Graphic test record "Acceleration - braking in 1st gear" (1951)

In this document

This handwritten sheet bears the title "Acceleration - braking in 1st gear" and the date "1951" p. 1.

It presents six superimposed curves, drawn by hand, corresponding to five sensors (numbered 1 to 5, with a variant noted 5') p. 1. Each curve has its own vertical scale in millimetres:

(scale values recorded p. 1)

The horizontal axis, common to all curves, is graduated in seconds, from 0 to approximately 11 p. 1. The handwritten traces show "irregular oscillations with peaks and damping varying according to the curve", characteristic of a dynamic recording during an acceleration phase followed by braking p. 1.

A number "9" appears at the bottom of the page, probably a page or file numbering p. 1.

Context

This type of handwritten graphic record corresponds to the test methods in use at Citroën in the early 1950s, a period when Paul Magès was developing the hydropneumatic suspension in the design office, the first plans for which date from 17 February 1944 (Plans for hydropneumatic suspension with differential interaction) and whose first tests on the 2 CV took place in May-July 1946 (Notebook of the first tests of the 2 CV with hydropneumatic suspension).

The "acceleration - braking" tests in first gear were probably aimed at measuring the dynamic behaviour of the suspension (travel, damping) under sudden loads — a central issue for the development of a hydropneumatic system, the culmination of which, the DS, would be presented on 6 October 1955. This general context is, however, not made explicit in the document itself.

Archivist's perspective

This graphic record is a raw technical document, without interpretative commentary: it provides only measurement traces p. 1. Its interest lies in the direct testimony of the experimental methods used to characterise the behaviour of the suspension — probably hydropneumatic, given the context of the Magès workshop at this time, although the document does not specify this explicitly.

It is likely a piece of a larger set of tests, the other sheets of which are not known here. This document is situated between the first tests of 1946 and the test of the 15-Six H of 3-5 April 1954 (Test of the 15-Six H ELV 412 by Paul Magès), and precedes by a few years the more administrative documents kept in the same collection, such as the Regulatory descriptive statement of the Citroën hydropneumatic sphere, which attests to the subsequent maturation of the system that these 1951 tests perhaps helped to develop.

The multiplicity of sensors (five distinct measurement points) suggests a carefully instrumented test, revealing the experimental rigour of the development team at this pivotal time.