Stuttgart – Mercedes-Benz Classic will be taking four genuine pre-war Silver Arrows to this year’s Goodwood Revival (14 – 16 September 2012). One of them is a Grand Prix car from the W 125 series which was specially constructed for the 1937 season. This car made its first appearance 75 years ago and promptly presented Mercedes-Benz with an extremely successful racing season, taking the brand onto the medallists’ podium once again.
At this year’s Goodwood Revival, Mercedes-Benz Classic will be taking part in the demonstration race of the 1930s Silver Arrows, together with Audi Tradition which will be represented by five cars built by Auto Union.
The historic racing cars being used in the race by Mercedes-Benz Classic meet the brand’s high standards regarding authenticity. They are genuine 1930s vehicles. Visitors to the Goodwood Revival will be able to experience a W 25 (1934), a W 125 (1937), a W 154 (1939) as well as a W 165 (1939) up close. They have been owned by the manufacturer without interruption right up to the present day and are original in almost all their details. In cases where parts had to be renewed, for instance, for safety reasons, they correspond exactly to the manufacturer’s specifications and standards. Daimler AG is in a unique position here: as the manufacturer of all the products and also as the sole supplier, the company has the whole spectrum at its disposal and can therefore provide the proof that the vehicle is genuine and can also ensure that it is kept in its original state.
1937 season extremely successful thanks to the W 125
During its premiere at the Tripoli Grand Prix on 9 May 1937, the supercharged engine roared huskily round the Mellaha racing circuit. It was – as was proved during the race under the North African sun – the call of the ultimate racing car of that year. The Mercedes-Benz W 125 not only won its premiere race with Hermann Lang at the wheel, but was also successful in many other races during the same year: Rudolf Caracciola once more managed to secure the 1937 European Championship title of the Association Internationale des Automobile Clubs Reconnus (AIACR) by winning three of the five races for Mercedes-Benz.
Great passion and the highest technical expertise combined to create the completely new design of this Grand Prix car. Using what was basically a completely new construction, the Mercedes-Benz racing department demonstrated the greatest faith in their own skills as the W 125 was designed especially for this particular year. 1937 was the fourth and at the same time the last season in which the 750 kilogram formula applied. After three years of using the W 25 for these races, the Stuttgart engineers did themselves proud by pulling a completely new racing car out of the hat just before the end of the era.
Great success at international races for the W 125
It was up to the W 125 to put its strongest competitors from the Auto Union once more into their place, after Bernd Rosemeyer had won the European Championship for the brand in 1936. And the car did just that by more than living up to all expectations. Rudolf Caracciola won the Grand Prix in Germany (Nürburgring), Switzerland (Bremgarten) and Italy (Livorno) which all counted towards the European Championship and Manfred von Brauchitsch was the first to see the chequered flag from behind the wheel of a W 125 at the Monaco Grand Prix.
Mercedes-Benz was also able to take home victories at Grand Prix races which were not counted towards the championship. Lang won in Tripoli and Caracciola took home the Masaryk Grand Prix in Brünn. In addition there were also second and third places for Caracciola and von Brauchitsch at the Eifel race and second place for Richard Seaman at the Vanderbilt Cup in New York (actually only the second race where the Stuttgart works team had taken part in the United States) as well as at the Coppa Acerbo in Pescara. At the Donington Grand Prix in England, von Brauchitsch crossed the finishing line in second place – in front of Caracciola who came third.
As well as the Grand Prix cars, which were specially designed for long-distance races, Mercedes-Benz also built two W 125 cars especially for hillclimb events. They were distinguished by their extremely light construction. Both the lighter version and the Grand Prix racing version of the W 125 were used for hillclimb racing in 1938 and 1939.
Turbocharger used to compress finished mixture
The wheelbase of the 4200 mm long, 1750 mm wide and only 1200 mm high racing car is 2798 mm long. Its track is 1473 mm at the front and 1412 mm at the rear. The whole car only weighs 749 kg without its driver, fuel and tyres. In this way the 750 kg formula was implemented very precisely.
The W 125 was powered by a straight eight-cylinder engine with 5660 cc displacement. There were two intake and two exhaust valves per cylinder arranged slanting overhead and activated by a rocker arm. Two suction carburettors were responsible for making the mixture and a Roots compressor was fitted behind them to provide the compression. The fact that the mechanical supercharger was fitted behind the carburettors so that the turbocharger then compressed the finished mixture was a premiere for Mercedes-Benz racing cars.
The engine with its top performance of almost 600 hp (441 kW) was also used in a special version of the W 25 which successfully took part in the Avus race. The W 25 version used by Caracciola and Lang for the race was given a streamlined body and powered by the M 125 engine of the current racing car of the time. It was with one of these cars that Hermann Lang won, while Richard Seaman, driving one of the classic W 125 Grand Prix cars without a streamlined body and with open wheels, only managed to cross the finishing line in fifth place. The use of streamlined vehicles in 1937 gave Mercedes-Benz important input for its research into developing racing and record vehicles with completely covered bodies.
Aerodynamic improvements were made to the record vehicle based on a W 125 driven by Rudolf Caracciola in 1938 and in which he achieved the fastest-ever measured speed on a public road. The record car – based on the W 125 and powered by a strong 736 hp (541 kW) V12 engine – achieved a record speed of 432.692 km/h over one kilometre with a rolling start and 432.360 km/h over one mile (1,609.30 m) with a rolling start on the Frankfurt–Darmstadt motorway.
Visionary technical details
The W 125 was mainly developed according to the ideas of construction engineer Rudolf Uhlenhaut who was appointed technical manager of the newly-created racing department in mid-1936. The backbone of the car was an extremely robust frame made of nickel-chrome-molybdenum steel with four cross members. Instead of having a frame with box sections as used for the W 25, the W 125 was given a tubular frame with an elliptic cross-section. In this way, the torsional strength of the vehicle without an engine was three times that of its predecessor.
The wheels were controlled at the front by double wishbone steering with coil springs. At the back, a De Dion double-jointed axle with lengthwise mounted torsion bar spring and hydraulic lever arm shock absorbers provided constant camber and the best-possible road holding. Suspension arms pass on the acceleration and braking torque to the chassis.
During extensive trials at the Nürburgring, Rudolf Uhlenhaut, the new technical racing manager, who was also a very talented driver and just as fast as the works racing drivers, personally tested the 1936 Silver Arrow, which was no longer able to compete. On the basis of this experience, he decided to use a revolutionary innovative chassis design for the new Silver Arrow W 125. He promptly reversed the suspension tuning normally used at that time – hard sprung with little cushioning – thus pointing the way to the future. The W 125 rolled to the start softly sprung with especially long spring travel and can therefore be regarded as the precursor for all modern Mercedes-Benz sports cars. The W 125 was unmistakable from the outside with the three air inlets at the front.
Memories of a successful season
The W 125 was only used for competing in Grand Prix races for a single year. In 1938 Mercedes-Benz replaced it with the W 154 which was constructed in accordance with the new 3-litre formula. However, the Mercedes-Benz experts were able to appreciate the pioneering technology used in the successful racing car from 1937. Chassis engineer Max Wagner took over the advanced chassis architecture of the W 125 almost unaltered for the W 154.
The legendary racing car which had its premiere in 1937 still holds a star position in our memories. For instance, the W 125 was “an extraordinary racing car which deserves its very special place in the annals of motor racing history,” wrote the famous motor racing historian and Silver Arrow expert Louis Sugahara in his standard work on the Mercedes-Benz Grand Prix vehicles from 1934 to 1955.