Citroën Traction Avant
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The Citroën Traction Avant (French pronunciation: [tʁaksjɔ̃ aˈvɑ̃]) is an executive car produced by the French manufacturer Citroën from 1934 to 1957. About 760,000 units were produced. This car pioneered mass production of three revolutionary features that are still in use today: a unitary body with no separate frame, four-wheel independent suspension, and front-wheel drive.
The Traction Avant, French for front-wheel drive, was designed by André Lefèbvre and Flaminio Bertoni in late 1933 / early 1934. Cars at this period in time were similar in concept to the Ford Model T – a body bolted onto a ladder frame which held all the mechanical elements of the car, a solid rear axle that rigidly connected the rear wheels, and rear wheel drive. The Model T school of automobile engineering proved popular, because it was thought to be cheap to build, but it did pose dynamic defects as cars became more capable, and resulted in a heavier car, which is why cars today are more like the Traction Avant than the Model T under the skin.
Along with DKW's 1930s models, the Traction pioneered front-wheel drive on the European mass car market. Front-wheel drive had just appeared for the first time through luxury vehicle manufacturers Alvis, which built the 1928 FWD in the UK, and Cord, which produced the L29 from 1929 to 1932 in the United States.
The Traction Avant's structure was a welded unitary body / chassis. Most other cars of the era were based on a separate frame (chassis) onto which the non-structural body ("coachwork") was built. Unitary construction (also called Unit Body or "Unibody" in the US) results in a lighter vehicle, and is now used for virtually all car construction, although body-on-frame construction remains suitable for larger vehicles such as trucks.
This unitary body saved 70 kg (150 lb) in steel per car. It was mass produced, using innovative technology purchased from the American firm Budd Company. Weight reduction was a motivation for Citroën that American manufacturers of that time did not have. This method of construction was viewed with great suspicion in many quarters, with doubts about its strength. A type of crash test was conceived, taking the form of driving the car off a cliff, to illustrate its great inherent resilience.
The novel design made the car very low-slung relative to its contemporaries – the Traction Avant was always distinctive, which went from appearing rakish in 1934 to familiar and somewhat old fashioned by 1955.
The suspension was very advanced for the car's era. The front wheels were independently sprung, using a torsion bar and wishbone suspension arrangement, where most contemporaries used live axle and cart-type leaf spring designs. The rear suspension was a simple steel beam axle and a Panhard rod, trailing arms and torsion bars attached to a 75-millimetre (3 in) steel tube, which in turn was bolted to the main platform.
Since it was considerably lighter than conventional designs of the era, it was capable of 100 km/h (62 mph), and consumed fuel only at the rate of 10 L/100 km (28 mpg-imp; 24 mpg-US).