Publication: The Electrical Engineer
New York, NY, United States
"METALLIC" INSULATORS FOR THIRD RAIL AND
THE third rail is rapidly coming to the front as a working conductor for electric railroads, and bids fair in time to supplant entirely the overhead trolley for suburban and interurban traffic. Placed so close to the ground the rail is specially subject to insulating strains, while at the same time it is exposed to mechanical strains which overhead conductors are not called upon to stand. A third rail insulator therefor for good service requires an insulation strong both electrically and mechanically.
To meet these requirements the Metallic Insulation Company, of New Brunswick, N. J., has just brought out a third rail insulator, shown in two views in Figs. 1 and 2. This insulator of iron consists of the base, which is attached to the cross-tie and of a petticoat top, to which the conducting rail is fastened by bolts.
[insert: image_11671;FIGS. 1, 2 AND 3. — "METALLIC" INSULATORS FOR THIRD RAIL AND CONDUIT CONDUCTORS.]
The insulator is coated completely with the "metallic" insulation, so-called because it has all the strain-resisting properties of metal, accompanied by high insulating qualities. The insulation, in fact, is an enamel applied at a high heat; it cannot be broken off with the blow of a hammer, forming, as it does, a perfect union with the iron to which it is applied.
These insulators will bear a deflective working strain of more than 10,000 pounds, with compressive and tensile strains in proportion. The insulating material is free from all vegetable material, is impervious to moisture, to all alkalies, and to most uestruetive acids, so that it is specially adapted to railroad work.
To meet the demand for an insulator for railway conduit work the Metallic Insulation Company have designed the type shown in Fig. 3. This is specially adapted to the present general type of conduit railway construction, and the insulators possess the same general properties of the third-rail insulator described above.