Railway Terminologies

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SLEEPER A railroad tie, cross tie, or railway sleeper is a rectangular object used as a base for railroad tracks. Sleepers are members generally laid transverse to the rails, on which the rails are supported and fixed, to transfer the loads from rails to the ballast and sub grade below, and to hold the rails to the correct gauge. Traditionally, ties have been made of wood, but concrete is now widely used, Steel ties and plastic composite ties are currently used as well, however far less than wood or concrete ties. As of January 2008, the approximate market share, in North America, for traditional wood ties was 91.5%, whereas the approximate combined market share for (all) concrete, steel, azobe (exotic hardwood) and plastic composite ties was 8.5%. (source: A & K Railroad Material co.) Ties are normally laid on top of track ballast, which supports and holds them in place, and provides drainage and flexibility. Heavy crushed stone is the normal material for the ballast, but on lines with lower speeds and weight, sand, gravel, and even ash from the fires of coal-fired steam locomotives have been used. 1

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Wooden Sleeper Timber ties are usually of a variety of hardwoods, oak being a particularly popular material. Some lines use softwoods, sometimes due to material necessity; while they have the advantage of accepting treatment more readily, they are more susceptible to wear. They are often heavily creosoted or, less often, treated with other preservatives, although some timbers (such as sal) are durable enough that they can be used untreated. The main problem with wood is its tendency to rot, particularly near the points where they are fastened to the rails. The timber industry has responded to decreased use of timber by promoting its advantages; wooden ties still dominate the North American market.

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Concrete Sleeper Concrete ties have become more common mainly due to greater economy and better support of the rails under heavy traffic. In the early period railway history, wood was the only material used for making ties in Europe. Even in those days, occasional shortages and increasing cost of wood posed problems. This induced engineers to seek alternatives to wooden ties. As concrete technology developed in the 19th century, concrete established its place as a versatile building material and could be adapted to meet the requirements of railway industry. In 1877, Mr. Monnier, a French gardener and inventor of reinforced concrete, suggested that cement concrete could be used for making ties for railway track. Monnier designed a tie and obtained 3

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a patent for it, but it was not successful. Designs were further developed and the railways of Austria and Italy produced the first concrete ties around the turn of the 20th century. This was closely followed by other European railways.

Major progress could not be achieved until World War II, when the timbers used for ties was extremely scarce due to material shortages. Due to research carried out on French and other European railways, the modern concrete tie was developed. Heavier rail sections and long welded rails were also being produced, requiring higher quality ties. These conditions spurred the development of concrete ties in France, Germany and Britain, where the technology was perfected. Toward the end of the 1990s, the Long Island Rail Road, followed by Amtrak, began rehabilitation of their lines in the New York metropolitan area by installing steel-reinforced concrete ties, updating some of the busiest rail lines in North America .

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Steel Sleeper Steel ties, which are relatively light in weight, are sometimes used for sidings and temporary tracks. They have the advantages of being relatively free from decay and attack from insects, as well as providing excellent gauge restraint, but are prone to rust and wear at the rail seat; they also require frequent replacement and tightening of fastenings. They are generally unsuited to railway lines carrying vehicles traveling at over 60 mph (100 km/h) because they provide no damping, all force being transmitted to the underlying track ballast. Prefabricated, all-metal "Jubilee" track, which was developed in the late nineteenth century for use in quarries and the like and saw some use in major civil engineering projects, is one example of steel ties in use. 5

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Standard gauge The standard gauge of 1,435 mm (4 ft 8½ in) was chosen for the first main-line railway, the Liverpool and Manchester Railway (L&MR), by the British engineer George Stephenson; however, the de facto standard for the colliery railways where Stephenson had worked was 4 ft 8 in. Whatever the origin of the gauge it seemed to be a satisfactory choice: not too narrow and not too wide. Brunel on the Great Western Railway chose the broader gauge of 2,140 mm (7 ft 0¼ in) partly because it offered greater stability and capacity at high speed, but also because the Stephenson gauge was not scientifically selected. The Eastern Counties Railway chose five-foot gauge, but soon realized that lack of compatibility was a mistake and changed to Stephenson's gauge. 6

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The conflict between Brunel and Stephenson is often referred to as the Gauge War. In 1845 a United Kingdom of Great Britain and Ireland Royal Commission recommended adoption of 1,435 mm (4 ft 8½ in) as standard gauge in Great Britain; and in Ireland a standard gauge of 5 ft 3 in (1,600 mm). The following year the Parliament of the United Kingdom passed the Gauge Act, which required that new railways use the standard gauge. Except for the Great Western Railway's broad gauge, few main-line railways in Great Britain used a different gauge. The last Great Western line was finally converted to standard gauge in 1892.

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TRACK BALLAST Track ballast forms the track bed upon which railroad ties (US) or railway sleepers (UK) are laid. It is packed between, below, and around the ties. It is used to facilitate drainage of water, to distribute the load from the railroad ties, and also to keep down vegetation that might interfere with the track structure. This also serves to hold the track in place as the trains roll by. It is typically made of crushed stone, although ballast has sometimes consisted of other, less suitable materials. The term "ballast" comes from a marine shipping term for the stones used to weigh down a ship.

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Material properties A good ballast should be strong, hard-wearing, stable, drainable, easy to clean, workable, resistant to deformation, easily available, and reasonably cheap to purchase. Early railway engineers did not understand the importance of quality track ballast; they would use cheap and easily-available materials such as ashes, chalk, clay, earth, and even cinders from locomotive fireboxes. It was soon clear that good-quality ballast made of rock was necessary if there was to be a good foundation and adequate drainage. Good quality track ballast is made of crushed natural rock with particles between 28mm and 50mm in diameter; a high proportion of particles finer than this will reduce its drainage properties, and a high proportion of larger particles result in the load on the ties being distributed improperly. Angular stones are preferable to naturally rounded ones, as these interlock with each other, inhibiting track movement. Soft materials such as 9

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limestone are not particularly suitable, as they tend to degrade under load when wet, causing deterioration of the line; granite, although expensive, is one of the best materials in this regard. In the early days of railroads in the United States, much material for ballast came from rock found in the local area. In the Midwest, for example, much use was made of quartzite, while states in the southeast, such as Florida, made use of limestone. One specific type of quartzite used in the Midwest earned the name "Pink Lady" due to its color; in other areas, the ballast can be a mix of light and dark colors called "Salt and Pepper". Construction The thickness of a layer of track ballast depends on the size and spacing of the ties, the amount of traffic expected on the line, and various other factors. Track ballast should never be laid down less than 150 mm (6 inches) thick; high-speed railway lines may require ballast up to half a metre (20 inches) thick. An insufficient depth of ballast overloads the underlying soil; in the worst cases, this can cause the track to sink. If the ballast is less than 300 mm (12 inches) thick, this can lead to vibrations, which can damage 10

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nearby structures (though increasing the depth beyond this has no measurable effect). Track ballast typically sits on a layer of sub-ballast; the latter is typically made of small crushed stones. It gives a solid support for the top ballast, and seals out water from the underlying ground. Sometimes, an elastic mat is placed under the ballast layer as well; this can allow for significant reductions in vibration. It is essential for ballast to be piled as high as the ties, and for a substantial "shoulder" to be placed at their ends; the latter being especially important, since this ballast shoulder is, for the most part, the only thing restraining lateral movement of the track. The ballast shoulder should be at least 150 mm (6 inches) wide under any circumstances, and may be as large as 450 mm (18 inches).

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Maintenance If ballast is badly fouled, the clogging will reduce its ability to drain properly; this, in turn, causes more debris to be sucked up from the sub-ballast, causing more fouling. Therefore, keeping the ballast clean is essential. It is not always necessary to replace the ballast if it is fouled, nor must all the ballast be removed if it is to be cleaned. Removing and cleaning the ballast from the shoulder is often sufficient, if shoulder ballast is removed to the correct depth. While this job was historically done by manual labour, this process is now, like many other railway maintenance tasks, a mechanised one, with a chain of specially-designed railroad cars handling the task. One wagon cuts the ballast and passes it via a conveyor belt to a cleaning machine, then the cleaning wagon washes the ballast, and deposits the dirt and ballast into other wagons for re-use or disposal, respectively. Such machines can clean up to two kilometres of ballast in an hour. Cleaning, however, can only be done a certain number of times before the ballast is damaged to the point that it cannot be re12

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used; furthermore, track ballast that is completely fouled cannot be corrected by shoulder cleaning. In such cases, it is necessary to replace the ballast altogether. One method of "replacing" ballast, if necessity demands, is to simply dump fresh ballast on the track, jack the whole track on top of it, and then tamp it down; alternatively, the ballast underneath the track can be removed with an undercutter, which does not require removing or lifting the track. Regular inspection of the ballast shoulder is important; as noted earlier, the lateral stability of the track depends upon the shoulder. The shoulder acquires some amount of stability over time, being compacted by traffic; maintenance tasks such as replacing ties, tamping, and ballast cleaning can upset this stability. After performing these tasks, it is necessary for either trains to run at reduced speed on the repaired routes, or to employ machinery to compact the shoulder again. If the trackbed becomes uneven, it is necessary to pack ballast underneath sunk ties to level the track out again. This is, in the mechanized age, usually done by a ballast tamping machine. A more recent, and probably better, technique is to lift the rails and 13

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ties, and to force stones, smaller than the track ballast particles and all of the same size, into the void. This has the advantage of not disturbing the well-compacted ballast on the trackbed, as tamping is likely to do. This technique is called pneumatic ballast injection (PBI; or, less formally, "stoneblowing"). However, this technique is not as effective with fresh ballast, as the smaller stones tend to move down between the larger pieces of ballast. RAILROAD SWITCH A railroad switch, turnout or [set of] points are a mechanical installation enabling railway trains to be guided from one track to another at a railway junction The switch consists of the pair of linked tapering rails, known as points (switch rails or point blades), lying between the diverging outer rails (the stock rails). These points can be moved laterally into one of two positions so as to determine whether a train coming from the narrow end will be led towards the straight path or towards the diverging path. A train moving from the narrow end towards the point blades is said to be executing a facingpoint movement. 14

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Unless the switch is locked, a train coming from either of the converging directs will pass through the points onto the narrow end, regardless of the position of the points, as the vehicle's wheels will force the points to move. Passage through a switch in this direction is known as a trailing-point movement. A switch generally has a straight "through" track (such as the main-line) and a diverging route. The handedness of the installation is described by the side that the diverging track leaves. Right-hand switches have a diverging path to the right of the straight track, when coming from the narrow end and a lefthanded switch has the diverging track leaving to the opposite side. A straight track is not always present; for example, both tracks may curve, one to the left and one to the right or both tracks may curve, with differing radii, in the same direction.

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Frog (common crossing) The frog (common crossing) refers to the crossing point of two rails. This can be assembled out of several appropriately cut and bent pieces of rail or can be a single casting. A frog forms part of a railroad switch, and is also used in a level junction (flat crossing). The frog is a point of weakness because the wheels are unsupported for a short distance and can inflict wear and damage. There is also a small risk that the wheels may go the wrong way. On lines with heavy and/or high-speed traffic, a swingnose crossing is often used. As the name implies, there is a second set of points located at the frog. This effectively eliminates the gap in 17

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the rail that normally occurs at the frog, so long as trains are moving in the direction to which the switch is aligned. Two switch machines are required to make a movable point frog switch work. This use of the word "frog" derives from the appearance of the triangular assemblage of rails which recalls the frog of a horse's hoof. How To Determine The Number of a Frog The frog number is the ratio of its length (measured on center line of frog) to its width, or the number of inches in length necessary for it to spread one inch in width. For example, a No. 3 frog spreads 1 in 3, a No. 5 spreads 1 in 5, a No. 8 spreads 1 in 8, etc. To determine the number of a straight frog, measure across the frog point at place (A) where the distance between the gauge lines is an even number of inches: measure again where the distance (B) is an inch greater than at (A); the number of inches (C) between the two measured sections (A and B) is the number of the frog as shown below.

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Guard rail (check rail) A guard rail (check rail) is a short piece of rail placed alongside the main (stock) rail opposite the frog. Guard Rail protects the frog point by preventing derailments and increasing the speed that traffic can move safely. These exist to ensure that the wheels follow the appropriate flangeway through the frog and that the train does not derail. Generally, there are two of these for each frog, one by each outer rail. Guard rails are not required with a 19

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"self-guarding cast manganese" frog, as the raised part of the casting serve the same purpose. These frogs are for low-speed use and are common in rail yards.

TIE PLATE A tie plate (US) or baseplate (UK) in railroading is a steel plate used between flanged T rail and the crossties. The tie plate increases bearing area and holds the rail to correct gauge. They are fastened to wooden ties by means of spikes or bolts through holes in the plate. The part of the plate under the rail base is tapered, setting the cant of the rail, an inward rotation from the vertical. The usual slope is one in forty (1.4 degrees). The top surface of the plate has one or two shoulders that fit against the edges of the base of the rail. The double-shoulder type is currently used. Older single20

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shoulder types were adaptable for various rail widths, with the single shoulder positioned on the outside (field side) of the rails. Most plates are slightly wider on the field side, without which the plates tend to cut more into the outsides of the tie, reducing cant angle. Tie plates came into use around the year 1900, before which time flanged T rail was spiked directly to the ties.

WELDED RAILS In this form of track, the rails are welded together by utilizing flash butt welding to form one continuous rail that may be several kilometres long, or termite welding to repair or splice together existing welded rail segments. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less 21

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maintenance. The first welded track was used in Germany in 1924 and the US in 1930 and has become common on main lines since the 1950s. Flash butt welding is the preferred process which involves an automated track laying machine running a strong electrical current through the touching ends of two unjoined pieces of rail. The ends become white hot due to electrical resistance and are then pressed together forming a strong weld. Thermite welding is a manual process requiring a reaction crucible and form to contain the molten iron. Thermite-bonded joints are also seen as less reliable and more prone to fracture or break. Because of the increased strength of welded track, trains can travel on it at higher speeds and with less friction. Welded rails are more expensive to lay than jointed tracks, but have much lower maintenance costs. Rails expand in hot weather and shrink in cold weather. Because welded track has very few expansion joints, if no special measures are taken it could become distorted in hot weather and cause a derailment (a condition known in North America as sun 22

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kink, and in Britain as buckling). In North America a rail broken due to cold-related contraction is known as a pull-apart. To avoid this, welded rails are laid on concrete or steel sleepers, which are so heavy they hold the rails firmly in place. Great attention is paid to compacting the ballast effectively, particularly the shoulder over the ends of the sleepers, to prevent them from moving. Even so, in extreme weather, foot patrols monitor sections of track known to be problematic.

RAIL ANCHORS

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Rail Anchors are designed to eliminate creepage of track by providing a large bearing surface against the rail base and tie. The anchors prolong the life of wood ties by preventing cutting and wear.

JOINTS These are points where steel rail tracks are joined in order to achieve to goal of making the track continuous. Because each joint is a relatively weak spot in a track, design engineers have reduced the number of joints by lengthening the rails. The customary length when locomotives were introduced was 0.9 m (3 ft), but in the 1830s this was increased to 4.6 or 6.1 m (15 or 20 ft). Early in the 20th century the most common length for rails was 9.1 m (30 ft), and this figure soon became 10 m (33 ft) when 12.2-m (40-ft) freight cars came into general use. To some extent the length of rails has been limited by difficulties in transporting them. Rails 18.3 m (60 ft) long, used on one British 24

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railroad as early as 1894, were installed on some United States railroads, others of which have 13.7-m (45-ft) rails. In the United States rails are often butt-welded together to form lengths as long as 0.4 km (0.25 mi). At first this was done cautiously for fear that expansion and contraction due to temperature changes would cause buckling in great lengths of continuous rail. Experience showed, however, that longitudinal expansion and contraction are not excessive and need not lead to buckling. Techniques were developed for making butt welds as strong as the rails themselves. Where welding is not used, rails are joined by bars bolted to the sides so as to cover the joint. Stevens is credited with inventing the first such joint. On earlier railroads using metal rails, the individual sections were not fastened together in any way. Advances in track construction in the 20th century included using longer and stronger joint bars and wider tie plates to spread the weight of trains more evenly on the ties. Tie plates with shoulders to brace the rail on either side are used, and nearly all U.S.

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railroads have special braces called anticreepers, designed to prevent longitudinal displacement.

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