290 RAILWAY CONSTRUCTION. 



To the ends of the girders are attached large roller wheels which 

 travel round a solid iron or steel roller-path laid down along the 

 circumference. These modern turn-tables are generally worked 

 on the balancing principle, by bringing the engine and tender to 

 a stand in such a position on the rails that the greater portion of 

 the weight is thrown on to the cup-shaped steel centre, so that a 

 small force applied to the long outrigged hand-levers at the ends 

 is sufficient to turn one of the heaviest locomotives. Figs. 441 

 and 442 give sketch plan and section of one of these steel-plate 

 girder turn-tables, which has few parts, and very little to get out 

 of order. The end rollers guide the table when making any 

 portion of a revolution, and carry such part of the weight as 

 may not be taken up by the centre. A recess is shown in side 

 wall to facilitate the inspection of end rollers. In the earlier 

 forms of engine turn-tables, the revolving movement was effected 

 by attaching to the upper portion of the girders a strong winch, 

 which acted upon gearing fixed either to the end rollers, or 

 direct on to a toothed ring forming part of the roller-path. In 

 cases where the engine turn-table was in constant use, as in con- 

 nection with a large running-shed, the winch was sometimes 

 driven by a small steam-engine to expedite the movement. 



The great increase in the lengths and weights of modern 

 locomotives has necessitated the removal of many of the old 

 small turn-tables, and replacing them with others of 45 or 50 feet, 

 or more, in diameter. 



An engine turn-table is a costly item in railway requirements, 

 not only in the girder- work, but in the large amount of building 

 in the side walls and centre pier, and an effort is always made to 

 avoid the outlay unless the table can be placed where it may be 

 of permanent use. In the construction of foreign railways, and 

 in our colonies, where the lines are opened in sections as the 

 work goes forward, the temporary arrangement shown in Fig. 

 443 is frequently used instead of an engine turn-table. The 

 sketch will almost explain itself. On the main line, A, B, C, D, 

 switches are placed at B and C, from which turn out curved 

 lines, uniting at the switches E. An engine proceeding from A, 

 and passing round the curve B, E, G, then round curve G, E,C, and 

 back along main line, D,C, B, A, will be turned round as efficiently 

 as on a turn-table. The writer has used this arrangement abroad 

 with great advantage. It involves very little work or expense 

 beyond laying down the permanent way, and so soon as the 



