Edmond Rumpler, a brilliant Austrian aircraft designer, introduced his unprecedented Tropfenwagen at the 1921 Berlin Auto Show. The teardrop-shaped body (tropfen translates to drop), with its curved glass greenhouse, produced a very low drag coefficient of only .28, which is on par with the aerodynamic cars of today. In addition to the shape of the body, the minimal horizontal fenders and the belly pan helped to achieve this figure.
Left and center: Rear views of the 1921 Rumpler Tropfenwagen. Right: 1923 Rumpler Tropfenwagen on exhibit at the German Museum of Technology
It appears that between 80 to 100 Rumpler Tropfenwagen’s were built in the four years that they were in production. Only two examples are known to have survived and both can be seen above: the German Museum of Urban Transport car built in 1921 has the earlier shorter style of passenger compartment; the 1923 German Museum of Technology Sedan features a longer cabin with the rear top-section of it used for storage.
The cars seated four or five passengers in the center of the body resulting in a very comfortable ride. A convertible version was also produced and can be seen in a line drawing below. That version with four passengers aboard weighed in at 3,000 lb. with the sedan at 3470 lb., both were capable of speeds above fifty mph.
The interesting video above shows a period film of a Rumpler Tropfenwagen being driven in several different scenes, possibly on the streets of London. Two things to note while watching it are: The fitted luggage and its compartment, and the trafficators Rumpler fitted for use as turn signals.
The car utlized a W6 Siemens & Halske-built, 157 ci. (2,580 cc) 36 hp. overhead valve engine. Three banks of paired cylinders were used, all working on a common crankshaft. Note one of the unique three connecting-rods units at number four in the image above.
The engine, clutch, three-speed transmission, and the final-drive were all together in a unit power plant. The rear swing-axles were suspended and located by angled cantilever leaf springs, while the beam front axle was suspended by a pair of parallel leaf springs of the same type.
The novel design of the car and the potential for a light-weight and excellent handling racing car attracted Benz chief engineer, Hans Nibel. The resulting Benz Tropfenwagen racer seen at the bottom used a Rumpler chassis with a 121.5 ci. – 80 hp. (1,991 cc) dohc straight-six. The cars that were built handled extremely well but were uncompetitive and were dropped after three years. The basic design was used later by Auto Union for its racing cars, VW and Porsche. Many other streamliners can be seen here on The Old Motor.