Knowledge and creation progress in the ﬁeld of the streamlined cars have been strongly inﬂuenced by the Romanian engineer Aurel Persu. Graduated with Honors from the Charlottenburg Higher Technical School in Berlin and awarded with a Medal by the Ministry of Public Education in Germany for his Diploma work, he attended after the 1st World War the courses of Aerodynamics and Car Engineering, which led him in 1922 to certiﬁcate a coachwork of aerodynamic shape and to achieve in 1923 an aerodynamic car.
All his life long he has fulfilled his duty towards his homeland as an officer in the war for national unity, as a professor of Mechanics and Car Engineering at the University and the Polytechnic Institute of Bucharest, as a scientist of Romanian Academy of Sciences, as a President of Romanian Automobile Club, as a General Director of Romanian Aeronautical Industry and as a Violoncello player in the Cinematography Symphonic and Engineer's Chamber Orchestras.
Such multilateral personalities as Aurel Persu are extremely rare in the history of any nation and they are worthy of the international acknowledgement and honor.
After seven years of aerodynamic automobile building, contemplating the last products of the most prestigious ﬁrms we realize today the importance assigned by the world to this technical question.
The ceaseless soaring of the cruise speed, the decrease of ﬁnal consumption and the enlarging of the action range of the aerodynamic automobile have been in this century, as they no doubt will be in the next, the main concerns of the specialists endowing car owners with a rapid, convenient and cheap means of transport, indispensable in a modern society, both in business and in private life.
From this point of view, the invention of the engineer Aurel Persu opened an inestimable way, since it is well known that at over 60 km/h the sum of the mechanical cruising resistant forces of an automobile are vertiginously overtaken by its aerodynamic resistance. The idea of an aerodynamic car shape was inseminated in Aurel Persu 's mind by his great passion for both motorcars and aviation, in inter-war Germany where research was exclusively directed toward glider construction and obtaining an optimal shape to increase ﬂying results, this is the possible reason why Aurel Persu used aluminum plates, together with incorporated wheels and head-lights. in building his aerodynamic automobile.
Of course, also in the generalization of this invention there were many impediments, but one of the most important for Aurel Persu was the penetration into the European markets of the American serial production, technologically advantageous, but non-aerodynamic, with the additional drawbacks of an absent Romanian car industry and the inventor's modest material means.
However, after 1930, the appearance of aerodynamic cars produced by such ﬁrms as Porsche, Mercedes-Benz, Auto-Union, Bugatti, Alfa Romeo, Volkswagen, Tatra, etc. meant the debut of the wide-spread adoption of this invention. But we owe Aurel Persu special respect, not only for a good intuition and correct design of an aerodynamic car shape together with the material and technical effort in devising the technology of the ﬁrst aerodynamic automobile, but also for his inexhaustible and successful activity in the ﬁelds of both automobile and aviation in Romania as well as abroad. It was materialized in published articles, given conferences at the Romanian Academy for Sciences, the Polytechnic School and Technical Museum in Bucharest, organized car races and aviation contests where prizes were awarded to encourage the participants, and his contribution to the development of aircraft construction at the Romanian Aeronautical Industry in Brasov.
To professor Aurel Persu we owe consideration for his special human qualities: a genuine scientist, a good patriot and a pious Christian. I remember him since my student days when I belonged to his last generation of electromechanical engineers at the Bucharest Polytechnic Institute (1948), as well as from my subsequent years as his collaborator. I keep in my mind unforgettable moments in his lectures, his elevating cello recitals of religious music, his ﬁrm accusations of the anti-national political campaigns from the usurpers of the Romanian scientiﬁc, technical, cultural and religious traditions.
Today, now it has become ﬁnally possible to celebrate the Romanian technical Genius, the jubilee of 70 years of world-wide application of Aurel Persu 's invention of the aerodynamic automobile, helps to promote the national technical prestige and calls for the recognition of an international human personality like that of Aurel Persu, rare and happy event in the life of any nation. This tribute paid to Aurel Persu under the Romanian National Commission for UNESCO is, perhaps, the most digniﬁed form of acknowledgement in the view of international vocation of the United Nations Organization for Education, Science and Culture.Prof. Dr. Eng. Mircea-Dimitrie Cazacu (publication coordinator)
He was born in 1890, 26 December: his parents: Ion Persu, an agronomist and farm owner in Buzau county, and Zoe Persu, daughter of the former assistant of Prince Alexandru loan Cuza, Colonel Stefan Stoika (whose family came from Fagaras and was related with Lucretiu Patrascanu's family).
Aurel Stefan Nicolae was born in his parents' house in Bucharest, Calea Victoriei 183. The house had been built by his father on a property received from his close friends, Alexandru and Zoe Filipescu.
The other four children of the Persu family were also born there:
Granted consent to choose the topic of his graduation paper from the ﬁeld of Theoretical Mechanics under the supervision of the famous professor Eugen Meyer, he obtained his Graduation Diploma with Honors in 1913.
Back at home, just before the outbreak of World War I, he was appointed Reader at the University of Bucharest. He served in the army in 1914 and was promoted to the rank of a lieutenant and, after Romania entered the war, he was called up for the automobile Traction Regiment to instruct motorized troops. He was awarded the Crown of Romanian order. After the war, beside his teaching activities, he became the technical manager of Constantin Leonida's repair workshop. He married Ioana Cantacuzino, of the ruling Cantacuzino family, and they subsequently left for Berlin to update his information on automobile and aircraft technology.
In 1922, he was granted a patent for aerodynamic automobile, which he managed to build with the technology available at the Deutz and Lloyd factories.
In 1925, he came back to Romania by riding his car, and resumed his teaching and technical activities, this time in the Direction for oil pipes at the Romanian Railways. King Alexander II of Yugoslavia awards him a medal at an international car-race.
He married for the second time. Elena Bratianu and became particularly concerned with the education of his sons whom he directed towards engineering studies.
Apart from his duties at the University and the Polytechnic School in Bucharest he was also active at the Romanian Academy for Sciences where he became a corresponding member in 1935, and read papers on the Aerodynamic Automobile and Mechanics.
He organized and directed several car and motorcyclist races: The Carpathian Cup, The Union Circuit, the Bucharest Grand Prix, The Brasov Grand Prix, The Coast Races at Sinaia (Furnica), Brasov (Poiana), Cluj (Feleacul), Sibiu (Vestem). where famous sportsmen from Romania and abroad came: Hans Stuck, N. Young, A. Erose, the counts E. and N. Festetics, Petre Cristea, Michael Sontag, Luca Niculescu, It. col. AI. Berlescu, His Royal Highness Prince Nicolae, Jean Calcianu, E.T. Manicatide, Al. Frim, Al. Papana.
In 1938, Aurel Persu was appointed by Royal Decree General Director of the Romanian Aeronautical Industry in Brasov, where he contributed to the development of aircraft constructions in Romania, together with other famous specialists like Acad. Elie Carafoli.
At the same time, he continued to lecture in Mechanics in Bucharest at the Polytechnic School. In 1940, he left the management of the Romanian Aeronautical Industry because of the growing Nazi inﬂuence in the political life of the country, which he resented, and after 1948 he was forced by the communist regime to leave higher education as well, so that between 1953 and 1962 he worked as a cellist in the Cinematography Symphonic Orchestra and collaborated with the Institute of Technical Documentation.
In 1969, after signs of a heart attack, his activity came to almost a standstill. He died on 5th May 1977, in Bucharest, leaving his aerodynamic automobile as a heritage to the whole World.Eng. Radu Moldoveanu
A graduate of the Charlottenburg Higher Technical School in Berlin Persu was the ﬁrst in his class to be admitted to the Mechanical Section "Mit Auszeichnung Bestanden".
Followinghis graduation, he attended Professor Eugen Meyer's lectures on Aerodynamik und Mechanik des Flugzeuges.
In 1914, he was awarded a medal by the Ministry of Public Education in Germany for his work “Die Schwingungen eines Stabes im freien Weltraum – Schiffsschwingungen”.
After The World War I, he returned to Berlin, where he attended lectures in Aircraft (by Professor Parseval); Light Explosion Engines (Professor Gabriel Becker); Aircraft Mechanics and Board Instruments (Professor F. Everling); Psychotechnics of Industrial Work (Professor Moede) and the Science of Finance (Professor Julius Wolf).
In 1914, after he received his diploma, he was appointed honorary Reader in Mechanics at the Electrotechnical Institute and then at the Institute of Industrial Chemistry, from the University of Bucharest.
A temporary Reader since October 1, 1920, and since July 1, 1932, Reader in his own right, Aurel Persu was also a Reader at the Polytechnic School between 1924 and 1929, where he lectured on Automobile Engineering.
In 1938 he was transferred, together with the Institutes of Electrotechnics and Industrial Chemistry, to the Bucharest Polytechnic School, where he was appointed Professor Head of Mechanics Department from 1944 to 1948, when he was obliged to give up teaching.
He authored many studies in specialty journals abroad: Elastische Verbrennungsmotoren; Neues Stromlinien Automobil; Luftwiderstand und Schnellkraftwagen; Der kunftige Schnellkraftwagen; Luftwiderstandverminderndes Fahrzeug System Persu; Streamlining: Short Back Axle; Uber die Stabilitatsbedingungen des Motorwagens.
In 1930, in Stockholm, he attended the 3rd International Congress of Applied Mechanics with his study “Ihrefuhrende Anschauungen in den Grundlagen der Mechanik”. Meanwhile, he contributed further articles to specialty journals abroad: Der aerodynamische richtige Wagen (1936) and Die Fahrwiderstande beim Kraftfahrzeug und die Mittel ihrer Verringerung (1938).
To these, one should add his university lectures: The Elasticity and Resistance of Materials; Hydrodynamic and Thermal Engines, Technical Mechanics (Statics and Dynamics). Professor Aurel Persu was granted patents for a series of inventions: on internal combustion engines (in Germany), the aerodynamic automobile (in Germany, Switzerland, Great Britain, Belgium, France, Austria, Hungary, Czechoslovakia and USA) and a combined pump indirectly driving the ﬂuid to be pumped.
For special scientific and technical merits, he was elected Corresponding Member of the Romanian Academy for Sciences in December 21, 1935.
At the Academy's scientific sessions, he read papers on Simplifying and Rectifying Views on the Study of Mechanics, which was particularly appreciated by Dimitrie Pompeiu, the distinguished mathematician of the University of Bucharest, who later wrote Persu a letter.
In 1945, his work was given the Romanian Academy Award. Main ideas may be summarized as follows:
Leaving aside the appreciation he enjoyed from such a reputed scientist as Dimitrie Pompeiu, Persu's ideas were also an object of criticism, namely, that the general equilibrium of the forces, postulated as a fundamental law of mechanics, is a purely ﬁctitious equilibrium in dynamics, since inertia forces do not act upon the considered body, but rather on the one with which it interacts.
Aurel Persu resumed these ideas in 1942 in two articles: “Le principe de la dualité des forces”, subtitled: “Considerations mécaniques pour apprendre a connaitre, définir et aprécier la notion de masse” (1971) and “Mon testament scientifique”, both published in Belgium by his son, Engineer Nicolae Persu.Acad. Radu Voinea
The concern for reducing air resistance to high speed ground vehicles started soon after the invention of the automobile, and related to attempts of reaching ever higher cruising speeds.
Among the remarkable achievements which preceded Aurel Persu's aerodynamic automobile, let us mention the cylindrical spindle or bullet shaped car, built by Jenatzy, the so-called “Jamais Contente”, which managed to break the 100 km/h threshold in 1899; also, Count Ricotti’s Alfa automobile, coachworked as skew spindle by Castagna in 1913, and Rumpler's Tropfenwagen (the “Raindrop” car), built in 1921.
All these achievements show on exclusive concern for the special design of the coachwork, which was placed above the wheels and the arched plate-suspensions, with the lights, the mud-protecting wings and the mounting steps added to the coachwork, which bear witness that the principles of aerodynamics were only partially grasped.
In 1922, while in Germany, Engineer Aurel Persu was granted patent no. 402683 of November 14, 1922, for the idea of an aerodynamically shaped automobile with all four wheels incorporated in the coachwork, and without any exterior piece. Persu's coachwork is the ﬁrst correct proposal for an aerodynamical automobile.
It is also accurately described in technical terms, which demonstrates the excellent competence of the author.
The automobile description appears in the many patents to follow: the Swiss Vierradriger Kraftwagen mit Stromlinienform (no.106911/9 October 1923), the English patent (no. 206823119 October 1923) Improvements In Streamline Power Vehicles, the Belgian patent (no. 314029/3 November 1923), the French patent (no. 572002/13 February 1924) Vehicule automobile affectant la forme bon projectile, the Austrian patent (no. 100478/10 July 1925) Stromlinienkraftwagen, the Hungarian in Gepkocsi (no. 89602/22 October 1925), the Czechoslovakian (no. 22721/30 March 1927) Stromlinienkrafwagen and the American (no. 1648505/8 November 1927) Streamline Power Vehicle.
The title is repeated in publications: Neues Stromlinien Automobil in Zeitschrift des Vereines Deutscher Ingenieure No. 28/11.07.1923, Luftwiderstand und Schnellkraftwagen in Zeitschrift fur Flugtechnik and Motorluftschiffahrt No. 374/26.02.1924, Der kunftige Schnellltraftwagcn in Allgemeine Automobil Zeitung No. 18/3.05.1924, Luftwiderstandverminderndes Fahrzeug System Persu in Motorwagen No. 22/10.08.1925, Streamlining: Short Back Axle in The Autocar No. 1581/5.02.1926, Der aerodynamische richtige Wagen in Allgemeine Automobil Zeitung No. 1/14.03.1936, L‘Automobile aérodinamique correcte in Comptes Rendues des Séances de l'Academie des Sciences de Roumanie Tome I/31.05.1936, Automobilul aerodinamic corect in Motor No. 57758/1.01.1937, Die Fahrwiderstande beim Kraftfahrzeug und die Mittel ihrer Verringerung in Automobiltechnische Zeitschrift No. 18/25.09.1938.
Here is how Professor Persu described his aerodynamic automobile:
The coachwork shape resembles the upper half of bird's body (say a pigeon), having a uniﬁed volume, of somewhat semicircular cross-section with the base downward, higher and broader in front, about one third of the vehicle's length whereupon the sections diminish gradually towards the rear, to avoid depressions during the cruise, which would slow down the automobile, drawing it backwards.
Given the shape of the coachwork, the chassis of such an aerodynamic automobile is implicit: the passenger seats will be placed in the more spacious front, the engine will be placed at the thinner rear, together with all organs of transmission and propulsion, which also allows for an equal distribution of the total weight on both decks of the car: all wheels must be within the outer—ranging surface of the coachwork free of over-structures, bulges, off-line headlights, step or wings; the distance between the rear wheels will be therefore reduced according to the thinned out coachwork end, making thus possible for the differential to be removed. This last recommendation should be particularly emphasized in his view as it seemed to diminish the vehicle's stability at the curves. Run tests on his experimental aerodynamic automobile (over 150000 km) showed that narrowing the distance between the rear wheels does not diminish the vehicle's stability at the curves.
The gauge of the directing front wheels is greater than of the engine-activated ones at the rear, all wheels are within the aerodynamic coachwork, the spare wheels are placed vertically in between the longitudinal frames of the chassis, more retracted than the rear wheels, the engine is placed horizontally and it drives the front wheels with the aid of a differential-free transmission system, the radiator is placed at the rear, and the gasoline tank is also at the rear.
Persu materialized his idea with the technical means available at the time. In November 1923, while in Berlin, he started to build his aerodynamic automobile. He placed an aluminum plated wooden coach on a metallic chassis (aircraft borrowed technique).
The distance between the front and rear axles of the car was 3.20 m, the front gauge between the wheels 1.20 m. the rear gauge 0.70 m, the total length of the car was 4.60 m, the maximum breadth 1.40 m and the maximum height 1.60 m.
The front, rear, half-proﬁle and top views of the car give a complete picture of this truly original shape. This shape was a technological approximation of the patented model.
The automobile had a 40 HP engine. made by the AGA-Werke ﬁrm in Berlin, with 4 water-cooled cylinders. Persu’s aerodynamic automobile aroused the interest of the greatest American manufactures, but the inventor refused to give them the patent because they did not guarantee the manufacturing of the vehicle. A remarkable precursor in automobile dynamics, the inventor demonstrated the advantage of a convenient coachwork proﬁle and its effect on the necessary engine power and fuel consumption. At the time when Persu patented and built his prototype, most cars had a resistance coefﬁcient to forward drive CX = 0.8 - 1.0, while shapes like the one designed by Persu proved, when measuring techniques developed, to have an aerodynamic coefficient CX = 0.20. This means that at a 100 km/h speed, the aerodynamic coachwork could reduce the necessary propulsion power to a mere ﬁfth of the value required by other contemporary coachworks.
With the theoretical and experimental developments in aerodynamics and with the continuous increase of the cruising speed on roads or highways, the ﬁeld of aerodynamics research expanded accordingly, ranging from the reduction of advancement resistance to the variation of load per wheel and the behavior of the vehicle under lateral wind.
The drive for a compromise between habitability and exterior designs, the long and costly series of experiments on coachwork models and prototypes, are as many reasons accounting for the delay of an aerodynamically correct automobile.
Aurel Persu dedicated a good part of his long period of activity to the promotion of car racing within the Royal Romanian Automobile Club between the two world wars.
As active chairman of the Motor Sporting Group. whose honorary president was His Royal Highness Prince Nicolae of Romania, Persu made an important contribution to motor-car racing in Romania.Acad. Constantin Arama
While still a student, the future engineer Aurel Persu understood the importance of adopting exterior shapes capable to determine a reduction in automobile drag.
Thus in 1914, he attended the lectures in Aerodynamik und Mechanik des Flugzeuges, taught by Professor Eugen Mayer of the Technical School in Berlin, but the outbreak of the World War I broke short his activities.
After the war, Persu returned to Berlin. In 1921 - 1922 he attended several modern lectures like the ones: on Aircraft, on Light internal combustion engines, on Aircraft mechanics and Board instruments.
Because he was appointed a Reader in 1921 by the Romanian Ministry of Public Education and as the author of three German licences in 1921 - 1922, he became in 1922 a member of the Wissenschaftliche Gesellschaft fur Luftfahrt - WGL Society, and in 1923 a member of the Automobil und Flugtechnische Gesellschaft —- AFG.
Convinced that automobile improvement depends on the strict application of the laws of aerodynamics, Persu obtained, starting with 1922, several patents for the improvement of the coachwork shape.
His theoretical research, published in German and Romanian journals at the time, were experimentally veriﬁed by model tests in the Aerodynamic Tunnel at the Polytechnic School in Bucharest.
The results of these tests were read before the members of the Romanian Academy of Sciences, in a plenary session of May 31. 1936. In his paper, the author discusses the following main ideas:
The link between the serious professor of mechanics and the young promoter of aviation will be established by his joining the enthusiastic members of the Royal Romanian Aeroclub in 1926.
His activity at the Club was rewarded by his appointment in the Manager's board in 1929, alongside such specialists as Prince George Valentin Bibescu, Professor Elie Carafoli, Radu Gabrielescu, Ion Stroescu, Alexandru Popovici and Gheorghe Negrescu.
A lover of aviation contests and meetings, Persu was always a member of the prize awarding commission. His results in this ﬁeld are exceptional.
With a scientist's authority, Professor Aurel Persu drafted the Special Statute for classifying teams in the aerocircuit of the Little Entente and of Poland.
Applying general considerations for classification in aviation contests, Persu reached a scientifically founded and more comprehensive relation regarding a team’s classiﬁcation:
N = C1(a/A) + C2(m/M) +C3(r/R)
The new relation is based on the three criteria, relating a team’s results to the best performance in the contest. The numerical values of the coefﬁcients (C1 + C2 + C3 = 100) are chosen according to importance given to the criteria in the end results.
Professor Persu's study deﬁnes:
His complex activity in the field of aviation also includes an important contribution to the management of the Romanian Aeronautic Industry in Brasov, whose General Director he was between the two world wars.Dr. Eng. Nicolae Florin Zaganescu
Aurel Persu was also devoted cellist who adored chamber and soloist music written for the instrument he was playing.
From his high-school years, he felt attracted by learning instrumental music. He studied the cello with famous professors at the Conservatoire in Bucharest (Constantin Dimitrescu and Dimitrie Dinicu) from whom he acquired a good technique of the left hand and the bow tone.
His musical training was also encouraged by the family atmosphere (his sister studied piano) and he was playing in chamber music and symphonic orchestras.
Not even in Berlin, where he came for engineering studies, did he betray his passion for music. He attended the cello classes at the Hochschule fur Musik, having the famous Hugo Becker as his teacher.
It was then that he played chamber music in the company of reputed musicians, like the violinist Bronisiav Hubermann and the pianist Ignaz Friedmann.
On his return to Romania. after he studied engineering, he continued his musical activity improving his artistic skill at the Pro Arte Conservatoire chaired by the cello maestro George Cocea.
In his parent’s home, at 159 on Calea Victoriei, chamber music was played every week. Had Persu's house not been demolished, it could now have made a wonderful memorial house.
In 1922, Aurel Persu founded his string quartet with maestro Metzner as ﬁrst violinist later followed by the engineer Constantin Iarca, the composer Grigore Cugler as a second violonist, Floricel Petrovici and Professor Engineer Ion Tomescu as violists.
On these weekly musical evenings one could listen music from sonatas to piano quintets, played by many engineers of broad musical knowledge and of excellent instrumental training as: Dr. Eng. Mircea Cazacu. architect Izu Broder, Dr. Emil Stoian, Eng. Mircea Tiucra. economist Ion Zankow, Dr. Eng. Aurel Avramescu, Eng. Aurel Ionescu, Eng. Romulus Argesanu, Eng. A. Frimu, Dr. Eng. Petru Ghenghea, Dr. Eng. Mario Checiulescu, Eng. Arnold Savin. Professor Filionescu, Academician Serban Titeica, Dr. Eng. Mihai Popov, corresponding Member of the Romanian Academy.
On occasion Aurel Persu played also chamber music with George Enescu at Constanta Cantacuzino's palace.
0n the initiative of some musician friends, Professor Aurel Persu who had meanwhile retired was hired 1953—1962, until he was 72, as a professional cellist in the Cinematography Symphonic Orchestra.
Playing with the Cinematography Orchestra was an opportunity for him to extend his repertoire with symphonic music as well; he played in regular concerts, at George Enescu festivals and was recorded under the baton of well-known conductors like: Constantin Silvestri. Emanoil Elenescu, Constantin Bugeanu, Paul Popescu and Mircea Cristescu. In 1957, he started playing as one of the founding members, with the Engineers' Chamber Orchestra, where he led the cello section, and played as the soloist in any concerts recorded by the Electrecord-House.
Professor Aurel Persu's musical activity came to an end in 1966, but the Engineers‘ Orchestra still hold him dear in their memory.Prof. Dr. Eng. Petru Ghenghea