The physical properties of lead cable-sheaths

The paper discusses some of the troubles that may arise in the practical use of lead cable-sheaths owing to physical weaknesses, and it shows how these weaknesses are connected with the inherent grain structure in the metal and the stream-line structure due to the extrusion process. In the early part of the paper existing metallurgical knowledge is reviewed for the benefit of electrical engineers, and illustrations are given from the authors´ own investigations into the crystal structure of cable sheaths. Various factors involved in the much discussed disintegration by vibration are examined, and the improvement of pure lead by the employment of alloying metals is treated both theoretically and practically. Special apparatus for the vibration tests is described, and the paper closes with a study of the ¿weld¿ and a description of a new type of cable press which produces a cable sheath that is weldless. The investigation has been carried out at intervals over the past 7 years in the Research Laboratories of Messrs. W. T. Henley´s Telegraph Works Co., to whom the authors are indebted for permission to publish the results.