Immediately after the end of the Second World War, motor sport activities had hardly any significance for the German motor vehicle manufacturers. Also in Neckarsulm the difficult new start demanded the concentration of all forces on the resumption of series production. When official motorbike races were held in Germany again for the first time in the summer of 1947, NSU – due to a lack of factory participation – was unable to match the successes of the pre-war years and prove the potential of the supercharged engine developed by Albert Roder for NSU in 1938, which produced proud 44 hp at 350 cc.

However, this new development had not left former works driver Wilhelm Herz in peace. In the spring of 1946, he began at his own expense to repair a supercharged machine that had been found shortly before in the ruins of the NSU factory. Since Germany was not represented in the Federation Internationale Motocycliste (FIM), which had excluded all supercharged machines from international races in 1945, Wilhelm Herz was

able to compete again for the first time with his supercharged machine at the Hamburg Stadtparkrennen in 1947. However, the efforts of Herz, a private driver, were not rewarded until 1948, when he won the German championship in the 350 cc class. In the same year, Hermann Böhm – also on a pre-war NSU machine – became German champion in the 600 cc sidecar class, having already won this title and the German mountain championship in the class up to 1,000 cc on NSU in 1947.

Due to these successes, the NSU management decided in 1948 to compete again with a works team the next year: Wilhelm Herz was signed up for the 350 class, Heiner Fleischmann for the 500 class and Hermann Böhm/Karl Fuchs for the 600 sidecar class. Although they were not yet able to match the performance of the BMW supercharged machines in 1949, NSU won a 3rd place and two 4th places in the German championship standings. The 1949 race at the Grenzlandring went down in history: With a lap average of 200 km/h and top speeds of 240 km/h, it was the

fastest race of all time for many years.

Unforgotten are the enduring duels between the two public favourites Schorsch Meier on BMW and Heiner Fleischmann on NSU, which have gone down in motorsport history as the “Duel of the Giants”. Both Heiner Fleischmann and Böhm/Fuchs became German champions in 1950 on NSU supercharged machines in the 350 cc and 600 cc sidecar classes respectively, while Wilhelm Herz was forced to take a break for the rest of the season due to a crash during training in Cologne.

With Germany’s readmission to the international events of the 1951 racing year, the era of German supercharged machines was also over. However, Neckarsulm had already thought about the requirements of the international regulations at the end of 1949. Under the direction of the NSU chief designer Albert Roder and the head of the racing department Dr. Walter Froede, a new, beefy 500 cc four-cylinder in-line engine was developed in

1950, which was installed transversely to the direction of travel and was intended to match the performance of the compressor machines.

However, the new engine proved to be less stable in the course of the 1951 season. Heiner Fleischmann could “only” take 3rd place on the Feldberg and 4th place in Schotten. Hermann Böhm barely achieved 2nd place in the side scales class on the Eilenriede. Gerd von Woedtke, who had stood in for the injured Wilhelm Herz, was unable to achieve a single place. Constant oil loss, major vibrations and cracked crankcases were the main causes for the poor performance in a season that was marked by technical failures for NSU. Therefore, after the weak practice for the first German Grand Prix at Solitude, the decision was made in Neckarsulm to finally shut down the new NSU four-cylinder racing machines.

Despite the lack of racing success, the development of the new

NSU four-cylinder engine was not in vain. The NSU designers took one of the four cylinders, developed a new crankcase and built everything into the central press frame of a 98 cc production Fox. In this way, the first 125 cc NSU racing motorbike was created within a few weeks in 1951. The only disadvantage was that the engine could only be installed at an angle for reasons of space, which led to the nickname “duckling with the crooked head”. This Rennfox was used for the first time at the 1951 Donauring race in Ingolstadt, where it failed, however, due to a technical defect. Although the first victories were achieved in the middle of the season, H. P. Müller’s lead over DKW in the German championship was already too large to be able to intervene decisively.

In 1952, Otto Daiker won the German Championship with the further developed Rennfox engine, which received an improved cylinder head. Werner Haas even managed to win his first World Championship race with it in the same year, and in 1953 he

contested the German and World Championships halfway in the 125 cc class with the “duckling”.