Paul Ernest Mary Magès was born in 1908 in Aussois, in the Savoie region. After graduating as a draftsman he was hired at the study center Citroën, where he quickly made a career. He occupied the drawing board for a few months, quickly moving on to the testing department where he stood out until he was noticed by the director of the department. The call to the project office, where the engineer also worked André Lefebvrewas propitious: the latter was the coordinator of studies such as that of PV (Petite Voiture, which will be the Traction Avant), TPV (Toute Petite Voiture, which will lead to the 2CV) and of VGD (Voiture à Grand Diffusion) which will become the DS19 .
While the engineer Lefebvre worried about the distribution of the masses, the center of gravity and the problems connected to the front wheel drive, Magès was asked to understand how to measure the braking according to the mass for what I will be the Type-H, one of the first modern commercial vehicles. Magès designed a brake limiter according to the angular position of the rear anti-roll bar. The principle is as follows: the more inclined it is, the greater the load and therefore the flow of fluid to the rear hydraulic brakes. At that moment Magès had an intuition: if the suspension could have “read” the load, it would have been possible to measure the braking. But how could the suspension, back in 1939, have measured the mass weighing on an axle? He needed another idea, not to mention that it would have been necessary to combine road holding with flexibility.
The game of balances is based on the balance between comfort and grip: if the suspension is too elastic, it bounces off obstacles, generating commuting and making the car swerve sideways on bumps. If, on the other hand, the suspension is stiff, the car stays on the road, however annoying the passengers through numerous shocks. So, suddenly, the solution came: a new suspension where the elastic element was no longer made up of metal springs but of an air cushion, soft, connected to the wheels by a liquid, incompressible. Air and water together: the suspension became hydropneumatic.
The tests began on the TPV, but for the cost of the elements the project was remodeled on the next VGD. So the 2CV was born in 1948 with interconnected suspensions and shock absorbers, very sophisticated for the car class but all in all traditional, while the VGD (the future DS) was based on the work of Paul Magès, inventor with merit. The first production Citroën to mount the hydropneumatic suspensions it was a special version of the Traction Avant, the 15Six H (like Hydropneumatique) launched in 1954, with hydraulic and self-leveling rear suspension. The 15Six H served as a “test bench” for the DS19, presented a year later and equipped with hydraulic suspension on all four wheels.
The DS19 was a commercial and exceptional success: 1.5 million units produced which led the way for other hydraulic Citroën such as the later SM, GS, CX and BX, as well as limited series of the Type-H van with hydropneumatic rear axle. , dedicated to the preparation of ambulances. The next step, many years later, was the entry into the system of theelectronics.
In 1988, at the Paris Motor Show, Citroën presented Activa. Alongside bold solutions such as hydrostatic transmission and on-board computer-controlled four-wheel steering, the car sported a variable-flexibility suspension called “hydractive” that will equip the next XM. L’Hydractive II, the second generation of the electronically controlled Citroën suspension, would have accompanied the launch of Xantia (1993). On that model the “Activa” suspension also found its debut, in which the roll was managed by the on-board computer to give the car a horizontal position.
Idractive III and Hydractive III plus they would have appeared on the C5 in 2000, to be further refined on the C6 with the introduction of AMVAR (AMmotizzamento VARiabile). In this system a diaphragm regulates the passage of liquid during each excursion of the suspension. The latest C5s with Idractive III plus suspension left the Rennes factory assembly line in June 2017.
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