Page:The Working and Management of an English Railway.djvu/214

178 When a train is intended to pass, the hook is lowered by the lever, but if it is desired to stop a waggon, the hook is raised by the lever, and catches the axle of the waggon, and the heavy cable attached to the hook, being drawn out of the tank, by its weight, when dragged over the ballast, soon stops the runaway. During the last twelve years this apparatus has come into use 135 times, and in no case has it failed to stop the waggons, without injury either to them or to their loads, or to the apparatus itself. At the present time there are six of these chain drags in use at Edge Hill, the cables varying in weight from 86 cwt. to 109 cwt.

The gradient of these sidings varies, according to requirements, from 1 in 60 to 1 in 115. For instance, through points and crossings, and round the standard curve of seven chains radius, the gradient is from 1 in 70 to 1 in 100, but on straight lines, where waggons have to. start singly, and enter curves, as, for example, at (1), the lower end of the upper reception lines; (2) the lower end of the sorting sidings ; and (3) the lower end of each siding in the gridirons, the gradient is one in 60. Again, on straight lines, where many waggons move together, and good "runners" compensate for bad, the gradient varies from 1 in 100 to 1 in 115. All the curves are of the same radius (seven chains), so that a shunter, in determining the speed necessary for any particular truck, may concentrate his attention upon it, knowing that the resistance of every curve it encounters will be the same. Speaking generally, the gradients are so regulated that the greatest momentum is imparted where the trucks are required to start quickly, and where there is the greatest amount of resistance to be overcome.