Persu: Forgotten Streamliner Pioneer

Romanian-born engineer, Aurel Persu built one of the earliest automobiles with an aerodynamically styled body in 1922. His prototype is also one of the first cars with enclosed wheels

Aurel Persu is revered in Romania as the man who built the first truly streamlined car in the world in 1922. Later calculations show that his prototype had a drag coefficient of just 0.22
In Romania, he is a national treasure; in 2010, his portrait and a car’s depiction were included on postage stamps.

A contemporary of Rumpler and Jaray, he was born in Bucharest, Romania. In 1909 he left for Berlin to study mechanical engineering. Granted consent to choose the topic of his graduation paper from the Field of Theoretical Mechanics under the supervision of Professor Eugen Meyer, he obtained his Graduation Diploma with Honors in 1913. During the first World War he was a military officer and was awarded the Crown of Romanian order. After the War he returned to Berlin to learn more about automobile and aircraft technology. At the 1921 Berlin Show he probably saw Rumpler’s Tropfenwagen, which inspired him to build his own version of a raindrop-shaped car.

He was allegedly inspired by a drop of water representing a perfectly aerodynamic shape. In 1922 he applied for a patent regarding an “Aerodynamically-shaped automobile with the wheels mounted inside the aerodynamic body”. He was granted the patent in 1924. The patent application mentions another inspiration – a piegon: “In horizontal section, the body resembles the upper half of a bird’s body (say a pigeon) with a semicircular profile, with about a third of the length of the vehicle sloping and narrowing backwards, thus reducing the frictional forces that can slow down the car while driving by pulling it backwards.”

In a patent application filed with the U.S. Patent Office in 1927, the car was given the designation Streamliner. It featured significant changes – it became a four-seater.

The original Persu prototype was 4.6 meters long, roughly like today’s Škoda Octavia. The wheelbase was over three meters, the front track was 1,2m, the rear only 70 centimetres. A spare wheel was placed longitudinally above the rear axle. Thanks to the narrow back, the car did not have to have a differential, and its absence added to its safety in sharp corners. In those, the rear axle behaved essentially like a modern rear wheel with a self-locking differential.

Source: Bundesearchive

The body had a steel frame. . The car had rear brakes only which were mechanically operated, as was standard at the time.

Aurel Persu lifted the engine and transmission from an AGA car. The four-cylinder engine gave a modest 20 horsepower, but thanks to its excellent aerodynamics, the car reached a stable cruising speed of around 80 kilometres per hour. Similar “people’s” cars from that time usually had slightly more powerful engines and although they also reached the eighties, but only as a maximum speed, the cruising range was between 50-60.

Until 1925, Persu had his car patented not only in Germany but practically throughout Europe. He was just waiting for a U.S. patent. The 35-year-old professor then received an offer from his homeland, so got in his car and drove it to Bucharest on his own. There he continued his scientific career,
worked for the Romanian railways and participated in the development of oil pumps for locomotives.

Photo credit: Taken from the book Asi Service “Quando le disegnava il vento” by Massimo Grandi

Meanwhile, he was still seeking a patent for his car in the world’s largest market – the United States. He definitely got it in 1927. And with it came a dream offer: Ford and General Motors were interested in the patent. Persu talked to them, but he was afraid that the Americans wanted to buy the patent to put it in a drawer, thus preventing competition from putting the car into production. So eventually he ended the discussions.

In addition to his scientific work, Persu also loved motorsport. Until the outbreak of World War II, he managed to organize dozens of races, some of which had an international dimension. In 1939, Persu started working at the Industria Aeronautică Română aircraft factory in Brasov and continued teaching at the Polytechnic in Bucharest.
Due to the growing influence of the Nazis, he retired in 1940 and returned to science after the war. After three years, however, he was ousted by the communist regime.

Curiosity, surprise or bewilderment?

An engineer and scientist who had written dozens of prized works and thirty years advanced the world aviation industry, and whose theoretical calculations had a significant impact on the development of the first helicopters, was suddenly out of work.

He eventually found a new path at the Bucharest Symphony Orchestra.
Years of semi-professional cello playing, which was mainly fun for him, were enough to join a professional orchestra at sixty. Persu remained there until 1969, until the age of seventy-eight.

When his health problems made it impossible for him to continue driving, he donated his prototype to the technical museum. The odometer is now around 120,000 kilometres, which he allegedly drove with his ingenious creation. The once-revered professor died in seclusion in 1977.

His car still stands in the Dimitrije Leonida Technical Museum in Bucharest. It is preserved as Aurel Persu handed it over.

Today it is in derelict state, but it is said that its restoration is planned.

Sources:
persu.ro
“Quando le disegnava il vento” by Massimo Grandi
Professor Engineer Dimitrie Leonida Technical Museum
rareandunique.media


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