Prior to WWII, Several of the German manufacturers, like many around the world, had discovered the allure of supercharging. NSU was one of them. Just as development was beginning to pay real dividends, the war interrupted efforts. After the war, supercharging became banned at the highest levels of international competition, but it was still perfectly allowable in national competitions within Germany. NSU applied its supercharging know how to the new 500cc version of its popular twin cylinder motorcycle. It was quickly competitive, and excelled in particular at high-speed venues. This caused a few people at NSU to think about developing a speed record breaking version of the motorcycle.
Work began in earnest in 1950 when a supercharged version of the 500cc Rennmax was coupled with a full fairing. It produced 100 BHP, which was roughly twice the output of the works 500cc in normally aspirated form. In April 1951, Wilhelm Herz rode the machine to a new record of 180.17 mph on the Autobahn between Munich and Ingolstadt. Herz said he could have gone faster but the overpasses created tremendous instability ! In spite of this, it broke the record formerly held by BMW. NSU also set other records including the sidecar record with Hermann Bohm, and the 350cc record. Later in 1954, Gustavo Baumm broke 11 world records for small bore machines from 50cc to 100cc. Baumm was a commercial artist, and the machines were of his own design using a recumbent position within the fish-like alloy fairing. They were dubbed the "flying hammocks".
Following these records, rumors began to circulate that several manufacturers were going to attempt to break 200 mph. It was clearly within striking distance, but NSU was initially not interested, having several world records to its name already. However, NSU had also recently withdrawn from grand prix racing, and there was a change of mind (or some heavy persuasion) with respect to now pursuing another speed attempt. The idea was to combine the design of Baumm with the supercharged Rennmax engine developed by Walter Froede. In May 1955, NSU successfully broke 22 world records on the Autobahn once again, in classes from 50cc to 350cc using the new combination of engines and designs. Unfortunately, Baumm was killed while testing not long after these records, which probably materially impacted the direction that NSU took in future years with its production motorcycles and cars.
Despite the loss of Baumm, and in the face of declining sales, NSU once again decided to assault the speed records. They produced a new fairing design which cut the coefficient of drag from .29 to .19. They decided to spare no expense this time around, fielding two different designs. One design was dubbed the Baumm II, while the other was the Delphin III, an evolution of the early 1950s work by the factory. The chosen location for the attempt was the Salt Lake flats in Utah. To emphasize the significance of this round of attempts, NSU chairman Viktor Frankenberger travelled to Utah. On August 4th 1956, with 46 year old Wilhelmina Herz at the controls, NSU established a new record of 210.64 mph for the 500cc class. This broke the existing record by 25 mph, and the unofficial record by about 15 mph ! When the speed trials concluded, NSU went home with more than 50 new records! The victorious machines then went on tour to help prop up sales, which seems are rather undignified end to a brilliant era of achievement in speed records at NSU.