Hydraulics Quiz No. 6 (second annotated copy) — power braking and ABS

In this document

This is a second copy of the sixth and final of the "Hydraulics Quizzes", a multiple-choice questionnaire intended to be returned "within fifteen days of receipt" p. 20, and presented as "the last of the six Hydraulics quizzes" p. 20.

The brake valve and power braking

The first questions concern the supply to the front and rear brake calipers, the operation of the brake valve (as a regulator then as a pressure compensator) and the BENDIX brake calipers p. 20. Two technical cross-section diagrams, "at rest (drawing 1)" and "during braking (drawing 2)", accompanied by two tables to be ticked listing nine chambers (a to i) and five pressure zones (PFAV, PFAR, Psus AR, HP, reservoir), allow for the verification of circuit understanding p. 20.

The ABS system

The second part asks about the ABS hydraulic braking circuit: its similarities to a classic circuit to which "a modulator unit" is added p. 21, the vehicle's behaviour in the event of an ABS failure, the role of the computer which "interprets the measurements from the speed sensors" p. 21, and the constituent elements specific to ABS (wheel speed sensors, electronic computer, hydraulic modulator block, modified brake valve).

Two chronological classification exercises concern the pressure modulation phases by solenoid valves on the XM (slow/fast intake, slow/fast release) and the associated physical phenomena (start of wheel locking, braking without ABS, step-by-step recovery, progressive relaunch) p. 21.

The document closes with a space for remarks that remains blank, a box to be filled in (study time, signature, place, date) bearing an oblique handwritten line near the "Signature" mention, and the instruction "Keep the carbon copy" p. 21.

Context

The ABS (Anti-lock Braking System) became widespread on automobiles from the 1980s-1990s, complementing the hydraulic power braking circuits already developed by Citroën thanks to hydropneumatics. The Citroën XM, cited in the quiz, is a model produced from 1989 to 2000, equipped with high-pressure hydraulic power braking inheriting the principles conceived by Paul Magès. This general context sheds light on the subject matter of the quiz but is not developed in the document itself.

Archivist's perspective

This document confirms, like its first copy (Hydraulics Quiz No. 6 (copy 1)), that the educational series ends with the most technologically recent subject addressed: electronics applied to hydraulic braking, articulated with the knowledge acquired from the five previous quizzes.

The presence of a second copy, with a handwritten line near the "Signature" box but without written remarks, probably suggests a use for verification or duplicate storage, in accordance with the final instruction "Keep the carbon copy" p. 21. It is part of the same training system as the Hydraulics Expert Notebooks, intended to transmit the technical knowledge inherited from the work of Paul Magès.