Assembly sheets for test cars with hydraulic suspension (Dec. 1951 – Feb. 1952)

In this document

These eleven pages bring together six technical notes signed by engineer Perrier, addressed by Mr. Cadiou to Mr. Poupon (the name varies according to the pages: "Pompon", "Pompey"), for the attention of Mr. Chalard of the laboratory. Each details the assembly of a test car ("PV" or "PVL") equipped with the first hydropneumatic suspension.

ELV 230 (28 Dec. 1951)

Reference car: accumulators inflated to 62 kg/cm², rear spheres to 43 kg/cm², pump cut-out at 165 kg/cm² p. 81. Load distribution recorded: 312/312 at the front, 255/253 at the rear — the handwritten note "false" suggests a contested value p. 81. Approximate height setting of 240 mm.

ELV 280 (8 then 29 Jan. 1952)

Settings close to the ELV 230 but pump cut-out at 140 kg/cm², spring set to 1 and 3/4 turns, axle with additional bar p. 82. A supplementary note from 29 January specifies the load distribution (309/300 front, 271/275 rear), a front height of 280-282 mm and a camber of 5 mm p. 83.

PVL6 ELV 136 "Beurlay" (16-18 Jan. 1952)

Pump cut-out at 160 kg/cm², spring set to 3/4 of a turn with two superimposed 5/100 valves p. 84. The following page gives a load distribution of 418/416 kg at the front and 287/290 at the rear, spheres at 52 kg/cm², accumulators at 70 kg/cm² and a height of 280 mm p. 85.

PVL ELV 324 "Grégoire" (28 Jan. 1952)

Pump cut-out at 130 kg/cm², spring set to 1 turn, axle with additional bar p. 86. The associated load distribution indicates 342/318 kg front and 256/265 rear, spheres at 44 kg/cm², accumulators at 70 kg/cm², height of 255 mm p. 87.

PV ELV 238 "Chinchina" (8 Feb. 1952)

Pump recovered already "in endurance" on a previous car, "letter H" distributor, two nylon seals p. 88. Load distribution: 295/300 at the front (L/R), 264/264 at the rear, height of approximately 250 mm p. 89.

PVL6 ELV 368 "Tudor" (25 Feb. 1952)

Pump cut-out at 130 kg/cm², "letter C" spring with 3 5/100 shims, height setting at 290 mm p. 90. Final distribution: 395/408 kg front, 285/271 rear; the spheres, initially inflated to 52 kg/cm², were reduced to 45 kg/cm² "due to valve knocking" p. 91.

Context

These tests took place at the very beginning of the 1950s, a period when Citroën was secretly developing the hydropneumatic suspension for which Paul Magès had drawn up the plans as early as 17 February 1944 (plans for hydropneumatic suspension with differential interaction and automatic leveling) and which, after the first tests on 2 CV in 1946 (notebook of the first tests of the 2 CV with hydropneumatic suspension), would only equip the DS upon its launch on 6 October 1955. The cars mentioned are likely test mules — discreet development cradles, running under internal designations ("ELV") rather than under the name of the final model. The vocabulary used (accumulators, distributors, spheres, leveling) already heralds the architecture of the system that would make the brand's reputation.

Archivist's perspective

This series of sheets, very repetitive in its form but precious in its detail, reveals the daily work of fine-tuning: each car receives slightly different settings (pressures, springs, distributors) which are adjusted throughout the road tests. The numerous handwritten corrections ("false", crossings-out) show an iterative process, almost empirical trial and error, rather than a fixed theoretical development.

It seems that Perrier played the role of technical field executor, reporting raw measurement data to Cadiou and Chalard intended to guide Paul Magès' decisions on the final tolerances. This corpus naturally extends the previous theoretical studies on hydropneumatic interaction, such as the plans for suspension with differential interaction and automatic leveling of 1944, of which it represents here the concrete translation into road tests.