Audi Auto Union Type C

The Auto Union Grand Prix racing cars types A to D, were developed and built by a specialist racing department of Horch works in Zwickau between 1933 and 1939.

Between 1935 and 1937 Auto Union cars won 25 races, driven by Ernst von Delius, Tazio Nuvolari, Bernd Rosemeyer, Hans Stuck and Achille Varzi. Much has been written about the difficult handling characteristics of this car, but its tremendous power and acceleration were undeniable - a driver could induce wheelspin at over 100 mph.

The cars throughout their production history were the main Grand Prix protagonists with Mercedes-Benz, particularly dominant in 1936. The dominance of the Silver Arrows of both brands was only stopped by the outbreak of World War II in 1939.

he layout of the car was unusual for the time, being mid-engined, years before the Cooper T53 rediscovered the advantages. Hence, the layout of the car front to rear was: radiator; driver; fuel tank; engine.
The problem with mid-engined design at the time was the stiffness of the contemporary ladder chassis and suspension, which resulted in a pronounced change in turning angle as the momentum of the centrally mounted engined changed on the chassis, and resulted in the car oversteering. The suspension was all-independent, using parallel trailing arms and torsion bars at the front, while at the rear Porsche tried to counter the natural oversteer tendency with the use of a then advanced swing half-axle rear suspension. It was only on the later Type D that the rear suspension would be replaced with a de Dion system, following the lead of Mercedes-Benz, but by then it was too late to do anything about the poor handling reputation the cars had gained.

The cars used supercharged engines that eventually produced almost 550 horsepower (which also contributed toward the handling difficulties, as it promoted oversteer which the cars already had in abundance). The engine was originally the V16 engine that Porsche had started designing earlier; when, starting in 1938, the maximum engine displacement for Grand Prix cars was limited to 3 litres for blown engines, it became a V12.

It was originally designed to 6 litre specifications, but would start at 4,360 cc and 295 bhp (220 kW). It had two cylinder blocks, inclined at an angle of 45 degrees, with a single overhead camshaft to operate all 32 valves. The cylinder heads were hemispherical, with the intake valves on the inside, directly connected to the camshaft through rocker arms. The rocker arms of the exhaust valves were connected to the camshaft by pushrods that passed through tubes situated above the spark plugs; thus the engine had three valve covers. The engine was designed to provide optimum torque at low engine speeds, with Bernd Rosemeyer later driving a car around the Nürburgring in a single gear, to prove the engine was flexible enough to do it.

The body was subjected to strenuous testing in the wind tunnel of the German Institute for Aerodynamics, a scientific organization that still exists. The fuel tank was located in the centre of the car, directly behind the driver, so that the car's front-rear weight distribution would remain unchanged as the fuel was used: exactly the same location used in modern open-wheel racing cars, and for the same reason. The chassis tubes were initially used as water carriers from the radiator to the engine, but this was eventually abandoned after they often sprung small leaks.

Source: Wikipedia, 2011

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