Test report no. 220.692: dismantling of the rear axle of the PVL6 ELV.136

In this document

This report from the André Citroën Laboratory (test no. 220.692) accounts for the dismantling and examination, in the presence of Mr. Magès, of the rear axle of the test car PVL6 - ELV.136, equipped with hydraulic suspension, after approximately 20,000 km of driving p. 104.

Incidents during endurance

Two incidents are reported: at 11,800 km, a rubber cup of the distributor was holed, and at 13,500 km, the loss of the distributor spool end p. 104. The inflation of the suspension spheres was lowered to 44 kg/cm² (instead of 52), and the shock absorber shims, shredded, were replaced by a 1/10 shim p. 104. The report notes that from this moment on, "the car bottomed out much less than before" p. 104.

Lockheed oil consumption

Three partial readings are given, i.e., approximately 270 cm³ for 10,000 km, a figure presented as a simple "order of magnitude" p. 104.

Findings upon dismantling

The pressures of the spheres and accumulators are checked p. 105. The suspension cylinders show oval wear measured precisely: for the right cylinder, ovalization of 0.14 mm; for the left, up to 0.29 mm in a plane at 45° p. 105:

This same phenomenon had already been observed on ELV.230 p. 105. The engineers request an increase in piston guidance and a revision of the piston-linkage travel diagram p. 105.

The left linkage "buckled" and had rotated 90° upon dismantling; it is forwarded to Mr. Blanc for examination p. 106. A handwritten annotation specifies that the linkages were not in place in their bearing, which "could have led to abnormal wear of the cylinder and even buckling" p. 106. Also noted: torn and dirt-filled protective skirts, oxidized reaction balls, oxidized right needle bearing, worn silentblocs of the triangulation bar p. 106-107.

The car is reassembled with new parts: left linkage, shock absorbers without shims, rubber protectors "new softer rubber", right-side needle bearing, plastic silentbloc on the axle side p. 107.

The report concludes with four requests: piston guidance, linkage centering, piston protection, sealing of the oscillation bearings "very defective" p. 108. A handwritten annotation marks "Done" next to the first two points p. 108.

Context

The André Citroën Laboratory, located on Rue Balard in Paris, was the brand's testing center where the systems that would equip the future DS 19 (1955) were developed, notably the hydropneumatic suspension. Endurance tests on mule vehicles (here designated by codes such as "PVL6" or "ELV.136/230") aimed to validate the reliability of components before their industrialization. The Lockheed mentioned refers to the hydraulic fluid then used in these circuits.

Archivist's perspective

This document concretely illustrates the development work carried out by Paul Magès: far from a fixed invention, the hydropneumatic suspension appears here as a system in continuous improvement, confronted with real wear (cylinder ovalization, linkage buckling) and corrected step by step p. 105-107.

The reference to ELV.230, another test vehicle already affected by the same defect p. 105, suggests a series of comparative tests followed rigorously within the laboratory. This report could thus find an echo in other documents in the same file, such as the Summary of folder 41-59, which traces the technical developments leading to the DS, or in the plans for suspension with differential interaction, which are earlier but belong to the same technical lineage.