What Makes Citroën So SpecialCitroën decided that this was an inefficient way of making cars, and it placed too much burden on the consumer. The Type A was designed to be a complete vehicle. The engine, drivetrain, chassis, and body and interior were all designed to be manufactured and assembled at the factory. When a consumer bought a Citroën, he was delivered a complete vehicle. This was very advanced thinking for the day, and it was not long before all automobile manufacturers operated in this paradigm.
 Type A In the early 1930's when it came time to replace the Type A with a more modern design, André Citroën investigated all the automotive innovations with which leading-edge designers were experimenting. Citroën was friends with an American engineer named Edward Budd, who had made the first vehicles whose design eschewed any wooden materials and were constructed entirely of metal. Budd had a concept for doing away with the chassis and making vehicles completely of sheet metal body "shells." American manufacturers were not adventurous enough to attempt implementing such a radical design, but Citroën was intrigued. From the start, he designed his new model to be based on this experimental method. Citroën also solidly embraced the concept of front wheel drive as a more logical and practical means of propelling an automobile. The newly innovated constant velocity joints made this possible. Citroën devised an all-new configuration whereby the transmission would be mounted in front of the engine block, with half-shafts extending out to the front drive wheels. This consolidated the entire drivetrain at the front of the vehicle, and eliminated the need for a drive shaft extending aft, as well as the heavy and cumbersome rear differential. This also allowed the car to be designed with unparalleled interior space relative to the exterior dimensions. In addition to this, Citroën recognized the torsion bar as a more space-efficient alternative to the coil or leaf spring. He also felt that it gave the vehicle a better ride and more responsive handling. He decided to use torsion bars on both the front and rear suspension. Cars of the day routinely had independent front suspension, but the rear differential was always implemented as a rigid unit. Having avoided this pitfall, Citroën was able to make his rear suspension independent as well. The final design incorporated four-wheel independent torsion bar suspension.
 Traction Avant By 1934 André Citroën had the vehicle in production. He called it the "Traction Avant," which literally translates to "drive up-front." Visually it did not look unlike other "old-timers" of the era, with the big fenders and bulbous headlights (although it had somewhat of a lower profile due to the front wheel drive), but the driving experience was unlike anything else on the road at the time. All the innovations that Citroën incorporated came together perfectly and created a truly remarkable unit. The front-wheel drive and fully independent torsion bar suspension gave the Traction Avant better roadability than anything manufactured before. In many ways, the Traction Avant was the first truly "modern" car. Some consider it to be the DC3 of automobiles. It was the first car in the world to be mass-produced without a chassis, and now unibody design has taken over the entire marketplace. Today it is extremely rare that a car would be built with a chassis (some low-volume sports cars still employ the design). Front-wheel drive took a little longer to catch on, but today almost every model of car being built incorporates it. Fully independent suspension is often reserved for performance-oriented vehicles, but is recognized as a superior design. It was present in virtually every Citroën designed hence. The Traction Avant was an instant success, and it catapulted Citroën into a prominent position in the global automobile market. The model was somewhat upscale, however, and after WWII Citroën set out to design a car that was more accessible. In typical style, greatest emphasis was placed on incorporating innovation. Today it is commonplace for automobile designers to target specific markets, but at this time manufacturers generally produced whatever kind of car they'd always been producing. Citroën intended this new car to be useful to the "masses," and the designers began by thinking about what the masses' specific transportation needs were. They needed to get from place to place, but reliability and ease of repair was much more important than speed. The masses generally lived in the countryside where terrain was rough. It was as important to be able to traverse a deeply rutted field as it was significant distances. The masses also needed to bring things with them from place to place, often things that were much too large or cumbersome to be easily transported in small cars. Finally, the masses didn't have a lot of money to invest into the purchase and maintenance of vehicles. The designers summed these goals in a semi-metaphoric example: the car should be capable of carrying a basket of eggs across a plowed field without any breaking. Their solution was the 2CV. It was introduced in 1948, and is one of the most utterly simple automobiles ever constructed. It is also one of the most entirely useful. Like the Traction Avant, it incorporated unibody construction and front wheel drive. It had a 375cc, 9bhp, air-cooled, 2-cylinder engine that was mounted in front of a 3-speed gearbox. Half-shafts came out each side to drive the front wheels.
 2CV The suspension was also fully independent. It was incredibly simple, but also ingenious. There were leading arms in front and trailing arms in the rear. One long tube spring ran along the rocker panel on either side. The front and rear swinging arms on that side were attached to either end of the spring. In this way, front and rear suspensions on each side worked against each other like the opposing sides of an arch, with the horizontal tube spring as the keystone. The configuration made for a very stable ride. The swinging arms on the light, boxy body allowed a tremendous amount of movement, and it was indeed possible to drive the car smoothly across a plowed field. The entire top of the 2CV was made of durable fabric which could be rolled back to entirely open up the passenger compartment. In this way, long and cumbersome objects could still be transported in the small vehicle. It was this feature that gave the car the nickname, "The Sardine Can."
The 2CV was another smashing success, and Citroën advanced its position in the global automobile market. But by the early 1950's the Traction Avant was becoming outdated. It was time for a modern replacement. In true Citroën fashion, it was to be unlike any other car ever created. The car was to embody the word, "innovation." They set out to create the most sophisticated automobile the world had ever seen.
The designers utilized a conventional, in-line 2-liter 4-cylinder engine. All other conventional knowledge about automobile construction was thrown out the window. They decided that there would be one master hydraulic system that would operate all major subsystems of the car. It would be powered by a high-pressure pump, and distributed where needed. The brakes, the power assisted steering, the semi-automatic transmission, and even the suspension supports would all be powered by this master hydraulic system.
Great attention was also placed in the appearance of the car. It was intended to be aerodynamic, and this gave it a natural sleek appearance. But it also incorporated some principles of Art Deco, which was popular in France at the time. Beyond sleek, the lines convalesced to form arguably the most pleasing automotive shape ever created. Everything about it, from the broad, sloped snout to the trim, minimalized rear, suggested graceful forward motion.
The layout was principally what Chrysler would decades later come to call "cab forward." The wheels were moved out to the corners. All major engine and drivetrain components were under the hood (although the ass-backwards engine did protrude into the passenger compartment a bit). Without a driveshaft, the floors were kept entirely flat straight across in both the front and the rear. The muffler was in the space under the front seats, and the gas tank was under the rear seats, giving the belly pan a very smooth profile. The independent rear suspension left space for a very deep and surprisingly spacious trunk for what from the outside appeared to be a very petite rear end.
The most striking aspect of the car was the hydraulic suspension. It gave an incredibly smooth ride, seemingly absorbing bumps and road imperfections. It was also tremendously responsive at high speeds. It was self-leveling, so even with a heavy load the car always rode at the same height. A control lever under the dashboard adjusted the mechanisms that accomplished the leveling, making it possible to actually change the ride height of the suspension. On the lowest level the car would settle practically to the ground. On the highest level it would be as if on jack stands. There were three driving height settings in between.
The advantage of this ability, aside from the potential for crowd-pleasing party tricks, came into play when it was time to change a tire. The operator would set the suspension in the high position, place a jack stand mid-way along the frame on the same side as the flat tire, and set the suspension in the low position. The jack stand would hold up one side of the car as the other settled down to the ground.
What was most amazing about this car is that all this was done with 1955 technology. All the mechanical, electrical, and hydraulic systems were typical of the day. This was just the first time that they'd been brought together in this application. Some parts of the hydraulic system have tolerance as small a 1 micrometer (for example the moving part of the hight corrrector)! The true miracle was that the engineers were able to mass produce them with 1955 production techniques, and that complex as they were, they were competitively priced with other luxury touring sedans.
The car was called the DS19. It was an instant success, and was quickly deemed "The Goddess" (the letters "DS" in french are pronounced homonymously with the French word for "Goddess"). It underwent modifications about halfway through its lifecycle and became the DS21, but the basic concept remained essentially unchanged until production ceased 20 years later. It's successor, the CX, is more modernized with respect to appearance, integration, and fit and finish, but the underlying layout and principle systems are essentially the same as with the DS series.
The Traction Avant and the DS series were two landmark designs in the history of the automobile. But while other manufacturers were quick to adopt the innovations of the Traction Avant, the complicated systems used in the DS series have not caught on. Many detractors use this as their principle criticism of the design.
In recent years, however, some examples of the use of these innovations have begun to appear. Certain luxury car makers have experimented with self-leveling systems on the rear suspension. The high-tech "fully active suspensions" on today's most sophisticated performance cars build upon the original hydraulic systems of the Citroën. American luxury car makers are now making brake, power steering, and automatic transmissions operate as subsystems off one main hydraulic system instead of having individual isolated systems each with its own reservoir and type of fluid. The Traction Avant was years ahead of its time. The DS series was so far ahead of its time that now, over 40 years later, time is just starting to show hints of catching up.
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