324 MARIENFELDE-ZOSSEN ELECTRIC-RAILWAY TRIALS. 



Prussian railwa3's, consisting of light rails of 33.4 kilograms per 

 meter (67 pounds per 3"ard), placed partly on wooden sleepers and 

 partly on short iron sleepers, the roadbed consisting mainly of inferior 

 material. Though it accordingly was anticipated at the very outset 

 that the existing permanent wa}' would not be sufficiently resistant for 

 maximum speeds as high as 200 kilometers per hour, it was decided 

 to begin the trials without any rebuilding of the track, apart from 

 some immaterial improvements. After the number of sleepers had 

 been somewhat increased, and the roadbed reenforced with consider- 

 able amounts of broken stone, the track stood perfectly well the strain 

 involved by speeds up to 130 kilometers (80.8 miles) per hour. As, 

 however, in connection with the experiments made in the fall of 1901, 

 serious troubles were experienced for the maximum speeds of 140 to 

 160 kilometers per hour, a thorough re))uilding of the track was 

 eventually carried out in the course of the summer of 1902. The new 

 rails have a weight of 42 kilograms per meter (about 84^ pounds per 

 3'ard) and a length of 12 meters, being placed on 18 tir sleepers with 

 hartl-wood pegs; 1.5,X)00 cubic meters broken l)asalt were vised for the 

 roadl)ed. About IT kilometers of the track were fitted with guard 

 rails such as used in connection with ordinary railways on bridges, etc. 

 These g'uard rails, the foot of which is ,^() millimeters distant from the 

 main rail, are fixed on cast-iron ))eds, screwed to every sleeper, this 

 arrangement, in addition to preventing derailments, imparting an 

 extraordinary strength to the whole of the roadbed. (Plate i.) 



The ovL'rhead Ihic. — The arrangement of the overhead line is shown 

 in plates i and ii, the middle of the pole l)eing about 2i meters distant 

 from the middle of the track and the three horizontal wires conduct- 

 ing the 3-phase current being about 1 meter apart. The whole of 

 the line is divided into sections of about 1 kilometer, each of which 

 is provided in the middle with a device for compensating losses in 

 pressure. The neutral point of the S3\stem is connected to the earth 

 and to the rails. The suspension point moves aside somewhat as the 

 collector presses against the horizontal wire, a satisfactory and simul- 

 taneous contact between the three horizontal wires and the contact 

 arcs being thus possible. This is insured l)y having the single parts 

 on the outrigger, intended for carrying the insulators, connected by 

 joints. The horizontal wires have a double insulation against earth, 

 and each insulation separately is susceptible of standing the whole of 

 the maximum pressure of 20,000 volts occurring during the service. 

 The wires have cross sections of 100 square millimeters (0.155 square 

 inch) each, the tension between each two wires varying between 10,000 

 and 12,000 volts. Hard copper wire with a breaking strength as high 

 as 38 kilograms per square millimeter and a conductivity more than 

 97 per cent of that of chemically pure copper is used; lightning 

 arresters are provided, as well as safety' devices in case of a fracture 

 by which the wire is automatically earthed. 



