Blueprint of the DS 7-piston high-pressure pump no. E 401.8444 (November 1958)

In this document

Divider (p. 20)

The item opens with a separator sheet bearing the inscription in blue ink "POMPE", underlined, as well as pencil annotations: "12 58" in red (the "12" appearing to have been traced over) and a grey mention read as "M-58" or "11-58" p. 20.

The technical blueprint (p. 21)

The drawing represents, in horizontal cross-section, a cylindrical mechanical assembly identified as a 7-piston pump with hydrostatic pads, expansion grooves and sleeve seal — this is the designation carried in the title block p. 21. One can distinguish a central splined shaft and a cylindrical body in cross-section showing pistons and internal grooves, with numerous reference lines pointing to numerical markers arranged around the drawing p. 21.

The title block identifies the blueprint under the number E 401.8444, reference E 42.401T, drawing BER.3159 p. 21.

About fifteen part markers are listed, among which: 49295, NK 20/16, E401.8450, E401.6986, E401.6983, E401.6990, E401.6988, E401.6991, E401.8446, E401.8445, E401.6987, E401.8447, E401.8449, E401.6989, E401.8448 p. 21.

The execution title block indicates: draughtsman Vivet J., dated "Nov.58" p. 21. A red handwritten annotation, of uncertain reading, could indicate "for test" p. 21.

The document bears the legal notice "SOCIÉTÉ ANONYME ANDRÉ CITROËN — REPRODUCTION INTERDITE" p. 21.

Context

This seven-piston high-pressure pump is a central component of the hydraulic system invented by Paul Magès for the Citroën DS, presented in 1955: it supplies pressure to the circuit ensuring the hydropneumatic suspension, the brakes and the power steering. The reference to "hydrostatic pads" and a "sleeve seal" refers to technical solutions intended to limit wear and internal leaks of the pump, a known reliability issue for this component during the years following the launch of the DS.

Archivist's perspective

Dated November 1958, this blueprint is likely part of an effort to refine the HP pump, a few months after the difficulties with the durability of bearing balls reported at the end of 1957 — see the memorandum by Paul Magès on defective DS HP pump balls and the SKF letter of the same day.

The contemporaneity with the DS HP pump flow curves and the request for a pre-series of 100 H.P. pumps, both from November 1958, suggests that this is the reference blueprint serving as a basis for these series validation tests. The annotation "for test", if the reading is correct, would support this.