Hydraulic suspension test on PV — Christ de Saclay, 19 October 1948

In this document

Technical settings of the test

The document opens with a settings sheet for a test on PV equipped with hydraulic suspension: new tyres inflated to 1.2 (front) and 1.4 (rear), flexibility of 180% at the front and 250% at the rear, volumes of 500 cc (front, inflation 70 kg) and 1500 cc (rear, inflation 50 kg), anti-roll bars of Ø 24 mm (front) and Ø 20 mm (rear), and "4 dampers" p. 67.

Circuit and teams

The route starts from Quai de Javel, passes through Bièvre and the Christ de Saclay to the Château fort, with a return to the Christ de Saclay p. 67. A first crew brings together Mr Boulanger at the wheel, Magès as front passenger and Lefebvre in the back; a second crew sees Magès driving, with Cadiou as front passenger and Boulanger in the back, on the Christ de Saclay – Château fort section, return "via the Belle Image" p. 67.

Cross-impressions

Boulanger notes, at start-up, "a jolt of greeting and a little bit of roll", not found afterwards; on average road at low speed (30/40 km/h) he judges the suspension "bad", as on "vehicle A"; in corners, "no worry" despite the fact that "one leans"; conclusion: "Very good suspension" p. 67.

A stop takes place in the middle of the Christ de Saclay – Bièvre straight line p. 68. The impressions note a balance at the rear, a "more noticeable" roll on cambered road, good centering in the seat (compared to "vehicle A"), no worry in corners, and the absence of pumping or nausea p. 68.

On the return, Boulanger, front passenger, judges the experience "less good", with more vibrations and less satisfactory centering than in the back p. 68.

Decision

The document concludes with a decision "to be executed urgently": give two endurance cars to the Laboratory, equipped as much as possible with the devices in their state of development, dated 19/10/48 p. 68.

Context

This test is part of the development work on the hydropneumatic suspension carried out by Paul Magès at Citroën, which he joined in August 1925 and where he became deputy head of the Super-Control (autobiographical notes). This 1948 road test is inserted between the establishment of the first hydropneumatic suspension plans on 17 February 1944 (hydropneumatic suspension plans) and the first tests on 2 CV of May-July 1946 (notebook of the first tests), in the long journey that will lead to the presentation of the DS on 6 October 1955.

The "PV" likely designates a test vehicle, probably based on the Traction Avant, serving as a rolling test bench.

"Vehicle A", mentioned several times as a point of comparison, probably refers to another test prototype from the same campaign, not identified in this document.

Archivist's view

This report offers a rare and vivid testimony of test work in real conditions: Paul Magès appears there not only as a designer but also as a driver and passenger, confronting his own impressions with those of his colleagues Boulanger, Cadiou and Lefebvre p. 67-68.

The precision of the settings (pressures, volumes, flexibilities, bar diameters) testifies to a rigorous test method, probably typical of Magès' experimental approach at this period.

The final decision, underlined with insistence in the original document, marks a probably significant step: the transition to endurance tests on two dedicated cars, a sign of growing confidence in the system despite the reservations noted (roll, low-speed behaviour).

This document finds its natural place in the "41.59" folder dedicated to hydropneumatic suspension; it can be compared to the "Theoretical study – hydropneumatic suspension 1943/44" folder, which documents the theoretical foundations of which this road test probably constitutes a concrete application.