An Important Feature of the Permanent Way
AN EXPRESS OF THE LNER is seen running at speed, headed by “Pacific” locomotive No. 2543 “Melton”. In the foreground is seen a “single slip” -
BY far the most costly part of the permanent way to construct and to keep in repair is the switch and crossing work. In the chapter, “The Permanent Way”, beginning on page 331, attention is given to railway track in general, and to the problems
which face the permanent-
In the above chapter emphasis is laid on the punishment to which railway track is subjected as the heavy weight of locomotives, coaches, and wagons rolls over it, sometimes at very high speeds. To the line-
First of all it is necessary to study the details of an ordinary “turn-
The essentials of a switch are two “tongue-
and each switch thus requires two stock-
rolling stock resting on the wheels, when the train, perhaps, is travelling very fast.
A variant of the knife-
A reverse bend, or “joggle”, has to be made in the stock-
two sets of switches and two common or acute rail crossings. Cross-
“trailing”, as are also siding connexions, in order to reduce to a minimum the number of facing
switches in the running lines.
The lateral movement of the tongue, from the closed to the open position, is usually from four to five inches. A special type of chair, known as a “slide chair”, is used throughout the movable part of the switch. That is to say, a chair with a jaw on one side only, to which the stock-
The heel is the point at which the gap between the stock-
wheels exert a strong outward thrust as they are diverted from their straight path by the tongue, and were it not thus held rigid throughout they might force the tongue out of gauge, and cause a derailment.
Connecting the two tongues together, so that they move in unison, are the stretcher-
It is vitally important that the switch tongue, when in the closed position, shall have moved fully home, as any projection of the tongue away from the stock-
Another important precaution is that of preventing the movement by a signal-
of the same coach. In consequence, the front bogie would take one track, and the rear bogie the other, and a disastrous
derailment would result.
At important facing switches in running roads “locking-
When a switch movement has to be made, the switch must first be unlocked. By pulling over the appropriate lever the signalman causes the rocker-
IN OLD OAK COMMON YARD on the Great Western Railway, near Paddington. To the right of the cabin is a single slip connexion, and behind that a single-
Now the rising of the locking-
Fouling bars are somewhat similar in construction, but serve a different purpose. They are of the same length, but are carried on spring brackets, and at such a height that they are depressed on their springs when a train is standing on or moving over them. When depressed, the bar completes an electric circuit, and the occupation of this section of line is thus electrically notified in the signal-
Reverting for a moment to switches, provided there is ample room available, the length of a switch is governed by the speeds which are to be run over the diverging line. The higher the speed, the longer the switch; and the longest switches are those laid in at junctions between two main lines, where more or less equal speeds are desired over either track. The chief difficulty is that of arranging for the necessary super-
As less in the matter of precautionary measures is needed with a trailing than with a facing switch, in running roads trailing switches are laid in wherever possible. Cross-
A STRIKING YARD LAY-
In the past, three-
because of the thinness of the inner set of tongues, and the general complexity of construction as compared with a pair of ordinary switches. Given adequate space, the permanent-
Another type of switch which may have puzzled some readers is a single tongue, set in one side only of a straight track -
RELAYING A “SCISSORS CROSSING”. This unit of track, weighing 25 tons, and 100 ft in length, has been assembled at the side of the main line, and is being moved into position on ball-
Proceeding from the heel of the switch, the outer rail of the diverging line has next to cross the inner rail of the straight line. A rail crossing of this description is known as a “common” or an “acute” crossing. Study of the photographs reproduced in this chapter will show how both running rails are bent outwards to form “wings”, enclosing the “nose” of the crossing, which
consists of two rails secured together, and planed down to a sharp point or nose. It is the straight rail, known as the “point-
Strong double chairs hold the rails through the crossing, and from the nose to the end of the wings each crossing chair, which is of considerable length, must hold four rails. In addition, cast iron blocks, accurately shaped, are fitted between the wings and the point and splice-
A SIDE VIEW of the movable diamond crossings at Old Oak Common.
The nose chair of the modern crossing is of a built-
Standard common crossings are made in all angles from 1 in 4 up to 1 in 12, together with half-
MOVABLE DIAMOND CROSSINGS provide a solid path for the wheels, as shown by the right-
This leads us to the consideration of complete crossings of one track over another, which are known as “diamond” crossings, from the diamond shape that is enclosed by the four rails. One diamond crossing occurs at every double line railway junction. At the extreme ends of such diamonds two common or acute crossings are needed; but at the centre there are two crossings of a different type, known as “angle” or “obtuse” crossings.
Several diamonds are seen in the photographs reproduced, from which the characteristic form of construction will be noted. There are in each obtuse crossing one wing rail, bent to an obtuse angle, and run over throughout its length; two point-
coming up to the centre of the crossing, or the “knuckle”. Endeavours are made to keep obtuse crossings to a maximum sharpness of 1 in 8 or 1 in 9, as with leads of 1 in 10 and upwards there is the risk of a wheel-
But any such risk can be overcome by the use of movable diamond crossings, which have the advantage of completely closing up the flange-
A Signal Safeguard
The two point-
such a way that one pair of flange-
are interlocked with the signals, in just the same way as the switches, and there is thus no possibility of a signalman
signalling a train in such a way as to permit it to pass through the closed side of the diamond. The Great Western and
Southern Railways have specialized in this form of junction construction, an example of which, at Old Oak Common West Junction on the Great Western Railway, figures in the illustrations above. Some use is also made by the Southern Railway of spring common crossings, which, similarly, give a solid path for the wheels through the crossing, but this track detail is more common in America than in Great Britain.
When tracks cross one another at about 1 in 8 or 1 in 9, especially in sidings, it is often desired to make connexion between the one track and the other. To do so with a maximum of economy in rails, the connexion is made within the two end crossings of the diamond. Because of the proximity of the rails at the two centre crossings, some very complicated chairs are required. A diamond crossing of this description with single connexion is known as a “single slip”. If a double connexion
is provided -
AMERICAN RAILROAD TRACK built up from flat-
Another complicated form of track construction is the double cross-
The title “double cross-
Whenever possible, track lay-
One of the most remarkable track lay-
Railway before the extension of electric working into that terminus. It was planned as one vast unit, built and assembled in sections in the contractors’ works at Sandiacre, near Nottingham; dismantled and reassembled in a field at New Cross; and finally, after all traffic into and out of Cannon Street had been temporarily stopped, and the old track on the bridge removed, it was laid in position, as shown in the fine photograph shown in the chapter on Electric Power on the Grand Scale.
It might be thought that the construction of crossing work would be simplified if a solid steel casting could be used for the central parts of the crossing. To some extent cast noses have so been used, but there are objections to the practice. Generally, castings have not the same capacity for resisting wear as the rolled rails from which the crossings are normally assembled, and of which the steel structure has been improved by the work done on it in the course of rolling, as described in the chapter From Iron Ore to Steel Rail beginning on page 557. The underlying nature of solid crossings also tends to
cause rough riding of rolling stock, especially when such crossings are traversed at speed. Where steel castings are used in crossing work, it is generally in connexion with flat-
The most successful use of castings has been in difficult and complicated locations, particularly where tracks cross each other at right-
Rails rolled from manganese steel are also used in the manufacture of switches and crossings for locations where the wear is excessively heavy. Another favourite alloy for this purpose is a steel containing 1 per cent of chromium. Heat treatment is also freely employed for the hardening of crossing noses, and rails which have been heat-
COMPLICATED TRACK CONSTRUCTION at Llandudno Junction, Wales, on the LMS Railway. From the right of the picture one track bears left and crosses the double line curving to the right almost at a right-