Modification schedule for the D.391.8 pressure regulator sleeve (DS/ID)

In this document

This sheet traces, in the form of a handwritten timeline, the monitoring of a technical modification concerning the D.391.8 pressure regulator sleeve: the drilling changes from ø3 "Currently" to ø4.2 "Requested" p. 254, illustrated by two small technical diagrams in the margin.

Chronology of stages (1957-1958)

The document lists, month by month, the milestones of industrialisation:

The handwritten note in the margin specifies that this modification allows "applying to the DS the guide for the small retaining ball (lantern)" already used on the ID, with an improvement in sealing and packaging p. 254. It also mentions that Study note 31827 incorporates "reinforcement of the body", linked to a launch on 9.5.58 referenced NE:29507 p. 254. The document is signed "P. Magès, 9.6.58" p. 254.

Context

The DS and the ID, launched by Citroën in 1955, share the same hydropneumatic suspension architecture designed by Paul Magès, but with different levels of finish — the ID being a simplified version intended to reduce costs. The "pressure regulator" mentioned here refers to the hydraulic components ensuring the regulation of this suspension. This type of tracking sheet, common in the Citroën industrial organisation of the time, made it possible to trace the back-and-forth between the design office, workshops, and scheduling departments before series production. This document dated June 1958 is part of the years when Paul Magès, who joined the design office in 1939-1940 and authored the first hydropneumatic suspension plans in February 1944 (Plans for hydropneumatic suspension with differential interaction), continued the development and industrialisation of the system on the DS and ID models born in 1955.

Archivist's perspective

This document is valuable because it documents, almost day by day, the concrete process of industrialising a technical modification at Citroën — from the initial presentation to final validation, i.e., nearly eight months of procedures p. 254.

It also illustrates the circulation of an improvement between models: the transition of a device from the ID to the DS, which probably testifies to a logic of technical sharing within the hydropneumatic range. The signature of Paul Magès dated 9 June 1958 makes it a direct testimony of his personal monitoring of this type of file, while he was a technical writer and then deputy head of Super-Control at Citroën, where he would remain for 49 years until his retirement in 1974 (Draft letter from Paul Magès to Mr. Sarre and maintenance plan of the 11).

This document is part of a larger file on the evolutions of the DS suspension; it can usefully be compared with the Summary of folder 41-59: hydropneumatic suspension, rubber and DS evolutions, which seems to constitute its general framework.