First handwritten sketch of a hydraulically operated gear change (1952)

In this document

This handwritten sheet, annotated in red "1er esquisse Ch. de Vit." p. 1, presents a technical diagram in pencil and coloured pencils of a hydraulically operated gear change circuit.

Annotated functions

The sketch distinguishes several components labelled by hand:

• the "high speed exhaust" associated with the clutch release p. 1;
• a "speed selector" and a "speed pusher" p. 1;
• a "re-clutching" and a "clutch release" p. 1;
• a "reservoir" connected to the circuit p. 1;
• a "gear pump driven by the engine" p. 1;
• a "pressure limitation" set at 1 kg/cm² p. 1.

Graphic representation

The drawing shows mechanical blocks connected by coloured piping (blue, red, yellow), a red spiral spring assembly, a hatched rectangular block suggesting a pump or a distributor, as well as a green spring cylinder at the bottom right, probably the gear pump mentioned. At the top right is a sketch of an articulated lever with a pusher. Some mentions remain uncertain, notably an element read as "bourdette" and a "forked lever" p. 1, which cannot be confirmed with certainty.

Page 2 is attached as the verso or continuation of the same sheet, with no distinct transcribed element usable here.

Context

The hydraulically operated gear change is a line of research associated, in the history of Citroën, with reflections conducted in parallel with the development of the hydropneumatic suspension, the flagship technology of the future DS presented in 1955.

The year 1952 corresponds to an intense period of research at Citroën on the uses of hydraulics applied to automotive mechanics, far beyond just suspension: braking, steering, and therefore transmission. This general context sheds light on the approach but is not mentioned in the document itself.

Archivist's perspective

This sheet likely has the value of a very first draft: the very term "esquisse" (sketch) inscribed by Paul Magès at the top of the page p. 1 suggests an exploratory stage, where the functions of the future mechanism (selection, clutch release, pressure limitation) are set out before any formalisation.

The presence of a numerical pressure value (1 kg/cm²) suggests that the reflection goes beyond the simple principle and already touches on dimensioning p. 1.

This document seems to be part of the same vein of work as the handwritten study "garage position", dated late September 1952, and the diagram plates P 1214, which could represent a subsequent clean version of the same principles.