Mercedes 90 hp Grand Prix racing car, 1913
The defeat of the French manufacturers at the Grand Prix de l'A.C.F. in July 1908 and their subsequent self-imposed abstinence from motorsport, in which they were joined by other automobile companies from Belgium, Italy and Germany, led to some manufacturers now seeking new challenges in the burgeoning US racing scene. In contrast to the factory involvement of Benz & Cie. there, Daimler-Motoren-Gesellschaft (DMG), which like its Mannheim-based rival had joined the Grand Prix boycott in Europe, restricted itself to selling the occasional racing car based on its top model Mercedes 37/90 hp to private drivers with racing ambitions. In the USA, these were Ralph DePalma and Spencer Wishart, who helped the brand to become better known overseas through outstanding results in numerous races.
In France, the up-and-coming Automobile Club de la Sarthe et de l'Ouest (ACSO), founded in 1906 as the Automobile Club de la Sarthe, attempted to fill the resulting vacuum as early as 1911 with a self-organised race on a 54.6 km track near Le Mans. With the approval and support of the Automobile Club de France, the ACSO named the race the "Grand Prix de France". To fill the field, not only the large-volume Grand Prix vehicles were allowed to start, but also smaller Voiturette cars. Despite this, only 14 participants took part in the 12-lap race on 23 July 1911.
Although this Grand Prix de France, from which the German manufacturers stayed away, was neither a sporting nor a commercial success, the ACSO was determined to organise the event in subsequent years. At the same time, both the A.C.F. and some of the domestic manufacturers felt renewed motivation to revive the Grand Prix de l'A.C.F. after four years. The race on 25 and 26 June 1912 aspired to restore the Grand Prix de l'A.C.F.'s former reputation as the most important event in European motor racing. It covered a total distance of around 1535 kilometres and - as had been the case originally with the Grand Prix - took place over two days. There were at least ten domestic manufacturers at the start; DMG, Benz & Cie. and Opel, on the other hand, did not send a racing team to the venue in Dieppe.
The same was true of the second ACSO Grand Prix de France, which was held at the beginning of September of the same year near Le Mans with the exclusive participation of French manufacturers.
Although both Grand Prix races in 1912 were still struggling with the effects of the manufacturers' boycott and the self-generated internal competition, there were a number of important findings: on the one hand, new competitors had entered the scene with powerful, innovative design features; on the other hand, new Voiturette racing cars had demonstrated how competitive vehicles with significantly smaller displacements could be.
With the expiry of the participation boycott, which was scheduled for the end of 1912, DMG found itself in a difficult situation with regard to a factory involvement in motor racing. The main aim was not only to match the technical progress made in racing engine design, but as far as possible to surpass it. Initially, however, the company wanted to approach the changed landscape cautiously, and entrusted the Belgian DMG importer Théodor Pilette with the management of semi-official works events for the races of the 1913 season. However, Pilette's entry of Mercedes racing cars for the Grand Prix de l'A.C.F. was rejected by the organisers, as only cars entered directly by the factory were eligible to start.
Up to this point, DMG had not yet been able to offer a newly designed racing car, so had to improvise, especially when it came to the drive system. The obvious choice was to use the new aircraft engines that were in the final stages of development, which had to meet very similar requirements to racing engines in motor racing.
In addition to the four-cylinder G 4 F with a displacement of 9.2 litres, the six-cylinder DF 80 also seemed very suitable for racing. With cylinder dimensions of 105 x 140 mm, the engine, in contrast to the four-cylinder, had a rather long stroke and was furthermore equipped with an overhead camshaft driven by a vertical shaft, which actuated an angled overtake intake valve and an exhaust valve via rocker arms. Two magnetos supplied two spark plugs per cylinder with power.
Beyond this, the six-cylinder had nothing in common conceptually with the four-cylinder. Instead, it was based on Wilhelm Maybach's six-cylinder racing engine from 1906 and had steel cylinders that were welded to the grey cast iron cylinder heads. The sheet steel cooling water jackets for each of the two cylinders were then welded on. As an aircraft engine, the unit produced 110 hp/81 kW with an enlarged bore of 120 mm. For use in racing cars, the bore size remained at 105 mm and the total displacement at 7.3 litres. In this form, the six-cylinder had a peak output of 91 hp/67 kW at 1600 rpm.
Undeterred by the seemingly overwhelming competition posed by the Grand Prix de l'A.C.F., which had been held just three weeks previously, the former ACSO, now renamed the Automobile Club de l'Ouest (ACO), organised its own Grand Prix, the Grand Prix de France, for the third time - and the starting field was certainly impressive. A total of six brands were represented, with a total of 15 Grand Prix cars, including several Mercedes. In contrast to the A.C.F., the ACO had accepted the nomination of the Mercedes cars by Théodore Pilette without any problems.
The somewhat disparate impression of the vehicle contingent that Pilette brought to the start seemed to indicate that the main aim at this stage was to gain experience in practical racing rather than to reap the rewards of victory. The drivers were Christian Lautenschlager, Otto Salzer, the Belgian Léon Elskamp and Pilette himself.
Unlike the previous year, the Grand Prix de France was once again held without a formula. The delegation from Untertürkheim comprised a total of four vehicles. Three of them were equipped with a modern aircraft engine as the drivetrain. In addition to Lautenschlager and Salzer, who each drove one of the six-cylinder 90 hp Grand Prix racing cars, Pilette drove a car with the 100 hp/74 kW four-cylinder G 4 F engine. The final entrant was Léon Elskamp in 37/90 hp racing car, similar to the one sold to Ralph DePalma and Spencer Wishart in the USA in 1911.
The three cars powered by an aircraft engine were largely similar in appearance. The versions with four and six-cylinder engines differed only in the number of exhaust manifolds visible on the left-hand side of the vehicle: four for the four-cylinder, three for the six-cylinder. Characteristic of both were the pointed radiators, the longitudinal frame members that tapered slightly towards the front end and the wire-spoke wheels with central wheel nut, which had replaced the old wooden-spoke wheels. Incidentally, all four Mercedes cars still had a chain drive to the rear axle - already an anachronism in 1913.
During the race held on 5 August near Le Mans, Lautenschlager and Salzer were unable to keep up with the pace set by the front runners in their six-cylinder cars. For flight operations, the maximum engine speed was limited to 1400 rpm. In hectic races, where the engine was often required to deliver the maximum power that didn't kick in until 1600 rpm, problems quickly became apparent. The crankshaft, which only had four bearings, developed massive torsional vibrations, not least because of the long stroke, which took on almost dramatic proportions as the race progressed. At the finish, the hands of Salzer and Lautenschlager, who finished fourth and sixth in the final classification, were covered in blisters due to the vibrations transmitted from the steering wheel.
Pilette in the four-cylinder Grand Prix racing car, on the other hand, was in the running to win for a long time, but had to settle for third place after suffering a puncture shortly before the end. Over 40 minutes behind Pilette, his compatriot Léon Elskamp finished seventh in the Mercedes 37/90 hp racing car. Overall, the results of the Grand Prix de France could nevertheless be considered satisfactory. The future prospects for the Mercedes racing cars were once again looking positive.