Diagram of the hydraulic installation of the 6 H vehicle (Citroën 15 Six-H)

Technical plate detailing, with the support of a diagram and nomenclature, the complete hydraulic installation of the Citroën 15 Six-H, ancestor of the DS hydropneumatic suspension.

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Presentation and original captions

In 1954, Citroën presented the first car equipped with a hydropneumatic suspension on the rear axle, the 15 SIX H. In May 1954, the Repair Methods department issued technical note no. 600 on this new vehicle, for the attention of the Dealers of the Citroën network. We are only publishing pages 1 and 2 as well as diagrams 2, 3, 4, 6 and 8 of this technical note. Note the simplicity of the diagrams of the hydraulic components; everything was still secret at the time. Special attention to diagram no. 8, it represents the fitting that ensures the sealing of the hydraulic connections. It will remain for posterity "THE MAGÈS FITTING" at Citroën.

Understanding this document

In this document

This is a unique schematic plate, titled « Schéma de l'installation hydraulique » (Diagram of the hydraulic installation), concerning the 6 H vehicle p. 3, designated Fig. 2 in the document.

The circuit legend

The diagram distinguishes four types of circuits, differentiated by graphic lines: Intake, Exhaust, Leak return, and Suction - Pump - Reservoir p. 3.

The nomenclature of components

Nine components are numbered and linked to the chassis drawing:

No.	Component
1	High Pressure Pump
2	Pressure Regulator
3	Accumulator
4	Latch
5	Reservoir
6	Height corrector
7	Suspension cylinder
8	Pneumatic block
9	Anti-roll bar

p. 3

The visual diagram superimposes these elements onto a chassis seen in perspective, with front and rear axles, piping, and lettered markers A and B whose precise meaning is not given in the transcribed text.

Context

The vehicle designated "6 H" corresponds, in the Citroën nomenclature of the time, to a version of the Citroën 15 Six-H, equipped with the hydropneumatic suspension developed by Paul Magès. He conducted the test from 3 to 5 April 1954 (Road test of the 15 Six H (ELV 412) by Paul Magès, 3-5 April 1954), shortly before the introduction of the device on this model and its subsequent generalization on the DS presented on 6 October 1955.

This suspension is based on a then-unprecedented principle: replacing metal springs with spheres containing pressurized gas (the "pneumatic blocks"), fed by a high-pressure hydraulic circuit including a pump, accumulator, and height corrector — all components precisely named on this plate.

Archivist's perspective

This document is likely a pedagogical or technical plate intended for the training or documentation of repairers, rather than a manufacturing blueprint: it synthesizes the entire circuit and its nomenclature in a single view p. 3, a function confirmed by its filing alongside a technical note to dealers on repair methods dated the same month.

It is likely a summary plate, complementary to the detail plates of hydraulic components which delve into certain components mentioned here (accumulator, pressure regulator).

It clearly illustrates Magès' systemic approach: each component only makes sense within the overall architecture of the circuit, which this Fig. 2 shows at a single glance.