DS hydraulic incident logbook: observations and modifications (1957-1958)

In this document

This tracking notebook, kept by Paul Magès between late 1957 and mid-1958, lists organ by organ the incidents observed on the DS/ID and the modifications undertaken to address them. It opens with a summary list of points "without NE ensuring a complete recovery" — LP pump, HP pump, hydraulic block, brakes, cut-out valve, steering, gearbox p. 214.

Hydraulic pumps

The 7-piston HP pump concentrates most of the issues: leaks at the rotary seal, ring seizing, and above all the sealing of the seven cylinder head gaskets, prone to extrusion under pressure. The solutions tested range from conical grinding of the cylinder head to testing Carro bronze and nitrided steel rings, with quantified test campaigns ("7 pumps running in the Lab without incident", p. 239-241). An incident involving flaked ball bearings is also followed in detail over several months p. 243-244.

Steering

The "central seal" is identified as "defect N°1" p. 227, with a replacement of metal washers by Rilsan washers, then the "Jacottet solution" tested in parallel. A broader study compares "closed-center" and "open-center" steering, concluding that "it is necessary, on the DS, to eliminate the dash-pots of the spools" p. 229.

Brakes and clutch

The notebook follows the braking distribution (debate around the "Francia theory", p. 238), the gear control cylinder (numerous successive NEs listed with precise dates, p. 221), and the adjustment of the automatic clutch with measurements of disengagement/engagement effort at "slipping" between 675 and 725 rpm p. 234.

Suspension

The "shock absorber noise" is explained by the "chattering of the piston seal support ring", reduced by decreasing a dimension D, with test campaigns since April 27, 1956 p. 252. The deflation of the spheres is linked to a lack of lubrication of the screw and seal, and to a porosity of the membrane rivet corrected by a change of material on 1.4.57 p. 253.

Conference reports (DS clutch of 27.2.58, p. 233; schedule of 7.1.58, p. 218) punctuate the tracking, involving Cadiou, Chalard, Guyetant, Louis, Sabrazat and Magès himself.

Context

These pages relate to the period when the DS 19, launched on October 6, 1955, was experiencing its first years of mass production, in direct continuity with Magès' work begun on February 17, 1944 and continued through the first 2 CV tests then the test of the 15-Six H. The complexity of its unique hydraulic circuit — suspension, brakes, steering and gearbox connected to the same high-pressure pump — explains the scale of the development work mentioned here.

This type of technical tracking notebook, kept day-by-day by the engineer in charge, is characteristic of post-war industrial development methods at Citroën, where customer feedback and bench/Lab tests continuously fueled a corrective cycle. Magès, who joined Citroën in August 1925 and was then deputy head of Super-Control (autobiographical notes), exercises there the rigor of a self-taught man who became responsible for the development of his invention.

Archivist's perspective

This document is one of the densest testimonies of Magès' daily activity during the critical phase of industrial maturation of the DS. It shows, organ by organ, the engineer's working method: investigation, hypothesis, quantified test, decision, scheduling — with an almost accounting-like rigor of dates and part references (NE, E 401...).

It usefully complements the Summary of folder 41-59, which seems to organize this same documentation on the hydropneumatic suspension, and is in line with Magès' older studies on the differential interaction suspension, revealing the persistence, fourteen years later, of the same concerns for sealing and hydraulic reliability.

The precision of the dates (day by day, often to the nearest hour) suggests the use of a personal logbook rather than an official report, which makes it a valuable source for tracing the real technical decision-making process, beyond formal reports.