Pressure readings for suspension pneumatic blocks (P 1662), 9 December 1957

In this document

This card stock sheet, referenced P 1662, records pressure measurements for the hydropneumatic suspension pneumatic blocks.

Reference values

Vehicle tests

The note mentions a "rear in vehicle tests" reading giving a value of 32 kg/cm², associated with the names of Mr. Cadiau (probably Cadiou) and Mr. Magès p. 4.

The vehicle concerned is identified by the registration "DA 136 ELV 605", with the mention "4 Oct" and a mileage of 9,104 km recorded "on 9-12-57" p. 4. The sheet also bears the handwritten date "9-12-57" in the header.

The medium is a printed Citroën form (tricolour banner, "N°" and "PAGE N°" mentions), used here as a notebook for handwritten measurements.

Context

The pneumatic blocks mentioned refer to the principle of the hydropneumatic suspension developed by Paul Magès for Citroën, where gas-filled spheres under pressure (generally nitrogen) act as springs. The precise control and adjustment of these pressures, differentiated between the front and rear axles, are characteristic of the fine-tuning required for this system, used notably on the DS/ID 19 launched in 1955. This document from December 1957 is situated in the period when Magès, who joined the Citroën design office as early as 1939-1940 and authored the first hydropneumatic suspension plans in 1944 (hydropneumatic suspension plans), was continuing the development and monitoring of the system on produced vehicles, two years after the presentation of the DS.

The monitoring of a specific vehicle over several months, with mileage readings, corresponds to the long-term road test practices conducted by Citroën test teams to validate the pressure resistance of components over time — a practice already attested to from the first tests of the 2 CV in 1946 (notebook of the first tests of the 2 CV with hydropneumatic suspension) and during the test of the 15-Six H in 1954 (test of the 15-Six H).

Archivist's perspective

This document is a modest but concrete technical piece: it sets setpoint values (59 and 26 kg/cm²) which probably served as a reference for checking the pneumatic blocks, and documents an actual test on a registered vehicle, followed over time p. 4.

The joint presence of the names Cadiou and Magès suggests shared fieldwork, the latter probably supervising the validation tests of his own system, as part of his role as deputy head of Super-Control at Citroën (autobiographical notes). The measurement of 32 kg/cm² at the rear, significantly higher than the reference value of 26 kg/cm² ± 2, could indicate a discrepancy observed in use — but the document does not specify an interpretation on this subject.

This sheet likely belongs to the same set of works as the handwritten note on the recovery and inspection of suspension bells, which deals with a similar check on bells recovered from customers.