Automotive History An Illustrated History Of Automotive Aerodynamics…

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Maybach W6/

Automotive History: An Illustrated History Of Automotive Aerodynamics – Part 1 (1899 – 1939)

January 26, 2012

That air presented the greatest obstacle to automotive speed and economy was understood at least intuitively, if not fully scientifically since before dawn of the automobile. Putting it into practice was quite another story. Dreamers, 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 highly aerodynamic cars are mainstream, but getting there was not without considerable turbulence.

The origins of streamlining go back two hundred years at least. The ideal streamlined form was described in 1804 by Sir George Cayley as “a very oblong spheroid”. And already in 1865, Samual Calthorpe patented an “air-resisting train”, looking remarkably advanced given the times.

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. And a crude preview of Bonneville Lakesters to come.

The evolution of aerodynamics for LSR cars was 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 documented attempt at streamlining a passenger car is this Alfa Romeo from 1914, built by the coach builder Castagna for the Italian Count Ricotti. A very advanced undertaking. straight out of a Jules Verne novel. Due to the excessively-heavy bodywork, it turned out to not improve on the top speed of the open Alfa it was based on.

The 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 (below) in 1979, and achieved a Coefficient of drag (Cd) of 0.28; a degree of slipperiness that VW’s Passat wouldn’t equal until 1988.

It’s important to remember that 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 0.295.  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 (Cd x Ft²).

The Rumpler’s shape was 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 puttering around Berlin because of their roomy minivan-like bodies. An ironic ending for Rumpler, but his ideas spawned imitations and extensions world-wide, and opened the whole field.

The Tropfenwagen’s influence in racing cars was much more immediate and lasting. The Benz Tropfenwagen racer of 1923 was a direct development of it, and used Rumpler components.

With a mid engine and swing axles at the rear, not only was it the direct ancestor of the legendary Auto-Union racing cars of the thirties, but of all mid-engined racing cars to this day. A true pioneer.

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 DeSoto proved in tests. It was also driven around the US in a publicity stunt to create awareness of automotive aerodynamics, as a prelude to the Chrysler Airflow. 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. Hopefully he was kidding.

Hungarian-born Paul Jaray used his experience working in the aeronautical field, 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 bizarrely tall, and with questionable proportions and space utilization.

Jaray’s patent was very influential, and his designs eventually became more mainstream. Mercedes (above), Opel, Maybach (below), and numerous other makes, primarily German, built special streamliner versions using Jaray bodies. It become a formula, resulting in look-alike cars.

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 were profoundly influential, and essentially set the template of what came to be known as the “streamliner” and influenced cars around the globe for years to come. (Tatra Automotive History here )

The compact Tatra v570 of 1933 (above) is the forerunner of both the larger Tatras soon to come, with its obvious Jaray influence, but not a licensed Jaray. It obviously reflects similarities to what Porsche was working on with his early developments that led to the Volkswagen. We’ll come back to Tatra later.

This Volkswagen prototype from 1934 (above) shows a very strong resemblance to the Tatra v570 indeed, 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.

The resemblance of the production KdF Wagen to Tjaarda’s 1934 prototype, especially certain details of the front end, seem like a bit too much of an accident. It turns out that Erwin Komenda, who actually penned most of Porsche’s design and the KdF Wagem, visited the US in 1934, saw Tjaarda’s prototype, and admits being influenced by it. The cross-Atlantic influence were well at work already, although back than it was usually in the other direction.

Maybach W6/

Of course, Americans’ introduction to streamlining had come two years earlier  in 1934, with the stunning Chrysler Airflow. An essentially pragmatic approach, the Airflow also kept the traditional front-engine RWD configuration, 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. As such, the Airflow predicted the same basic body packaging configuration as American cars from the late forties and early fifties, even if they weren’t so aerodynamically designed. Progress is not always linear.

The failure of the Airflow probably comes down to one primary aspect: 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 Lincoln Zephyr (1936), a pragmatic adaptation of Tjaarda’s prototype, still retained its prow, and was a sales success, despite being not nearly as a good a car as the Airflow mechanically.

An even less pragmatic but highly advanced 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. It’s not like those were selling well just then either.

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. And 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 0.195.  A stunning achievement, the long-tailed T77 was powered by a rear air-cooled V8, and began a long series of Tatras until the 1980s along similar lines.

Tatra became synonymous with the advanced streamliner of the pre-war era, enabling 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 allegedly Hitler forbade his best men to drive them.


To demonstrate just how rapidly and far the aerodynamic envelope was pushed in this golden decade of streamlining, this 1939 Schlörwagen prototype was tested originally at Cd 0.186, and a model of it was retested by VW in the seventies yielding a Cd of 0.15. 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  0.137 (Full list here ). 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 on it as a propeller driven vehicle. It represents a state of aerodynamic efficiency in league with the most aerodynamic prototypes 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 based on the assumption that average driving speeds would be on the rise with modern highways to come. This made it a forward looking undertaking, as most drivers were still  plodding along at 35-45 mph outside of cities.

But the first freeways were already 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, where these early VW prototypes (VW 30) are shown being tested. The KdF was designed to have a top (and cruising) speed of exactly 100 kmh (62 mph), and experiments showed that about 20hp would be adequate for that, with advanced streamlining.

I have not attempted to survey the broader influence of aerodynamics on the styling of cars in the latter thirties and up to WW II. Needless to say the influence was 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 this Pierce Arrow Silver Arrow (above), or Bugatti Atlantique coupe (below) are undeniable, but beyond our scope here.  [Continue to Part 2 ]

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