It's time for the Auto Union Type D racer - the last but not the least in line.
By limiting the maximum weight of Grand Prix cars from the 1934 season onwards to 750 kg, the sport's governing body, the Association Internationale des Automobiles Clubs Reconnus (AIACR), figured the performance of the racing cars would be sufficiently limited. Judging from the Bugattis, Maseratis, Mercedes-Benz and Alfa Romeos of the day, they believed that with this maximum weight it would be highly unlikely to exceed an engine displacement of three litres*. This was done for safety and economic reasons, but in the following years, the very fast and high tech machines proved them very wrong. Instead of keeping the displacement down, weight was saved by extensive cross drilling the every part of the chassis and suspension, which did not make the cars any safer at all. To set things straight, the AIACR set new rules limiting supercharged engines to three litres and Naturally Aspirated ones to four and a half.
The 750 kg era was dominated by the two government backed German Mercedes-Benz and Auto Union teams. While the former could build on some previous racing experience, the success of the Auto Union was, simply put, down to engineering abilities of Ferdinand Porsche and even more so the driving abilities of Bernd Rosemeyer. Porsche had come up with a single seater powered by a mid-mounted V16 engine that eventually grew in size to six litres and produced a staggering 520 bhp. The Auto Union racer quickly built a reputation for being nearly impossible to drive, at the time wrongly attributed to the unconventional location of the engine. In reality the unpredictable handling was caused by Porsche's typical swing axle rear suspension and also the outdated tires, which were not able to cope with the power and speed. The former motorcycle racer, Rosemeyer was the only one capable of really taming the beast, but nevertheless the underdog, Auto Union, took 18 victories against 'only' 22 for the Mercedes-Benz team.
If the major rule changes were not enough, the departure of Auto Union's two biggest 'assets' were a blow few manufacturers could have successfully dealt with. Porsche had left early in 1937 to completely focus on the Fuhrer's Volkswagen and for Rosemeyer tragedy struck on January 28th in 1938 when he lost control of a special Auto Union Type C during a speed record attempt on the Autobahn**. Especially the death of their star driver hit the small team hard and it has forever left the question unanswered how good the young German really was as the only car he ever raced was the V16 Auto Union. Amazingly two highly capable replacements were found in the form of designer Prof. Eberan von Eberhorst and later in the season racing legend Tazio Nuvolari. All teams had to start from scratch, but the major personal changes put Auto Union even more behind. After forfeiting the first three races, the all new Type D made its debut at the French Grand Prix.
At first glance there was a resemblance between the Type C and new Type D, but other than the basic chassis design everything was different. The tubular ladder frame was retained together with the torsion bars fitted inside the frame members. Taking a page out of the Mercedes-Benz book, the rear suspension now featured a DeDion tube with single radius arms. The engine was again mounted behind the driver, but was of a completely new V12 design. With the displacement limited to just three litres, a much higher specific output was required and a somewhat unusual valve train was installed. The intake valves were operated through push-rod actuated by a single camshaft mounted inside the V, while each bank of exhausts valves had their own camshaft, so Von Eberhorst's V12 sported three camshafts. Helped by a Roots-Type Supercharger, the new V12 produced a competitive 420 bhp at 7000 rpm. Another major change was the move of a single central mounted fuel tank to two side-tanks, which enabled the driver to sit further back in the chassis.
Although there were new cars from Italy and France, the Type D's only serious competition came from arch-rivals Mercedes-Benz, who had also constructed a three litre Grand Prix racer, but of a more conventional design. Weighing in at 100 kg under the new Mercedes W154 while matching its power, the expectations for the Type D were high. Sadly the debut at the French Grand Prix was nothing short of embarrassing with both cars entered retiring in the opening lap. The low morale was given a good boost when Tazio Nuvolari was hired to headline the team for the remainder of the 1938 season. Despite his rarely matched abilities, the 'Flying Mantuan' struggled to get to grips with the Type D.
Tazio Nuvolari at Italian Gran Prix (above) and Donington Grand Prix (below). 1938
Once he did there was no stopping him and he took a well deserved victory in the Italian Grand Prix at Monza and the Donnington Grand Prix. For 1939, the chassis and suspension were further refined and the handling problems that had dogged previous Auto Unions were completely forgotten. A new twin-stage blower literally boosted the power to 485 bhp and the team was ready to take on the boys from Stuttgart once again.
Sadly world affairs caught up with racing and the start of the War cut the season short after just four Grands Prix, one of which was won by the twin-stage Auto Union Type D. For political reasons, the championship was awarded to Mercedes' Hermann Lang even though Auto Union's HP Muller had scored more points.
In the years after the Second World War, the Auto Unions quickly gained legendary status, thanks in no small part to the fact that it was believed that none of the racing cars had survived the War... But then the Silver Fish started to resurface here and there. To learn the story of the D Type 19, now owned by Audi AG, please read an article by Terry Shea on Hemmings Blog.
*An article by Wouter Melissen, Ultimatecarpage (2009)
** This tragic story is worth a separate article. Stay tuned!