Hydropneumatic suspension with automatic levelling (1944)

In this document

Title page

The page 1 presents a framed handwritten cartouche, drawn in capital letters in violet/brown ink: « SUSPENSION HYDRO-PNEUMATIQUE À INTER-ACTION DIFFERENTIELLE ET CORRECTION AUTOMATIQUE DE L'ASSIETTE ». It is a "Principle Assembly" at 1/2 scale, signed "Magès" and dated 17 February 1944 p. 1.

The technical diagram

The page 2 repeats the same title in a cartouche and bears a technical plan (heliographic/ozalid type print) detailing several annotated sub-assemblies:

• an « CLOCHET A AIR » (cross-section of a cylindrical element, numbered references 1, 2, 2, 1);
• a « BLOC de GONFLAGE & d'EQUILIBRAGE », equipped with fittings and a tripod stand;
• a « CYLINDRE de SUSPENSION », vertical jack connected to a « ROUE ARRIERE »;
• an « ELECTRO-DISTRIBUTEUR » with wiring and piping;
• a « RELAIS-BILAME »;
• a « CONTACTEUR de ROUE ».

Other mentions, whose legibility is uncertain, evoke a "VERIN D'INFLATION à la CHASSE de l'AMORTISSEUR", a "VOIE D'INSTALLATION DIFFERENTIELLE" and a "POINTEAU DIFFERENTIEL" — these elements remain to be considered with caution due to their uncertain nature p. 2. A partially legible sentence mentions a "service float valve" whose closure would be linked "to the operating regime" and "to the steering", a mention also uncertain p. 2.

The cartouche on page 2 repeats the title and the 1/2 scale mention, with a date where the month remains uncertain ("17.[uncertain].1944"), Magès' signature being present p. 2. The page also bears two dark marks, possible stamps, whose exact nature is not assured p. 2.

Context

This type of plate is part of the research conducted at Citroën during the 1940s on liquid and gas suspension, which would lead after the war to the hydropneumatic suspension mounted on the Traction 15-Six H (1954) then generalized on the DS (1955). The automatic levelling, mentioned as early as this document, would become one of the major technical signatures of this suspension. These contextual elements fall under the general history of the automobile and are not stated in the document itself.

Archivist's view

Dated 17 February 1944, this plate testifies, if one sticks to its date, to a very early reflection by Magès on differential interaction and automatic levelling — years before the DS was brought to market. It seems that this document constitutes an important conceptual milestone in the engineer's path towards his major invention, even if several technical legends remain uncertain due to lack of perfect legibility p. 2.

The repeated presence of the same title on both pages, as well as the handwritten signature, suggest that it is a coherent set designed as a principle file, probably intended to formalize an idea before further technical development.