railway nails

The "Nail (object)" nails, traditionally used to fix the rails to wooden sleepers, are large steel bolts (around 15 cm) with smooth faces, and have a laterally displaced head that serves to secure the lower part of the rail. The invention of this type of nail is credited to Robert Livingston Stevens,[6]​ first used in 1832.[7]​ At that time, English railways used heavy and expensive cast iron bed plates to secure the T-shaped rails. Stevens found a much simpler solution, adding a support base to the T-rail, which in this way could be fixed with a simple nail.[8]​[9]​ The generalization of this invention is It was due in part to the incipient state of industrialization in the United States at the beginning of the century, a circumstance that prioritized the use of simple construction materials. In 1982, nails were still the most common rail fastening in North America. They have a square section, with sizes between 14 and 16 mm on each side, and a length between 140 and 150 mm.[10]​.

A railroad nail is chisel-shaped and has a flat tip. It is introduced with the edges perpendicular to the direction of the wood grain, which gives it greater resistance to loosening.[11]​ Its main function is to maintain the distance between the two lanes according to the nominal width of the track. When used to secure tie plates, the fixture is made as strong as possible, while when securing the rail to the base plate, they typically allow the rail a minimum of freedom of movement.[10]​.

In localized work, nails are still driven into wooden sleepers by hammering with a special pick-like sledgehammer, although this manual work has largely been replaced by hydraulic tools[12]​ capable of both driving nails in and removing them.[13]​ To prevent wooden sleepers from opening when driving nails, it is common to prepare them with pre-drilled holes, and to place specially tensioned steel straps around their ends.[10]​.

They are manufactured with steel. Thus, in the United States, the ASTM A65 standard establishes three types of steel with different carbon contents.[14]​.

A dog-head nail (so called because of the resemblance to the head of this animal) is a particular type of nail with a specially designed head, provided with a lug on each side to facilitate the unnailing operation. Typically, they have a pointed end rather than a flat end.[15]​.

Screw bolts

Lag screws for rail fastenings are large threaded steel bolts (about 150 mm long and about 25 mm in diameter), used to fix the supports (for old bullhead type rails), the seat plates (for flat base rails) or to directly fasten a rail to a wooden sleeper. They are typically screwed into pre-drilled holes.[16]​ Lag screws have a higher manufacturing cost than nails, but have the advantage of greater holding force—approximately twice that of a nail—[17]​ and can be used in combination with spring washers.

Screw bolts were first introduced in 1860 in France, and became increasingly common in continental Europe.[18]​.

The term dog screw is a commercial name by which screws are sometimes called in English.[19]​.

Anchor screws

Anchor screws are threaded bolts, usually with a square or hexagonal head, that are inserted through a hole made in a sleeper, and that are held at their other end by a nut with serrated faces, designed to be driven into the lower surface of the sleeper. To secure the flat base rails, lip washers are used to clamp the edge of the rail. This type of fastenings are more resistant to loosening caused by vibrations and rail movement,[20]​ which is why they are used in places where the passage of trains involves greater mechanical stress, such as in "Detour (railway)" track devices[21]​ and in closed curves.[22]​.

Spring Nails

Spring nails or spring rail nails[24]​ are used with flat-bottomed rails, base plates and wooden sleepers. They hold the rail down and prevent it from tilting, and also serve to secure the base plate to the sleeper.[25]​ The Macbeth nail (trade name) is U-shaped with two points (like a staple) and is bent in the middle so that it appears in an M shape when viewed from the side.[26]​[27]​ Single-point "J"-shaped nails have also been used. inverted.[28]​.

Fixing equipment

To drive the nails, the nailing hammer "Nailer Hammer (railway)") is used, a special type of hammer with dimensions similar to those of a pick "Pico (tool)"), but configured with a long and narrow head to be able to precisely access the small space between the head of the nail and the top of the rail.[29]​[30]​.

Manual drilling and inserting and removing nails or screws have been replaced by semi-automated or automated machines, which are electrically, pneumatically or hydraulically driven, or powered by a two-stroke engine. The machines that remove the nails are called denailers.[31]​[32][33]​.

The first rail brackets, made of cast iron and introduced around 1800, were used to fix and support cast iron rails at their ends[2]​ and to join adjacent rails.[34]​.

In the 1830s, when laminated rails with a T section (with one or two lower flanges) and I sections (called bull's head) appeared, it was necessary to use cast iron anchors to support them.[35]​ Originally, iron key pieces were used to press fit the rail into the parallel vertical jaws of the anchor; but they were later replaced by completely wooden wedges.[35] These wedges, made of oak wood, were softened with steam, compressed with hydraulic presses and stored in a drying warehouse. When inserted into the anchor, exposure to the humid atmosphere caused the wedge to expand, firmly holding the rail.[36] The wedges could be inside or outside the rail. In Britain, they were generally on the outside.[37]​.

The anchors were fixed to the sleeper with wooden dowels (dowels), screws, bolts or nails.[38]​.

In most of the world, flat-bottom rails and base plates became a near-universal standard. However, in Great Britain, the bull's head profile rails and their anchors remained in use until the middle of the century,[25]​ as in some secondary facilities of the London Underground, despite being a completely obsolete technology.

A bed plate or base plate is a steel platform placed between the flat base of a rail and the top face of a sleeper. It serves to increase the support area of ​​the rail on the sleeper (distributing the loads more effectively) and to adjust the separation of the rails to the nominal track width. They are attached to the sleepers using nails or lag screws through a series of holes in the plate.

The part of the plate located under the base of the rail is machined with a determined slope, corresponding to the design inclination of the rail with respect to the rolling plane, a rotation towards the inside of the track with respect to the vertical usually of 1/40 (1.4 degrees). The top surface of the plate also has one or two shoulders that fit against the edges of the rail base. Older single-shoulder types were adaptable for various lane widths, with the single shoulder placed on the outside side of the track, although these days they are typically used with two shoulders. Most plates are slightly wider on the outside, to avoid the tendency of the plates to dig deeper into the outside sides of the wooden sleepers, which would reduce the design slope angle of the rail.

Many railroads use large lag screws to attach bedplates to sleepers, especially when the sleepers are made of concrete.

Bedplates came into use around 1900. Previously, the T-track with lower flanges was nailed directly to the sleepers.

rail anchors or anti-slip clips, are flexible steel pieces that are attached to the bottom of the seat plate and rest against the sides of the sleepers to prevent longitudinal movement of the rail, either due to temperature changes or vibration.

A diferencia de las sujeciones rígidas, las sujeciones elásticas que utilizan clips continúan manteniendo la posición del carril, aunque ceden momentáneamente bajo el efecto de las cargas del tráfico. Por lo tanto, se oponen al deslizamiento longitudinal instantáneo, y son adecuadas para la instalación de carriles en forma de barras largas soldadas").

Los diferentes tipos de sujeciones elásticas se basan en el uso de una pieza metálica elástica (clip) fijada a la traviesa, que presiona la base del carril contra una almohadilla elastomérica. Durante el paso de la circulación, el resorte acompaña el movimiento del carril, mientras asegura constantemente su acción de retención.

Se instalan con suelas elastoméricas, que se colocan entre la parte superior de la traviesa y la cara inferior del carril. Estas suelas tienen la función de amortiguar parte de las vibraciones y de permitir desplazamientos longitudinales lentos del carril sin dañar las traviesas.

A menudo también se montan cuñas de plástico de alta resistencia, que se utilizan para proporcionar soporte lateral al carril.

Las diferencias entre los distintos cierres elásticos disponibles se relacionan esencialmente con el tipo de resorte utilizado, así como con su método de fijación a las traviesas.

Existe una gran variedad de diferentes tipos comerciales de clips de alta resistencia, utilizados para sujetar los carriles a la placa de asiento subyacente. Entre los más comunes figuran la sujeción Pandrol"), con una particular forma retorcida similar a una letra "e",[39]​ y la abrazadera Vossloh,[40]​ con una configuración que recuerda a una letra "M" con los vértices redondeados (ambos dispositivos llevan el nombre de sus empresas fabricantes).

Elastic fasteners fixed with screws or lag bolts

The fasteners are fixed to the sleepers using lag screws, tightened using motorized torque wrenches:.

Indirect installation consists of using an intermediate metal plate, which is fixed to the sleeper using traction screws. The advantage of this method is that it does not wear out the sleeper during disassembly and assembly of the fastening during rail maintenance work.

Precise tightening must be scrupulously observed, adjusting the torque applied when fixing the lag bolts to ensure optimal rail maintenance. To do this, torque wrenches must be used, capable of adjusting the tightening torque. As fasteners tend to loosen gradually due to vibrations caused by rolling stock, it is necessary to check at regular intervals that the fastening pressure is sufficient, and increase it if necessary.

In wooden sleepers, it is always an indirect fixation. The metal part that presses on the rail shoe is held under pressure by a screwed helical spring.

This type of fastening is very widespread.

The function of the spring is ensured by the use of a more or less flat piece of metal fixed to the crossbar, which presses the rail shoe. In this family of fastenings we can mention the "RN" and "Nabla" types, of French design. They have been installed on numerous roads in France, as well as in other countries to which this technology has been exported.

As in the case of tongue clips, a metal piece is used that tightens the rail skate, but in this case it is a spring made with a steel bar with a circular section folded in the shape of an "M", which is fixed to the sleeper by means of a system of lag bolts.

This type of fastening was developed by the Vossloh company, and tends to replace spring fastenings with indirect fixation during track renovations.

Elastic snap fasteners

It is a fastening whose spring, of the same type as that of the "M" fastening, is not fixed by screwing it, but by forcing it to pass through a ring fixed to the crossbar. The elastic deformation to which the spring is subjected ensures both its retention in its installation location and the elastic fixation of the rail (the device for installing the clips weighs 143 kg).

The absence of screws eliminates "de facto" the risk of unscrewing. Therefore, it is no longer necessary to periodically check the pressure of the clips, and therefore it is possible to "set them and [forget them]". (Set and forget, manufacturer's motto). This is a point of view or a sales argument, because this type of binding tends over time to come off your chair, which is as problematic as loosening it. Furthermore, during interventions that require the removal of the clips, their replacement requires that the sleeper be at the same level as the rail flange, which in the case of tracks in poor condition is not always easy, and may require additional operations to be carried out. Unlike a more traditional fastening with traction lag screws (Nabla or others), in which simply tightening the traction screw allows the sleeper to be raised.

This type of fastening was developed by the British manufacturer Pandrol. It is very widespread in the United Kingdom, but also, due to its great ease of use and lack of maintenance (questionable point of view), in a large number of networks that do not have reasons of a protectionist nature to favor other types of fastenings. In France, Fastclip fastenings are used on new tracks (mainly high speed), as well as during certain track and ballast renewal operations of a certain length. The Pandrol quick clip mounts at right angles to the rail. Due to its captive configuration, it must be installed at the time of manufacturing the concrete sleeper, to be later adjusted to the rail flange on site.

railway nails

The "Nail (object)" nails, traditionally used to fix the rails to wooden sleepers, are large steel bolts (around 15 cm) with smooth faces, and have a laterally displaced head that serves to secure the lower part of the rail. The invention of this type of nail is credited to Robert Livingston Stevens,[6]​ first used in 1832.[7]​ At that time, English railways used heavy and expensive cast iron bed plates to secure the T-shaped rails. Stevens found a much simpler solution, adding a support base to the T-rail, which in this way could be fixed with a simple nail.[8]​[9]​ The generalization of this invention is It was due in part to the incipient state of industrialization in the United States at the beginning of the century, a circumstance that prioritized the use of simple construction materials. In 1982, nails were still the most common rail fastening in North America. They have a square section, with sizes between 14 and 16 mm on each side, and a length between 140 and 150 mm.[10]​.

A railroad nail is chisel-shaped and has a flat tip. It is introduced with the edges perpendicular to the direction of the wood grain, which gives it greater resistance to loosening.[11]​ Its main function is to maintain the distance between the two lanes according to the nominal width of the track. When used to secure tie plates, the fixture is made as strong as possible, while when securing the rail to the base plate, they typically allow the rail a minimum of freedom of movement.[10]​.

In localized work, nails are still driven into wooden sleepers by hammering with a special pick-like sledgehammer, although this manual work has largely been replaced by hydraulic tools[12]​ capable of both driving nails in and removing them.[13]​ To prevent wooden sleepers from opening when driving nails, it is common to prepare them with pre-drilled holes, and to place specially tensioned steel straps around their ends.[10]​.

They are manufactured with steel. Thus, in the United States, the ASTM A65 standard establishes three types of steel with different carbon contents.[14]​.

A dog-head nail (so called because of the resemblance to the head of this animal) is a particular type of nail with a specially designed head, provided with a lug on each side to facilitate the unnailing operation. Typically, they have a pointed end rather than a flat end.[15]​.

Screw bolts

Lag screws for rail fastenings are large threaded steel bolts (about 150 mm long and about 25 mm in diameter), used to fix the supports (for old bullhead type rails), the seat plates (for flat base rails) or to directly fasten a rail to a wooden sleeper. They are typically screwed into pre-drilled holes.[16]​ Lag screws have a higher manufacturing cost than nails, but have the advantage of greater holding force—approximately twice that of a nail—[17]​ and can be used in combination with spring washers.

Screw bolts were first introduced in 1860 in France, and became increasingly common in continental Europe.[18]​.

The term dog screw is a commercial name by which screws are sometimes called in English.[19]​.

Anchor screws

Anchor screws are threaded bolts, usually with a square or hexagonal head, that are inserted through a hole made in a sleeper, and that are held at their other end by a nut with serrated faces, designed to be driven into the lower surface of the sleeper. To secure the flat base rails, lip washers are used to clamp the edge of the rail. This type of fastenings are more resistant to loosening caused by vibrations and rail movement,[20]​ which is why they are used in places where the passage of trains involves greater mechanical stress, such as in "Detour (railway)" track devices[21]​ and in closed curves.[22]​.

Spring Nails

Spring nails or spring rail nails[24]​ are used with flat-bottomed rails, base plates and wooden sleepers. They hold the rail down and prevent it from tilting, and also serve to secure the base plate to the sleeper.[25]​ The Macbeth nail (trade name) is U-shaped with two points (like a staple) and is bent in the middle so that it appears in an M shape when viewed from the side.[26]​[27]​ Single-point "J"-shaped nails have also been used. inverted.[28]​.

Fixing equipment

To drive the nails, the nailing hammer "Nailer Hammer (railway)") is used, a special type of hammer with dimensions similar to those of a pick "Pico (tool)"), but configured with a long and narrow head to be able to precisely access the small space between the head of the nail and the top of the rail.[29]​[30]​.

Manual drilling and inserting and removing nails or screws have been replaced by semi-automated or automated machines, which are electrically, pneumatically or hydraulically driven, or powered by a two-stroke engine. The machines that remove the nails are called denailers.[31]​[32][33]​.

The first rail brackets, made of cast iron and introduced around 1800, were used to fix and support cast iron rails at their ends[2]​ and to join adjacent rails.[34]​.

In the 1830s, when laminated rails with a T section (with one or two lower flanges) and I sections (called bull's head) appeared, it was necessary to use cast iron anchors to support them.[35]​ Originally, iron key pieces were used to press fit the rail into the parallel vertical jaws of the anchor; but they were later replaced by completely wooden wedges.[35] These wedges, made of oak wood, were softened with steam, compressed with hydraulic presses and stored in a drying warehouse. When inserted into the anchor, exposure to the humid atmosphere caused the wedge to expand, firmly holding the rail.[36] The wedges could be inside or outside the rail. In Britain, they were generally on the outside.[37]​.

The anchors were fixed to the sleeper with wooden dowels (dowels), screws, bolts or nails.[38]​.

In most of the world, flat-bottom rails and base plates became a near-universal standard. However, in Great Britain, the bull's head profile rails and their anchors remained in use until the middle of the century,[25]​ as in some secondary facilities of the London Underground, despite being a completely obsolete technology.

A bed plate or base plate is a steel platform placed between the flat base of a rail and the top face of a sleeper. It serves to increase the support area of ​​the rail on the sleeper (distributing the loads more effectively) and to adjust the separation of the rails to the nominal track width. They are attached to the sleepers using nails or lag screws through a series of holes in the plate.

The part of the plate located under the base of the rail is machined with a determined slope, corresponding to the design inclination of the rail with respect to the rolling plane, a rotation towards the inside of the track with respect to the vertical usually of 1/40 (1.4 degrees). The top surface of the plate also has one or two shoulders that fit against the edges of the rail base. Older single-shoulder types were adaptable for various lane widths, with the single shoulder placed on the outside side of the track, although these days they are typically used with two shoulders. Most plates are slightly wider on the outside, to avoid the tendency of the plates to dig deeper into the outside sides of the wooden sleepers, which would reduce the design slope angle of the rail.

Many railroads use large lag screws to attach bedplates to sleepers, especially when the sleepers are made of concrete.

Bedplates came into use around 1900. Previously, the T-track with lower flanges was nailed directly to the sleepers.

rail anchors or anti-slip clips, are flexible steel pieces that are attached to the bottom of the seat plate and rest against the sides of the sleepers to prevent longitudinal movement of the rail, either due to temperature changes or vibration.

A diferencia de las sujeciones rígidas, las sujeciones elásticas que utilizan clips continúan manteniendo la posición del carril, aunque ceden momentáneamente bajo el efecto de las cargas del tráfico. Por lo tanto, se oponen al deslizamiento longitudinal instantáneo, y son adecuadas para la instalación de carriles en forma de barras largas soldadas").

Los diferentes tipos de sujeciones elásticas se basan en el uso de una pieza metálica elástica (clip) fijada a la traviesa, que presiona la base del carril contra una almohadilla elastomérica. Durante el paso de la circulación, el resorte acompaña el movimiento del carril, mientras asegura constantemente su acción de retención.

Se instalan con suelas elastoméricas, que se colocan entre la parte superior de la traviesa y la cara inferior del carril. Estas suelas tienen la función de amortiguar parte de las vibraciones y de permitir desplazamientos longitudinales lentos del carril sin dañar las traviesas.

A menudo también se montan cuñas de plástico de alta resistencia, que se utilizan para proporcionar soporte lateral al carril.

Las diferencias entre los distintos cierres elásticos disponibles se relacionan esencialmente con el tipo de resorte utilizado, así como con su método de fijación a las traviesas.

Existe una gran variedad de diferentes tipos comerciales de clips de alta resistencia, utilizados para sujetar los carriles a la placa de asiento subyacente. Entre los más comunes figuran la sujeción Pandrol"), con una particular forma retorcida similar a una letra "e",[39]​ y la abrazadera Vossloh,[40]​ con una configuración que recuerda a una letra "M" con los vértices redondeados (ambos dispositivos llevan el nombre de sus empresas fabricantes).

Elastic fasteners fixed with screws or lag bolts

The fasteners are fixed to the sleepers using lag screws, tightened using motorized torque wrenches:.

Indirect installation consists of using an intermediate metal plate, which is fixed to the sleeper using traction screws. The advantage of this method is that it does not wear out the sleeper during disassembly and assembly of the fastening during rail maintenance work.

Precise tightening must be scrupulously observed, adjusting the torque applied when fixing the lag bolts to ensure optimal rail maintenance. To do this, torque wrenches must be used, capable of adjusting the tightening torque. As fasteners tend to loosen gradually due to vibrations caused by rolling stock, it is necessary to check at regular intervals that the fastening pressure is sufficient, and increase it if necessary.

In wooden sleepers, it is always an indirect fixation. The metal part that presses on the rail shoe is held under pressure by a screwed helical spring.

This type of fastening is very widespread.

The function of the spring is ensured by the use of a more or less flat piece of metal fixed to the crossbar, which presses the rail shoe. In this family of fastenings we can mention the "RN" and "Nabla" types, of French design. They have been installed on numerous roads in France, as well as in other countries to which this technology has been exported.

As in the case of tongue clips, a metal piece is used that tightens the rail skate, but in this case it is a spring made with a steel bar with a circular section folded in the shape of an "M", which is fixed to the sleeper by means of a system of lag bolts.

This type of fastening was developed by the Vossloh company, and tends to replace spring fastenings with indirect fixation during track renovations.

Elastic snap fasteners

It is a fastening whose spring, of the same type as that of the "M" fastening, is not fixed by screwing it, but by forcing it to pass through a ring fixed to the crossbar. The elastic deformation to which the spring is subjected ensures both its retention in its installation location and the elastic fixation of the rail (the device for installing the clips weighs 143 kg).

The absence of screws eliminates "de facto" the risk of unscrewing. Therefore, it is no longer necessary to periodically check the pressure of the clips, and therefore it is possible to "set them and [forget them]". (Set and forget, manufacturer's motto). This is a point of view or a sales argument, because this type of binding tends over time to come off your chair, which is as problematic as loosening it. Furthermore, during interventions that require the removal of the clips, their replacement requires that the sleeper be at the same level as the rail flange, which in the case of tracks in poor condition is not always easy, and may require additional operations to be carried out. Unlike a more traditional fastening with traction lag screws (Nabla or others), in which simply tightening the traction screw allows the sleeper to be raised.

This type of fastening was developed by the British manufacturer Pandrol. It is very widespread in the United Kingdom, but also, due to its great ease of use and lack of maintenance (questionable point of view), in a large number of networks that do not have reasons of a protectionist nature to favor other types of fastenings. In France, Fastclip fastenings are used on new tracks (mainly high speed), as well as during certain track and ballast renewal operations of a certain length. The Pandrol quick clip mounts at right angles to the rail. Due to its captive configuration, it must be installed at the time of manufacturing the concrete sleeper, to be later adjusted to the rail flange on site.