Pump drawing QM.399 D / E42.401 T: nomenclature and machining critique (29 October 1951)

In this document

The drawing and its official title block

The page presents an assembly drawing of a pump, referenced QM.399 D, stamped by the Technical Services of the Sté Anonyme André Citroën, with the printed date "29 OCT 1961" p. 2. The title block specifies that this drawing is "VALID FOR E42.401 T" and bears the mention "Launch 23/10/[uncertain: '51']" as well as a purple "EXAMINATION" stamp p. 2.

The drawing also refers to a set of supplementary sheets referenced E401.144c.147c p. 2.

Parts nomenclature

Numerous part references are listed and linked to the drawings by lines: numerical codes (1633S, 2458S, 2071S, 648S, 248.9S, 2513S) and drawing marks in the E401 series (134c to 143c, 145c, 568c, 560c, 561c, 770b, 8176), as well as two mentions of "Franite seal no. 14" and a "Circlips 27e" p. 2. A mark "∅ 6X8" also appears among the codes p. 2.

Critical handwritten note

A handwritten annotation indicates that "this pump [uncertain: 'to'] be replaced by a new 4-page drawing", specifying that it concerns a drive "on the Fan control shaft" and that a "Drawing in progress at the B.E.A. on 15/11/[uncertain: '51'] will replace the above" p. 2.

The note continues by severely judging the machining: "The machining of this pump is, moreover, unacceptable", citing two specific examples — a) a ∅10 cylinder over a length of 58, mounted with a clearance of 0.005; b) grooves [uncertain: 'precise'] in the pump body, with a second handwritten mention "on 15/11/[uncertain: '51']" p. 2.

Context

In the early 1950s, Citroën was actively developing the technologies that would lead to the hydropneumatic suspension of the future DS, presented on 6 October 1955 — a development in which Paul Magès, who joined the design office as early as 1939-1940 and authored the first hydropneumatic suspension drawings in 1944 (Hydropneumatic suspension plans with differential interaction (17 February 1944)), played a central role. Hydraulic pumps — like this one, intended for fan control — are critical components whose machining precision determines the reliability of the system.

The acronym "B.E.A." likely designates a Design Office (internal to Citroën), responsible for producing the new drawings mentioned in the note. This general context is not stated as such in the document, but it clarifies the industrial stakes of the criticism formulated.

Archivist's perspective

This drawing illustrates the iterative process of developing a mechanical component at Citroën: a validated drawing (QM.399 D) is quickly deemed insufficient, its machining defects being noted with numerical precision (clearance of 0.005 on a ∅10 cylinder) which betrays a requirement for very fine tolerance, typical of the work of Paul Magès on hydraulic components, he who was a technical writer and then deputy head of the Super-Control at Citroën for 49 years (Draft letter from Paul Magès to Mr. Sarre and interview plan of 11 May 1969) p. 2.

The repeated mention of the date of 15 November and the B.E.A. directly links this piece to other documents in the same file, notably the drawing E401.144c-147c with handwritten observations by Magès and the handwritten note on the replacement of the pump drawing, which seem to form the same chain of technical correction.

This is likely a pivotal stage: the initial drawing, dated late October 1951, is already about to be replaced barely three weeks later.