By Christopher A. Sawyer
On January 28, Mercedes celebrates the 75th anniversary of a speed record that stands to this day: 432.7 km/h (268.9 mph). The two-way average was set by Mercedes Silver Arrows driver Rudolf Caracciola on the then-new German autobahn between Frankfurt and Darmstadt, and included a one-way top speed of 436.7 km/h (271.4 mph). Bernd Rosemeyer was set to try and beat this mark that same day, but his Auto Union streamliner was caught by a gust of wind, and he was killed in the resulting crash. Part of the Nazi regime’s propaganda campaign to show the superiority of the National Socialist system, these record runs were cut short by the outbreak of World War II.
Based on the W 125 Silver Arrow grand prix car, the record breaking Mercedes was equipped with a 5.6-liter twin-supercharged V12 producing 736 hp. The engine did not have a radiator or even an opening to admit cooling air. The radiator was immersed in a 500-liter (17.7 ft3) chest filled with ice and water. To slice through the air, the hand-hammered aluminum body had been developed in a wind tunnel at the German Institute for Aviation Research, and boasted a drag coefficient of Cd = 0.157. (Previous record cars had been tested at the Zeppelin wind tunnel in Friedrichshafen, Germany.)
Setting speed records was a matter of pride, Mercedes having lost the title in October 1937 when Rosemeyer’s Auto Union became the first automobile to travel in excess of 400 km/h (248 mph) on public roads. Chastened by this defeat at the hands of the upstart Auto Union, the Mercedes team went back to the factory to regroup. Certain of beating their racing rivals with the W 125-based car, Mercedes petitioned the Supreme National Sports Authority (ONS) to sanction a record run in January 1938, just prior to the Berlin Motor Show. It was at this event that Mercedes seized the record, and Rosemeyer lost his life.
Increased specialization saw Mercedes create two W154-based record cars for 1939, one designed specifically for maximum flying-start speed, and the other from standing-start sprints. And while Caracciola took this under 3.0-liter bullet to several speed records, they fell short of the record set by the W 125 record car. That didn’t mean Mercedes was done, however. It had plans to make an all-out assault on the land speed record with its three-axle, six-wheeled T80 in 1940. A duel between British drivers George Eyston and John Cobb in August 1939 had seen this record raised to 595 km/h (369.7 mph) on the salt flats in Bonneville, Utah.
The T80 stretched 8.24 meters (27 ft), and was powered by a 44.5-liter inverted V12 DB 603 RS aircraft engine that normally would be found powering a Messerschmitt Bf 109 fighter aircraft at approximately half the horsepower. It produced 3,452 horsepower at 3,460 rpm, and ran an exotic fuel mixture: 63% methyl alcohol, 16% benzene, 12% ethanol, 4.4% acetone, 2.2% nitrobenzene, 2% avgas and 0.4% ether, with a methanol-water injection system to prevent detonation.
With its Cd = 0.18 low-drag body, side-mounted stabilization wings, enclosed cockpit and twin tail booms (to help control airflow over the rear body), it was projected that the T80 would take driver Hans Stuck, to a top speed of 750 km/h (465 mph). Stuck, a protégé of Hitler’s convinced Mercedes-Benz to build the Porsche-designed car, even though he and Porsche both worked for rival Auto Union. Though the war prevented the car from ever being run (Mercedes has it on display at its museum in Stuttgart), 24 years would elapse before Art Arfons exceeded the T80’s projected top speed in his jet-powered Green Monster. No wheel-driven land speed record car would achieve or better the T 80’s projected speed until 2001.