Mercedes-Benz W 25

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W 25 from 1934
Mercedes W 25 from 1934, side view
Mercedes W 25 from 1934, rear view
W25 streamlined record car from 1936

The Mercedes-Benz W 25 was a single-seater racing car with free-standing wheels that Mercedes-Benz built from 1934 to 1936 for the "750 kg formula". “750 kg formula” meant that the car with wheels but without tires, without fuel, oil and cooling water could weigh a maximum of 750 kilograms. The chief designer was Hans Nibel . Other designers worked on the project Max Wagner, responsible for the chassis tuning, Albert Heeß and Otto Schilling for the engine. Overall responsibility for the project was carried out by Fritz Nallinger .

technology

The Mercedes-Benz W 25 had an in-line eight-cylinder supercharged engine with an initially 3.36 liter displacement (bore 78 mm, stroke 88 mm), four-valve technology and an output of 354 hp (260 kW). In order to achieve the performance mentioned, the engine needed a mixture of 86% methyl alcohol, 4.4% nitrobenzene, 8.8% acetone and 0.8% ether as fuel. The car was further developed into the W 25 B with 4 liter displacement and 430 hp from 1935 , 4.3 liter displacement in 1936 and finally 4.7 liters. The fuel consumption of the engines was around 100 liters per 100 km.

The engine weighed 211 kilograms (another source cites 114 kilograms). Manual transmission and differential were on the rear axle. Two U-profile longitudinal members with cross struts formed the frame on which a hand- driven aluminum body with a tapering rear was placed. Up to 1935, the wheels were individually suspended, at the front on double wishbones with coil springs, and at the rear on a pendulum axle ("swing axle") with quarter-elliptic leaf springs. In 1936, instead of the pendulum rear axle, there was a rigid De Dion axle . The drum brakes on both axles were operated hydraulically.

Races

After test drives in Monza , Italy, among other places , the Mercedes-Benz W 25 was supposed to start the AVUS race for the first time in 1934 , but was not ready to race in time. First use of the car was therefore on June 3 at the Eifel race on the Nürburgring in one set with 44 starters field, Manfred von Brauchitsch with 1:20 minutes ahead of Hans Stuck on Auto Union Type A won. Von Brauchitsch drove the 15 laps or 342.150 kilometers on the Nordschleife in 2: 47: 36.4 hours, which corresponds to an average speed of 122.48 km / h. At the German Grand Prix on June 28th at the Nürburgring, which was held over 570.250 kilometers, Luigi Fagioli in a Mercedes-Benz finished second in 4: 40: 26.2 hours, 2:07 minutes behind Hans Stuck on Auto Union . This was followed by victories at the Coppa Acerbo as well as the Italian Grand Prix and the Spanish Grand Prix . At the French Grand Prix, however, all W 25s were eliminated.

1935 was Rudolf Caracciola 25 with the W European champion . Mercedes won nine out of ten races. Among other things, Caracciola won the Eifel race with 1.9 seconds ahead of Bernd Rosemeyer in Auto Union. Hermann Lang in a Mercedes-Benz, who drove his first race, was fifth; Manfred von Brauchitsch dropped out. At the German Grand Prix , von Brauchitsch drove the fastest lap on the Nürburgring to date with 10:32 minutes, but lost victory seven kilometers from the finish due to a blown tire. Caracciola came third.

In the 1936 season , Auto Union with Bernd Rosemeyer was the superior brand. Mercedes-Benz only won the Monaco Grand Prix and the Tunisian Grand Prix , both with Rudolf Caracciola. The reason for the unsatisfactory success was possibly the chassis with a shorter wheelbase of the M 25 that was modified in 1936.

Record car

Based on the Grand Prix car, a streamlined vehicle with a 12-cylinder V engine was built for record drives in 1936. On October 26, 1936, Rudolf Caracciola reached a top speed of 366.9 km / h with this car on the Frankfurt – Heidelberg motorway. The engine had a displacement of 4980 cm³ with an output of 540 hp (420 kW). As early as December 1934, Caracciola had set a record with a W 25, the engine of which had been enlarged to 3990 cm³. He reached a speed of 311.38 km / h with the monoposto on the AVUS, measured over a 5 km distance with a flying start.

Technical specifications

Parameters Data
Publishing year 1934 1935 1935 1936
Engine type M 25 A M 25 A / B M 25 B M 25 C
engine Eight-cylinder four-stroke in-line engine, 5 crankshaft bearings, 2 rising current carburettors (Mercedes-Benz),
2 overhead camshafts with spur gear drive, 4-valve technology,
1 Roots compressor, water cooling
Displacement 3360 cc 3710 cc 3990 cc 4310 cc
Bore × stroke 78 × 88 mm 82 × 88 mm 82 x 94.5 mm 82 × 102 mm
Power (mean) 314 hp at 5800 rpm 348 hp at 5800 rpm 430 hp at 5800 rpm 402 hp at 5500 rpm
transmission 4-speed gearbox (installed on the rear axle),
gate shift to the right of the driver's seat
chassis U-profile ladder frame
Front suspension double wishbones with coil springs
Rear suspension Swing axle (pendulum axle) with quarter elliptic leaf springs De Dion axis,
quarter elliptic leaf springs
Shock absorbers Friction shock absorbers hydraulic dampers
Brakes Drum brakes (hydraulically operated)
wheelbase 2717 mm 2464 mm
Front / rear track 1422/1473
Tank capacity 215 liters

Source: Silver Arrows - The legendary racing cars from 1934 to 1955 . Heel Verlag, Königswinter 1995, ISBN 3-89365-428-3 .

Silver arrow

With the Mercedes-Benz W 25, the term Silver Arrow allegedly came about after - as it is said - the cars for the Eifel Race in 1934 were one kilogram too heavy and the mechanics sanded off the paint the night before the start to reduce weight. The matt silver shimmering aluminum came to light and was the reason for the name. There have long been doubts about this story, and the reasons for this are various. Among other things, the radio reporter Paul Laven had already described a Mercedes-Benz SSKL with a silver streamlined body at the German Grand Prix at the AVUS in 1932 as the “silver arrow”. In addition, it is unlikely that Mercedes-Benz traveled to the Nürburgring with cars that were too heavy and trusted that the excess weight would not be noticed.

Web links

Commons : Mercedes-Benz W 25  - Collection of pictures, videos and audio files

Individual evidence

  1. motor catalog race cars, race tracks, racing driver. 3. Edition. Gildeverlag Hans-Gerhard Dobler, Alfeld (Leine) 1963, p. 13.
  2. a b c Klaus-Achim Peitzmeier: Silver Arrows . Eco Verlag, Cologne 1998, ISBN 3-933468-81-7 , pp. 19-23.
  3. Klaus-Achim Peitzmeier: Return of a legend - "Silver Arrows" . ECO Verlag, Cologne 1998, ISBN 3-933468-81-7 , p. 108.
  4. a b c d e f Halwart Schrader: Silver Arrows - The legendary racing cars 1934 to 1955 . Heel Verlag, Königswinter 1995, ISBN 3-89365-428-3 , p. 31 ff.
  5. a b Denis Jenkinson : The Mercedes-Benz Grand Prix Car W 125, 1937 . Motorbuch Verlag, Stuttgart 1971, pp. 7-10.
  6. mercedesamgf1.com
  7. a b mercedesamgf1: Mercedes W 25 Accessed June 8, 2017.
  8. a b c Michael Behrndt, Jörg-Thomas Födisch, Matthias Behrndt: ADAC Eifelrennen . Heel Verlag, Königswinter 2009, ISBN 978-3-86852-070-5 .
  9. a b Thora Hornung: 50 years of the Nürburgring . Görres-Verlag, Koblenz.
  10. https://www.mercedesamgf1.com/de/heritage/silberpfeile/mercedes-w-25/ "The vehicle frame consists of two longitudinal members in a U-profile with cross bracing, for weight reasons, like on the SSKL, with multiple holes."