded-on cooling-water jacket. The fuel used was a highly reactive Esso mixture with code RD 1, concocted from 45 percent benzene, 25 percent methanol, 25 percent 110/130 octane petrol, three percent acetone und two percent nitro-benzene. This blend would have eaten away a tank made of unprotected steel overnight, as Hans Herrmann remembers.
The W 196 R's track record was impressive indeed: nine victories and fastest laps, as well as eight pole positions in the twelve Grand Prix races in which it was entered, and, of course, Fangio's world champion’s titles in 1954 and 1955. There was little room for improvement.