. La ferrovia e la rivista di ingegneria. Cheapness nel primo costo. Per il servizio comunale a bassa tensione m Parigi, si utilizzano conduit di calcestruzzo in cui sono legnature fisse che portano supporti di ferro. Queste cornamesare di legno circa 1.50 m. (4.93 poll.) a una distanza di. Il pezzo superiore del telaio di legno è rrtopable e può essere messo giù rapidamente.i cavi impiegati sono ben coperti con gomma. Il sistema è mostrato in fig. 9. Per il sistema ad alta tensione si utilizzano i conduttori di nome, ma i cavi poggiano in supporti legnosi fi.xed nel condotto. In Germania il sistema Siemens, illustrato nelle figure ID e II, è

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. The railroad and engineering journal . cheapness in first cost. For the municipal service at low tension m Paris, con-duits of concrete are used in which are fixed woodenframes carrying supports of iron. These wooden framesare about 1.50 m. (4.93 in.) apart. The top piece of thewooden frame is rrtovable, and can be put down rapidly.The cables employed are well covered with rubber. Thissystem is shown in fig. 9. For the high-tension system thesame conduits are used, but the cables rest in woodenholders fi.xed in the conduit. In Germany the Siemens System, which is shown in figs.ID and II, is used almost exclusively. The copper cablesare covered with a thick coating of jute saturated withbitumen and rendered flexible by the addition of heavy oil.The cable is then covered by a lead pipe, then by anotherlayer of jute and by two layers of wire rolled or wrappedone over the other in the same direction, the outer onecovering the joints of the inner, and finally by a glazingwhich^is intended to preserve the wire. These cables are. placed directly in the ground, and are joined by junctionboxes shown in figs. 10 and 11. The connection havingbeen made, the junction box is filled with melted tar andthe opening is then closed by a cover screwed on. ^ The principal system employed in London is the Cramp-ton plan. In this the conductors used are of a square sec-lion, presenting much stiffness, so that the supports can beplaced a long distance apart. They are carried by insula-tors of glass, which are joined to others fixed upon trans-verse girders by light bars. At intervals man-holes per-

Parole chiave associate all'immagine

• bookcentury1800
• bookdecade1880
• booksubjectrailroa
• bookyear1887