An Illustrated History Of Automotive Aerodynamics – In Three Parts
[Note: A significantly expanded and updated version of this article can be found here]
That air presented the greatest obstacle to automotive speed and economy was understood intuitively, if not scientifically since the dawn of the automobile. Putting it into practice was quite another story. Engineers, racers and entrepreneurs were lured by the potential for the profound gains aerodynamics offered. The efforts to do so yielded some of the more remarkable cars ever made, even if they challenged the aesthetic assumptions of their times. We’ve finally arrived at the place where a highly aerodynamic car like the Prius is mainstream. But getting there was not without turbulence.
Racers, particularly those chasing the coveted Land Speed Record (LSR), were generally the first to employ aerodynamic aids. The La Jamais Contente (The Never Satisfied) was the first automobile to break the 100kmh (62 mph) record, in 1899. Like all the first batch of LSR holders, it was an EV. The driver’s position seems to negate the aerodynamic aids, or maybe he was just posing, and more likely crouched down for the actual run.
The evolution of aerodynamics for LSR cars was remarkably rapid, as this Stanley Steamer Rocket of 1906 evidently shows. And the increase in speed was even more dramatic: the Rocket broke the 200km barrier, with a run of 205.44 kmh (127.66 mph). That would not be bettered until 1924, and not until 2009 for steam powered vehicles.
The first known attempt at streamlining a passenger car is this Alfa Romeo from 1914, built by the coach builder Castagna for the Italian Count Ricotti. Due to the very heavy bodywork, it turned out to not improve on the top speed of the open Alfa it was based on.
Undoubtedly, the real breakthrough aerodynamic passenger car was the German Rumpler “Tropfenwagen” (teardrop car) of 1921. Unlike the impractical and heavy Castagna Alfa, the Rumpler was as dramatically different (and influential) for its completely integrated and original design and engineering. It had a mid-engined W6 engine, and four wheel independent suspension using swing axles which Rumpler patented. The Tropfenwagen was tested in VW’s wind tunnel in 1979, and achieved a remarkable Coefficient of drag (Cd) of .28; a degree of slipperiness that VW’s Passat wouldn’t equal until 1988.
It’s important to remember that the Cd is a coefficient, and denotes the relative aerodynamic slipperiness of a body, regardless of its overall size. A brick of any size has a Cd of 1.0; a bullet about .295. To arrive at the critical total aerodynamic drag that determines power required and efficiency, the frontal area (cross section of the vehicle looking straight on) is multiplied by the Cd. The Rumpler was relatively very aerodynamic, but it was also quite tall and boxy, which resulted in the one hundred or so production cars being used primarily as taxis. An ironic ending for Rumpler, but his ideas spawned imitations and extensions world-wide, and opened the whole field.
To put the nascent field of automotive aerodynamics in perspective, the typical two-box car of the twenties was more aerodynamic going backwards than forwards, as this ass-backwards car showed. That brings back memories of Bob Lutz stating that the Volt concept would have had better aerodynamics if they put it in the wind tunnel backwards.
Hungarian-born Paul Jaray used his experience working int the aeronautical field, and especially designing Zeppelins, to develop a specific formula for automotive aerodynamic design principles that lead to a patent, applied for in 1922 and issued in 1927. His approach was influential, and numerous companies used Jaray licensed bodies during the streamliner craze that unfolded in the early thirties. His early designs tended to be very tall, and with questionable proportions and space utilization (below).
His designs eventually became more mainstream, and Mercedes, Opel, Maybach, and numerous other makes, primarily German, built special streamliner versions using Jaray bodies, like this Mercedes below:
The limitation of these cars is like the Castagna Alfa, they were re-bodied conventional cars with frames, front engines and RWD. Jaray only addressed the aerodynamics, not the complete vehicle like Rumpler had. It was a start, but others were taking up where Rumpler left off, like the English Burney, below:
Obviously more Rumpler influenced and less by Jaray, the 1930 English Burney featured a then-radical rear engine and also four wheel independent suspension.
One of the most influential and lasting designers of the whole era was Austrian Hans Ledwinka. After he took over as chief design engineer at the Czech firm Tatra in 1921, he developed the basis of a series of remarkable Tatra cars and eventually streamliners with platform frames, independent suspensions and rear air-cooled engines that Ferdinand Porsche cribbed from heavily in his design of the Volkswagen (VW made a substantial payment to Tatra in the 1960s to compensate them for this theft of IP).
The compact Tatra v570 of 1933 (above) is the forerunner of both the larger Tatras soon to come, and obviously of the Volkswagen. We’ll come back to Tatra later.
This Volkswagen prototype from 1934 (above) shows a very strong resemblance to the cribbed Tatra v570, with the benefit of some further refinement. Although the visual cues are not really as significant as they might appear to us now, because these were the leading-edge design elements of the time, and widely imitated or shared, on both side of the Atlantic.
As this 1934 prototype for an American rear-engined sedan by John Tjaarda shows, the Europeans weren’t working alone. This fairly radical design became tamed-down for the production 1936 front-engined Lincoln Zephyr, of which the less common but handsome coupe version is shown below:
Of course, Americans’ introduction to streamlining had come two years earlier in 1934, with the stunning Chrysler Airflow (below). An essentially pragmatic approach, the Airflow also kept the traditional Body On Frame (BOF) front-engine RWD standard, but made some significant advances in terms vehicle design by pushing the engine further forward over the front wheels. This, combined with a wider body, dramatically improved interior space and accommodations. The Airflow had the same basic configuration as American cars from the late forties and early fifties. Progress is not always linear.
The failure of the practical Airflow can probably comes down to one thing: that overly flat waterfall grille. That was too much of a break for the symbolism still engendered in the remnants of the classic car prow. The Zephyr had one, and it was a success, despite not being nearly as a good a car as the Airflow.
An even less pragmatic but remarkably practical and effective American vehicle was the Stout Scarab (above). Aviation engineer William B. Stout designed this extremely roomy mini-van precursor using a unitized body structure and a rear Ford V8 engine. The first was built in 1932, and several more variations, a total of nine, were built in the mid thirties, but series production never got off the ground, due to an asking price almost four times higher than a Chrysler Imperial Airflow of the times, and even those weren’t selling so well just then.
A much more radical approaches to streamlining was Buckminster Fuller’s Dymaxion. The first of several prototypes also saw the light of day in 1933, in the midst of this fertile period on both side of the Atlantic. The Dymaxion also had a rear Ford V8, but with a tricycle carriage and rear wheel steering, which allowed it to turn on the length of its body.
Another lesser-know variation of the popular Ford V8 engined aerodynamic vehicles was this Dubonnet Ford of 1936, whose very slippery body allowed it to reach 108 mph. I appears to have Isetta-type front doors for the front seat passengers. About as much crumple zone too.
Let’s jump back to Czechoslovakia and the fertile Tatra design studios. Here are some clays from about 1933 or so, showing the development of both the smaller VW-like v570 on the right, and the larger streamliners in the rear. The first of these, the T77, arrived in 1934 (below):
The T77 was measured to have a Cd of .212, a number that was not broken by a production car until GM’s EV-1 of 1995, which measured at .195. A remarkable achievement, the long-tailed T77 was powered by a rear air-cooled V8, and began a long series of Tatras until the 1980’s along similar lines. My retrospective of Tatra is here.
Tatra became synonymous with the advanced streamliner of the pre-war era, enabling remarkably fast travel (100 mph) on the fledgling Autobahns of the Third Reich. Favored especially by Luftwaffe brass, they had a nasty habit of killing them, due to its wickedly-abrupt oversteer, thanks to the combination of rear V8 and swing axles. That earned it the nick name of “the Czech secret weapon”. So many died at its hands, that supposedly Hitler forbade his best men to drive them. In many (other) ways, the Tatra 87 was the Porsche Panamera of its time.
To demonstrate just how far the aerodynamic envelope was pushed in this golden decade of streamlining, this 1939 Schlörwagen prototype was tested originally at Cd .186, and a model of it was retested by VW in the seventies with a Cd of .15. Either of these values put the “pillbug” at or near the top of the list of the most aerodynamic concept cars ever built, like the Ford Probe V of 1985, with a Cd of .137. Built on the chassis of the rear-engine Mercedes 170H, it was substantially faster as well as 20% to 40% more fuel efficient than its donor car. The Russians took the Schlörwagen as war booty and conducted tests as a propeller driven vehicle. It represents a state of aerodynamic efficiency in league with the most aerodynamic cars being considered today, such as the Aptera.
Its important to note that the rise of interest in aerodynamics in the 1930s arose out of the desire to reinvent the automobile from its horse and wagon origins and the assumptions that average driving speeds would be on the rise with modern roads. This made it a forward looking undertaking, as most drivers were plodding along at 35-45 mph outside of cities. But the first freeways were being built in Germany, and improvements in US roads, including the first parkways and freeways were taking place. It also explains the particularly strong interest and adoption of streamlining in Germany.
Note that I have not attempted to survey the influence of aerodynamics on the styling of cars in the latter thirties and up to WW II. Needless to say the influence was utterly profound, and gave us some of the most remarkable cars of the late classic era. But this had relatively more to do with style (and even affectation) than a genuine effort to push the envelope in terms of leading edge aerodynamics. Nevertheless, the benefits and beauty that resulted, like in this Bugatti Atlantique coupe are undeniable, but beyond our scope here.
NeilBlanchard on Feb 24, 2010
Hi Paul, I have another car that you could include; the 1939 Maybach Stromlinien Karosserie (aka Stromlinienkarosserie), which was a car that was made to do high speed tire testing: http://www.maybach.de/images/263_1.jpg http://www.maybach.de/images/263_2.jpg http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/sw38-ds04.jpg http://blog.goo-net.com/chez2007/img/163/inline_15.jpg My info is that it had a Cd of 0.16, and it could go 150mph with a 150HP engine. All the pictures I have see (the four I linked to) appear to be scans of a newspaper, unfortunately. It certainly appears to have sophisticated cooling vents (on the sides just behind the front wheels and the slots on the hood), and it had a full belly pan, too. Sincerely, Neil
Chris Raber on Oct 14, 2010
Paul, Wow, this is a terrific piece of work! Great research on so many vehicles. Another one you might want to check on as an American example would be the Auburn Boat Tail Speedster of 1929 and the succeeding models through the early thirties. Very beautiful streamlined bodies that also incorporated advanced engineering. Again, fascinating articles! Thanks! Chris Raber Chambersburg, PA
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