Activity report of 15 June 1964 on the work of the Hydraulic Study Group

In this document

This handwritten note, dated 15 June 1964 p. 47, provides an overview of the projects underway at the Hydraulic Study Group led by Paul Magès.

DS/ID damping and anti-roll

A new damping law allows for the limitation of heavy undulations at high speed "without losing too much in ride comfort" p. 47. It brings a clear improvement in cornering road-holding and reduced body roll. The "series" production forms are still under study, and the improvement of the suspension links, linked to this new shock absorber, is in the process of industrialisation p. 47. The hydraulic anti-roll system is still being tested, but without any practical application possible without changing the front axle architecture p. 47.

Headlights and power-assisted steering

A solution is mentioned to automatically correct the orientation of the headlights according to pitch movements, deemed applicable to the "D 61" p. 48. Several "power-assisted steering" systems are installed or being installed at the BEA and the LABO; the criticism of a return that is too fast is "practically no longer an issue" after the latest adjustments. The gear ratio remains to be decided, and roll stiffness tests (reinforced front, softened rear) are being considered to increase "self-stability" p. 48. A version for heavy goods vehicles is also being assembled on an experimental basis p. 48.

Gearbox, braking and transmission

The hydraulic shifting of the synchronised 1st gear on the DS has been resolved, as well as a clear improvement in the clutch p. 49. A new, "fresher" hydraulic pressure regulator is awaiting industrialisation p. 49. Regarding DS/ID braking, a "slip limiter" is undergoing successful tests for trajectory control; the author also argues for rear disc brakes, deemed inexpensive but not a priority p. 49. For heavy goods vehicles, power braking is progressing. Finally, the hydrostatic transmission is undergoing satisfactory endurance tests, with a target of 3 CV running cars around January 1965, and 100-120 CV transmission plans expected by the same deadline p. 50.

Context

At that time, Citroën was actively developing the hydropneumatics introduced on the DS (1955) and extended to the ID. The mention of the "D 61" probably refers to an internal project or model year of the DS/ID range from the early 1960s. Research into hydrostatic transmission for small and medium engine sizes (3 CV, future higher power projects) was part of the attempts, which remained largely experimental at Citroën, to create hydraulic automatic gearboxes.

Archivist's perspective

This activity report offers a rare and synthetic overview of the scale of the projects carried out simultaneously by Magès and his team in 1964: damping, steering, braking, transmission. It seems that this document serves as a progress report for management, given how composed and argued the formulations are, particularly regarding the rear disc brakes where Magès insists on the perceived urgency p. 49.

This text extends work documented as early as 1961 on the DS clutch and gear control and echoes the road tests on the anti-roll and power-assisted steering of 1962, described in the road test report of 2 to 5 April 1962. The continuity of the themes shows Magès's perseverance on long-term technical problems.