SKF letter of 2 December 1957 regarding defective balls for the DS 19 HP pump

In this document

This letter is addressed by the company SKF (Compagnie d'Applications Mécaniques, 15 avenue de la Grande Armée, Paris) to the Société Anonyme André Citroën, "for the attention of Mr. MAGÈS", dated 2 December 1957 p. 12.

Results of the ball examination

SKF indicates having examined "2 balls of 13/32" (10.319 mm)" entrusted by Citroën, "deteriorated in the DS 19 hydraulic pump thrust bearing" p. 12. The verdict is clear: "These balls are defective. They have been over-hardened, and exhibit an excessively coarse grain, particularly on the surface", with "grinding cracks" leading to the detachment of "surface films" p. 12.

SKF adds an explicit doubt regarding the origin of the parts: "We would be very surprised if these were SKF-manufactured balls" p. 12 — suggesting that they could be balls from another source, fitted in error or as a replacement.

The associated washer

The SKF laboratory also reports, regarding a washer that was also submitted, "the beginning of flaking due to excessive metal fatigue" on the track p. 12.

The document bears a receipt stamp "- 3 DEC. 1957", a red handwritten circle around the name "MAGÈS" and a red brace in the margin highlighting the paragraph on the washer — likely traces of careful reading upon receipt p. 12.

Context

The DS 19, introduced in 1955, relies on a centralized hydraulic system designed by Paul Magès, powered by a high-pressure pump. Having joined Citroën in August 1925 as a technical writer and then deputy head of the Super-Control before joining the design office in 1939-1940 (autobiographical notes), Magès is the designer of this hydropneumatic suspension and the natural recipient of quality alerts affecting his hydraulic components. The reliability of the components of this pump — bearing balls, thrust bearings — was a major industrial challenge in the first years of production, a period when defects from suppliers or subcontractors could disrupt the development of the system.

SKF (Svenska Kullagerfabriken) was one of the world's leading suppliers of bearings and precision balls, with whom the French automotive industry worked commonly at that time.

Archivist's perspective

This letter is part of a quality incident concerning the DS 19 HP pump, at a time when defective balls p. 12 were visibly causing problems in the field or during testing. The fact that SKF doubts its own paternity of these balls p. 12 is revealing: it could be a component substitution, a point that likely required corrective action on the Citroën side.

This document finds a direct echo in the Paul Magès internal memo on defective balls for DS HP pumps, dated the same day, which seems to constitute the response or the internal action following this SKF alert. It can also be linked to the Flow curves of the DS HP pump — Hydraulic Laboratory tests, one year later, which could testify to the monitoring of the reliability of this pump after this episode.