Plan D314-02: clutch control cylinder and piston (Citroën, 1954)

In this document

This technical drawing concerns the clutch control cylinder and piston assembly (assembled), referenced D314-02 (with associated parts D314-12 for the piston and D314-11 for the cylinder), established by the Citroën design office p. 9-10.

Manufacturing tolerances

The "SPECIFICATIONS" table p. 9 details precision requirements relative to a reference diameter Ø1:

The "Detail of type" and "Section A" diagrams specify numerous dimensions (diameters, radii, 35° and 60° angles, m7/m8 fits) that describe the fine geometry of the part p. 9.

Leak test

An annotation, present on both pages, indicates that the assembly "must satisfy an air-tightness test of 5 kg cm² applied at P", with point P being located on the cross-sectional diagram of the cylinder-piston by an arrow p. 9-10.

Identification block

The plan is released via note no. 105444 p. 9 — page 10 bears a divergent reading "19544", likely a reading variant of the same number. It is dated and signed by several departments: drawing by Vielle G. on 14.1.54, industrialisation by Guyétant and laboratory (BEA) by Cadiou, both on 20.1.54 p. 9-10. A modification "(m1)" is referenced under no. 8-21094 p. 9-10, as well as two other modifications "(m5)" and "(m6)" on page 9.

Context

The clutch slave cylinder is a classic hydraulic component of the power-assisted systems developed by Citroën in the 1950s, a period when the brand was generalising the use of hydraulic pressure (brakes, suspension, steering) on its vehicles, particularly in preparation for the future DS.

Air-tightness testing under pressure, as described here, is a common test method in industrial quality control to verify the absence of leaks on parts intended to convey fluid under pressure — general knowledge, not specific to the document.

Archivist's perspective

This drawing falls under the daily work of the Citroën design office on the car's hydraulic components, a field in which Paul Magès played a central role as the inventor of the hydropneumatic suspension. However, the document does not explicitly mention Magès among the visible signatories p. 9-10; the link to his work is therefore contextual rather than attested by the piece itself.

The degree of detail in the tolerances (run-out, warp, m7/m8 fits) testifies to the care taken in the manufacture of this part, which is essential for the proper functioning of the power-assisted clutch system.

This plan D314-02 is part of a series of documents relating to the same assembly, notably the piston plan D314-12 dated 29 July 1954, which is a few months later, and a revised version from 1957 available in the DS314-02 cylinder plan and its leak meter test, which allow the evolution of this part to be followed over time.