Assembly plan for the front/rear cylinders of the hydraulic gear control (E806-2336/2337)

In this document

This technical plan, signed by Védie on 5 May 1957 p. 25, describes the assembly of two cylinder sets for the hydraulic gear control, designated as "Pistons on gearbox cover" p. 25.

Two referenced assemblies

The document distinguishes between:

• E806-2336: "Cylinder assembly 1. REAR";
• E806-2337: "Cylinder assembly 2.3.4" p. 25.

Matching instructions

A handwritten annotation specifies: "Acid-etch the same number as Face F of E 806-2.342/43" and "Match parts Clearance = 0.1" p. 25 — a tight tolerance requirement between matched parts.

Parts list (extracts)

The stamp indicates that this plan is "VALID FOR TEST 42.806" p. 25, linking it to a specific test campaign. The title block also mentions the general designation "Hydraulic Gear Control" p. 25.

Context

At Citroën, the hydraulic gear control refers to the semi-automatic gearbox systems associated with the DS and its derivatives, where high-pressure oil (LHM or its predecessor) actuates pistons to select gears, in addition to the hydropneumatic suspension developed by Paul Magès.

This type of assembly plan, with parts list and matching dimensions, corresponds to the design office methods of the time to ensure the interchangeability of mass-produced parts.

Archivist's perspective

This plan testifies to the care taken in the mechanical matching of pistons and cylinders, with a tight clearance of 0.1 mm p. 25, a sign of high sealing requirements — likely to limit pressure leaks in a hydraulic control circuit.

The explicit reference to test 42.806 p. 25 suggests that this document is part of an organized test campaign, of which other parts might be preserved in the same file, such as the BEA inspection of the clutch release cylinder D 314-02 or the handwritten divider on clutch release cylinders, which belong to the same technical family and the same period.

The signature of Védie, rather than Magès, reminds us that the latter worked in a team and that this type of execution plan was likely entrusted to design office draftsmen under his supervision.