Road test of the 15 Six H (ELV 412) by Paul Magès, 3-5 April 1954

In this document

The test report (p. 118)

The document records the road test of the 15 Six H (referenced ELV 412), equipped with power steering and hydraulic brakes, conducted on "3.4.5 April 1954" p. 118.

The route is detailed day by day:

• Saturday: departure from Chaville at 4:15 am, via Mâcon, Lyon, Avignon, to Saint-Tropez at 2:55 pm, i.e., 921 km covered "in 10H40 – 23'" at an average of about "90 km/h" p. 118.
• Sunday: from Saint-Tropez to Laffrey via La Garde-Freinet, Draguignan, Digne, Sisteron, Gap, the Col Bayard and Corps, i.e., 263 then 344 km in total, on "winding road" at an average of 60 km/h, then a "night journey in the mountains limited by side lighting" p. 118.
• Monday: return from Laffrey to Chaville (660 km in 7h45, about 85 km/h) p. 118.

Annotations note stops for lack of water or petrol, as well as a "cylinder head tightening" and a "seat stud" underlined twice p. 118.

Technical observations by Paul Magès (p. 119)

On the power steering: "Lack of fixed point in a straight line", driving with hands on thighs, elbows against the backrest, where "the wrist alone does the work most of the time". Magès notes the desire for "two armrests" and judges that on winding mountain roads, the seat should be "bucket-style" because one cannot brace oneself against the steering wheel p. 119.

He develops a reflection on the balance between steering effort and centrifugal force, the latter being proportional to the driver's weight — an argument taken from Mr. Hermet, a long-time proponent of enveloping seats. Conclusion: "Seat study essential" p. 119.

On the servo-brake: "Too much brake at the rear when empty" p. 119.

On the suspension: the road circuit is judged "truly ideal for tasting the suspension in all cases", with mention of "1st model deformable disc shock absorbers" p. 119.

Engine side: oil consumption "1° per 1000 approximately", water consumption "without overheating", and the hydraulic system judged "N.A.R." p. 119.

A reported memory (p. 120)

Magès relates the fears of Mr. Cadiou, before the release of the 15 CV, regarding the road holding of the 15 H, judged less good than the "15 with bars". Tests "head-to-head" at La Ferté-Vidame, in search of the speed limit for cornering, allowed him to "convince Mr. Cadiou of the opposite" p. 120, an operation he himself describes as dangerous.

Context

The 15 Six H (known as "15 H") is an evolution of the Citroën Traction Avant 15 Six, equipped in 1954 with a hydropneumatic rear suspension — a full-scale test bench for the technologies that would soon equip the future DS. The La Ferté-Vidame test track, mentioned on page 120, is Citroën's historic test circuit.

The "15 with bars" refers to the version with classic springs and torsion bars, a natural reference for comparison to judge the qualities of the new hydropneumatic suspension.

This test of 3-5 April 1954 is located in the final phase of the long development work of the hydropneumatic suspension conducted by Magès: from first plans as early as 17 February 1944, through first tests on 2 CV in 1946, until the presentation of the DS on 6 October 1955.

Archivist's perspective

This report illustrates the field work of Paul Magès: beyond calculation and drawing, the real road test, over several days and several hundred kilometres, in varied conditions (road, mountain, night), seems to be an essential validation step.

The attention paid to the seat and driving position, in connection with steering efforts and centrifugal force, announces ergonomic concerns that go beyond mere mechanics — a point that Magès himself judges "essential" to study p. 119.

The anecdote on page 120, opposing Mr. Cadiou's doubts to Magès's convincing demonstration at La Ferté-Vidame, sheds light on the internal tensions surrounding the adoption of the hydropneumatic suspension a little over a year before its full deployment on the DS, presented on 6 October 1955. This document is part of the same documentary set as the folder "Theoretical study – hydropneumatic suspension 1943/44", testifying to the continuity of Magès's work on this system since the 1940s.