Oleopneumatic suspension of the Panther 100 motorcycle (Phelon & Moore) — translated notice, 1949

In this document

Presentation

This is a translated excerpt ("Translated from English", handwritten annotation p. 7) from the Maintenance Manual (page 17 of the original) of the Panther model 100 motorcycle, built by Phelon & Moore in London p. 7. A handwritten annotation indicates the recipient: "Monsieur Magès" p. 7, accompanied by an acronym close to "B E A" and a mention "Trabaud", likely the author of the translation.

The Oleomatic (Dowty) fork

The text describes the OLEOMATIC (Dowty) fork, "air-sprung and oil-damped" p. 7. The pneumatic suspension is presented as offering "great flexibility to absorb normal road irregularities without bottoming in extreme cases" p. 7. The movement of rubber cushions in oil produces a damping effect "approximately equal in both directions", without wear from contact, and oil cushions prevent bottoming in both extension and full compression p. 7.

Inflation valve

A specific valve, with a valve and seat made of oil-resistant rubber, is required; the text insists: "Under no circumstances should this valve body be replaced by that of an ordinary valve" p. 7.

Load adjustment and topping up

Adjustment is carried out by visual reference: a "red line" drawn on the lower tubes must coincide with the bottom of the skirts when the passenger is in place p. 7-8. The detailed procedure for inflation/deflation using a pump is provided p. 8. Topping up, necessary only in case of persistent bottoming, requires a 25 mm block under the engine crankcase before filling with oil p. 8.

Recommended oils

The text specifies that these oils with stable temperature viscosity make oil replacement unnecessary "for the entire life of the machine" p. 8.

Context

The Panther model 100 is a British motorcycle manufactured by Phelon & Moore, a company known for its large inclined single-cylinder motorcycles. The Dowty Oleomatic fork, which appeared in the late 1940s, is one of the first telescopic forks to combine a pneumatic spring and hydraulic damping, an architecture then competing with classic metal spring forks.

This solution belongs to a period when several British and French manufacturers were exploring air or oil suspensions, in parallel with the research conducted at Citroën on hydropneumatic suspension — research already initiated by this date by Paul Magès, who joined the design office in 1939-1940 and authored hydropneumatic suspension plans as early as 17 February 1944 (Hydropneumatic suspension plans with differential interaction (17 February 1944)), with the first tests on the 2 CV having taken place in May-July 1946 (Notebook of the first 2 CV hydropneumatic suspension tests (May-July 1946)).

Archivist's perspective

This document appears to be a technical monitoring piece commissioned for Paul Magès: a foreign manual translated and transmitted for comparison with internal developments on the Citroën hydropneumatic suspension, then in full swing since the 1944 plans and the 1946 2 CV tests. The air/oil principle of the Dowty fork, described on p. 7, presents obvious functional similarities with Magès' work on systems combining gas and liquid.

It seems that this type of documentation fueled reflection on shock absorbers and suitable oils, as evidenced by the possible link with test no. 219.084 on Vacuum 45 and VP 100 oils, conducted in the same year 1949, where the question of temperature viscosity stability — central to this manual p. 8 — also arises.

The annotation "Monsieur Magès" p. 7 confirms that this document did indeed circulate in his office — Magès, then a technical writer and later deputy head of Super-Control at Citroën (Draft letter from Paul Magès to Mr. Sarre and interview plan of 11 May 1969) — no doubt as monitoring documentation rather than a direct source of invention.