Direct-acting brake master cylinder, study of 24 April 1940

In this document

Page 17 — the main sketch

The sheet is dated "24. 4. 40" and bears the handwritten title "Maitre cylindre de frein a attaque directe" p. 17. It presents a cross-sectional sketch of a brake master cylinder arranged vertically: a central axis passes through a hatched body (metal parts in section), with threaded elements at the top and bottom, two columns of small circles suggesting washers or seals, and a spiral spring to the left of the body p. 17.

Several handwritten arrows point to details of the mechanism, but the words accompanying them are [illegible] or [uncertain], so no annotation can be restored with certainty p. 17. A lighter sketch in the background seems to depict a chassis or an overview of the vehicle, without it being possible to say more p. 17.

An isolated digit, possibly "10", appears but remains uncertain p. 17.

Page 18 — a first phase of operation

The following page bears a fragmentary mention, read with uncertainty as "1er phase / mise au P M" p. 18, which suggests the description of an operating stage of the mechanism (perhaps a neutral point). The associated technical sketch shows nested rectangular blocks, suggesting a cylinder or a hydraulic distributor, connected by curved piping, with a dimension marked by a ">" symbol p. 18.

A second, smaller and lighter sketch appears at the bottom of the page: it represents an assembly with two vertical rods and a tubular elbow, which may correspond to a fitting or a mechanical part p. 18. A handwritten annotation of several lines accompanies this drawing, but its content is not transcribed in an exploitable way p. 18.

Context

Paul Magès is best known for his work on the hydropneumatic suspension developed at Citroën, notably for the future DS. Assisted hydraulic braking would also be one of the striking innovations associated with this vehicle, with a disc brake system and power distribution linked to the central hydraulic circuit.

In 1940, Citroën was going through a troubled period due to the outbreak of the war and the Occupation which began a few weeks later: this historical context does not appear in the document but sheds light on the environment in which this sketch was produced. This study is contemporary with the work that would lead, from 17 February 1944, to the first hydropneumatic suspension plans: Magès, who joined Citroën in August 1925 and was then a technical writer in the design office, was therefore exploring several hydraulic avenues in the years preceding this major breakthrough.

Archivist's perspective

This sheet dated 24 April 1940 testifies, it seems, to an early reflection by Magès on hydraulic braking systems, well before their industrial fruition at Citroën p. 17-18. The technical vocabulary used — "master cylinder", "direct attack" — indicates an already fairly advanced study of a hydraulic component, consistent with the interest the engineer would later take in pressurized circuits.

The mention of a "1st phase" of operation p. 18 suggests that this document was part of a series of successive studies, now incomplete or dispersed in the collection. The context of this 1940 file, which also includes work on a pedal car and general vehicle layout sketches, shows a Magès with varied mechanical concerns at this pivotal period, only a few years before he embarked on the study of the hydropneumatic suspension that would make him famous.