Technical Notebook No. I of the Association Amicale Citroën on belt transmissions (P. Pusard, January 1937)

In this document

General presentation

This booklet is Technical Notebook No. I of the Association Amicale Citroën, dated January 1937, sold for the price of 1 franc. It reproduces the "calculation notes" supplementing the lecture given by P. Pusard on 16 November 1935 on Belt Transmissions, as well as his eponymous work p. 29.

Choice of thickness and pulley diameter

The document details the rules linking the diameter of the small pulley and belt thickness according to materials: leather (40 to 50 times the thickness), rubber/flexible textile (30 to 35 times), leather on edge (with a correspondence table from I00 to 550 mm), and Texrope V-belts in corded rubber, with normal pulley diameters ranging from I00 to 550 mm depending on the section p. 29.

Arc of contact and minimum surface

The minimum arcs of contact on the small pulley are set (from I20°-I30° for Texrope V-belts to I50°-I60° for leather), with a formula for calculating the arc based on diameters and the center distance p. 29. A formula for minimum contact surface (A = L×l×V/C) is given, with TITAN reference values according to operating conditions, from "Very good" to "Bad" p. 30:

The text also recommends increasing this surface by 5% for the joint and by I0 to I5% in dusty or humid environments p. 30.

Passage frequency and advantages of V-belts

The number of passages per second on the pulleys must be checked to avoid wear-inducing "reptilian motion"; ranges are given by material, from leather (1.4 to 2) to endless Texrope V-belts (5 to I0) p. 30.

Pusard then states the advantages of endless V-belts in industrial use (reduced center distance, direct ratio up to 1 to 10, lower traction between bearings, resistance to humidity, silence, absence of slippage) and specifies that BNA standards only concern automotive fans, not industrial transmissions p. 31.

A table of characteristic results notably cites "2 air compressors (CITROËN)", 2I0 HP, speed of 720 to 2I5 rpm, ratio 3.34, center distance 2 m 480 p. 31.

Add-on rims

The booklet describes add-on rims in thin sheet metal with calibrated V-grooves (patent Boulant), allowing the adaptation of V-belts to existing flywheels, for powers up to 250 HP and up to I5 grooves p. 32. Finally, it refers to Pusard's work published by Goodrich-Colombes in 1935 p. 32.

Context

Paul Pusard was a recognized engineer specializing in belt transmissions in the interwar period; his reference work, published by Goodrich, long served as a technical manual in France. The Association Amicale Citroën distributed this type of technical notebook to its members to popularize general mechanical knowledge useful to the automotive engineering of the time.

V-belts (also called "V-type"), popularized by the Texrope brand, largely replaced flat belts in the industry during the 1930s thanks to their better efficiency and compactness — a context that explains the document's enthusiasm for this type of transmission.

In January 1937, Paul Magès, who joined Citroën in August 1925, had been there for over ten years as a technical writer and then deputy head of the Super-Control (autobiographical notes); this technical notebook of the Association Amicale Citroën falls under the same culture of internal mechanical popularization within the brand as the one in which he was then evolving.

Archivist's perspective

This notebook does not bear Paul Magès's signature, but its presence in his archives suggests a personal or professional interest in mechanical transmission issues, in connection with his activity as a technical writer within the Citroën Super-Control during this period, a few years before he turned to work on suspension and hydraulic systems.

The explicit mention of use for "2 air compressors (CITROËN)" p. 31 shows that this generalist technical document had a direct and concrete resonance in the brand's workshops.

This piece can be compared to the Citroën "Mechanical Manufacturing" Standards, which testify to the same concern for normative rigor in Citroën's industrial practices of the period.