Ancillary uses of hydrostatic transmission: alternator, fan, air conditioning (3 April 1974)

In this document

This handwritten note, dated "3.4.74" at the top right (the "74" is marked in red), constitutes Chapter IV of a work plan by Paul Magès dedicated to the "ancillary uses of HT" (hydrostatic transmission).

Alternator

The text indicates that "studies and tests have been carried out" and that "patents have been filed" on this point. Magès notes that it is now necessary to "draw conclusions and plan the future programme" p. 182.

Cooling fan

Tests [uncertain: "carried out"] in March 1974 reportedly showed "the value of cooling using a hydraulic motor". A test report is in progress, attributed to Mr. Corbel. Magès plans for "study work to be prepared" as well as patents for "the various types of possible regulation" to be filed p. 182.

Air conditioning compressor

A study of a "free-piston" compressor is envisaged, with "diagrams and possibly patents", and the question of regulation remains open ("Regulation?") p. 182.

Continuation of the plan

The note outlines two subsequent chapters not developed here: "V Flexibility of use" and "VI New possibilities for the engine", with the general mention "development of all these chapters". A final line, in the margin, mentions a "Manually remote-controlled rear wiper" p. 182.

Context

The hydrostatic transmission mentioned here is part of the research conducted by Citroën during the 1960s-1970s on the applications of hydraulic fluid, beyond the hydropneumatic suspension already used on the DS. The idea of using a hydraulic circuit to drive accessories (alternator, fan, air conditioning compressor) follows an engineering logic aimed at simplifying or improving classic mechanical components using hydraulic pressure, a technology that Magès mastered particularly well.

This type of reflection on "ancillary uses" testifies more broadly to an era when manufacturers sought to diversify the uses of a single central technology to amortise its development. This note from April 1974 is situated in the final months of Magès' career at Citroën, where he remained a technical writer and then deputy head of the Super-Control from his arrival in 1925 (Draft letter from Paul Magès to Mr. Sarre and interview plan of 11 May 1969) until his retirement in September 1974 (Photographs of Paul Magès' retirement (1974)), which sheds light on the summary and "future" programme tone adopted here.

Archivist's perspective

This document takes the form of a synthetic work plan, almost a personal roadmap for Paul Magès for the year 1974. It seems to reflect a phase of assessment and projection: each sub-theme (alternator, fan, air conditioning) is treated according to the same pattern — state of research, patents to be filed, work remaining to be done. Written a few months before his retirement, this plan takes on the value of a technical testament, where Magès seems to want to pass on a "future programme" p. 182 to those who will continue this research after him.

The mention of tests carried out "in March 1974" p. 182 suggests that this note was probably written in the immediate aftermath of these tests, which is consistent with the "3.4.74" date written at the top.

One can compare this reflection on the hydraulic alternator with previous exchanges with the C.G.E. on hydraulic motor alternators, which date back to 1961: this 1974 note could thus mark a culmination, or a relaunch, of work begun more than a decade earlier.