Saturday, April 20, 2019

Auto Union Type C

Mercedes-Benz domination in Grand Prix ended with the Auto Union Type C. It took a few  years to get it right, but Ferdinand Porsche’s daring design with a mid-mounted V16 finally won. It claimed many victories from 1936 to 1938 until the three litre formula was laid out for 1939.

The Type C was a third evolution of Auto Union’s racecar. It primarily competed with Mercedes-Benz but also raced against Alfa Romeo’s 12C-36, the Maserati V8RI and Bugatti 59/50. Type C won six victories in 1936 and made Bernt Rosermeyer world champion.

With the financial backing of Adolf Rosenberger, Ferdinand Porsche started his company with some former co-workers from Steyer. In 1932 Auto Union was formed, comprising struggling auto manufacturers Audi, DKW, Horch and Wanderer. Along with building passenger cars, a goal of the new company was to enter Grand Prix. They did so in 1934 with a daring mid-engined race car called the Type A. This evolved into the slightly larger Type B the following year and the Type C was fitted with a much larger engine for 1936.

The Type C represented the pinnacle in the development of racing car that had been designed by Ferdinand Porsche according to the 750 kg formula (max. Mass, dry, without wheels and tyres). It clocked a top speed of 340 kmph. The key design feature was the 16-cylinder engine positioned directly behind the driver (mid-mounted engine). It was the most successful German racing car, winning three of the five Grand Prix races, half of the circuit races and all the hill-climbs that Auto Union entered.

Ferdinand Porsche championed his mid-engined design for Type C, first used on the 1923 Benz Tropfenwagen. Weight distribution was his primary motivation in this choice. The driver could sit lower with no drive shaft and the front to rear weight distribution was much more even. Furthermore, the fuel tank was also located centrally for balance. Despite these efforts, 60% of the weight still remained on the rear axle.

What made the car unbalanced was its heavy engine and comparably small chassis and body. The design team engineered the largest possible engine within the 750 kg weight limit. This resulted in the largest capacity engine to compete during 1936 and 1937.

The engine for this new car would be a 6 litre V16 supercharged engine producing 520 hp. It had two cylinder blocks inclined at an angle of 45 degrees with a single overhead camshaft to operate the 32 valves.

The engine was designed to provide optimum torque at low engine speeds. The suspension would be all independent but unlike the Mercedes would use half-axles and torsion bars at the front while at the rear it used wishbones and a transverse leaf spring. The fuel tank was located in the center of the car directly behind the drive who would be placed well towards the front. The chassis tubes were initially used as water carriers from the radiator to the engine but often sprung small leaks. Additional work needed to be done on the cars behavior during cornering. Accelerating out of a corner would cause the inside rear wheel to spin furiously. This was much abated by the use of a ZF manufactured limited differential for the 1936 season. The body was subjected to strenuous testing in the wind tunnel of the German Institute for Aerodynamics.

Much has been written about the difficult handling characteristics of this car but its tremendous acceleration was undeniable. A driver could induce wheelspin at 150 mph! The high power to weight ratio, uneven weight distribution and Porsche’s swing axle suspension system made the Type C over steer. Drivers of the car had a hard a hard time predicting slip velocity and the forward driving position made it worse. Only a couple of drivers were able to take the Type C to its full potential.

Of all the Type Cs constructed, only one is believed to have survived. It now resides in the German Museum of Munich.

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