International Avus Race on 30 May 1937. Photo taken before the start, far right: Manfred von Brauchitsch in the Mercedes-Benz W 25 Avus streamlined racing car with twelve-cylinder engine (race number 36). Other racing cars from right to left: Rudolf Hasse (race number 34, Auto Union), Luigi Fagioli (race number 33, Auto Union streamlined racing car) and Hermann Lang (race number 37, Mercedes-Benz streamlined racing car with eight-cylinder M 125 F engine). (Photo index number in the Mercedes-Benz Classic Archives: U17171)
Streamlined: Flowing curves and curved surfaces of silver-coloured sheet metal envelop the W 25 streamlined racing car in the Mercedes-Benz Museum. Almost organically, the front and rear wheel arches curve upwards from the aerodynamically optimised vehicle body. At the sides, the wheels are clad up to under the hubs with ingenious covers that can be folded up for maintenance work. For this one-off vehicle, the Mercedes-Benz engineers consistently explored the possibilities of streamlining and drive technology available at that time.
Trio: Mercedes-Benz entered no fewer than three streamlined racing cars in the formula-free International Avus Race in Berlin on 30 May 1937. They look similar, but have technical differences. In addition to the W 25 streamlined racing car with 5.6-litre twelve-cylinder MD 25 DAB engine on display in the Mercedes-Benz Museum, two vehicles with the 5.7-litre eight-cylinder M 125 F engine from the then current W 125 formula racing car were also developed for the race.
Three times on the podium: The novel vehicles were successful across the board. Rudolf Caracciola won the first preliminary race. Manfred von Brauchitsch won the second preliminary race with the vehicle exhibited in the Mercedes-Benz Museum. And the overall winner of the main race was Hermann Lang. Richard Seaman had no chance against all three, competing in a classic Mercedes-Benz W 125 with free-standing wheels.
Technology: It was also a victory for aerodynamics. Because on the straights, the vehicles reached almost 380 km/h. Even on the newly built, even steeper north curve of the Avus, the speed was still just under 370 km/h. By comparison, the last development stage of the W 25 formula racing car with free-standing wheels and 4.7-litre eight-cylinder engine from 1936 reached around 300 km/h.
Exclusive: Even conventional racing cars were made by hand and in very small series. The streamlined racing cars were even more exclusive. Von Brauchitsch’s vehicle was based on a W 25 record car with a twelve-cylinder engine that the brand with the star successfully used in 1936. An optimal starting point for the “fastest race in the world at the time” on the Avus. This is how Hermann Lang described this competition. The body of the record-breaking car had been significantly modified for the Avus Race.
Flap: Only the heads of the racers in the Mercedes-Benz streamlined racing cars could be seen during the International Avus Race in 1937. This was because, after the racing drivers had taken their seat in the vehicle, a streamlined sheet metal cover hinged at the front was folded down over the cockpit – shoulders and arms disappeared. Protection against the wind was provided by a wind deflector consisting of three small panes mounted on the flap.
Viewpoint: The wind deflector also allowed visibility of the track during the speedy ride. This was an impressive experience, especially on the extremely steep curves. Hermann Lang wrote about this later: “Driving through this Avus-Nordschleife – a unique curve – properly was a problem and required a lot of training. At first, I just couldn’t take my eyes off the line indicating the centre line of this track. Later, I ventured a glance to the side now and then. If I looked to the right, I had the strange impression of driving up a vertical wall; if I looked to the left, I seemed to see, deep below me, a sea of faces filling the interior of the curve.”
Science: The optimised aerodynamics of the streamlined body accounted for a considerable part of the speed of the Mercedes-Benz streamlined racing cars. Here, the engineers were also able to draw on findings from the record-breaking runs of 1936, for which they examined the vehicle in the wind tunnel in Friedrichshafen, among other places. In 1936, the “Allgemeine Automobil-Zeitung” (an automotive newspaper) wrote about the important effect of supposedly insignificant details such as the clad wheels: “That was wasted effort. Because the drag of the unclad wheels swallowed up three quarters of the total power.”
Automotive marvels: The three Mercedes-Benz streamlined racing cars must have seemed particularly futuristic to many fans at the 1937 Avus Race. For in the Grand Prix races of this era, the brand did not yet enter its Silver Arrows in the 750-kilogram formula with such aerodynamically clad bodywork. That would not happen until almost twenty years later in Formula One with the W 196 R. On 4 July 1954, this racing car with streamlined fairing made a furious return of the brand to Grand Prix racing with a double victory in the French Grand Prix in Reims – also known today as the “Miracle of Reims” in reference to the winning of the Football World Cup that same weekend. The W 196 R is in the Mercedes-Benz Museum just a few metres away from the W 25 streamlined racing car.
First success: Nevertheless, aerodynamic innovation had a certain tradition at the 1937 race – especially for Manfred von Brauchitsch. For it was on this track that the racing driver had won the Avus Race five years earlier on 22 May 1932 in a private Mercedes-Benz SSKL with an innovative streamlined body designed by aerodynamics pioneer Reinhard von Koenig-Fachsenfeld. This success finally put the importance of an aerodynamically designed body on the engineers’ agenda – first for racing cars and exclusive vehicles with “motorway courier” bodies, and later for production vehicles as well
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