The Rumpler Tropfenwagen was a car developed by Austrian engineer Edmund Rumpler. Rumpler, born in Vienna, was known as a designer of aircraft when at the 1921 Berlincar show he introduced the Tropfenwagen. It was to be the first streamlinedproduction car, before the Chrysler Airflow and Tatra T77. The Rumpler had a drag coefficient of only 0.28, a measurement which astonished later engineers and would be competitive even today. For comparison: the top ten most aerodynamic production cars in 2014/2015 worked their way down from a value of 0.26. The Fiat Balilla of the mid-1930s, by contrast, was rated at 0.60. To enable the car's aerodynamic shape, the Tropfenwagen also featured the world's first curved windows. Both the windscreen and the side windows were significantly curved. The car featured a Siemens and Halske-built overhead valveW6 engine, with three banks of paired cylinders, all working on a common crankshaft. Producing, it was mounted just ahead of the rear axle. The engine, transmission, and final drive were assembled together and installed as a unit. The Rumpler-invented rear swing axles were suspended by trailing leaf springs, while the front beam axle was suspended by leading leaf springs. 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, the Tropfenwagen was nevertheless capable of on its mere. This performance got the attention of Benz & Cie.'s chief engineer, Hans Nibel. Nibel conceived the Mercedes-Benz Tropfenwagen racers using the virtually unchanged Rumpler chassis. Poor sales and increasing losses led Benz to abandonthe project. Later Auto Unionracing cars resembled the Benz Tropfenwagen racers and were built in part by Rumpler engineers. Rumpler made another attempt in 1924, the 4A106, which used a inline4-cylinder engine. This compelled a growth in wheelbase, with a consequent increase in seating to six or seven. Although the car was very advanced for its time, it sold poorly – about 100 cars were built. Sales were hindered by small problems at the start, the appearance of the vehicle, and the absence of a luggage compartment. Most were sold as taxis, where easy boarding and the high ceiling were advantages. The last cars were built in 1925. The Tropfenwagen did become famous thanks to the film Metropolis, in which Rumplers found a burning end. It also inspired the Mercedes-Benz 130H / 150H / 170H road cars. Only two examples are known to survive, one in the Deutsches Museum's Verkehrszentrum in Munich and one in the Deutsches Technikmuseum Berlin.
