Stanesby, “Railways”, part 5

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Gauge, Width between Tracks, &c.—The gauge or width between the two rails forming a track is one of the points in railway practice which has excited much discussion. On the old railways four feet was not an uncommon width, but many lines were less. Some of the colliery railways in Northumberland are four feet eight inches and a half, and from these the Stockton and Darlington, Liverpool and Manchester, and other lines, took their gauge. The advantage of uniformity has led most companies to follow this example, and for a time it was rendered imperative by Parliament, but at present no standard is fixed by the legislature. The ordinary width being considered inconveniently limited, Brunel fixed upon seven feet as the gauge of the Great Western and its tributary lines. Much opposition has been made to this bold step, mainly on account of the inconvenience of not being able to connect with other lines, which is in some degree obviated by laying an inner rail for the use of narrow carriages on any portion of railway passed over by two companies whose lines are laid of different widths. The superiority of this enlarged gauge is apparent in the increased power and speed of the engines, and the stability and convenience of the carriages; but many who admit the inconvenience of the narrow gauge consider seven feet to be beyond the most advantageous width. Six feet two inches has been recommended by the Irish Railway Commissioners. Six feet is the width of some of the continental lines. The Dundee and Arbroath, and Arbroath and Forfar railways are five feet six inches; and the Eastern Counties, and London and Blackwall, about five feet. The ordinary standard in North America is four feet eight inches and a half, having been copied from the Liverpool line. Several recent lines in this country have been made four feet nine inches, to allow rather more play to the flanges than the common width. One of the great recommendations of a wide gauge is the scope that it allows for improvements in machinery; a circumstance evidently of much importance when it is considered that the experience of ten years only has led to the enlargement of locomotive engines to so great a degree that their weight and cost are now nearly treble what they were when the Liverpool and Manchester Railway was opened.

The width between the two tracks is a matter of much less consequence. On the Liverpool and Manchester line it is four feet eight inches and a half. The London and Birmingham Railway, and many others, have a space of six feet, which allows loads of ten feet wide to be carried with safety. The same intermediate space on the Great Western Railway, in consequence of the increased gauge, allows a maximum load of twelve feet. The space which is necessary outside the tracks is dependent on the width of load provided for, and seldom exceeds four feet, except on embankments, where a little more is sometimes allowed, so that, in case of carriages getting off the track, there may be width for them to run on the ballasting until the inner wheels come in contact with the outer rail, which will in most cases prevent the train from overturning.

In laying the rails, allowance should be made for the effect of temperature, which will cause a difference of length in a fifteen-feet rail, exposed to a range of 76° Fahrenheit, of about 1/11th of an inch. The insertion of a piece of wood between the ends of two rails is an ingenious mode of avoiding concussion from the opening of the joints from this cause, for the wood expands as the iron contracts.

In the description of fig. 8 it is stated that the wheel-tires are made slightly conical, in order that the flanges may come in contact with the rails as little as possible. In ordinary wheels three inches and a half wide, the inclination of the tire is about 1 in 7, the diameter at the outside being an inch less than close to the flange. The wheels are so fixed that, when running straight, the flanges are about an inch from the rails. When the rails are fixed vertically, the line of contact between them and the wheels is, in consequence of their conical shape, so narrow as to cause considerable wear. Most engineers, therefore, give a slight inclination inwards to the rails, that they may present a greater surface to the wheels, although the friction is increased by the rubbing of the conical tire. This inclination is stated by Lecount to be 3/8th of an inch in eleven inches, or about 1 in 29, on the Birmingham Railway. On the Great Western it is 1 in 20.

In running on a straight road, the conical tires keep the carriage in the true line of direction, because any deviation from it causes the wheels on one side to roll on an increased, and those on the other on a reduced periphery—an irregularity which immediately checks itself. But on a curved track the centrifugal force overcomes that of gravity so far as to cause the flange on the outer side of the curve to approach the rail, and consequently the opposite wheels to roll on unequal peripheries, thereby avoiding part of the friction consequent on the wheels (which are fixed to the axle) being compelled to revolve with equal velocity, though the outer one has to pass over a greater length of rail than the other. To prevent unnecessary friction between the flange and the rail, it is usual to lay the outer rail on curves rather higher than the inner one, that the opposing forces may be so balanced as to cause average loads moving at the medium speed employed to pass round the curve without the flanges on either side coming in contact with the rails, and with the wheels rolling on diameters unequal in a degree corresponding with the radius of the curve. A pair of ordinary coned wheels, three feet diameter, might run in a circle of only 565 feet radius without the flanges touching; and as no curves of such small radius are admitted on a main line of railway, it is evident that, in theory, nothing more than an accurate adjustment of the outer rail with reference to the speed of transit is necessary to enable trains to pass along any ordinary railway without the flanges being called into action, unless by accidental circumstances. The following is selected from a much more extensive table by the Chevalier de Pambour, to show the proper elevation of the outer rail on a line of four feet eight inches and a half gauge, under given circumstances. The calculations are suited to the use of three-feet wheels, coned as above described:—

Stations, Passing-Places, &c.—As a general rule it is best to have the stations and depots as nearly as possible on a level with the surrounding land, both to save expense in construction, and to avoid inconvenience in the transfer of goods from the railway to common road vehicles. Wherever a higher or {76} lower level is unavoidable, approaches of moderate inclination should be made for carriages. The station of the Brandling Junction Railway at Gateshead is of novel and ingenious design. The line is on a viaduct, the arches of which are prolonged so as to support a level of considerable extent. A branch track at right angles with the main line is laid along the crown of each arch, by which waggons are conducted to platforms that form part of the railway level, but may be lowered, with waggons upon them, to that of the warehouses, which are underneath the arches, and communicate with the natural surface. Stations vary in character, from mere booking-offices, where passengers and parcels wait to be taken up by passing trains, to great establishments covering several acres of ground, with separate offices for passengers, parcels, and heavy goods; facilities for transferring carriages, horses, and cattle to or from the railway; extensive sheds for trains to stand under; repairing-shops for engines and carriages; and many other necessary erections. The stations of the London and Birmingham Railway at Euston Square, Camden Town, and Birmingham, extend collectively over a space of about fifty acres; besides which the company have establishments of great magnitude at Wolverton, Rugby, and Hampton, and several of smaller dimensions.

Contrivances for conducting engines and carriages from one track to another are required in a variety of situations. They generally consist of switches and turn-tables. Switches are moveable rails placed at the point where two tracks fall into one, and they are capable of adjustment so as to guide vehicles from the single track into either of the two, or from either of the two into the single track. In the old railways this was effected by short tongues of iron, moved by hand; but it is necessary where locomotives are used to have the transition from one track into the other as gradual and free from concussion as possible, and therefore the moveable bars are made of considerable length, seldom less than eight or ten feet, and, on the Great Western Railway, fifteen feet. Fig. 16 represents a switch formed on the model of the old contrivance of moveable tongues. The black lines are the fixed rails which at A form one track, and at B two tracks. The double line from c to d indicates the switch, which is pivoted at d, and tapered to a point at the other end. From its under edge proceeds the bar e, which passes under the rail to a lever or eccentric placed in a convenient situation for being moved by an attendant. In the position represented by the engraving, the switch would conduct a train along the upper track from A to B, because free passage is allowed for the flange between the switch and the upper rail, while the inside of the flange pressing against the switch c d prevents the flange on the opposite side of the track from quitting the straight course. If, however, by turning the lever or eccentric connected with e, the switch be moved in the direction indicated by the arrow, the case will be reversed: the switch being brought into contact with the rail at c, the flange will be compelled to move along its inner side, and consequently that on the opposite side of the track will pass along the opening by the side of the lower rail. f f are fixed bars called guard-rails, which prevent the switch moving too far, and protect the narrow ends of the switch and rail from injury. Switches on this principle sometimes connect three tracks with one, by two moveable pieces, of which an example is in use at the Great Western Railway station at Paddington. It is a great recommendation of this kind of switch, that, unless the moveable rails are fixed in a wrong direction, a train can never get off the track, as the momentum enables the flange to open the switch and pass through. In some situations a spring or weight is applied with great advantage, to hold the switch in the position most commonly required, and return it to that position immediately after being acted upon. The double rail represented in fig. 17 is a contrivance much used as a switch, and affords a very smooth transition from one track to another. In this the two tracks terminate in two double rails, c d and c′ d′, pivoted at d d′, and shifted as occasion requires in a similar manner to the former, the rails being connected by cross-pieces, so that the whole are moved simultaneously. In the present position of the apparatus the lower track is that connected with the single line; but by moving the switches in the direction of the arrow, the lower track would be disconnected, and the upper one made to join the track at A. These switches, like those previously described, are occasionally used treble; and they are sometimes made to unite two tracks in each direction.

Fig. 18 is designed to illustrate the manner in which switches are applied at passing-places and crossings. a b is a passing-place for a single line of railway where the traffic is about equal in each direction. It should be observed that the angles in this figure are, to save room, made more abrupt than they should be on a public railway, where angles of more than 2° or 2½° are considered objectionable. In this arrangement every train from a to b takes the lower track, and those from b to a the upper one. Switches of the kind first described are used at the points a and b, and, as they have always to be passed through in the same order, they are made self-acting, that at a being held by springs in the position for guiding carriages on to the lower track, and being opened by the flanges of the engine wheels for the passage of the trains in the contrary direction, while that at b in like manner conducts trains passing towards a into the upper track. This kind of passing-place has been successfully used on the Newcastle and Carlisle, and other railways. c d represents another arrangement for the same purpose, which may have the same kind of switch, but is generally used without any, the impetus of the train always keeping it to the straight track, while if suitable openings be made for the flanges it cannot escape from the rails in running from the double into the single part. e f shows the arrangement of a crossing on a railway with two tracks, switches being placed at both junctions, which, being only for occasional use, are worked by band, men being stationed at g g for the purpose. The risk of accident, arising from the neglect or misplacing of the switches, is somewhat reduced by affixing a signal-apparatus to them; which, by {77} displaying a coloured disc, or lamp, to the engine-driver, indicates their position as he approaches.

At the points where two rails cross, grooves are formed to allow the flanges to pass; and to check any tendency in the wheels to escape from the rails, guard-rails, as indicated in fig. 18, are fixed within the track, to guide the inside of the flanges.

Turn-tables are useful in transferring single carriages from one track to another, which they do in much less space than any arrangement of crossings and switches. They consist of circular platforms of iron and wood, fixed on a level with the tracks, and mounted on friction-wheels, so as to turn on their centres with great facility. Fig. 19 represents two turn-tables so laid as to communicate with one another. Four rails are laid across each, and made to tally precisely with those of the track. If it be desired to transfer a carriage from the track a to that marked b, it is rolled on the turn-table at d, and then, the catches which held the turn table steady being released, the platform, with the carriage upon it, is turned a quarter round. The carriage is then rolled on the turn-table e, and being again turned a quarter of a circle, is in a right position for running on the track b. Carriages may in like manner be transferred to a cross-track, as at c. Locomotive-engine houses are frequently made octagonal, with eight radiating tracks, the engines being moved to or from any of them, by means of a large turn-table in the centre.