An article that recently appeared in Issue 510, December 9th 2008 of the Australian online automobile magazine, AutoSpeed, reminded me of this event and, since the record still stands, those of you unfamiliar with the details may find the account interesting. The article is titled "The Record Breakers" and is available at:
http://autospeed.com:80/cms/A_110813/article.html
In 1934 Germany, the newly-founded AutoUnion, one of the precursors of Audi, established the one-hour world speed record in a first attempt. This was a challenge that Mercedes-Benz was compelled to address. At the end of 1934, the great Rudolf Caracciola, M-B top racing driver at the time, established new records in Gyon, Hungary, and on the AVUS racetrack in Berlin. For a brief biography of this accomplished race driver, go to:
http://en.wikipedia.org/wiki/Rudolf_Caracciola
For the next couple of years, the two marques fought each other in the major European GP 750 kg formula races. In May 1937, the AVUS racetrack was the venue for a free-formula race (cars that weighed more than 750 kg with no upper limit). Hermann Lang, in a fully streamlined M-B W125, won the race at an average speed of 261.7 km/h (162.6 mph). The car was powered by a V12 engine rather than the V8 used in the 750 kg racing formula. The outcome prompted M-B to attempt a world record run later in the year using this engine.
AVUS (Automobil Verkehrs und Ubungs-StraBe) was a racetrack on the southwestern outskirts of Berlin. Designed in 1907 by the Automobilclub von Deutschland, after many delays the circuit opened in 1921. At the time of opening, AVUS was 19.5 km (12 miles) long - each straight being approximately half that length, and joined at each end by flat, large-radius curves. From 1927, AVUS faced competition from the Nurburgring so in an effort to make AVUS the world's fastest track, the north curve was turned into a steep banking (43 deg) made of bricks. This was its configuration during the Lang and Caracciola record attempts in the 1930s. Subsequently, the track has been reconfigured and shrunk, and today no longer exists as it is part of the public highway system, Autobahn A115 (I think).
Since Europe lacks anything remotely similar to the Bonneville Salt Flats, with the permission of the German government the decision was made to use a section of the Autobahn which was under construction in Germany at the time. A 34 km (21.1 mile) length of a brand-new, absolutely level stretch of roadway that ran between Frankfurt and Darmstadt was chosen. I think it's designated A5 today.
The DAB V12 engine was developed for GP racing. With a displacement of 5577 cc (340.3 CID), it wasn't much larger than the V8 but had more power than any other M-B engine at the time. In its final form it developed 736 HP at 5800 rpm and 1000 Nm (738 lbs/ft) torque. The cylinder bank angle was 60 deg to ensure equal firing intervals and unlike most V-engines, the cylinders of each bank were exactly opposite each other rather than offset. This was accomplished by using a blade and fork big end construction for the con rods. Such a design produces minimal crankshaft length for lowest tosional vibration. Like the inline-6 engine, the V12 has both its primary and secondary unbalanced forces completely eliminated.
The aluminum crankcase had forged steel cylinders with 4-valves per cylinder operated by DOHCs in each welded on cylinder head. Two Roots-type superchargers arranged in a V-shape at the front of the engine were driven by a hollow-shaft extension of the crankshaft. The boost pressure was 1.28 atmospheres (1.3 bar; 18.8 PSI). To provide adequate VE at high rpm, the engine was equipped with two carburetors per bank. The engine was front-mounted along the longitudinal axis of the car and the rear wheels were driven. A 4-speed M/T was fitted.
Front suspension consisted of double wishbones with coil springs and hydraulic shocks while the rear was fitted with a De Dion axle with torsion bar springs and hydraulic shocks. Steering was by worm and nut. Braking was carried out by light-alloy drums fitted with cast iron liners.
The streamlined body was under continuous development from its inception in 1935 until the record run at the beginning of 1938. Aerodynamic lift was a continuing problem that revealed itself as racing speeds increased. In the fall of 1936, Caracciola established three class records over five and ten kilometers, and ten miles, on the autobahn near Frankfurt. At an average speed of 333.5 km/h (207.2 mph), the ten mile run was also a world record. In the May 1937 AVUS race, the front of Lang's car lifted off after driving across a bump in the road at 370 km/h (230 mph) because of too little downforce. After this was corrected, the car was taken to Frankfurt for another record attempt to be held between October 25th and 31st 1937. On a test run, Caracciola's car lifted off again and was sent back to the factory for nose modifications and the addition of 90 kg (198.4 lb) of lead to the front end. Back on the road, Caracciola reached a speed of 397 km/h (247 mph) on one kilometer from a flying start, but the AutoUnion car was still faster at 406 km/h (252 mph).
The German sanctioning body at the time, the ONS, arranged a return match in January 1938. After the October disappointment, the DAB V12 engine received modified pistons, piston clearance, wrist pins, carburetors, intake manifold and supercharger drive. The body received its final shape through testing in an aircraft wind tunnel in Berlin instead of using a scale model as in previous aerodynamic modifications. With a Cd (aerodynamic drag coefficient) value of 0.157, unmatched by any other motor vehicle at the time, a dry weight of 1185 kg (2612.5 lb), and riding on 6.25 x 22" front tires and 7.00 x 24" tires at the rear, the car was now ready for its record-setting run.
On January 28th 1938 shortly after 8 am, Caracciola made a trial run and then, after a few last minute adjustments, immediately made his record attempt. The speeds he attained that day, 432.7 km/h (268.9 mph) over one kilometer from a flying start, and 432.0 km/h (268.4 mph) over one mile from a flying start have to this day remained the highest speeds ever recorded on a public road.
The car is on display at the M-B museum in Stuttgart.
Happy Motoring!
Below is a photo of the streamliner as it appears at the museum.
http://autospeed.com:80/cms/A_110813/article.html
In 1934 Germany, the newly-founded AutoUnion, one of the precursors of Audi, established the one-hour world speed record in a first attempt. This was a challenge that Mercedes-Benz was compelled to address. At the end of 1934, the great Rudolf Caracciola, M-B top racing driver at the time, established new records in Gyon, Hungary, and on the AVUS racetrack in Berlin. For a brief biography of this accomplished race driver, go to:
http://en.wikipedia.org/wiki/Rudolf_Caracciola
For the next couple of years, the two marques fought each other in the major European GP 750 kg formula races. In May 1937, the AVUS racetrack was the venue for a free-formula race (cars that weighed more than 750 kg with no upper limit). Hermann Lang, in a fully streamlined M-B W125, won the race at an average speed of 261.7 km/h (162.6 mph). The car was powered by a V12 engine rather than the V8 used in the 750 kg racing formula. The outcome prompted M-B to attempt a world record run later in the year using this engine.
AVUS (Automobil Verkehrs und Ubungs-StraBe) was a racetrack on the southwestern outskirts of Berlin. Designed in 1907 by the Automobilclub von Deutschland, after many delays the circuit opened in 1921. At the time of opening, AVUS was 19.5 km (12 miles) long - each straight being approximately half that length, and joined at each end by flat, large-radius curves. From 1927, AVUS faced competition from the Nurburgring so in an effort to make AVUS the world's fastest track, the north curve was turned into a steep banking (43 deg) made of bricks. This was its configuration during the Lang and Caracciola record attempts in the 1930s. Subsequently, the track has been reconfigured and shrunk, and today no longer exists as it is part of the public highway system, Autobahn A115 (I think).
Since Europe lacks anything remotely similar to the Bonneville Salt Flats, with the permission of the German government the decision was made to use a section of the Autobahn which was under construction in Germany at the time. A 34 km (21.1 mile) length of a brand-new, absolutely level stretch of roadway that ran between Frankfurt and Darmstadt was chosen. I think it's designated A5 today.
The DAB V12 engine was developed for GP racing. With a displacement of 5577 cc (340.3 CID), it wasn't much larger than the V8 but had more power than any other M-B engine at the time. In its final form it developed 736 HP at 5800 rpm and 1000 Nm (738 lbs/ft) torque. The cylinder bank angle was 60 deg to ensure equal firing intervals and unlike most V-engines, the cylinders of each bank were exactly opposite each other rather than offset. This was accomplished by using a blade and fork big end construction for the con rods. Such a design produces minimal crankshaft length for lowest tosional vibration. Like the inline-6 engine, the V12 has both its primary and secondary unbalanced forces completely eliminated.
The aluminum crankcase had forged steel cylinders with 4-valves per cylinder operated by DOHCs in each welded on cylinder head. Two Roots-type superchargers arranged in a V-shape at the front of the engine were driven by a hollow-shaft extension of the crankshaft. The boost pressure was 1.28 atmospheres (1.3 bar; 18.8 PSI). To provide adequate VE at high rpm, the engine was equipped with two carburetors per bank. The engine was front-mounted along the longitudinal axis of the car and the rear wheels were driven. A 4-speed M/T was fitted.
Front suspension consisted of double wishbones with coil springs and hydraulic shocks while the rear was fitted with a De Dion axle with torsion bar springs and hydraulic shocks. Steering was by worm and nut. Braking was carried out by light-alloy drums fitted with cast iron liners.
The streamlined body was under continuous development from its inception in 1935 until the record run at the beginning of 1938. Aerodynamic lift was a continuing problem that revealed itself as racing speeds increased. In the fall of 1936, Caracciola established three class records over five and ten kilometers, and ten miles, on the autobahn near Frankfurt. At an average speed of 333.5 km/h (207.2 mph), the ten mile run was also a world record. In the May 1937 AVUS race, the front of Lang's car lifted off after driving across a bump in the road at 370 km/h (230 mph) because of too little downforce. After this was corrected, the car was taken to Frankfurt for another record attempt to be held between October 25th and 31st 1937. On a test run, Caracciola's car lifted off again and was sent back to the factory for nose modifications and the addition of 90 kg (198.4 lb) of lead to the front end. Back on the road, Caracciola reached a speed of 397 km/h (247 mph) on one kilometer from a flying start, but the AutoUnion car was still faster at 406 km/h (252 mph).
The German sanctioning body at the time, the ONS, arranged a return match in January 1938. After the October disappointment, the DAB V12 engine received modified pistons, piston clearance, wrist pins, carburetors, intake manifold and supercharger drive. The body received its final shape through testing in an aircraft wind tunnel in Berlin instead of using a scale model as in previous aerodynamic modifications. With a Cd (aerodynamic drag coefficient) value of 0.157, unmatched by any other motor vehicle at the time, a dry weight of 1185 kg (2612.5 lb), and riding on 6.25 x 22" front tires and 7.00 x 24" tires at the rear, the car was now ready for its record-setting run.
On January 28th 1938 shortly after 8 am, Caracciola made a trial run and then, after a few last minute adjustments, immediately made his record attempt. The speeds he attained that day, 432.7 km/h (268.9 mph) over one kilometer from a flying start, and 432.0 km/h (268.4 mph) over one mile from a flying start have to this day remained the highest speeds ever recorded on a public road.
The car is on display at the M-B museum in Stuttgart.
Happy Motoring!
Below is a photo of the streamliner as it appears at the museum.
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