Railway Construction

by William Hemingway Mills

It was soon observed that sand and fine particles of gravel from the ballast worked their way into the lower part of the recess, and became so compact as to prevent the wooden wedges working further down to increase their grip on the rail. Even when the recess was kept free and clear of sand, the enormous pressure exerted by the wooden wedges broke the iron at A,

although an extra thickness was given to that part of the section. The cast-iron was exposed to the greatest strain at the point where it was the least capable of offering resistance.

Much ingenuity was displayed in many of the patterns brought forward, but in dealing with a hard unyielding material like cast-iron, it is difficult, if not impossible, to impart any soft, elastic effect; and the different systems of cast-iron sleepers failed to become popular on our home railways, on account of the noise and vibration when trains passed over them. Another objection was the great multiplicity of parts required in many of the types, and the constant and severe strain produced on the fastenings on the passing of every wheel. The bolts might be made tight at first, but the incessant shaking would work them loose, the threads became stripped, and the rails ceased to be held in a proper and secure position.

The cast-iron sleeper road was considered unsuitable for the heavy and fast traffic of our home lines, and was ultimately all taken up and replaced with wooden transverse sleepers. At the same time, there is no doubt that cast-iron sleepers have been of great value in India and tropical climates, where timber sleepers were not only scarce, but perish very rapidly. Very large numbers of them have been laid down abroad of patterns very similar to those shown in [Figs. 309, 310, and 311], and have done good service for many years. They are not affected by rain or heat, but, unfortunately, being castings, are liable to considerable annual loss from breakage.

Improvements in plate-rolling machinery, and in appliances for bending and stamping wrought-iron, have materially assisted in developing the introduction of wrought-iron and steel sleepers. Cast-iron and wrought-iron are, in the abstract, hard and non-elastic as compared with wood; but whereas cast-iron can only be made into fixed, unyielding shapes, wrought-iron and steel can be worked into forms that possess a certain spring-like effect, which not only enables them almost entirely to resist fracture, but also imparts a measure of elasticity to the permanent way.

The simplest form of wrought-iron sleeper would be a plain, flat plate, to which the chair, or rail-bracket, would be attached; but as this form would have bearing surface only, without any lateral hold on the ballast to keep the rails to line, it could not be adopted.

During the last few years very many types of wrought-iron and steel sleepers have been introduced, and nearly all of them of the transverse-sleeper pattern, formed out of rolled plates; the sides, and in some cases the ends also, are bent, or turned down to obtain a hold in the ballast. Where bull-head or double-head rails are used, cast-iron chairs, or wrought-iron bracket chairs, are bolted, or otherwise secured to the upper surface of the sleeper, a layer of felt, tarred paper, or other soft material being placed between the two metal surfaces. Where flange rails are used, they are fastened to the sleepers either by bolts, clamps, or clips raised up out of the iron sleeper, and bent over to hold tightening keys. Rolled transverse sleepers can readily be bent, or set in the centre to give the proper cant at the rail-seat; and in some types the sleepers are pressed in the machines, so as to be narrower towards the centre, and with a deeper turnover, to obtain increased stiffness.

In [Figs. 314 to 319] are shown some of the patterns which have been brought out, laid down in actual practice, and in use at the present time.

From the fact that wrought-iron and steel sleepers have been laid down in so many places where cast-iron sleepers were discarded or refused a trial, it is evident that the former are considered to have qualities which the latter did not possess. Rolled iron or steel sleepers are coming more and more into use, especially on foreign or colonial railways. So long, however, as good, well-creosoted timber sleepers can be obtained for our home railways at prices from 3s. 8d. to 4s. 8d. each, and last from fourteen to twenty years, there is little probability that they will be supplanted by iron sleepers at double the cost. But abroad the circumstances of cost and durability are different, and there the rolled iron or steel sleepers, which will outlive two or three sets of wooden ones, must claim advantages which cannot be overlooked. The difficulty will be in the fastenings, the mode of attaching the rails to the sleepers. The constant hammering of metal upon metal, resulting from the vibrations of every passing load, will quickly wear or loosen bolts, rivets, or wedges, and the fastenings which will prove the most efficient will be those that are the simplest and most readily adjusted.

Fastenings.—Figs. 320 to 335 illustrate some types of the principal fastenings used in connection with the chair road, and with flat-bottomed or flange rails.