BBC conferences of 28 Nov. and 13 Dec. 1960: DS suspension, clutch and braking

In this document

These three pages gather the handwritten notes taken by Paul Magès during two conferences held with Messrs. Bercot, Brueder and Cadiou, on 28 November and 13 December 1960 p. 7-9. They cover three major technical projects for the DS: suspension, clutch/gearbox, braking.

Suspension

Magès lists research in series preparation or in progress: the quick-return height corrector (stability, height adjustment, comfort improvement, headlights) and full-travel damping, already tested on three running cars, including one at the Laboratory since 25 October 1960 p. 7.

He also mentions more experimental avenues: variable flexibility anti-roll bars, an air suspension on 2 CV (with a handwritten cross-reference to "Bougeard"), a 2 CV hydraulic suspension adaptable to AM, and several variants of hydraulic anti-roll ("100%", "compromise", "leaning turn"), as well as an "anti-pitch" device linked to acceleration and braking. Finally, he notes that "friction harms the suspension — DS-ID!" and that a simplification of the front axle is planned with a new steering system p. 7.

Clutch and gear shifting

The text details the centrifugal regulator of the clutch and emphasizes that the improvement of friction "remains to be done" despite a 10 kg gain p. 8. Magès analyzes the accelerated idle integrated into the carburetor: it allows for reduced speed for low braking pressure, but over-disengaging requires too high a pressure (8 to 9 kg/cm²). He proposes several avenues: obtaining 15 to 20 kg more at disengagement, removing the clutch corrector spring for clearer operation in parking, and linking the clutch corrector to the engine-wheel speed difference p. 8.

He also mentions a supply via reduced pressure (80 kg/cm²) for gear shifting, aiming for noise reduction, time saving and less effort on forks and seals p. 8.

Braking

Magès lists improvements in progress or applied: the suspension-powered brake ("brake 12"), a maximum pressure reduced to 110 instead of 175, the improvement of the pedal assembly, a spool valve without a seal with a reduced groove for progressiveness, the removal of the "dash pot", a widened brake pad, and an inverted stop contact to eliminate the "threshold" p. 9.

He points out a limit: "solid braking is running out of steam - pressure/torque control impossible" and calls for direct torque control. He mentions an "AV blocking stop" to control front drift, and anticipates a future "hydraulic transmission braking" where torque would be proportional to pressure, with no possible locking or wear p. 9.

Context

At the time of these conferences, the DS had been marketed since 1955 and its hydropneumatic suspension, designed by Paul Magès, was already a major Citroën innovation. The personalities cited — Bercot (General Manager), Brueder and Cadiou — were senior executives of the brand, which places these exchanges at the level of technical management.

These studies on damping, anti-roll and hydraulic braking announce developments that would be taken up, refined or abandoned in the following years of Magès' career at Citroën.

Archivist's perspective

This document offers a rare and precious view of Paul Magès' collective reflection work with his superiors: it is not a final report but a living status report, mixing solutions already in series, tests in progress and ideas under study p. 7-9.

The insistence on "friction" harming the suspension and on the limits of "solid braking" (p. 7, p. 9) shows a mindset turned towards the increasing integration of hydraulics into all the car's systems, an orientation that seems to have durably structured Magès' research.

These notes find a direct echo in the BBC meeting summary of 22 February 1962, which continues the same themes with the same interlocutors, as well as in the notes on the clutch and gear control of 28 March 1961, which seem to extend the avenues mentioned here.