Sketch of an air/oil device to replace the oil dipstick

In this document

The document is a handwritten sketch in blue ink occupying a page of a pre-printed form whose text remains [illegible] in the background.

It represents a long, thin tube, drawn in cross-section, with both ends annotated "Air" and "oil". The handwritten annotation specifies that this device "Goes in place of the oil dipstick" p. 15.

Another indication, accompanied by a double vertical arrow delimiting the length of the tube, specifies that this "length [is] to be determined according to the maximum reached" p. 15 — which suggests that the part is not yet definitively dimensioned.

At the bottom of the sketch, a dotted line connects the lower end of the tube (annotated "Air" and "oil") to the mention "oil dipstick" p. 15, confirming that this new device explicitly aims to replace this classic component.

No date, project name, or part reference appears on this page.

Context

Historically, the oil dipstick is a simple visual inspection component for the oil level in an engine crankcase — a graduated rod that is removed to read the level.

At Citroën, Paul Magès is best known as the inventor of the hydropneumatic suspension, a system combining air and liquid under pressure, introduced on the DS in 1955. The principle of associating air and oil in the same circuit to obtain a specific mechanical behavior (elasticity, measurement, regulation) is a recurring signature of his research, well beyond just the suspension.

However, nothing in the document allows this specific sketch to be linked to a dated or named project.

Archivist's perspective

This small sketch catches the eye due to its unusual object: it is not about suspension here, but a simple oil level measuring component, rethought according to an air/oil logic rather than by simple visual reading on a rod.

It seems to be a reflection sketch, probably preparatory, as the mention "length to be determined according to the maximum reached" p. 15 betrays a reflection still open on dimensioning.

The file contains a very similar variant, the Handwritten sketch of an air/oil tube replacing the oil dipstick, which seems to take up the same idea — both pieces would benefit from being compared to follow the evolution of this minor but revealing invention of Magès' method: transposing a principle (here air/oil) to very diverse technical problems, including the most modest ones like checking an oil level.