Dealer Note No. 600: repairing the hydropneumatic suspension of the 15 Six-H

In this document

This internal technical note, addressed by the Société Anonyme André Citroën to dealers under No. 600, sets out the repair methods for the hydropneumatic suspension of the 15 Six-H.

General presentation of the rear suspension

The document specifies that at the front, the bars are "longer" and supplemented by an anti-roll bar, while at the rear "the usual torsion bar has been replaced by a piston compressing, by means of a liquid, a gas enclosed in a sealed container" p. 1.

The rear suspension is described as consisting, on each side, of a pivoting arm, a cylinder-piston connected by a lever, and a sphere with a damping device p. 1. The assembly is connected by an anti-roll bar.

Supply and control components

The circuit includes a supply reservoir with a filter, a high-pressure pump, a cut-out valve, an accumulator, an isolation valve, and a height corrector p. 1.

The role of each component is detailed:

• The reservoir uses "the same" liquid as the hydraulic brakes p. 1.
• The high-pressure pump features 7 pistons controlled by a swash plate, driven by the engine via a V-belt p. 1.
• The cut-out valve regulates the pressure between two limits p. 2.
• The accumulator supplies the suspension cylinders p. 2.
• The isolation valve unlocks automatically "at the first declutching" p. 2.
• The spool-type height corrector maintains a constant rear height regardless of the load; its spool is controlled by a tab linked to a torsion rod fixed to the anti-roll bar p. 2.
• The sphere attached to the cylinder contains gas under pressure and incorporates a valve-based shock absorber p. 2.
• A manual control on the corrector allows the car to be raised or lowered for changing a rear wheel p. 2.

Repairs

The "Repairs" section begins with the front suspension: replacement of the torsion bars after removing the upper conical stops, then adjustment of the anti-roll bar (text interrupted at the end of page 2).

Context

The 15 Six-H, produced by Citroën in the early 1950s, was one of the first models to receive, on the rear axle, the hydropneumatic suspension developed by Paul Magès — technology on which he had been working since his plans of 17 February 1944 and which he was still testing during the test of the 15-Six H of 3-5 April 1954, only a month before this note; it would be generalized on the future DS 19 presented on 6 October 1955.

This distribution to dealers, in May 1954, was part of Citroën's commercial logic: preparing the network for the maintenance of an innovation still unprecedented for the general public, before its deployment on a larger scale.

Archivist's perspective

This document is one of the very first technical training notes intended for the commercial network concerning the hydropneumatic suspension, one year before the unveiling of the DS, and written in the immediate aftermath of Paul Magès' own tests on this model. Its numbering "No. 600" suggests a continuous series of notes to dealers p. 1.

The pedagogical insistence — definition of each component, precise role, still hesitant vocabulary ("pneumatic block" for the sphere, p. 2) — reflects Citroën's concern to support a network unfamiliar with this unprecedented mechanics.

This text is best read alongside the detail plates of the hydraulic components and the diagram of the hydraulic installation, which likely illustrate the components described here in text.