Mercedes-Benz-Blog TRIVIA: From "Sport Light" to SL Legend - PART I


Stuttgart, Germany, Feb 20, 2002

1952: The 300 SL racing sport coupe

* From idea to reality
* The beginnings of the "300 Sport"
* "300 Sport Light"
* On the way to lightness
* Cd value of 0.25 and gullwing doors
* Comfortable cockpit
* The roadster lineup
* Triumph in the Carrera Panamericana Mexico

The Le Mans 24 Hour race has been ranking among the motor sport season's highlights ever since 1923. The competitors – and even more so the winners – have always attracted the undivided attention of the spectators as well as of the buyers, victory in Le Mans being equivalent to a boost in both image and sales figures.

In 1952, Daimler-Benz AG entered three of the newly developed, futuristically designed Mercedes-Benz 300 SL racing sports coupes in this traditional long-distance race. The competitors were taken by surprise but not disquieted because first of all, Mercedes had never before done particularly well in Le Mans, and secondly, the cars from Untertürkheim were inferior to the cars of the French, British and Italians in terms of performance. Nevertheless, however, Mercedes again faced up to the competition. The new SL cars had demonstrated speed and stamina for the first time in the Mille Miglia in early May and finished in a respectable second place in this renowned long-distance race. The 300 SL hit the headlines again with its triple victory in the Bern Grand Prix.

And now they were to race in Le Mans. In practice, one of the Mercedes cars caused quite a stir: an air brake was mounted on its roof, which, when raised to an upright position, was enormously effective in braking down the car from high speed. However, the contraption's brackets were rattled severely by the forces generated in the process and Mercedes decided not to use this brake in the race after all.

It turned out to be a sensational demonstration of reliability on the part of Mercedes-Benz. On Saturday, June 14, 1952, at 16:00 hours, 58 top-class racing cars lined up at the start. At halftime, 31 cars were still running. The SL team of Karl Kling and Hans Klenk was among those who had to withdraw, in their case with alternator failure. The two other SL cars ran like clockwork, eventually occupying places two and three. Four hours before the end of the race, just 19 cars were still running, their number dropping to 17 after 23 hours. At that point in time, the Mercedes cars were out in the lead, out of reach for anyone else.

The winners were Hermann Lang and Fritz Rieß who, at 155.575 kilometers per hour, established a new average speed record in Le Mans history. Second place was occupied by Theo Helfrich and Helmut Niedermayr. This double victory was a success nobody had expected, not even the organizers who simply hadn't thought of providing a tape with the German national anthem. The SL cars, however, had laid the foundation stone of their legend.

From idea to reality

What kind of cars were these, emerging virtually out of nowhere to appear on the racetracks and obviously continuing in the best of Mercedes-Benz Silver Arrow tradition?

Decisions on the future product range had been taken at a memorable meeting of Daimler-Benz's Board of Management in December 1947. At the time, conditions were anything but rosy: few production facilities were still in working order, raw materials were extremely scarce, designs were outdated. However, the glance into the future vaguely revealed not only a representative limousine but also the outlines of a sports car – its realization being fairly utopian at the time, however. But the idea had come up and was there to stay.

Just six weeks after the meeting, Rudolf Uhlenhaut, a passionate automotive engineer and never at a loss for new ideas, submitted a draft to the Board of Management that proved to be visionary as it already incorporated several revolutionary elements which – quite literally – turned out to be highly becoming. And that was how the sports car became Uhlenhaut's baby, so to speak.

Another decision was made two years later. As the sports car started taking shape, it was to be designated "300 Sport". A new engine would have had to be developed to give the car its target output of 200 hp, but the engineering department didn't have the capacity. They had to make ends meet with what was available, and that was not exactly exciting.

The beginnings of the "300 Sport"

A promising engine for further development was the robust M 159, as it was called internally – a 2.6 liter six-cylinder unit that had been developed in the late thirties for the new 260 model but did not make it to large-scale production because of the outbreak of World War II. Nevertheless, the engine did not remain at the testing stage – it proved itself many times over in light trucks and fire-fighting vehicles. This engine became the basis for a new series. Its – originally progressive – concept incorporated overhead valves suspended in the cylinder head in V-shape and operated from a camshaft below, as well as a spark plug located in the pent-roof shape combustion chamber between the valves. The engine was designed for a high level of fuel economy and an output of between 60 and 70 hp.

After World War II, the M 159 was taken through several evolutionary stages. It eventually entered large-scale production in the form of the M 186, with an oblique contact surface between cylinder head and engine block, overhead camshaft, large intake valves, combustion space in piston and engine block, a displacement of three liters and an output of 115 hp. It was the silky-smooth powerplant of the representative Mercedes-Benz 300 limousine launched in April 1951, also known as the "Adenauer Mercedes". A higher-performance version of this engine with the designation M 188 powered the highly exclusive, sporty 300 S, two-seater available as a coupe, cabriolet and roadster and introduced six months later. This car was the top-of-the-range model in the Mercedes-Benz line-up.

"300 Sport Light"

On June 15, 1951 the Board of Management decided to compete in sports car racing again from 1952, thereby given the final green light for the production of the "300 Sport Leicht" (300 Sport Light), as the car was christened. The engineers speedily continued their search for additional power potential as plenty of muscle was required for the envisaged long-distance races – and to stand up to the competition. Extensive fine-tuning boosted output to some 170 hp but for the time being, no more was to be gained from the configuration. The sports car engine with the designation M 194 differed from its civilian three-liter brethren not only in terms of output but also in that it was installed horizontally at a 50° angle towards the left. It was connected to a four-speed transmission adopted straight from the 300 – a robust assembly but, like the engine, quite heavy.

On the way to lightness

There was nothing to be done about the weight of the engine and transmission of the maturing W 194. The axles, equally adopted from the 300 and based on a racing design of 1939, were also made of steel. So the focus had to be placed on potential weight reductions elsewhere. At the time, these were to be found only in the design of the frame and bodywork and in streamlining the car to the greatest possible extent.
The X-shaped tubular frame of the 300 and a relatively light ladder-type tubular frame of a pre-war racing car were out of the question. So Rolf Uhlenhaut returned to his idea of a lightweight tubular frame he had already had in mind several years earlier. His engineers developed this idea to perfection. The result was a lightweight, grid-type tubular frame, made up of very thin tubes welded into triangles and forming a torsionally extremely stiff assembly that was subjected to compression and tensile stresses only. It weighed a meager 50 kilograms and eventually became a famous backbone, not just of the W 194 and its production version launched in 1954 but also of the successful racing and racing sports cars of 1954/55.

Cd value of 0.25 and gullwing doors

The bodybuilders in Untertürkheim and Sindelfingen went to particularly great pains in designing the aluminum body. Thanks to the obliquely installed engine and its aerodynamic styling, the body was very low as well as devoid of any frills; it featured a flat front end, rounded, aerodynamically efficient lines, fully integrated headlights and wheels that were fully covered by bodywork. The classical Mercedes radiator was dispensed with in favor of a flat, pre-war racing car face.

But there was still a Mercedes star – large and conspicuously mounted on the cooling air intake grid. The coupe roof was made as narrow as possible. The windshield was set at a distinctive angle and rounded at its A-pillar corners. The large, elongated rear screen merged into the aerodynamically efficient rear end. The result was a relatively small frontal area of 1.8 square meters and a phenomenal Cd value of 0.25.
The doors were a story all to itself. For a tubular grid-type frame to have a high level of stability, it had to be as wide as possible in the area of the passenger compartment. This necessity gave rise to the spectacular gullwing doors which were to become so famous. On the first cars, the door cutout started at waistline level. The doors, extending far into the roof, opened upwards and, being reminiscent of spread wings, were christened "gull wings" by the Americans. Driver and passenger climbed into the car from above. To facilitate the climb over the high side edge, the bodybuilders integrated a step in the lower section of the side.

Incidentally, the FIA regulations did not specify the type and direction of opening doors at the time. In spite of this, the stewards got a bit hot under the collar when the car was presented to them for scrutineering before the Mille Miglia in May 1952. To forestall any protest at a later stage, the doors were extended further into the sides after the race in Italy, thereby assuming their final shape.

Comfortable cockpit

The interior was designed as a workplace in which the driver was to feel at ease; it was therefore fully padded and lined, radiating a level of comfort that was unusual for racing cars. Speedometer and rev counter were accommodated under a common hood, below that and in somewhat smaller format were the gauges for water temperature, fuel pressure, oil temperature and oil pressure. Even a stopwatch was installed.
The bucket-type seats with high side sections and thin but comfortable upholstery were covered with tartan-style woolen fabric; the four-spoke steering wheel was removable to facilitate climbing in. The long, angled shift lever protruded from underneath the dashboard, and a walking-stick-like parking brake was located in a flat position at the left-hand sidewall. Head restraints, seat belts and power steering were still unheard of.

The archetype of the 300 SL, chassis number W 194 010 00001/52, completed its first tests in November 1951, on the Solitude racetrack just outside Stuttgart, on the Nürburgring and on the Hockenheimring. It still had narrow standard tires on steel rims, without central wheel locks but with hubcaps. The dashboard was not yet lined and the floor was not yet covered with velour carpeting. Equally, the Mercedes star and the 300 SL logo on the trunk lid had not yet found their final positions.
On March 12, 1952, the Mercedes-Benz 300 SL racing sport coupe, unusually smooth and, at a height of just 1,225 millimeters, unusually low, was presented to the excited and stunned press on the motorway between Stuttgart and Heilbronn.

The roadster lineup

After the Le Mans race, it was planned to enter the SL – of which eleven units were built altogether – in a sports car race on the Nürburgring. To shed as much weight from the four competing cars, the engineers cut the roofs off three coupes without further ado. A fourth car had been set up as a roadster right from the start. To permit easy access, the section of the door extending into the side of the car was retained, and a small windshield was mounted to deflect air and flies. The range of instruments was limited to rev counter, oil pressure and water temperature gauges. The tailpipe, previously protruding quite a way from underneath the rear end on the right-hand side, emerged from the right-hand side on the roadster. The latter was some 100 kilograms lighter than the coupe.

As well prepared as this, the 300 SL cars performed a formation 'flight' on the Nürburgring, scoring an unchallenged quadruple victory with Lang ahead of Kling, Rieß and Helfrich.

Triumph in the Carrera Panamericana Mexico

The year 1952 was an extremely successful one for Mercedes-Benz racing cars: second and fourth places in the Mille Miglia; triple victory in the sports car race in Bern; double victory in Le Mans; quadruple victory in the sports car race on the Nürburgring. After these races, the season was almost over for Mercedes.

There was one last – and big – challenge in store for the racing team, instigated by Prat Motors S.A., the resourceful Mercedes-Benz agents in Mexico City: participation in the third Carrera Panamericana Mexico, a race over five days and eight stages, 3,100 kilometers through Mexico.

Daimler-Benz accepted the challenge and engaged in scrupulous preparations, leaving nothing to chance. They even tested fuel mixtures – perfect engine operation had, after all, to be ensured at altitude differences ranging from sea level to 3,196 meters.

Four SL cars were entered in this rally, all powered by 3.1 liter engines with an output meanwhile boosted to 180 hp. Two coupe versions were driven by the teams of Kling/Klenk and Lang/Grupp. One of the two roadsters was piloted by John Fitch, an American who had joined the team and was accompanied by a dyed-in-the-wool Swabian racing mechanic by the name of Geiger. The second roadster and reserve car was driven by Günther Molter, commissioned to work as the racing team's press spokesman and assistant to Alfred Neubauer. At a later stage, he headed the Daimler-Benz press department for many years.

92 thoroughbred racing cars lined up at the start in Tuxtla Gutiérrez in the south of Mexico at 7.00 o'clock in the morning of November 19. The first to set off, at one minute intervals, were a Cadillac and a Jaguar. The Mercedes cars set off with start numbers 3 (Lang), 4 (Kling) and 6 (Fitch).

The first three sections of the 1,100 kilometer long, mountainous stage through southern Mexico saw the 300 SL out in front – as well as faced with problems, however. On the very first leg, Kling had his notorious accident with the vulture which crashed through the windshield and knocked out navigator Klenk. A dog ran straight out in front of Lang's car, damaging the latter's front end. All three cars had to change tires time and again, the rubber being literally devoured by the roads. After the third stage, Mercedes drivers Kling, Fitch and Lang occupied places 2, 3 and 4. Molter, driving the reserve car, was quite capable of keeping up with the rest although racing hors concours. He, too, had an unpleasant encounter – with a donkey.

The 2,000 kilometer northern stage from Mexico City extended over five sections to the finish in Ciudad Juarez on the Rio Grande del Norte. These were high-speed sections, taking the drivers and their cars to their very limits. Kling won the second of these sections despite a damaged tire. However, his main opponent in the Mille Miglia, Giovanni Bracco driving a Ferrari, was still seven minutes ahead of him in the overall ranking. Lang occupied third place.

The next section was equally won by Kling. At the start of the last but one stage, he was only 3.45 minutes behind Bracco who eventually informed the Mercedes-Benz crew via his friend Günther Molter that his Ferrari was unlikely to make it to the finishing line. The car's power transmission was going to pieces. This was no pretense but true sportsmanship – the Ferrari did indeed break down shortly afterwards. Fitch, occupying fourth place at that point in time, was disqualified due to an infringement of the regulations that has continued to be controversially discussed to this day; he was nevertheless allowed to finish the race hors concours.
The last section of the Panamericana, starting from Chihuahua, saw Kling and Lang out in the lead. They drove like a bat out of hell, and Fitch, too, charged ahead irresistibly. It was an unparalleled riumphal 'procession' – an average speed of 218.495 kilometers per hour was recorded for Kling on the 358 kilometer distance and entered in the official reports.

Hence, the Carrera Panamericana Mexico in 1952 had left nothing to be desired in terms of suspense and drama. The impressive double victory in this merciless long-distance race moved the gullwing coupe into the limelight for good.

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