Plates P 1214_1 and P 1214_2: diagrams of the hydraulic gear shift

In this document

Plate P 1214_1 (Fig. 1)

This first plate p. 5 presents a single pencil technical diagram, framed, occupying the entire page and referenced P 1214_1. It illustrates a complete hydraulic system: a reservoir numbered 1, connected by piping to circular elements (2, 3, 4), then to a line (5) leading towards a central mechanical assembly composed of striated parts (12, 43, 49, 47, 54, 16, 46, 48, 9, 10, 11, 53, S1, 19, A, 45).

There is also a horizontal axis equipped with double arrows indicating a back-and-forth and rotational movement (markers 7, 8, associated with 37 to 42 and 50 to 52, 55), a circle containing a spring (55) and gears (13, 14, 15), as well as a cylindrical assembly in section (26, with 27 to 36) connected by a pipe (25). On the right, a line (19) serves a small mechanism equipped with an angled lever (21) and a block in section (20). A handwritten annotation in red ink, at the top left, bears the mention "ch.V." followed by an uncertain sign p. 5.

Plate P 1214_2 (Fig. 2 to 4)

The second plate p. 6, referenced P 1214_2, groups three detailed views. Fig. 2 shows a longitudinal section of an elongated and symmetrical mechanism, with visible helical springs (markers 32, 34) and a set of associated markers (35, 36, 27, 28, 33, 31), all surmounted by the circled marker "26". A small detail in section of a T-fitting completes this drawing (markers 29, 30).

Fig. 3, at the bottom left, details a section of a stack of parts (markers 42, 40, 7, 55, 8, 37). Fig. 4, at the bottom right, presents a front view of a circular part with a hatched inner circle and dotted axes.

Context

These plates date from 1952, a period when Paul Magès, an engineer at Citroën, was working on the development of hydraulic devices intended to equip the brand's future models — work that would notably lead to the hydropneumatic suspension of the DS, presented in 1955.

The hydraulically controlled gear shift documented here is part of this same research into applying the hydraulic principle to various mechanical components of the automobile, long before its generalization. This context remains external to the document, which itself mentions neither Citroën nor the DS.

Archivist's perspective

These two plates numbered P 1214_1 and P 1214_2 seem to constitute a set of detail diagrams, complementary to more general sketches of the same device. The systematic numbering of the parts (up to more than fifty markers) and the precision of the sections suggest an already advanced stage of development, where each component is identified with a view to manufacturing or patent filing p. 5-6.

It is probable that these plates are attached to the same documentary set as the First sketch of a hydraulically controlled gear shift, of which they could constitute a more accomplished technical development. The comparison with the sketch of hydraulic circuit with piping markers could also shed light on the logic of the circuits represented here.