Brake distributor and its control — Citroën technical sheet (P.M. 12.1.42)

Citroën technical sheet detailing the brake distributor and its control device, with its connections to the front and rear axles — a milestone in Paul Magès' research on braking around 1955.

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Presentation and original captions

In February 1955, Paul MAGÈS put his reflections on braking down on paper. Long before, in January 1942, he had imagined, in order to distribute braking according to the load on the axles, and thus avoid untimely wheel locking, to control the front and rear braking circuits of a PUD7, by means of 2 master cylinders, the control of which was carried out by means of a carriage, the point of application of which varies according to the load on the rear axle. Many years later, he would apply this solution for the braking of the DS 19.

Understanding this document

In this document

This technical sheet bears the header Société Anonyme A. CITROEN and presents the brake distributor and its control, referenced "P.M. 12.1.42" — initials that refer to Paul Magès p. 3.

Elevation view of the control device

The diagram shows a mechanical part articulated on a pivot, connected to a rod marked "A". A double arrow indicates the "Load difference between the front and rear" p. 3, which appears to be the physical quantity captured by the device. The arm extends (with a break in the drawing indicating a reduced length for the diagram) to the Rear Axle p. 3.

Plan view

Two plan views complete the elevation:

that of the control device, with rod "A" connected to an angled part pivoting at "B", explicitly referring to the elevation above p. 3;
that of the distributor itself, showing two superimposed cylinders/actuators connected by helical springs to an articulated central part. The conduits are annotated "Rear wheels" and "Front wheels", with an inlet indicated "To brake pedal" p. 3.

The cartouche at the bottom of the sheet confirms the title: "REPARTITEUR de FREIN et sa COMMANDE" p. 3. A handwritten annotation in red, in the margin, seems to correspond to pagination, but its content is not clear enough to be restored with certainty.

Context

The brake distributor is a component that automatically adjusts the braking pressure between the front axle and the rear axle according to the vehicle load — an important safety issue on cars with variable suspension like the future DS 19, whose development took place precisely around 1955.

At Citroën, this research on braking is part of Paul Magès' broader work on hydraulic circuits, which would give birth to the hydropneumatic suspension system and, later, the high-pressure assisted disc braking of the DS. This sheet does not, however, mention the DS 19 itself; this connection is part of the general historical context.

Archivist's perspective

This sheet is likely a study document or a technical development, closer to an engineer's drawing than a final manufacturing plan: the handwritten annotations and the "break" in the drawing on the control arm suggest a working document p. 3.

It is likely part of the same line of thought as the note "Reflections on braking", dated February 1955, which could shed light on the general intentions behind this distributor. The link with the sketch of the disc brake block also suggests the same overall project around the hydraulic braking circuit developed by Magès during this period.