Auto Union racing cars

Auto Union Type C

The Auto Union racing car types A to D, were built as Grand Prix racing cars, between 1934 and 1939.

Between 1935 and 1937 Auto Union cars car won 25 races, driven by Ernst von Delius, 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 (160 km/h).

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.

Background

P-Wagen project

Having been redundant from Steyr Automobile, Dr. Ferdinand Porsche founded Porsche in Stuttgart, with engineering colleagues including Karl Rabe, and financial backing from Adolf Rosenberger. Unfortunately, car commissions were low in the depressed economic climate, so Porsche founded a subsidiary company Hochleistungs Motor GmbH (High Efficiency Engines Ltd.) in 1932 to develop a racing car, for which he had no customer.

In 1933, Grand Prix racing was dominated by Italian marques Bugatti, Alfa-Romeo and Maserati. In early 1933, AIACR announced a new formula, with the main regulation meant that the weight of the car without driver, fuel, oil, water and tire was not allowed to exceed 750kg. The was created to restrict the size of engine that could be used, with the authority estimating that this weight limit would allow around 2.5 litre engines.

Based on Max Wagner's mid-engined layout 1923 Benz Tropfenwagen, or "Teardrop" aerodynamic design; the experimental P-Wagen project racing car (P stood for Porsche), was designed according to the regulations of the 750Kg formula. On November 15 chief engineer Rabe submitted the first draft to the planning office of a racing car for the new formula, with Josef Kales responsible for the V16 engine, while Rabe also held responsibility for the chassis.

Auto Union

In 1932 Auto Union Gmbh was formed, comprising struggling auto manufacturers Audi, DKW, Horch and Wanderer. The Chairman of the Board of Directors, Baron Klaus von Oertzen wanted a show piece project, so at fellow director's Adolf Rosenberger insistence, von Oertzen met with Porsche, who had done work for him before.

At the 1933 Berlin Motor Show, German Chancellor Adolf Hitler announced two new programs:

• The people's car: a project that would eventually become the Volkswagen Beetle
• A state-sponsored motor racing programme: to develop a "high speed German automotive industry," the foundation of which would be an annual sum of 500,000 Reichmarks to Mercedes-Benz

German racing driver Hans Stuck had met Hitler before he became Chancellor, and not being able to gain a seat at Mercedes, accepted the invitation of Rosenberger to join him, von Oertzen and Porsche in approaching the Chancellor. In a meeting in the Reich Chancellory, Hitler agreed with Porsche that for the glory of Germany, it would be better for two companies to develop the project, resulting in Hitler agreeing to split the money between Mercedes and Auto Union with 250,000Reichmaks to each company. This highly annoyed Mercedes, who had already developed their Mercedes-Benz W125, and resulted in a heated exchange both on and off the racing track between the two companies for the period until World War Two.

Having garnered state funds, Auto Union bought Hochleistungs Motor GmbH and hence the P-Wagen Project for 75,000 Reichsmarks, relocating the company to Chemnitz.

Design

The layout of the car was unusual for the time, being mid-engined, where the driver sat in front of the engines. 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 contemporary 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.

V16 engine installed inside a Type C

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.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: the exact 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.

Racing

Development

The first Auto Union vehicles ran in the winter 1933/34 on the Nürburgring, AVUS and Monza. The joint project then developed from a specialist department of the Horch work in Zwickau, based on the P-Wagen Project. It was found that additional work was needed on the car's cornering behavior, as when accelerating out of a corner would cause the inside rear wheel to spin furiously. This was much abated by the use of a Porsche innovation, a ZF manufactured limited slip differential, introduced at the end of the 1935 season.

This co-operation between Porsche and Auto Union continued through Types A, B and C until the 750Kg formula ended in 1937, as the regulations had resulted in huge engines in lightweight vehicles creating great horsepower, and hence high speeds and excessive accidents. Dr. Ing. Robert Eberan von Eberhorst became responsible for the new Type D car, which while still retaining the 750Kg weight limit, also restricted capacity to 3Litre with a compressor, or 4.5Litres without. The Type D deployed a 12 cylinder engine, while the hill climbing versions of the Type D where the capacity limit was not enforced used a changed gearbox and final drive to retain the 16-cylinder engine of the Type C.

Racing results

Driver Bernd Rosemeyer in car No.1, rounding the Nürburgring

This section only includes results of second or better.

The list of drivers for the initial 1934 season was headed by Hans Stuck; he won the German, Swiss and Czechoslovakian Grand Prix races (as well as finishing second in the Italian and Eifel Grands Prix), along with wins in a number of hill-climb races, becoming European Mountain Champion. (There was no European Championship for the circuit races that year, or he would have won that too). August Momberger placed second in the Swiss Grand Prix.

In 1935, the engine had been enlarged to five litres displacement, producing 370 bhp (280 kW). Achille Varzi joined the team and won the Tunis Grand Prix and the Coppa Acerbo (along with placing second in the Tripoli Grand Prix). Stuck won the Italian Grand Prix (along with second at the German Grand Prix), plus his usual collection of hill-climb wins, again taking the European Mountain Championship. The new sensation, Bernd Rosemeyer, won the Czech Grand Prix (and managed a second at the Eifel Grand Prix and Coppa Acerbo).

Hans Stuck in an aerodynamic Type C in Italy

Hans Stuck also managed to break speed records, reaching 199 mph (320 km/h) on an Italian autostrada in a streamlined car with enclosed cockpit. Lessons learned from this streamlining were later applied to the T80 land speed record car.

For 1936, the engine had grown to the full 6 litres, and was now producing 520 bhp (390 kW); in the hands of Rosemeyer and his team-mates, the Auto Union Type C dominated the racing world. Rosemeyer won the Eifelrennen, German, Swiss and Italian Grands Prix and the Coppa Acerbo (as well as second in the Hungarian Grand Prix). He was crowned European Champion (Auto Union's only win of the driver's championship), and for good measure also took the European Mountain Championship. Varzi won the Tripoli Grand Prix (and took second at the Monaco, Milan and Swiss Grands Prix). Stuck placed second in the Tripoli and German Grands Prix, and Ernst von Delius took second in the Coppa Acerbo.

File:DR 1939 687 Automobilausstellung Auto-Union und Mercedes-Benz.jpg

1939 German Post Office stamp, dramatising the battle of the Silver Arrows

In 1937, the car was basically unchanged and did surprisingly well against the new Mercedes-Benz W125, winning 5 races to the 7 of Mercedes-Benz. Rosemeyer took the Eifel and Donington Grands Prix, the Coppa Acerbo, and the Vanderbilt Cup (and well as second in the Tripoli Grand Prix). Rudolf Hasse won the Belgian Grand Prix (Stuck placed second). von Delius managed second in the Avus Grand Prix.

In addition to the new 3-litre formula, 1938 brought other challenges, principally the death of Rosemeyer early in the year, in an attempt on the land speed record. The famed Tazio Nuvolari joined the team, and won the Italian and Donington Grands Prix, in what was otherwise a thin year for the team, other than yet another European Mountain Championship for Stuck.

In 1939, as war clouds gathered over Europe, Nuvolari won the Yugoslavia Grand Prix in Belgrade (with a second place in the Eifel). Hermann P. Müller won the 1939 French Grand Prix (and took second in the German Grand Prix). Hasse managed a second place in the 1939 Belgian Grand Prix, and Georg Meier a second in the French.

Cars today

1938 V16 Type C/D at the Audi museum, Ingolstadt

Very rarely were racing cars of the period kept, as components of early cars if required were scavenged for later models and repairs. Secondly, what did remain was often scrapped to provide funds for additional development. Hence, it is presently understood that no Type A or Type B cars exist today.

After the Second World War, since Auto Union was based in Zwickau which was now located in Soviet Union controlled Communist East Germany, what little of the Auto Union racing cars existed was claimed and retrieved to Russia. Today, only one Type C and three Type D cars, and a Type C/D hill climbing car remain.

The sole remaining Type C was originally left to a German museum by Auto Union, after the death of Bernd Rosemeyer resulted in only two or three of these historic cars running. Damaged by bombing during the war, its body today still shows these marks. In 1979/80, Audi commissioned restoration of the car, undertaking a preservation-level overhaul to the body, engine and transmission.

1938 V12 Type D saved from being cut up for scrap, now preserved in Riga Motor Museum

A Type D car was recovered and taken to Moscow to study its technology. In 1976, the car was at the ZIL factory in Moscow and scheduled to be cut up for scrap metal, but Viktors Kulbergs, president of Antique Automobile Club of Latvia, brought it to Riga Motor Museum.

After the collapse of the Soviet Union, a 16cylinder hill climbing car - a combination of types C and D - was discovered in Riga by Audi engineers. In exchange for providing Riga Motor Museum with an exact replica, in 1997 Audi commissioned British engineering companies Crostwaite & Gardiner of Buxted and Roach Manufacturing of Ower to undertake the work. The original now resides in the Audi Motor Museum, the replica on display in Riga.

Replicas

Audi has rebuilt some cars recently based upon remaining parts, plans and knowledge. A hill climbing version was recently rebuilt by the Audi factory, and toured the major car shows, driven by Hans Stuck Jr., son of the original driver Hans Stuck, a long-time Audi race driver himself.

For 2000, Audi commissioned a Type C Streamline, which in May 2000 raced around the banked curve of the famous French circuit at Montlhéry. This was 63 years after its premier at AVUS in May 1937, when Bernd Rosemeyer took a car of this type to a speed of 380 km/h on the straights. Now resident in the Audi Mobile museum in Ingelstadt, the car has appeared at various autoshows around the world, including the 2008 Goodwood Festival of Speed commemorating Audi's 100th birthday.

Technical details

Auto Union Racing Cars
Characteristic	Type A (1934)	Type B (1935)	Type C (1936-37)	Type D (1938)	Notes
Engine	V16	V16	V16	V12	Type D brought about by change or rules
Cylinder angle	45°	45°	45°	60°
Orientation	Longitudinal	Longitudinal	Longitudinal	Longitudinal
Capacity	4358 cm ³	4956 cm ³	6010 cm ³	2990 cm ³
Bore/Stroke		72.5x75.0mm	75.0x85.0mm	65.0×75.0mm
Crankshaft	one-piece from Cr-Ni steel	one-piece from Cr-Ni steel	slidingstored (Hirth)	roll-stored
Control	Single camshaft	Single camshaft	Single camshaft, 2xignition magnetos	Triple camshaft
Aspiration	1xRoots supercharger	1xRoots supercharger	1 or 2xRoots supercharger	2xRoots supercharger
Compressor pressure	0.61 bar	0.75 bar	0.95 bar (Max)	1.67 bar
Power	220 KW (295 HP) @ 4500/min	276 KW (375 HP) @ 4800/min	357/382 KW (485/520 HP) @ 5000/min	357 KW (485 HP) @ 7000/min
Torque	530 Nm @ 2700/min	660 Nm @ 2700/min	853 Nm @ 2500/min	550 Nm @ 4000/min
Transmission Gears	5	5	5	5
Maximum speed	280 km/h		340 km/h	340 km/h
Brakes	400-mm, system Porsche hydraulic	400-mm, system Porsche hydraulic	400-mm, system Porsche hydraulic	400-mm, system Porsche hydraulic
Shock absorber	Friction absorber	Friction absorber	Friction absorber	Front: hydraulic Rear: hydraulic/friction
Front Suspension			Crank semi-trailing arm (see VOLKSWAGEN beetle)	Crank semi-trailing arm
Rear Suspension			Pendelachse with torsion bar suspension (in the back)	De-Dion-axle with torsion bar suspension
Body	Steel tube leader framework, main pipe diameter: 75 mm	Steel tube leader framework, main pipe diameter: 75 mm	Steel tube leader framework, main pipe diameter: 75 mm
Wheelbase			2900 mm	2800 mm
Track width			1420 mm	1390 mm
Dimensions Length × width × height			3920 × 1690 × 1020 mm	4200 × 1660 × 1060 mm
Fuel Capacity			200 Litres
Dry weight	825 kg	825 kg	824 kg	850 kg

References

• Stefan Knittel: Car union Grand Prix car, Schrader & partner GmbH, Munich 1980, ISBN 3-922617-00-X, P. 30 (units partly converted)
• Karl-Heinz noble/Wolfgang Roediger: The German running vehicles, technical book publishing house Leipzig 1990, ISBN 3-343-00435-9
• Richard von Frankenberg: The unusual history of the house Porsche, Motorbuch publishing house, Stuttgart 1969
• Boschen/Barth: The large book of the Porsche special types and - constructions, engine book publishing house, Stuttgart 1984, ISBN 3-87943-805-6
• Jonathan Wood: German automobiles, university part University of, Stuttgart 1986, ISBN 3-8122-0184-4