With the Mercedes-Benz W125 the German brand achieved a speed record that lasted 80 years.
On January 28, 1938 the German Rudolf Caracciola, aboard a Mercedes-Benz W125 Rekordwagen with a twelve-cylinder engine, set the world record on a public highway by reaching the 432,692 km/h on the highway between Frankfurt and Darmstadt. But to achieve that milestone, the Stuttgart house had to work hard and in a short time ...
After having excelled in 1937 with several triumphs, Mercedes-Benz set out to close the season by beating the speed record. However, this company was doomed to failure. During a week in October, the three-pointed star W125 Rekordwagen cruised the highway several times, but could not improve the records of its rival. Auto Union.
It was thus that he withdrew the car from the competition and decided to develop it exhaustively for another attempt agreed for the first month of the following year. In just eight weeks, Rudolf Uhlenhaut, technical manager of the Mercedes racing department, and the member of the Board of Directors for development, Max sailer, they completed the difficult mission.
The company's engineers modified the chassis, engine and created a completely new structure. The reason was that the front axle of the 1937 version was raised excessively and that prevented the pilot from controlling the prototype.
Special attention was also paid to aerodynamics and for that Mercedes-Benz received help from companies linked to the aeronautical industry like airplane manufacturers Ernst heinkel y Willy Messerschmitt, what did you recommend shorten and lower the front sector and give the vehicle a rounder front.
THE IMPROVEMENTS TO THE MERCEDES-BENZ W125 REKORDWAGEN
The car's cross section was also more rounded, reducing susceptibility to crosswinds. Another important change from the previous vehicle was to cover the wheels. Finally, a drop-like glazing was added to the cabin.. Although Caracciola had previously rejected this part due to the risk of distorted visibility, Mercedes-Benz found a proposal visually and aerodynamically acceptable.
Another innovative solution was to use a ice cooling that allowed the diameter of the air inlets at the front to be reduced to a minimum. The radiator was housed in a container containing 48 liters of water and 5 kilograms of ice. In this way, the strong air flow through the radiator, which would have been felt with a higher drag coefficient, was eliminated. The suggestion to use ice cooling came from the German Aviation Test Institute in Berlin-Adlershof.
The V12 engine with a displacement of 5.577 cm3 that had been used during the aborted registration attempt in October 1937 was completely disassembled and optimized. Its reliability was increased by means of a richer combustion mixture and reinforced piston pins. Other improvements included nickel-plated piston crowns to reduce the risk of charring. And finally, a constant supply of fuel / air mixture to each cylinder was ensured.
The tests on the test bench confirmed the success of all this work. On December 29, 1937 a test carried out in the bank showed a power of 714 horses no additional slide carburettor. While on January 6, 1938 the engine was equipped with these carburettors and achieved 765 hp.
THE DAY D
On the morning of January 28, 1938, shortly after 8 o'clock, Caracciola reached the highest speed ever recorded on a public highway. He nailed the speedometer at 432,692 km / h in the kilometer thrown and also broke the record in one mile (1.609 meters) with 432,360 km / h. In each case the speeds were calculated as the average in both directions. “The car grips the road wonderfully. This is already remarkable. It feels quite different from last year's design. "said the European champion in 1935 and 1937.
Auto Union attempted to break this new Mercedes-Benz record that very day. Nevertheless, Bernd rosemeyer, the most successful racing driver of the time, was in a fatal accident when his car was caught in a gust of wind at full speed and he went off the road. Some claim that at the time of the mistake the vehicle had reached the 479 km / h ...
Caracciola's speed record on a public road remained intact for almost eight decades. It was only on November 4, 2017 that a new mark of 445,54 km / h was achieved. The car that did it was the super sports car the Koenigsegg Agera RS, which has a V8 5.0 twin turbo engine of 1.360 horses. This makes the Mercedes-Benz W 125 a shining example of efficiency to this day.