The Full Wiki

Rail profile: Map

Advertisements
  
  

Wikipedia article:

Map showing all locations mentioned on Wikipedia article:

Rail from 1896


The rail profile is the cross sectional shape of a railway rail, perpendicular to the length of the rail.

In all but very early cast rails a rail is hot rolled steel profile of a specific shape or cross section (an asymmetrical I-beam) designed for use as the fundamental component of railway track.

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. It took many decades to improve the quality of the materials, including the change from iron to steel. Minor flaws in the steel that pose no problems in reinforcing rods for buildings, can, however, lead to broken rails and dangerous derailments when used on railway tracks.

By and large, the heavier the rails and the rest of the trackwork, the heavier and faster the trains these tracks can carry.

The rails represent a substantial fraction of the cost of a railway line. Only a small number of rail sizes are made by the steelworks at the one time, so a railway must choose the nearest suitable size. Worn, heavy rail from a mainline is often reclaimed and downgraded for re-use on a branchline, siding or yard.

Rail sizes

Pound is a railroad term that indicates the weight of rail per yard. For example one yard of "132 pound rail" weighs 132 pounds. Depending on the use of imperial or metric units, rail sizes are usually expressed in terms of pounds per yard or kilograms per metre. Coincidentally, the pounds-per-yard figure is almost exactly double the kilograms-per-metre figure, making rough conversions easy. Rails in Canadamarker, the United Kingdommarker, and United Statesmarker are still described using imperial units. However, in Australia they are now described in metric units and always have been on mainland Europe.

Europe

Rails are made in a large number of different sizes. Some common European rail sizes include:


In the countries of former USSR rails are common. Thermally hardened rails also have been used on heavy-duty railroads like Baikal-Amur Mainline, but have proven themselves deficient in operation and were mainly rejected in favor of rails.

North America

Weight mark on a jointed segment of "Pennsylvania Special" rail.
The heaviest grade of rail ever mass produced.
The American Society of Civil Engineers (or ASCE) specified rail profiles in 1893 for increments from . Height of rail equaled width of foot for each ASCE tee-rail weight; and the profiles specified fixed proportion of weight in head, web and foot of 42%, 21% and 37%, respectively. ASCE profile was adequate; but heavier weights were less satisfactory. In 1909 the American Railway Association (or ARA) specified standard profiles for increments from . The American Railway Engineering Association (or AREA) specified standard profiles for , and rails in 1919, for and rails in 1920, and for rails in 1924. The trend was to increase rail height/foot-width ratio and strengthen the web. Disadvantages of the narrower foot were overcome through use of tie-plates. AREA recommendations reduced the relative weight of rail head down to 36%, while alternative profiles reduced head weight to 33% in heavier weight rails. Attention was also focused on improved fillet radii to reduce stress concentration at the web junction with the head. AREA recommended the ARA profile. Old ASCE rails of lighter weight remained in use, and satisfied the limited demand for light rail for a few decades. AREA merged into the American Railway Engineering and Maintenance-of-Way Association in 1997. By the mid-20th century, most rail production was medium heavy ( ) and heavy ( ) Sizes under rail are usually for lighter duty freight, low use trackage, or light rail. Track using ( ) rail is for lower speed freight branch lines or rapid transit (for example, most of the New York City Subway system track is constructed with rail). Main line track is usually built with rail or heavier. Some common North American rail sizes include:
Rail Bender


Some common North American crane rail sizes include:


Australia

Some common Australian rail sizes include:
  • 50 kg and 60 kg are the current standard, although some other sizes are still manufactured.
  • Some American sizes are used on northwest Western Australianmarker iron ore railways.


History

Specimen of fishbelly edge rail laid on stone blocks
Cross sections of early rails
Early rails were used on horse drawn wagonways, initially using strap-iron rails, which consisted of thin strips of iron strapped onto wooden rails. These rails were too fragile to carry heavy loads, but because the initial construction cost was less, this method was sometimes used to quickly build an inexpensive rail line. Strap rails sometimes separated from the wooden base and speared into the floor of the carriages above, creating what was referred to as a "snake head." However, the long-term expense involved in frequent maintenance outweighed any savings.

These were superseded by cast iron rails which were flanged (i.e 'L' shaped) with the wagon wheels being flat, an early exponent being Benjamin Outram. His partner William Jessop had pioneered the use of "edge rails" in 1789 where the wheels were flanged and, over time it was realised that these worked better.

The earliest of these in general use were the so-called cast iron fishbelly rails from their shape. Rails made from cast iron were brittle and broke easily. They could only be made in short lengths which would soon become uneven. By 1840, wrought iron in longer lengths replaced cast iron as rolling techniques improved. The cross-section varied widely from one line to another, but were of three basic types as shown in the diagram. The parallel cross-section which developed in later years was referred to as Bullhead.

Meanwhile, in May 1831, the first flanged T rail (also called T-section) arrived in America from Britain and was laid into the Pennsylvania Railroad by Camden and Amboy Railroad. They were also used by Charles Vignoles in Britain.

The first steel rails were made in 1857 by Robert Forester Mushet, who laid them at Derby stationmarker in Englandmarker. Steel is a much stronger material, which steadily replaced iron for use on railway rail and allowed much longer lengths of rails to be rolled.

The American Railway Engineering Association (AREA) and the American Society for Testing Materials (ASTM) specified carbon, manganese, silicon and phosphorus content for steel rails. Tensile strength increases with carbon content, while ductility decreases. AREA and ASTM specified 0.55 to 0.77 percent carbon in rail, 0.67 to 0.80 percent in rail weights from , and 0.69 to 0.82 percent for heavier rails. Manganese increases strength and resistance to abrasion. AREA and ASTM specified 0.6 to 0.9 percent manganese in 70 to 90 pound rail and 0.7 to 1 percent in heavier rails. Silicon improves steel by increasing density. AREA and ASTM specified 0.1 to 0.23 percent silicon. Phosphorus and sulfur are impurities causing brittle rail with reduced impact-resistance. AREA and ASTM specified maximum phosphorus concentration of 0.04 percent.

The use of welded rather than jointed track began in around the 1940s and had become widespread by the 1960s.

Axleloads and speeds

Rail weights are very important in determining axleloads and speeds. These limits are so low that sharp curves hardly impose any extra speed limits.

Types

Baulk rail

Barlow rail



Barlow rail was invented by William Henry Barlow in 1849. It was designed to be laid straight onto the ballast, but the lack of sleepers meant that it was difficult to keep it in gauge.

Vignoles rail

Vignoles rail is the popular name of the flat-bottomed rail used internationally for railway track, recognising engineer Charles Vignoles who introduced it to Britainmarker.

Flat bottomed rail was first introduced in Americamarker by R.L.Stevens in 1830. There were no steel mills in America capable of rolling long lengths, so it was manufactured in Britain. Charles Vignoles observed that wear was occurring with steel rails and steel chairs upon stone blocks, the normal system at that time. In 1836 he recommended flat-bottomed rail to the London and Croydon Railway for which he was consulting engineer.

His original rail had a smaller cross-section to the Stevens rail, with a wider base than modern rail, fastened with screws through the base. Other lines which adopted it were the Hull and Selby, the Newcastle and North Shields, and the Manchester, Bolton and Bury Canal Navigation and Railway Company.

When it became possible to preserve wooden sleepers with mercuric chloride (a process called Kyanising) and creosote, they gave a much quieter ride than stone blocks and it was possible to fasten the rails directly using clips or rail spikes. Their use spread world-wide and acquired Vignoles' name.

Flanged T rail

Cross section of new rail.
Railroad track attachment to ties


Iron-strapped wooden rails were used on all American railways until 1831. Col. Robert L. Stevens, the President of the Camden and Amboy Railroad, conceived the idea that an all-iron rail would be better suited for building a railroad. He sailed to Englandmarker which was the only place where his flanged T rail (also called T-section) could be rolled. Railways in England had been using rolled rail of other cross-sections which the ironmasters had produced.

In May, 1831, the first 500 rails, each long and weighing , reached Philadelphiamarker and were placed in the track, marking the first use of the flanged T rail. Afterwards, the flanged T rail became employed by all railroads in the United Statesmarker.Col. Stevens also invented the hooked spike for attaching the rail to the crosstie (or sleeper). At the present time, the screw spike is being used widely in place of the hooked spike, perhaps because it is possible to install the screw spike by using a labor-saving machine that replaces salaried workers.

At the present time, crossties or sleepers constructed of concrete are in use in some places. The use of creosote as a treatment for wooden crossties has been declared to be detrimental to the health of people and plants. The crossties or sleepers are embedded in ballast in order to provide stability and drainage.

The joint where two rails are connected is the weakest part of a rail line. The earliest iron rails were joined by a simple fishplate or bar of metal bolted through the web of the rail. Stronger methods of joining two rails together have been developed. When sufficient metal is put into the rail joint, the joint is almost as strong as the rest of the rail length. The noise generated by trains passing over the rail joints, described as "the clickity clack of the railroad track", can be eliminated by welding the rail sections together forming a continuous rail. One kind of welding is the Thermite welding process.

Double-headed rail

In late 1830s Englandmarker, railway lines had a vast range of different patterns. One of the earliest lines to use double-headed rail was the London and Birmingham Railway, which had offered a prize for the best design. This rail was supported by chairs and the head and foot of the rail had the same profile. The supposed advantage was that, when the head became worn, the rail could be turned over and re-used. In practice, this form of recycling was not very successful as the chair caused dents in the lower surface, and double-headed rail evolved into bullhead rail in which the head was more substantial than the foot.

Bullhead rail

Bullhead rail is similar to double-headed rail but with a heavier profile to the top edge. It became the standard for the British railway system until the mid-20th century but has now been largely replaced by flat-bottom rail. Bullhead rail is still used on the London Underground and survives on the national rail system in some sidings.

LR55 rail

LR55 cross section
LR55 rail is a special rail section, designed for use in embedded tramway track installations. It is a top-suspended rail: the load is transmitted by the rail head, rather than the base. The rail is laid in concrete troughs in slots cut in the roadway; a polyurethane mastic provides a resilient cushion between the rail section and the concrete, minimising transmitted noise, and providing insulation against leakage currents. Since the load is spread across a wider base, it requires less depth for a sub-base than conventional tramway track avoiding the need to disturb existing underground utility services. The installation and maintenance time, and hence cost, is thus greatly reduced. Gauge is maintained by the pavement in which it is installed; there is no need for separate gauging bars between the rails. LR55 has been tested in parts of the Sheffield Supertram network.

The same rail has been tested to axle loadings for mainline use, and can be used in tunnels and other locations where the loading gauge is restricted. Replacing flat bottom girder rails on sleepers and ballast with LR55 in tunnels can increase the head room by a minimum of , without the need to excavate the tunnel invert. A method statement to undertake this transformation allows contractors to proceed on an incremental basis without closing the tunnel to rail traffic. Temporary transition rails link flat bottom and LR55 rails, until the conversion is completed. The extra loading gauge can then be used to install OHL electrification, or to move larger rail vehicles. These can include double deck passenger trains and freight trains with high cube ( ) maritime containers.

Manufacturers

Rails are made from high quality steel and not in huge quantities compared to other forms of steel, and so the number of manufacturers in any one country tends to be limited.

   Edgar Allen


Defunct manufacturers



See also



References

External links




Embed code:
Advertisements






Got something to say? Make a comment.
Your name
Your email address
Message