Note from Pierre Bercot and Paul Magès's reply regarding AP vibrations (28 February 1966)

In this document

Pierre Bercot's note

President Pierre Bercot sends a handwritten note to Paul Magès, dated 28 February 1966, to congratulate him on a study he "read with great interest" p. 61. He questions the generalisation of this type of analysis: "Is this being done in the Design departments wherever it should be known? Is it being used intelligently?" p. 61.

The attached sheet mentions a translation of an SAE Preprint (May 1965, No. 65050) entitled "Vehicle sensitivity to disturbances transmitted by tyres", noted as coming from the Engineering Staff of Chrysler Corp. p. 61.

Magès's reply: from observed defects to research organisation

Magès explains that "very significant defects" in behaviour and comfort, highlighted at the end of January on the AP, triggered "a series of experiments" followed by all those concerned p. 62.

Mr. de Lassus conducted, with limited means, experiments highlighting part of the problems to be solved. Deemed insufficient, they were supplemented by Mr. Handel's department, in charge of systematic vibration measurements on the AP and other vehicles, as low-frequency problems are "now accessible to calculation" p. 62.

Since February, a method of recording on the road has been found; combined with stationary measurements, it allowed the calculation office to isolate the influence of the various parameters via "analogue computing machines", with results deemed "remarkable" p. 62.

Two distinct zones: low frequency and "noise zone"

Magès distinguishes the low-frequency zone, on a "good path" despite reduced means p. 63, from the "noise zone", deemed much more complex, requiring experimental research conducted by personnel who are "very observant, patient" and "clever" p. 63.

He points out that Mr. de Lassus only has one engineer available for this work, whereas two additional positions had been requested in July 1965 p. 63. He insists: these researches cannot be "broken down into several sub-contractable slices", as everything is linked p. 63.

A translation of SAE Preprint No. 660101, "Study of the dynamics of an automobile structure with the Cadillac road simulator", is attached to illustrate the difficulty of the subject p. 63. The note is signed at the bottom by the three collaborators mentioned: de Lassus, Handt, Vassal p. 63.

Context

AP designates, in the internal Citroën vocabulary of the time, a vehicle project under development — this document is therefore situated in a phase of preparatory studies, not documented more precisely here.

Pierre Bercot, president of Citroën from 1958 to 1970, personally followed major technical files, which explains his direct interest in a vibration study transmitted by Magès.

The use of American publications (SAE, Chrysler) translated internally testifies to the international technical monitoring practised at the time by automotive design offices, without it being possible to specify here the exact use made of them at Citroën.

Archivist's perspective

This exchange concretely illustrates the daily operation of the BEA: a concrete technical problem (comfort defects on the AP) triggers a coordinated mobilisation between road tests, instrumented measurements and analogue computing — three approaches that can be found, in other forms, in the 1960 BBC Conferences and in the 1962 road test report.

Magès's tone, both reassuring towards his president and lucid about the limits of human resources (only one engineer for a vast problem), gives a precious and rare image of the internal tensions between technical ambition and allocated resources.

It seems that this note, written two years before the well-known difficulties of the future DS/AP, testifies to a pivotal moment where analogue computing began to structure vibration research, complementing the empirical approach that had prevailed until then p. 62-63.