Handwritten note of 29 June 1959: capacity per side vs capacity per axle

In this document

This handwritten page, dated 29.6.59, is titled "Case 1 [word crossed out] capacity per side" p. 12. Paul Magès continues a technical reflection here that was initiated a few days earlier (24.6.59, mentioned as a reference in the text itself).

Comparison of the two arrangements

He contrasts the solution studied here — a capacity per side — with that of a capacity per axle. In the "per side" case, the pistons on the same side move in the same direction, which makes the balance more difficult to maintain "because there is a variation in pressure in the capacity" p. 12. Magès notes that a "special device" would be needed to cut the "L R" communication when there is an "exchange flow" p. 12.

Supplementary note of 1.7.59

A second note, added under a crossed-out date and then rewritten as 1.7.59, develops a similar idea: it is advantageous to give the cylinder only the volume strictly generated by the piston's movement over its stroke. The volume necessary for the desired flexibility must be separated "by a wall or a conduit", both for the travel and for the counter-travel p. 12. This arrangement would allow, according to Magès, to obtain maximum damping, as this can only be done "by throttling at the passage from the cylinder to the capacity and vice versa" p. 12.

Several words and passages in the text are crossed out or uncertain; no conclusion can be drawn from them.

Context

At the end of the 1950s, Citroën was developing and refining the hydropneumatic suspension equipping the DS, launched in 1955. The design office engineers, including Paul Magès, were then seeking to optimise the hydraulic circuits connecting cylinders and capacities (the suspension spheres), in order to finely tune the damping and the distribution of pressures between wheels.

These researches were also part of exchanges with external contacts regarding competing or complementary "air suspension" solutions, as evidenced by other documents in the same file — this point relates to the general context of the archive and not to the content of this specific page.

Archivist's perspective

This page probably belongs to a series of work notes close in time: it explicitly refers to a reflection from 24.6.59 and itself bears two dates, 29.6.59 and then 1.7.59, suggesting that Magès returned to it a few days apart to complete his reasoning p. 12.

It concretely sheds light on the engineer's working method: arbitration between hydraulic architecture ("per side" vs "per axle"), concern for minimising dead volumes to preserve damping, and vigilance regarding pressure exchanges between circuits.

It is likely linked to the same line of thought as the handwritten note of 24 June 1959 on the effects of a capacity per side or per axle and the one dealing with the case of a capacity per axle, which address the same technical comparison a few days earlier.