Handwritten chronology of hydraulic transmission and suspension tests (1955-1960)

In this document

This document is a handwritten chronological logbook in three pages, titled "Etudes N.elles et Transmission Hydraulique — Etapes du 22.12.55 au 17.11.59" p. 141. It records day by day the tests conducted on hydraulic transmission and hydropneumatic suspension.

1955-1956: the beginnings

The account starts on 22 December 1955 with the "1° essais de transmission hydraulique" on a 4 cm³ generator p. 141. This is followed by tests of 15 CV receivers, a presentation to "M. BBL" and "M. Bercot" (23-24.2.56), then tests of a 24 cm³ pump gradually increasing in pressure: 300 kg, 400 kg, 600 kg p. 141.

1957: the 2 CV enters the scene

On 29 May 1957, the "1°. Essais 2 CV TH" took place, followed by mileage runs: 49 km (6.6.57) then 59 km (20.6.57) p. 141. A conference with "M. BBCL" closes this sequence.

1958: diversification of tests

The year 1958 p. 142 saw an increase in tests involving both hydraulic transmission and hydropneumatic suspension: 57 cm³ generator (17.1), power-assisted steering, hydraulic start tests, brakes powered by the suspension (21/5), first 2 CV "Susp. H 3ᵉ disposition" run (15/10), and above all the appearance, on 7 November, of the "moteur hydraulig 1,3 cm³" which "turns for the 1st time" — soon used to drive a fan (26/11) then a windshield wiper (10/12) on a DS. The month of December ends with non-public 2 CV suspension tests (22/12) and forward-reverse maneuvers (30/12).

1959: acceleration and P38 truck

Page 143 opens with the "1.er sortie Camion P38 suspension H." in January. This is followed by regular transmission regulation tests (22.1), 2 CV TH road tests (20.2, 3.3, 9.3…), 6 cm³ pump tests, and pressure tests reaching "600 kg/cm²" (8.34) then "510 kg/cm²" during a climb of a 14% slope on 17 November 1959 p. 143. A comparative consumption measurement is noted on 15.10: the 2 CV 530 consumes "86%" on national roads and "88.5% in town" compared to a 2 CV 425 "same load" p. 143.

The document closes with two later entries, added subsequently: a climb of the Ventoux on 20.6.60 ("900 Km of road in this test") and a "1st turn of the hydraulic motor by alternator" on 21.10.60 (p. 141, p. 143).

Context

These tests are part of the research conducted by Paul Magès at Citroën during the second half of the 1950s, a period when the DS (launched in 1955) served as a test bench for numerous hydraulic components, and when the 2 CV became the preferred experimental vehicle for hydrostatic transmission. The P38 truck mentioned here is a Citroën model of the time, here equipped with an experimental hydraulic suspension. This work foreshadows the later developments of hydrostatic transmission which would continue into the 1970s.

Archivist's perspective

This logbook is probably one of the most valuable pieces in the Magès collection: it condenses, in three pages, nearly four years of technical trial and error, with their precise dates, their failures (crossed-out dates) and their milestones marked with a cross. It seems to have been written retrospectively, perhaps to prepare for a conference or a summary ("Date of the first conference" p. 141).

The recurrence of the 2 CV / hydraulic transmission pair directly heralds the developments documented in later pieces such as the Note from Magès to Cadiou on the endurance of hydraulic motors or the Follow-up of endurance tests of the 2 CV A12, which extend this chronology into the 1960s.