Laboratory Report No. 223 080: DS cold weather tests (8 February 1956)

In this document

This report from the André Citroën Laboratory (53, rue Balard, Paris), signed by Messrs. Magès and Louis, reports on DS tests carried out "in cold weather", taking advantage of the atmospheric conditions of the previous week, with a minimum ambient outdoor temperature of "-14°/-15°" p. 136.

Gearbox and clutch

The "new gear shift corrector" works without problems after 2 or 3 shifts, but the authors note that too little clearance between the piston and the body seems to lengthen cold shift times. A defect in the rubber used as a spring for the reverse gear notch, which prevented this gear from engaging in extreme cold, is reported as "corrected by replacing the rubber with a spring". Re-engagement is a little long for 3 or 4 manoeuvres then becomes "very satisfactory" p. 136.

Suspension

Below "-5°/-10°", height correction is slowed down by the "dash-potting of the correctors", with a risk of "scraping the underbody or the exhaust"; the authors recommend indicating in the manual to let the engine run for a few minutes before driving. The manual height control requires a great deal of cable effort in extreme cold, with a supplier being asked for a suitable grease p. 136.

Brakes

A "dead time before braking" is observed in the cold, attributed to the resistance of the 2 mm piano wires in the front brake supply tubes (internal ø 3 mm). The authors ask for the "single supply tube, without resistance" to be generalised quickly p. 137.

Additional notes

Two endurance DS parked in the Morvan started at "-21°" without any notable incident. Rusted tubes and a rear corrector bowl filled with dirt are reported on a vehicle with manual lifting. In hydraulic summary: "no problem for operation in the cold (at least down to -20°)" p. 137.

Fuel supply

Two Lab cars experienced a fuel failure at start-up due to an "ice plug" in the pipe; the authors ask for the fuel suction in the tank to be reviewed p. 137.

Context

The DS, presented by Citroën in 1955, incorporates the hydropneumatic suspension designed by Paul Magès, a major innovation for the time. Cold weather tests, common in automotive development, aim to validate the reliability of a complex hydraulic system under extreme conditions, a particularly sensitive issue for a still young technology.

Archivist's perspective

This document concretely illustrates the continuous development work carried out by Magès and his team after the launch of the DS: it is not theoretical research but feedback from field tests, with very operational recommendations (user manual, choice of tubes, specific grease).

It usefully complements the hydropneumatic suspension plans and the summary of folder 41-59, which document the evolution of the suspension and the DS within the same collection. The tone of the report, both precise and pragmatic, seems to reflect Magès' constant concern to ensure the reliability of his invention under real-world conditions.