Types of lanes
Contenido
A continuación se incluye una relación de los distintos tipos de carriles empleados desde la aparición del ferrocarril, con una sucinta descripción de los mismos.
Belt rail
The first rails were simply wooden slats. To resist wear, a thin iron strap was placed over the wooden rail to reduce its wear, offsetting the higher cost of the metal with the longer life of the wood. The system had the defect that every so often the passage of the wheels on the rail caused the belt to detach from the wood. This problem was first pointed out by Richard Trevithick in 1802. The use of belt rails in the United States (for example, on the Albany and Schenectady Railroad (circa 1837)) led to the safety of travelers being compromised, threatened by the formation of "snake heads" when the belts lifted and could accidentally puncture the floors of the cars.[9].
T-rail
The T-rail was a development of the strap rail which had a 'T' cross section (without wings at the foot) formed by widening the top of the strap by a head. This form of railroad was generally short-lived and was phased out in the United States beginning in 1855.[16].
Flange Rail (L)
The plateway was a primitive type of rail that had an 'L' cross section, in which the wing of the profile served to keep the flangeless wheels of a carriage aligned on the track. The flanged rail experienced a minor revival in the 1950s when it was used as a "guide bar" on the Paris Tire Métro and more recently on guided buses. On the Cambridgeshire Guided Busway* the rail is a 350 mm (13.8 in) thick concrete beam with a 180 mm (7.1 in) lip to form the flange. The buses run on normal road wheels, but also have side-mounted guide wheels to roll on the guide rail wing. These buses are driven in the usual way when outside the guide rail, analogous to the carriages of the century that could be maneuvered without restrictions around mine shafts before joining the flanged track for a longer route.
bridge lane
The bridge lane has an inverted U shaped profile. Its simple shape is easy to manufacture, and it was widely used before more sophisticated profiles were cheap enough to be produced on a large scale. In particular, it was used on the longitudinally supported wide gauge tracks of the Great Western Railway, designed by the British engineer Isambard Kingdom Brunel.
Barlow Lane
The Barlow rail was invented by William Henry Barlow in 1849. It was designed to be placed directly on the ballast, but lacking sleepers that gave transverse rigidity to the assembly, it was difficult to maintain the track width, requiring continuous maintenance. Although cross pieces were designed to try to solve this problem, the design was not successful and was quickly abandoned.
Flat bottom rails
The flat bottom rail is the dominant profile worldwide, being universally used with slight local modifications by practically all railway companies.
The T-rail with foot was the first type of flat-bottomed rail used in North America, where it was called "flanged T rail" or simply "T-section", although this last name can be confused with that of the primitive "T" rails without foot, which lacked a flat bottom). In the beginnings of the railroad in the United States, until 1831, wooden rails with iron straps were used. But Colonel Robert Livingston Stevens, president of the Camden and Amboy Railway, conceived the idea that an all-iron rail would be more suitable for building a railroad. There were no steel mills in the United States capable of rolling pieces of great lengths, so he traveled to Great Britain, which was the only place where his flat-footed T-rail could then be produced.[17] Railways in the United Kingdom had been using rolled rails with other cross sections, produced by the main ironworks in the country.
In May 1831, an order for 500 flat-bottom T-track bars, each 15 feet (4.6 m) long and weighing 36 pounds per yard (17.9 kg/m), arrived in Philadelphia, where they were placed on a track for the first time. Subsequently, all railroads in the United States used the footed T-rail devised by Stevens, who also invented nails for attaching rails to wooden sleepers (later generally replaced by threaded lag bolts).
Starting from a similar idea, the Vignoles rail was developed, a type of flat-bottomed rail that owes its name to the engineer Charles Blacker Vignoles, who introduced it to Great Britain. Vignoles noted the high wear and tear of wrought iron rails fastened with cast iron plates on stone blocks, the most common system at the time, and in 1836 recommended flat-bottomed rail to the London and Croydon Railway"), for which he was consulting engineer.
Its original rail had a smaller cross section than Stevens' rail, with a wider base than modern rails, and was fastened with screws running through the base. Other lines that adopted it were the Hull and Selby), the Newcastle and North Shields lines, and the Manchester, Bolton and Bury Canal and Railway.[18]
When it was possible to treat wooden sleepers with mercury chloride "Mercuric(II) chloride") (a process called Kyanizing")) and with creosote, a much quieter rolling was obtained than with stone blocks, and it was possible to attach the rails directly to the sleepers using clips or other systems. Their use spread throughout the world under the name Vignoles rail.
The point where the ends of two rail bars connect to each other is the weakest part of a railway track. The first iron rails were held together by a simple metal plate or bar bolted across the flange of the rails. Later, more efficient methods were developed to join two bars together, such as welding. When enough metal is placed, the joint is almost as strong as the rest of the length of the rail. In addition, the welding of consecutive rail sections eliminates the traditional rattle of the old tracks with flanged bars, by allowing the railway track to have a continuous and uniform running surface even at the joints.
Double headed rails
In the late 1830s in Britain, railway lines had a wide range of different patterns. One of the first lines to use double-headed rails was the London and Birmingham Railway, which had offered a prize for best design. This rail was supported by vertical flanges, and the head and foot of the rail had the same profile. The supposed advantage was that when the head wore out, it could be flipped onto the rail and reused. In practice, this form of recycling was not very successful, as the clamping flanges caused damage to the underside, so the symmetrical double-headed rail evolved to become the bullhead rail, in which the head was more solid than the foot.
bull head rail
Bullhead rail became the standard of the British railway system from mid-century to mid-century. For example, in 1954 bullhead rails were used for the construction of 449 miles (722.6 km) of new track, and flat-bottom rails were used for 923 miles (1,485.4 km).[19] One of the first British Standards, BS 9, set the conditions for bullhead rails. Originally published in 1905, it was revised in 1924. Rails manufactured to the 1905 standard were called "O.B.S." (Original) and those manufactured to the 1924 standard as "R.B.S." (Revised).[20].
The bullhead rail is similar to the two-headed rail, except that the head profile is not the same as the foot profile. Since it did not have a symmetrical profile, it was not possible to turn it over to use the foot as a head. Therefore, because it no longer had the advantage of being reusable, it was a very expensive method of laying rails. Heavy cast iron seats were needed to hold the rails, in turn secured to the chairs by wooden (later steel) wedges, which required constant maintenance.
Systematically replaced by the flat-bottom rail on British railways, the bullhead rail survives vestigially on some sectional tracks or branch lines with reduced traffic. It can also be found on historic trains, due to both the desire to maintain the original appearance of the tracks and the rescue and reuse of old track components from main lines. The London Underground continued to use bullhead rails after they were phased out elsewhere in Britain, but concerted plans have been made to replace them with flat-bottomed rails.[21] However, the process of replacing tracks in tunnels is a slow process, due to the inability to use heavy machinery and equipment.
slotted rail
When a rail is placed flush with the road surface or pavement, or within grass surfaces, a slot&action=edit&redlink=1 "Slot (engineering) (not yet drafted)" must be provided in the head of the rail to accommodate the wheel flange. The rail is then known as slotted rail, grooved rail or grooved rail. The slot is delimited by the rail head on one side and by a protection strip on the other. This band does not support the weight of the vehicle, and only acts as a counterrail.
The slotted rail was devised in 1852 by Alphonse Loubat", a French inventor who developed improvements in trams and railway equipment, and who contributed to the implementation of tram lines in New York City and Paris. Slots can become filled with gravel and dirt (particularly if used infrequently or after a period of inactivity) and require regular cleaning, which is carried out with special maintenance vehicles. Keeping the slots clear is essential to ensure smooth rolling, avoiding damage to the wheels or the rails themselves, and the risk of derailment.
The traditional slotted rail shape is the section illustrated to the right. It is a modified form of flat-bottom rail, and requires special mounting to facilitate weight transfer and ensure track width stability. If the weight is supported by the subsoil of the roadway, steel ties are needed at regular intervals to maintain the width of the road. Its installation implies that the entire surface occupied between the lanes must be excavated and subsequently rehabilitated.
The block rail is a lower profile form, with the head solidified and the web removed. Removing the web directly, and combining the head section directly with the foot section of a rail with check rail, would result in a profile that is too weak, so the combined section requires additional thickness.[23].
A modern block rail, with a further reduction in the required steel mass, is the LR55 rail,[24] which is housed in a prefabricated concrete beam, and to which it is secured by a polyurethane grout. It can be placed by making small ditches in the surface of existing paved roads, and is suitable for trams and light trains.[25].