Actually, the first teardrop- or bullet-shaped cars were built before the Great War (Camille Jenatzy's land speed record electric vehicle, 1899; Neander-Opel, 1911; Count Ricotti's Alfa Romeo, 1914). But the first scientifically designed streamlined car appeared only in 1921, at the car show in Berlin.
In 1902, he had quit Daimler to become technical director of Adler. There he designed the first German vehicle to have engine and gearbox as a unit. The next year, he patented a swing axle rear suspension system (an idea later adopted by Ferdinand Porsche for the KdF Wagen/VW and Porsche 911, as well as by Chevrolet for the Corvair).
Rumpler's efforts produced a car with an astoundingly low drag coefficient of only 0.28 (when tested in 1979); the Fiat of the period, by contrast, was 0.60.
Able to seat four or five, all the passengers were carried between the axles, for maximum comfort, while the driver was alone at the front, to maximize view. With the 1923 model, two tip-up seats were added. Weighing nearly 3,000 lb (1,361 kg), the Tropfenwagen was nevertheless capable of 70 mph (110 km/h) on its mere 36 hp (27 kW).
Fritz Lang employed a number of Tropfenwagen in his great Metropolis (1927):
The Rumpler design inspired the 1923 Benz Tropfenwagen (which used the virtually-unchanged Rumpler chassis, see below) and Auto Union (also built in part by Rumpler engineers) Grand Prix racers.
Rumpler's Tropfenwagen failed to achieve a commercial success, and only 100 Tropfenwagen were built.
Just two survive, one in the Deutsches Museum's Verkehrszentrum in Munich and one in the Deutsches Technikmuseum Berlin.
Rumpler returned to aircraft - and in the late 1920's his Berlin workshop built a small number of streamlined trucks:
Because Rumpler was Jewish, he was imprisoned after Adolf Hitler took power in 1933, and his career was ruined, even though he was soon released. He died in 1940, and the Nazis destroyed his records.
Source: Wiki (1, 2)