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Rail Track

Rail gauge
Broad gauge
Standard gauge
Scotch gauge
Narrow gauge
Dual gauge
Break-of-gauge
Rail tracks
Tramway track
List of rail gauges
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Enlarge picture
Rail tracks.
Rail tracks are used on railways (or railroads), which, together with railroad switches (or points), guide trains without the need for steering. Tracks consist of two parallel steel rails, which are laid upon sleepers (or cross ties) that are embedded in ballast to form the railroad track. The rail is fastened to the ties with rail spikes, lag screws or clips such as Pandrol clips.

The type of fastener depends partly on the type of sleeper, with spikes being used on wooden sleepers, and clips being used more on concrete sleepers.

Usually, a baseplate tie plate is used between the rail and wooden sleepers, to spread the load of the rail over a larger area of the sleeper. Sometimes spikes are driven through a hole in the baseplate to hold the rail, while at other times the baseplates are spiked or screwed to the sleeper and the rails clipped to the baseplate.

Steel rails can carry heavier loads than any other material. Railroad ties spread the load from the rails over the ground and also serve to hold the rails a fixed distance apart (called the gauge.)

Rail tracks are normally laid on a bed of coarse stone chippings known as ballast, which combines resilience, some amount of flexibility, and good drainage. Steel rails can also be laid onto a concrete slab (a slab track). Across bridges, track is often laid on ties across longitudinal timbers or longitudinal steel girders.

Additional detail on tracks used for tram and light rail operations, as opposed to heavy rail, is available at tramway track.

Railway rail

Main article: Rail profile

See also

Jointed track

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Track joint.
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Alternative view of track joints
There are different ways of joining rails together to form tracks. The traditional method was to bolt rails together in what is known as jointed track. In this form of track, lengths of rail, usually around 20 metres (60 feet) long, are laid and fixed to sleepers (UK) (crossties, or simply ties in North American parlance), and are joined to other lengths of rail with steel plates known as fishplates (UK) or joint bars (N.A.).

Historically, North American railroads until the mid to late 20th century used sections of rail that measured 39 feet (11.9 m) long so they could be carried to and from a worksite in conventional gondolas, which often measured 40 feet (12.2 m) long; as car sizes increased, so did rail lengths.

Fishplates or joint bars are usually 60 centimetres (2 feet) long, and are bolted through each side of the rail ends with bolts (usually four, but sometimes up to six.) Small gaps known as expansion joints are deliberately left between the rails to allow for expansion of the rails in hot weather. The holes through which the fishplate bolts pass are oval to allow for expansion.

British practice was always to have the rail joints on both rails adjacent to each other, while North American practice is to stagger them.

Because of the small gaps left between the rails, when trains pass over jointed tracks, they make a "clickety clack" sound. Unless it is well maintained, jointed track doesn't have the ride quality of welded rail, and is unsuitable for high speed trains. A major problem is cracking around the bolt holes, which can lead to the rail head breaking. This was the cause of the Hither Green rail crash which caused British Railways to begin converting much of its track to Continuous Welded Rail. However, it is still used in many countries on lower speed lines and sidings. Jointed track is still extensively used in poorer countries due to the lower construction cost and lack of modernisation of their railway systems.

Insulated joints

Where track circuits exist for signalling purposes, insulated block joints are required. These compound the weakness of ordinary block joints. Specially made glued joints, where all the gaps filled with epoxy resin increases the strength again. Audio frequency track circuits such as those made by CSEE replace the conventional block joint with a tuned loop which uses say 20m of the rail as part of the blocking circuit. Axle counters can also reduce the number of track circuits and thus the number of insulated rail joints.

Continuous welded rail

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welded rail joint
Most modern railways use continuous welded rail (CWR); in this form of track, the rails are welded together by utilising the thermite reaction or flash butt welding to form one continuous rail that may be several kilometres long. Because there are few joints, this form of track is very strong, gives a smooth ride, and needs less maintenance. Welded track has become common on main lines since the 1950s.

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 America as sun kink, referred in Britain as "buckling").

To avoid this, welded rails are very often laid on concrete or steel sleepers, which are so heavy they hold the rails firmly in place. After new segments of rail are laid, or defective rails replaced (welded in), the rails are artificially stressed. 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.

The stressing process, involves either heating the rails causing them to expand,[1] or stretching the rails with hydraulic equipment. They are then fastened (clipped) to the sleepers in their expanded form. This process ensures that the rail will not expand much further in subsequent hot weather. In cold weather the rails try to contract, but because they are firmly fastened, cannot do so. In effect, stressed rails are a bit like a piece of stretched elastic firmly fastened down.

Engineers try to heat the rail to a temperature roughly midway between the average extremes of hot and cold (this is known as the 'rail neutral temperature'). If temperatures reach outside normal ranges however, welded rail can buckle in a hotter than usual summer or can actually break in a colder than anticipated winter.

Joints are used in continuously welded rail when necessary; instead of a joint that passes straight across the rail, producing a loud noise and shock when the wheels pass over it, two sections of rail are sometimes cut at a steep angle and put together with a gap between them - a breather switch (referred to in Britain as an expansion joint). This gives a much smoother transition yet still provides some expansion room.

Methods of fixing rail to sleepers/ties

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Cross-sections of flat-bottomed which can rest directly on the sleepers, and bullhead rails which sit in chairs (not shown).
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Screwed rail attachment
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Rail Bender
There are several methods used to fasten rail to wooden sleepers / ties. The worldwide standard type of rail used today is flat-bottomed rail (Vignoles rail), which has a flat base and can stand upright without support. A flat-bottomed rail has a cross-section like that of an upside-down 'T' and is usually held to the sleeper with a baseplate, a metal plate attached to the sleeper; although for lower cost construction FB rails can be laid directly onto the sleepers.

Modern sleepers can be made of reinforced concrete and pressed steel, with rubber pads inserted between the sleeper and rail. This is done for two reasons: to give a smoother ride and to prevent the sleeper from shorting the track circuit, a low voltage passed through the rails for signalling purposes. This is different from a "traction current," which powers electric trains. See also [1]

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A rail clip
A variety of different types of heavy-duty clips are used to fasten the rails to the underlying baseplate, one common one being the Pandrol fastener (Pandrol clip), named after its maker, which is shaped like a sturdy, stubby paperclip.[2], [3] and [4]. Another one is the Vossloh Tension Clamp.[5]

North American practice normally uses rail spikes, which are very large nails with over hanging heads to clasp the flat-bottomed rail. These are cheaper and simpler to install but can loosen if the tie rots, much more easily than the British chair (a type of baseplate) does. This is mitigated by using very large and solid creosoted ties or using another rot-proofing preservative. See also timber treatment.

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A fishplate between two sections of jointed bullhead rail, with a rail chair screwed into a wooden sleeper, the keys are on the opposite side of the rail and not visible here. This example of traditional British practice was photographed at Cardiff Bay railway station
In traditional British practice, cast metal chairs were screwed to the sleepers, which took a style of rail known as bullhead that was somewhat figure-8 in cross-section — wider at top and bottom (known as the head and foot respectively) and smaller in the middle (the web). Keys (wedges of wood or sprung steel) were then driven in between chair and rail to hold it in place. This was common practice on British railways until the 1950s, but is now largely obsolete.

The idea behind bullhead rails was that because both the top and bottom of the rails were the same shape, when one side of the rail became worn, the rail could be turned over to the unused side, thus extending the rail's lifespan. However the bottom head turned out to get dented, rendering the original idea useless. Since the turnover requirement was no longer needed, bullhead rails came to have a flat base (narrower than flat-bottomed rail), and the top part has curved edges that fit the profile of the train wheels.

In recent years, methods have been developed to put tracks on concrete without using conventional sleepers or track ballast. While this method's construction cost is high, this system is expected to have significantly lower maintenance cost than conventional tracks. It is mainly used on high-speed lines and in tunnels, where maintenance access is difficult.



Wooden Sleepers

Concrete Sleepers

Steel Sleepers

Iron & Brick Sleepers

Sleeper-less track

Spring clip and spike with baseplates on adjacent sleepers at welded joint

Roaring Camp and Big Trees Narrow Gauge Railroad trestle burned in 1976 showing damage to sleepers and rails


See also

Track maintenance

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An abandoned railroad trestle in Skagway, Alaska
Track needs frequent maintenance to remain in good order; the frequency increases with higher-speed or heavier trains. Without frequent maintenance, a slow zone may occur due to damage on the tracks. Track maintenance was formerly hard manual labour, requiring teams of labourers (US: gandy dancers, GB: plateplayers or navvies), who used levers to force rails back into place on steep turns, correcting the gradual shifting caused by the centripetal force of passing trains. Currently, maintenance is facilitated by a variety of specialised machines.

The profile of the track is maintained by using a railgrinder.

Common maintenance jobs include spraying ballast with weedkiller to prevent weeds growing through and disrupting the ballast. This is typically done with a special weedkilling train.

Over time, ballast is crushed or moved by the weight of trains passing over it, and periodically it needs to be leveled (tamped) and eventually cleaned or replaced. If this is not done, the tracks may become uneven causing swaying, rough riding and eventually the risk for derailment.

Rail Inspections utilize nondestructive testing methods to detect internal flaws in the rails. This is done by using specially equipped HiRail trucks, inspection cars, or in some cases handheld inspection devices.

Broken or worn-out rails also need replacing periodically. Mainline rails that get worn out usually have life left in branch line or rail siding use and are "cascaded" to those branch lines.

See also Maintenance of way

History

Main article: Rail profile

Gauge

Main article: Rail gauge
During the early days of rail there was considerable variation in the gauge used by different systems. Today, sixty percent of the world's railways use a gauge of 4 ft 8 in (1435 mm), which is known as the standard or international gauge. Gauges wider than standard gauge are called broad gauge, those smaller than standard narrow gauge. Some stretches of track are dual gauge, with three (or sometimes four) parallel rails in place of the usual two, to allow trains of two different gauges to share the same track. [2].

U.S. track classes

In the United States, the Federal Railroad Administration has developed a system of classification for track quality. The class a track is placed in determines speed limits and the ability to run passenger trains. In addition to class, maximum track speed is also subject to specific regulatory restrictions known as rules. For example, the rules restrict speeds within recognized rail yards to 10 mph. The rule governing the maximum permissible speed of a train operating on curved track is determined by the following formula:


where is the amount in inches that the outside rail is superelevated above the inside rail on a curve and is the degree of curvature in degrees per 100 feet. is given in miles per hour.

Track unbalanced superelevation in the U.S. is restricted to 3 inches, though 4 inches is permissible by waiver. There is no hard maximum set for European railways, some of which have curves with over 11 inches of unbalanced superelevation to permit high-speed transportation. [3]

Other types

In the early years of railways, there was much experimentation with rails and sleepers and fixtures, before the better designs emerged.

Wooden rails with a metal strap on top was tried to save costs, but the straps had a tendency to come loose and penetrate the carriages going over them. These were commonly known as "snakeheads".

"Pole Roads" were used in past American logging operations in place of the more expensive standard railroad. They consisted of wooden poles laid end to end and parallel to each other in place of the steel rails. Locomotives and rolling stock on pole roads used concave wheels (double flanged) as opposed to the single flange used on most railway lines. Fordson tractors were often converted into pole road locomotives. The major setback to these lines was that the primitive (often home-made) locomotives tended to derail on curves.

The "flangeway" was an early type of railway, the rails of which were equipped with a flange, while the locomotives and rolling stock that ran on it had wheels with plain rims. However switches/turnouts were very primitive, and high speeds could not be achieved, thus leading to the demise of the flangeway and the rise of today's "edgeway".

Barlow rail had a wide cross section to spread the load, but the rail itself tended to spread and go out of gauge. There are some examples in the Powerhouse Museum in Sydney.

Brunel's Great Western Railway used longitudinal sleepers, with piles to hold the track down, but as the earthworks settled, the piles came to hold the track up.

References

1. ^ Continuous Welded Rail. Grandad Sez: Grandad's Railway Engineering Section. Retrieved on .
2. ^ message in the mailing list '1520mm' on Р75 rails.
3. ^ The Shasta Route - Curve speeds: what's possible and what's real. [6]

See also

External links

This article or section may contain original research or unverified claims.
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Broad gauge railways use a rail gauge (distance between the rails) greater than the standard gauge of 4 ft 8 in (1435 mm).

List

For a list see: List of broad gauges, by gauge and country

Details


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standard gauge of 1,435 mm (4 ft 8½ in), allowing inter-connectivity and the inter-operability of trains. Currently 60% of the world's railway lines are built to this gauge. It is also named Stephenson gauge after George Stephenson.
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Scotch gauge was the name given to a 4 ft 6 in (1384 mm) rail gauge, the distance between the inner sides of the rails, that was adopted by early 19th century railways mainly in the Lanarkshire area of Scotland.
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narrow gauge railway (or narrow gauge railroad) is a railway that has a track gauge narrower than the 1,435 mm (4 ft 8½ in) of standard gauge railways. Most existing narrow gauge railways have gauges of 3 ft 6 in (1067 mm) or less.
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Dual-gauge or mixed-gauge railway is a special configuration of railway track, allowing trains of different gauges to use the same track. Generally dual-gauge railway consists of three rails, rather than the standard two rails.
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break-of-gauge is where a line of one gauge meets a line of a different gauge. Trains and rolling stock cannot run through without some form of conversion between gauges, and freight and passengers must otherwise be transloaded.
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Tramway track is used on tramways or light rail operations, which, together with points guide trams, streetcars or light rail vehicles without the need for steering. Grooved rails (or girder rails) are often used in order to make street running feasible.
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Rail gauge
Broad gauge
Standard gauge
Scotch gauge
Narrow gauge
Dual gauge
Break-of-gauge
Rail tracks
Tramway track
List of rail gauges
edit

Broad gauge railways, by gauge and country


Gauge Country Notes
Metric
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Edit means to revise, correct, or improve, and may also refer to:
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Rail transport is the transport of passengers and goods by means of wheeled vehicles specially designed to run along railways or railroads. Rail transport is part of the logistics chain, which facilitates the international trading and economic growth in most countries.
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railroad switch is a mechanical installation enabling trains to be guided from one track to another. In the UK and Commonwealth countries, railroad switches are known as (sets of) points. In technical usage switches are also called turnouts.
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train is a series of rail vehicles that move along guides to transport freight or passengers from one place to another. The guideway (permanent way) usually consists of conventional rail tracks, but might also be monorail or maglev.
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Steel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight (C:1000–10,8.67Fe), depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese and
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Rail profile is a hot rolled steel profile of a specific shape or cross section (an asymmetrical I-beam).

Unlike some other uses of iron and steel, railway rails are subject to very high stresses and have to be made of very high quality steel.
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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
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Track ballast forms the trackbed upon which railroad ties (US) or railway sleepers (UK) are laid. It is packed between, below, and around the ties.<ref name="Sol18" /> It is used to facilitate drainage of water, to distribute the load from the railroad ties, and
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Rail transport is the transport of passengers and goods by means of wheeled vehicles specially designed to run along railways or railroads. Rail transport is part of the logistics chain, which facilitates the international trading and economic growth in most countries.
..... Click the link for more information.
Rail profile is a hot rolled steel profile of a specific shape or cross section (an asymmetrical I-beam).

Unlike some other uses of iron and steel, railway rails are subject to very high stresses and have to be made of very high quality steel.
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spike is a large nail with an offset head that is used to secure rails or fishplates (or baseplates) to ties in the track. Spikes are driven into wooden ties either by hammering them with a spike hammer by hand, or in an automated fashion with a spiker.
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screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force.
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Pandrol is a British company, which manufactures clips used on rail tracks. It was established in 1937. Nowadays it is worldwide-spread. Pandrol has plants in 12 countries and 82 markets. Over 240 railway systems in 91 countries adopted its products.
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Concrete is a construction material that consists of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate such as sand or
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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 aera and holds the rail to correct gauge.
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The WOOD callsign may refer to:



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This article or section may contain original research or unverified claims.
Please help Wikipedia by adding references. See the for details.
This article has been tagged since September 2007.

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Track ballast forms the trackbed upon which railroad ties (US) or railway sleepers (UK) are laid. It is packed between, below, and around the ties.<ref name="Sol18" /> It is used to facilitate drainage of water, to distribute the load from the railroad ties, and
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Drainage is the natural or artificial removal of surface and sub-surface water from a given area. Many agricultural soils need drainage to improve production or to manage water supplies.
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Lumber or timber is a term used to describe wood, either standing or that has been processed for use — from the time trees are felled, to its
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Steel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight (C:1000–10,8.67Fe), depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese and
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