Paul Jaray and his cars

Paul Jaray was the man who brought rigor to the aerodynamic designs of cars.?

Born in 1889 in Vienna, Jaray worked as an engineer for an aircraft manufacturer, designing seaplanes in the German town of Friedrichshafen. Located on Lake Constance, this town was also the home of??Zeppelin airships, and in 1915 Jaray joined Luftschiffbau Zeppelin. Airships were then state of the art in engineering and construction techniques but lacked effective aerodynamic streamlining.?

Jaray established Zeppelin’s first wind tunnel, which was 1 metre (about 3ft) in diameter and powered by a 163kW (220hp) engine. The powerplant drove a four-bladed propellor and could produce a maximum airflow speed of 200 km/h (125 mph). A year later, another wind tunnel was constructed, this time 2.9 metres (9.5ft) in diameter.?

The wind tunnels were used in the development not only of airship shapes, but also in the design of airship hangers and their doors – airships being at their most vulnerable to wind gusts when being moved in and out of the huge sheds that housed them.?

In 1922 Jaray and colleague Wolfgang Klemperer began testing car shapes in the Zeppelin wind tunnels.?Wooden models with a scale of 1:10 were used. The findings of these tests were presented in a contemporary magazine, with the best measured drag coefficient being 0.28. (A subsequent test in 1939 gave a figure of 0.245. Remember, though, that these were of models, not of full-size cars equipped for the road.)

Jaray understood that it was both the shape and the details that were important to achieving low drag. In an interview conducted just before his death in 1974, Jaray said:

“It was the overall concept that mattered. All cars should be enclosed on the bottom but that alone wouldn’t make sense if nothing else was done. You can’t change lights and say it is better. We didn’t put door handles on my cars, for instance. Only a hole and you kept the key in your pocket. But for somebody to say, ‘okay, no handles’, well, that wouldn’t mean the car was streamlined.”

The first full-size Jaray car was built at the Zeppelin works in 1922. Based on a commercially available chassis, a 2-litre Ley T6, the Jaray version had better fuel economy, reduced noise and improved ventilation over the normally-bodied version.?

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Jaray patent drawing from 1922. The fundamental Jaray approach can be seen: two streamlined shapes, one perched on the other. The car is narrow and tall, with the cabin particularly cramped.

In 1923 Jaray moved to Switzerland and opened a design office. He was then engaged by the UK government to consult on airship design. Having seen the progress that Germany had made with airships, Britain had decided to build two large airships – the R100 and R101. Unfortunately, the R101 crashed on its maiden flight, and airship construction in the UK was abandoned. Jaray then decided to capitalise on his low-drag designs for cars.

In 1927 he and Zurich businessman, P Susmann, founded Stromlinien Karosserie Gesellschaft – literally, the Streamlined Body Company. Here Jaray prepared numerous designs for streamlined cars and issued licenses to manufacturers to allow them to use his patents. However, his company made little money. His patents were infringed, sufficient styling changes were made that infringement could not be proved, or car manufacturers said that they’d be prepared to wait until the patents lapsed. Perhaps the idea of patenting car shapes was seen as preposterous.

But one-off versions of Jaray cars were built in the late 1920s and early 1930s. In 1923 Jaray commissioned Heinrich Glaser in Dresden to fit a Dixi chassis with a streamlined body. However, the public showed little interest in the car. Other cars followed, including on Mercedes Benz, Opel, Wikov, Fiat, Maybach and Audi chassis.?

?A 1923 one-off car with Jaray body. (Courtesy Audi)

The only car shape that Jaray consulted on which was built in large numbers was the Tatra T87, which was based on the shape of the T77.

However, Paul Jaray had a major influence on car aerodynamics, especially in moving designers from thinking only in two dimensions to realising that airflow around car bodies is three dimensional. Along with Edmund Rumpler, Jaray was also instrumental in introducing wind tunnel testing of models to automotive body design.

This is an extract from my book A Century of Car Aerodynamics - the science and art of cars and airflow.