Mercedes-Benz W125
Encyclopedia
The Mercedes-Benz W125 was a Grand Prix
racing car
designed by Rudolf Uhlenhaut
to race during the 1937 Grand Prix season
. The car was used by Rudolf Caracciola
to win the 1937 European Championship
and W125 drivers also finished in the second, third and fourth positions in the championship.
The supercharged engine, with 8 cylinders in line (94.0 x 102.mm) and 5,662.85 cc (345.56 CID), attained an output of up to 595 horse power (444 kW) in race trim. The highest test bed power measured was 637 BHP (646 PS) at 5,800 rpm. It gave 245 BHP (248 PS) at a mere 2,000 rpm. In 1938, the engine capacity of supercharged Grand Prix cars was limited to 3000cc, and the W125 was replaced by the Mercedes-Benz W154
.
The W125 was considered the most powerful race car ever for about 3 decades, until large capacity US-built V8 engines in CanAm
sportcars reached similar power in the mid 1960s. In Formula One
racing itself, the figure was not exceeded until the early 1980s, with the appearance of turbo-charged engines in Formula One.
The W125 reached race speeds of well over 300 km/h (186.4 mph) in 1937, especially on the AVUS
in Berlin
, equipped with a streamlined body.
In land speed record
runs, a Mercedes-Benz W125 Rekordwagen
was clocked at 432.7 km/h (268.9 mph) over a mile and a kilometer. This car was fitted with a DAB V12 engine (82.0 x 88 mm) of 5,576.75 cc (340.31 CID) with a power of 726 BHP (736 PS) at 5,800 rpm. The weight of this engine caused the car to weigh over the 750 kg maximum limit, so it never appeared in Grand Prix.
midway through the year in order to concentrate on designing a car that would see them return to the top of the rankings. A new racing department ('Rennabteilung') was set up within Mercedes-Benz in order to work on the car. Rudolf Uhlenhaut
, previously a production car engineer for the company, was selected to lead the design team. Uhlenhaut had not previously designed a racing car, but had significant experience testing road cars on the Nürburgring
race track, experience which allowed him to adapt his knowledge relatively easily to race cars.
When testing the old W25 car, Uhlenhaut remarked that the suspension was too stiff, preventing the wheels from following the road. During the test session, a wheel came off the car, yet Uhlenhaut continued to drive the car as if nothing had happened. This stiffness caused the chassis to flex and the rear axle to bend by up to 7-10 cm (3-4 inches) under braking. The brief for the new car included a stiffer chassis and more travel on the suspension to avoid the problems experienced in the 1936 car.
The W125 had a much stiffer tubular frame construction compared to the previous W25 model. This was achieved using oval tubes made of nickel-chrome molybdenum steel which flexed considerably less than the frame used in the W25.
The bodywork of the W125 was aluminium metal, which like its predecessor was left unpainted in its bare silver colour. This brought Mercedes' cars during this period (and rivals Auto Union
, whose cars were the same colour) the nickname of Silver Arrows, the racing colours of Germany being silver.
Like its W25 predecessor, the W125 used a 4-speed manual transmission. The gearbox design was changed to a constant mesh type, which provided better reliability compared to the unsynchronized transmission of the M25. In a constant mesh gearbox, the transmission gears are always in mesh and rotating, but the gears are not rigidly connected to the shafts on which they rotate. Instead, the gears can freely rotate or be locked to the shaft on which they are carried. The previous unsynchronised transmission required the gears to be spinning at roughly the same speed when engaged; otherwise, the teeth would refuse to mesh.
with Mercedes-Benz entering four cars. German Hermann Lang
won his first Grand Prix motor race to give the W125 a victory on its début and provide Mercedes with their first victory over rivals Auto Union since May 1936. The next race was held at the AVUS
motor-racing circuit in Germany, a 12 miles (19 km) long circuit consisting of two long straights of approximately 6 miles (10 km) length joined at either end by a curve. As such, it was possible for a car to reach its top speed. Mercedes entered two W125 cars, a streamliner which was modified from the original design to increase its top speed on the straights and a standard car driven by Richard Seaman in case of problems with the streamliner. The streamliner had a top speed 25 km/h (16 mph) faster than the regular car. On lap three of the race, the streamliner retired while leading due to a gearbox failure. Seaman's regular W125 finished in fifth position.
At the Eifelrennen held at the Nürburgring circuit, Mercedes entered five W125's, including one driven by Christian Kautz
fitted with the new suction carburettor supercharger system. Kautz finished in ninth, while team-mates Rudolf Caracciola
and Manfred von Brauchitsch
finished in second and third places. For the next race, Mercedes split their entries between two races which occurred within a week of another. Two cars were sent to the USA to compete in the Vanderbilt Cup
, one of which was fitted with the suction carburettor supercharger used on Kautz's car, and three cars went to Belgium to compete in the first round of the 1937 European Championship. Richard Seaman finished second in the Vanderbilt, and third and fourth place were achieved in the Belgian Grand Prix
. Following Seaman's success in the Vanderbilt with the new supercharger system, it was fitted to all of the W125s.
The following two races were also both part of the European Championship. The next round in Germany saw both Mercedes and rivals Auto Union competing on home soil. Mercedes triumphed, as Rudolf Caracciola
took his first victory of the year and Manfred von Brauchitsch
followed him home in second position. In the next round at Monaco, the positions were reversed as von Brauchitsch won and Caracciola finished in second. A third Mercedes W125, driven by Christian Kautz, took third place.
The non-championship Coppa Acerbo
in Italy was the next event the W125 entered. During practice Richard Seaman crashed into a house and destroyed his car. Therefore only von Brauchitsch and Caracciola started the race. During the race, Seaman took over from Caracciola and despite an engine fire, he finished the race fifth. von Brauchitsch fared better finishing in second position. The Swiss Grand Prix was the penultimate round of the 1937 European Championship. Like in Monaco, Mercedes W125s finished in the top three places, Caracciola taking the win with Hermann Lang in second and von Brauchitsch third. The final round of the championship marked a return to Italy, where at the Livorno Circuit, Caracciola held off team-mate Lang to win the race by 0.4 seconds and become European Champion. von Brauchitsch retired from the race and took second place overall in the Championship. Kautz and Lang took third and fourth places meaning Mercedes drivers occupied the top four positions in the championship table.
The W125 entered into two non-championship events before the end of the season. The Masaryk Grand Prix in Czechoslovakia gave the W125 its final victory when Caracciola won the race, von Brauchitsch finished second and Seaman came in third. The race was marred as Hermann Lang had crashed into spectators on lap five, resulting in twelve injuries and two deaths. The final competitive race Mercedes entered the W125 into was the 1937 Donington Grand Prix. Rosemeyer prevailed, von Brauchitsch finished in second place and Caracciola in third while both of the other W125s failed to finish. The British ERA were outclassed, failing to get classified in their home race.
, and the W125 was withdrawn from racing.
†Seaman's car was destroyed in practice and did not start. During the race, Seaman took over Carraciola's car and finished fifth.
Grand Prix motor racing
Grand Prix motor racing has its roots in organised automobile racing that began in France as far back as 1894. It quickly evolved from a simple road race from one town to the next, to endurance tests for car and driver...
racing car
Auto racing
Auto racing is a motorsport involving the racing of cars for competition. It is one of the world's most watched televised sports.-The beginning of racing:...
designed by Rudolf Uhlenhaut
Rudolf Uhlenhaut
Rudolf Uhlenhaut , was an Anglo-German engineer and executive for Mercedes-Benz...
to race during the 1937 Grand Prix season
1937 Grand Prix Season
The 1937 Grand Prix season was the fifth AIACR European Championship season. The championship was won by Rudolf Caracciola, driving for the Mercedes-Benz team...
. The car was used by Rudolf Caracciola
Rudolf Caracciola
Otto Wilhelm Rudolf Caracciola , more commonly Rudolf Caracciola , was a racing driver from Remagen, Germany. He won the European Drivers' Championship, the pre-1950 equivalent of the modern Formula One World Championship, an unsurpassed three times...
to win the 1937 European Championship
European Championship (auto racing)
The European Drivers' Championship was an annual competition in auto racing that existed prior to the establishment of the Formula One world championship in 1950...
and W125 drivers also finished in the second, third and fourth positions in the championship.
The supercharged engine, with 8 cylinders in line (94.0 x 102.mm) and 5,662.85 cc (345.56 CID), attained an output of up to 595 horse power (444 kW) in race trim. The highest test bed power measured was 637 BHP (646 PS) at 5,800 rpm. It gave 245 BHP (248 PS) at a mere 2,000 rpm. In 1938, the engine capacity of supercharged Grand Prix cars was limited to 3000cc, and the W125 was replaced by the Mercedes-Benz W154
Mercedes-Benz W154
The Mercedes-Benz W154 was a Grand Prix racing car designed by Rudolf Uhlenhaut. The W154 competed in the 1938 and 1939 Grand Prix seasons and was used by Rudolf Caracciola to win the 1938 European Championship....
.
The W125 was considered the most powerful race car ever for about 3 decades, until large capacity US-built V8 engines in CanAm
CanAm
The Canadian-American Challenge Cup or Can-Am, was an SCCA/CASC sports car racing series from 1966 to 1986.-History:Can-Am started out as a race series for Group 7 sports racers with two races in Canada and four races in the United States of America . The series was initially sponsored by Johnson...
sportcars reached similar power in the mid 1960s. In Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...
racing itself, the figure was not exceeded until the early 1980s, with the appearance of turbo-charged engines in Formula One.
The W125 reached race speeds of well over 300 km/h (186.4 mph) in 1937, especially on the AVUS
AVUS
The Automobil-Verkehrs- und Übungs-Straße, better known as AVUS, is a public road that was also used as a motor racing circuit. It is located in the south-western districts of Berlin, Germany, between Charlottenburg and Nikolassee, and is nowadays an important part of the public highway system, as...
in Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, equipped with a streamlined body.
In land speed record
Land speed record
The land speed record is the highest speed achieved by a wheeled vehicle on land. There is no single body for validation and regulation; in practice the Category C flying start regulations are used, officiated by regional or national organizations under the auspices of the Fédération...
runs, a Mercedes-Benz W125 Rekordwagen
Mercedes-Benz W125 Rekordwagen
The Mercedes-Benz W125 Rekordwagen was an experimental, high-speed automobile produced in the late 1930s. The streamlined car was derived from the 1937 open-wheel race car Mercedes-Benz W125 Formel-Rennwagen, of which also a streamlined version was raced at the non-championship Avusrennen in...
was clocked at 432.7 km/h (268.9 mph) over a mile and a kilometer. This car was fitted with a DAB V12 engine (82.0 x 88 mm) of 5,576.75 cc (340.31 CID) with a power of 726 BHP (736 PS) at 5,800 rpm. The weight of this engine caused the car to weigh over the 750 kg maximum limit, so it never appeared in Grand Prix.
Concept
Due to the uncompetitiveness of their W25 car, Mercedes pulled out of the 1936 Grand Prix Season1936 Grand Prix Season
The 1936 Grand Prix season was the fourth AIACR European Championship season. The championship was won by Bernd Rosemeyer, driving for the Auto Union team...
midway through the year in order to concentrate on designing a car that would see them return to the top of the rankings. A new racing department ('Rennabteilung') was set up within Mercedes-Benz in order to work on the car. Rudolf Uhlenhaut
Rudolf Uhlenhaut
Rudolf Uhlenhaut , was an Anglo-German engineer and executive for Mercedes-Benz...
, previously a production car engineer for the company, was selected to lead the design team. Uhlenhaut had not previously designed a racing car, but had significant experience testing road cars on the Nürburgring
Nürburgring
The Nürburgring is a motorsport complex around the village of Nürburg, Germany. It features a modern Grand Prix race track built in 1984, and a much longer old North loop track which was built in the 1920s around the village and medieval castle of Nürburg in the Eifel mountains. It is located about...
race track, experience which allowed him to adapt his knowledge relatively easily to race cars.
When testing the old W25 car, Uhlenhaut remarked that the suspension was too stiff, preventing the wheels from following the road. During the test session, a wheel came off the car, yet Uhlenhaut continued to drive the car as if nothing had happened. This stiffness caused the chassis to flex and the rear axle to bend by up to 7-10 cm (3-4 inches) under braking. The brief for the new car included a stiffer chassis and more travel on the suspension to avoid the problems experienced in the 1936 car.
Chassis and suspension
The bodywork of the W125 was aluminium metal, which like its predecessor was left unpainted in its bare silver colour. This brought Mercedes' cars during this period (and rivals Auto Union
Auto Union
Auto Union was an amalgamation of four German automobile manufacturers, founded in 1932 and established in 1936 in Chemnitz, Saxony, during the Great Depression. The company has evolved into present day Audi, as a subsidiary of Volkswagen Group....
, whose cars were the same colour) the nickname of Silver Arrows, the racing colours of Germany being silver.
Engine and transmission
With no regulations limiting engine size, other than the 750 kg total car weight limit, Mercedes designed a 5.6 litre engine configured with eight inline cylinders and an overhead camshaft for the W125. Named the M125, the engine was also fitted with a Roots type supercharger producing 632 lbft of torque at the start of the season. The engines built varied in power, attaining an output between 560 and 595 horse power (418-444 kW) at 5800 rpm. Fuel used was a custom mix of 40% methyl alcohol, 32% benzene, 24% ethyl alcohol and 4% gasoline light. The engine weighed 222 kg (490 lbs) - approximately 30% of the total weight of the car, and was mounted in the front of the car.Like its W25 predecessor, the W125 used a 4-speed manual transmission. The gearbox design was changed to a constant mesh type, which provided better reliability compared to the unsynchronized transmission of the M25. In a constant mesh gearbox, the transmission gears are always in mesh and rotating, but the gears are not rigidly connected to the shafts on which they rotate. Instead, the gears can freely rotate or be locked to the shaft on which they are carried. The previous unsynchronised transmission required the gears to be spinning at roughly the same speed when engaged; otherwise, the teeth would refuse to mesh.
Racing history
The W125 made its first competitive outing in May at the 1937 Tripoli Grand PrixTripoli Grand Prix
The Tripoli Grand Prix was a motor racing event first held in 1925 on a racing circuit outside Tripoli, the capital of what was then Italian Tripolitania...
with Mercedes-Benz entering four cars. German Hermann Lang
Hermann Lang
Hermann Lang was a German champion race car driver.Born in the Bad Cannstatt district of Stuttgart, Baden-Württemberg, Germany, at age fourteen Hermann Lang had to go to work to help support his family following the death of his father...
won his first Grand Prix motor race to give the W125 a victory on its début and provide Mercedes with their first victory over rivals Auto Union since May 1936. The next race was held at the AVUS
AVUS
The Automobil-Verkehrs- und Übungs-Straße, better known as AVUS, is a public road that was also used as a motor racing circuit. It is located in the south-western districts of Berlin, Germany, between Charlottenburg and Nikolassee, and is nowadays an important part of the public highway system, as...
motor-racing circuit in Germany, a 12 miles (19 km) long circuit consisting of two long straights of approximately 6 miles (10 km) length joined at either end by a curve. As such, it was possible for a car to reach its top speed. Mercedes entered two W125 cars, a streamliner which was modified from the original design to increase its top speed on the straights and a standard car driven by Richard Seaman in case of problems with the streamliner. The streamliner had a top speed 25 km/h (16 mph) faster than the regular car. On lap three of the race, the streamliner retired while leading due to a gearbox failure. Seaman's regular W125 finished in fifth position.
Christian Kautz
Christian Kautz was an auto racing driver from Switzerland.Son of a Swiss multi-millionaire, his career started with Mercedes-Benz as a junior driver in 1936, then as an Auto Union junior driver in 1938, starting in three Grands Prix. Kautz was a testpilot for Lockheed in the USA during the Second...
fitted with the new suction carburettor supercharger system. Kautz finished in ninth, while team-mates Rudolf Caracciola
Rudolf Caracciola
Otto Wilhelm Rudolf Caracciola , more commonly Rudolf Caracciola , was a racing driver from Remagen, Germany. He won the European Drivers' Championship, the pre-1950 equivalent of the modern Formula One World Championship, an unsurpassed three times...
and Manfred von Brauchitsch
Manfred von Brauchitsch
Manfred Georg Rudolf von Brauchitsch was a German auto racing driver who drove for Mercedes-Benz in the famous "Silver Arrows" of Grand Prix motor racing in the 1930s....
finished in second and third places. For the next race, Mercedes split their entries between two races which occurred within a week of another. Two cars were sent to the USA to compete in the Vanderbilt Cup
Vanderbilt Cup
The Vanderbilt Cup was the first major trophy in American auto racing.-History:An international event, it was founded by William Kissam Vanderbilt II in 1904 and first held at a course set out in Nassau County on Long Island, New York. The announcement that the race was to be held caused...
, one of which was fitted with the suction carburettor supercharger used on Kautz's car, and three cars went to Belgium to compete in the first round of the 1937 European Championship. Richard Seaman finished second in the Vanderbilt, and third and fourth place were achieved in the Belgian Grand Prix
Belgian Grand Prix
The Belgian Grand Prix is an automobile race, part of the Formula One World Championship....
. Following Seaman's success in the Vanderbilt with the new supercharger system, it was fitted to all of the W125s.
The following two races were also both part of the European Championship. The next round in Germany saw both Mercedes and rivals Auto Union competing on home soil. Mercedes triumphed, as Rudolf Caracciola
Rudolf Caracciola
Otto Wilhelm Rudolf Caracciola , more commonly Rudolf Caracciola , was a racing driver from Remagen, Germany. He won the European Drivers' Championship, the pre-1950 equivalent of the modern Formula One World Championship, an unsurpassed three times...
took his first victory of the year and Manfred von Brauchitsch
Manfred von Brauchitsch
Manfred Georg Rudolf von Brauchitsch was a German auto racing driver who drove for Mercedes-Benz in the famous "Silver Arrows" of Grand Prix motor racing in the 1930s....
followed him home in second position. In the next round at Monaco, the positions were reversed as von Brauchitsch won and Caracciola finished in second. A third Mercedes W125, driven by Christian Kautz, took third place.
The non-championship Coppa Acerbo
Coppa Acerbo
The Coppa Acerbo was an automobile race held in Italy, named after Tito Acerbo, the brother of Giacomo Acerbo, a prominent fascist politician. Following Italy's defeat in World War II, and the consequent demise of fascism, the race was renamed the Circuito di Pescara, and in some years was also...
in Italy was the next event the W125 entered. During practice Richard Seaman crashed into a house and destroyed his car. Therefore only von Brauchitsch and Caracciola started the race. During the race, Seaman took over from Caracciola and despite an engine fire, he finished the race fifth. von Brauchitsch fared better finishing in second position. The Swiss Grand Prix was the penultimate round of the 1937 European Championship. Like in Monaco, Mercedes W125s finished in the top three places, Caracciola taking the win with Hermann Lang in second and von Brauchitsch third. The final round of the championship marked a return to Italy, where at the Livorno Circuit, Caracciola held off team-mate Lang to win the race by 0.4 seconds and become European Champion. von Brauchitsch retired from the race and took second place overall in the Championship. Kautz and Lang took third and fourth places meaning Mercedes drivers occupied the top four positions in the championship table.
The W125 entered into two non-championship events before the end of the season. The Masaryk Grand Prix in Czechoslovakia gave the W125 its final victory when Caracciola won the race, von Brauchitsch finished second and Seaman came in third. The race was marred as Hermann Lang had crashed into spectators on lap five, resulting in twelve injuries and two deaths. The final competitive race Mercedes entered the W125 into was the 1937 Donington Grand Prix. Rosemeyer prevailed, von Brauchitsch finished in second place and Caracciola in third while both of the other W125s failed to finish. The British ERA were outclassed, failing to get classified in their home race.
Retirement from racing
1938 saw changes in the rules, with the maximum limit on weight being replaced with a maximum limit on engine capacity and a minimum weight for the car being introduced; the W125 was no longer eligible for entry without major modification. Instead, Mercedes-Benz developed a new car, the Mercedes-Benz W154Mercedes-Benz W154
The Mercedes-Benz W154 was a Grand Prix racing car designed by Rudolf Uhlenhaut. The W154 competed in the 1938 and 1939 Grand Prix seasons and was used by Rudolf Caracciola to win the 1938 European Championship....
, and the W125 was withdrawn from racing.
European Championship
(results in bold indicate pole position)EWLINE
|
Non Championship results
| Year | Team | Engine | Drivers | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|---|---|---|
| 1937 1937 Grand Prix Season The 1937 Grand Prix season was the fifth AIACR European Championship season. The championship was won by Rudolf Caracciola, driving for the Mercedes-Benz team... |
Daimler-Benz AG Daimler-Benz Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had... |
Mercedes-Benz Mercedes-Benz Mercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG... M125 |
TRI | AVUS | EIF | VAN | ACE | MAS | DON | |
| Hermann Lang Hermann Lang Hermann Lang was a German champion race car driver.Born in the Bad Cannstatt district of Stuttgart, Baden-Württemberg, Germany, at age fourteen Hermann Lang had to go to work to help support his family following the death of his father... |
1 | 9 | DNF | DNF | ||||||
| Rudolf Caracciola Rudolf Caracciola Otto Wilhelm Rudolf Caracciola , more commonly Rudolf Caracciola , was a racing driver from Remagen, Germany. He won the European Drivers' Championship, the pre-1950 equivalent of the modern Formula One World Championship, an unsurpassed three times... |
6 | DNF | 2 | DNF | 5† | 1 | 3 | |||
| Richard Seaman Richard Seaman Richard John Beattie "Dick" Seaman , was one of the greatest pre-war Grand Prix drivers from Britain.... |
7 | 5 | DNF | 2 | DNS/5† | 4 | DNF | |||
| Manfred von Brauchitsch Manfred von Brauchitsch Manfred Georg Rudolf von Brauchitsch was a German auto racing driver who drove for Mercedes-Benz in the famous "Silver Arrows" of Grand Prix motor racing in the 1930s.... |
DNF | 3 | 2 | 2 | 2 | |||||
†Seaman's car was destroyed in practice and did not start. During the race, Seaman took over Carraciola's car and finished fifth.
Further reading
- Chris Nixon, Racing the Silver Arrows: Mercedes-Benz versus Auto Union 1934-1939 (Osprey, London, 1986)