Handwritten note by Magès: installation of a hydrostatic unit on the front axle

In this document

This handwritten note by Paul Magès sets out the conditions to be met for the installation of a hydrostatic powertrain on the front axle.

Positioning of the centre of gravity

For a vehicle with the engine and transmission grouped on the drive axle, Magès poses two requirements: the centre of gravity of the assembly must be as close as possible to the axle axis, and as low as possible — which implies reducing the distance between the crankshaft axis and the transmission shaft output axis to a minimum p. 13.

Hydrostatic transmission and vibration filtering

The note highlights the benefit of reducing piping lengths and eliminating joints p. 13. Magès also recommends not designing the engine-transmission assembly as a single rigid block ("mono-bloc"), in order to allow for engine suspension that filters its vibrations as much as possible, while maintaining a rigid attachment of the transmission block to transmit transmission and braking torques to the chassis p. 13.

He specifies that an engine suspension point is provided on the chassis, with the annotation "torsion foot stiffness" in the margin. As the mechanical clutch becomes unnecessary, the engine can be moved closer to the transmission unit, with the flywheel moved to the other end of the crankshaft p. 13.

The patented pressure generator

The note describes a pressure generator barrel bearing, on its smallest diameter, gear teeth meshing with a hollow pinion coupled to the crankshaft by a torsion shaft, calculated to accept the relative displacements of the engine on its flexible suspension. This barrel is mounted on two bearings allowing slight axial displacement, resting on a spherical distributor that centres itself within it. The document explicitly indicates "(Patent.—)" at this point p. 13.

The partially visible printed header bears the mentions "...ANDIS CITROËN", "AMORTISSEUR" and "REPRODUCTION INTERDITE"; a circled handwritten annotation "1960" appears at the top right.

Context

At Citroën, Paul Magès was the inventor of the hydropneumatic suspension, deployed notably on the DS from 1955 onwards. The reflection on a hydrostatic transmission integrated into the front axle is part of a broader research, typical of automotive engineering of this period, aiming to combine motorisation, transmission and suspension into compact, vibration-filtered assemblies — although, outside of this document, it is not possible to attribute this project to a specific production model.

Archivist's perspective

This note seems to belong to the design or technical prospective phase, rather than a test report: it sets out general principles (centre of gravity position, vibration filtering, barrel architecture) rather than measured results p. 13.

The explicit mention of a patent associated with the pressure generator and spherical distributor device suggests that it is likely an invention specific to Magès, in continuity with his work on hydraulic suspension components, such as those found in the Magès calculation note: P55 suspension, leaf spring and 6 hydropneumatic bells.

The question of the barrel-distributor contact, central here, also echoes the Handwritten note on the barrel-distributor contact and pressure reversal, which could further clarify this same device.