WO2003025286A1

WO2003025286A1 - Rail installation

Info

Publication number: WO2003025286A1
Application number: PCT/GB2002/004275
Authority: WO
Inventors: Barnaby Temple; Charles Penny; Mike Robertshaw
Original assignee: Balfour Beatty Plc
Priority date: 2001-09-17
Filing date: 2002-09-17
Publication date: 2003-03-27
Also published as: GB2379701A; GB0122362D0

Abstract

A system for aligning rails includes a alignment system (100) having a lateral bar (108) supporting rails (4) by clamps (112) having a ratchet. Support members (102) are fixed to the track bed (90) and adjustable supports (110) are mounted on the support members on rollers to allow the supports (110) to slide laterally. Screws are provided to adjust the position of the lateral bar (108) and hence the rails (4). The ratchet and roller combination allow easy raising of the rails and alignment of the rails even by a single operator. A complete rail installation kit and method is also described.

Description

RAIL INSTALLATION

The invention relates to a method of rail installation and apparatus for rail installation, especially a rail installation method and apparatus suitable for slab track systems.

Conventional rail laying apparatus and methods present a number of difficulties in the construction of all kinds of track, including embedded rail track forms, and consequently there is a need for new methods and handling procedures and corresponding equipment to overcome these difficulties and to improve the speed and accuracy of installation.

In particular, the alignment of rails may be critical. For example, there may be a requirement to super-elevate the outer rail to assist high speed trains traverse curves. Further, rails need to be aligned to have the correct gauge and height and inclination along the length of the track. Accordingly, there is a need for apparatus to accurately align rails.

A specific example of a rail system is described in WO99/63160, which describes a slab track system having a railway or tramway rail and rail fastening system. A rail is mounted in a longitudinal channel formed, for example, in cast concrete. In a system described in WO99/63160, a rail having a waist is held in a suitably formed longitudinal channel by means of a resilient filling inside an outer shell. The arrangement is such that pinch points are produced which hold the rail in place. Alignment of rails in this and other slab track systems is a particular difficulty.

Accordingly, there is a need for systems for laying rail for all kinds of system, and in particular but not exclusively in embedded rail systems. According to the invention, there is provided a rail alignment support for aligning rails with respect to a track bed comprising: a lateral support beam; a plurality of laterally spaced clamps fixed to the support beam for gripping a corresponding plurality of longitudinal rails from above; adjustable supports for supporting the support beam whilst allowing lateral and vertical motion of the support beam; and an adjustment mechanism for adjusting the position of the support beam laterally and vertically with respect to the track bed to align the rails.

By holding the rail from above and providing an adjustment mechanism it becomes possible to lift, align and incline rails, to hold them at the desired gauge width, and providing a means of adjustment both for vertical and lateral position of the rails in conjunction with the desired gauge and inclination. Note that in the arrangement according to this aspect of the invention the position of the lateral support beam is adjusted, when clamped to the rails, to allow the fine adjustment of rail position to be carried out independently of the clamp mechanism for gripping the rails. This allows for accurate positioning - a coarse grip mechanism used to grip and hold rails is difficult to produce in a fashion that allows fine adjustment.

A ratchet mechanism is preferably provided to lift the rails, in combination with a fine adjustment mechanism to accurately locate the lateral support beam vertically and laterally. The fine adjustment mechanism may be implemented using screws. By providing a combination of a ratchet mechanism to position the rail coarsely and a fine adjustment mechanism the rail can be both readily lifted and easily and accurately positioned.

The ability to move the beam sideways allows also for accurate lateral positioning of the rail maintaining the gauge. An adjustment mechanism may be provided to adjust the gauge.

Preferably, a sliding bearing is provided on the underside of the adjustable supports arranged to allow the support beam to slide laterally. In preferred embodiments, the sliding bearing may be provided by rollers or ball bearings - alternative arrangements may use a low friction material on the underside of the support. This allows a single person to slide the beam sideways to align the rail.

The support system may further comprise support members for fixing with respect to the track bed for carrying and supporting the rail alignment supports, and in particular the sliding bearings. Preferably, each adjustable support can be adjusted vertically and laterally with respect to the support members. Preferably the support members have a substantially horizontal upper surface for carrying the sliding bearings of the adjustable supports.

In order that the system is suitable for use with a slab track system, each clamp may further comprise a fastening for supporting a shell extending under the rail from one side of the rail to the other. The fastening may, for example, be a hook for supporting a flange in the shell or a strap.

The support can be used for rails, shellsj or a combination of rails and shells, or to hold moveable alignment supports. As well as the above system for aligning rails, the system of the invention includes, in another aspect, a rail laying trailer unit comprising: a frame; at least two laterally spaced wheels on the underside of the frame for supporting the frame and allowing the frame to be wheeled longitudinally; and rail supports fixed to the frame above the laterally spaced wheels, each rail support including a pair of laterally opposed guides and a roller between the guides with its axis aligned laterally for supporting a rail whilst allowing longitudinal movement.

A plurality of rail laying trailer units can be fixed together to provide a rail laying train. This system has a number of advantages. Each of the units can readily be manhandled, yet the combination provides a stable articulated rolling bed support to guide rails without twist or sagging. The rail laying train is towable to allow it to be manoeuvred out from under completed, continuously welded, rail lengths. The low resistance to towing afforded by virtue of the roller supports mean that the rail laying train can be operated, even in the case that the train is a long train made up of a large number of units.

The modular nature of the rail laying train, made up of a plurality of units, allows a variable number of trailer units to be used depending on the length of rail to be handled.

In embodiments of the invention, there may be provided a special end unit having a frame, a pair of laterally spaced rail support units for supporting a rail, each rail support unit including at least one wheel on the underside of the rail support and a plurality of longitudinally spaced rollers having a laterally aligned roll axis for supporting the rail as it is extended longitudinally from the end train unit. This unit may support the curved cantilevered section of rail as the support systems are attached and the rail is lowered into a desired position on the track, for example a channel for an embedded rail slab track system.

In a yet further aspect, there is provided a rail laying train assembly comprising: a train of rail laying trailer units fixed together longitudinally; a plurality of wheels under the train assembly to support the assembly and allow wheeled motion; a plurality of rollers for supporting at least one length of rail at a plurality of points spaced along its length allowing the rail to be rolled longitudinally on the rollers; and a plurality of guides for laterally locating the at least one length of rail. The invention also relates, in another aspect, to a rail lifting beam comprising: a longitudinal beam made up of a plurality of modular sections; a plurality of lifting points longitudinally spaced on the upper side of the beam for lifting the beam; and a plurality of rail carrying units spaced longitudinally along the beam, each rail carrying unit comprising a pair of lateral members extending downwardly from the beam and defining a pair of laterally opposed holes, and a rail support pin passing through the laterally opposed holes to support a rail from below.

The rail lifting beam supports the rail under the rail foot avoiding any damage to the head or web of the rail. It can pick up rail from either side of a stack, and uses removable locking bearing pins to support the rail by its base. By virtue of the shape of the frame at the bearing points it holds the rail stable.

A key aspect of this design is the modular nature of the beam sections which enable both convenient transportation and storage, and mean that different lengths can be assembled, according to particular need. The joint sections are each preferably permanently fixed onto one beam section and releasably fastened to an adjoining beam section. The releasable fastening may be a nut and bolt arrangement.

In another aspect, there is provided a rail support system for supporting a stack of rails comprising: a base unit having cross beam with a base surface and an upper surface and a plurality of pins spaced along the cross beam extending from the upper surface; and a plurality of intermediate units having a cross beam with a lower surface and an upper surface and a plurality of pins spaced along the cross beam extending from the upper and lower surfaces; wherein the shape and spacing of the pins is arranged to hold and support rails between adjacent pins at a suitable spacing for lifting. This enables, in particular, the lifting beam (above) to pick up rails from a stack in a convenient and efficient manner. Accordingly, the invention also relates to a system including a lifting beam and the support system.

The invention also relates to a method of aligning track using a rail alignment support having a plurality of laterally spaced clamps for gripping a corresponding plurality of longitudinal rails from above and adjustable supports for supporting the rail alignment supports, the method comprising: fixing the rail alignment support to a plurality of laterally spaced rails from above using the plurality of inverted clamps; adjusting the adjustable supports to align the rails, and fixing the rails in place in their aligned position.

By holding the track from above using a rail alignment support and then fixing the rails in place the rails can be correctly aligned, inclined and positioned before fixing.

Preferably, a plurality of rail alignment supports are fixed to the rails longitudinally spaced from one another to align a length of track.

The method has particular application for aligning rails within channels of a slab track system, by supporting a shell extending under the rail within the channel, wherein the step of fixing the rails in place includes filling the gap between the shell and the inner side of the channel with fixing material.

By using the alignment system according to the invention, it becomes possible to lay slab track having rails accurately aligned without requiring similarly accurate alignment of the track bed. Using more conventional methods, the rails simply follow the channels of the track bed.

In another aspect the invention relates to a method of laying track, including: mounting a rail section on rollers on a wheeled rail laying train on a track bed; and moving the wheeled rail laying train longitudinally with respect to the rail laying train to remove the wheeled rail laying train from under the rail section to lay the rail section on the track bed. Preferably, the rails remain substantially in place as the wheeled rail laying train is removed from under the rails.

In particular, the method may include mounting a further rail section on the wheeled train in alignment with the original rail section when part only of the original rail section is still on the wheeled train and welding the further rail section to the original section.

As well as the wheeled train providing an alignment support for welding, and other further operations, such as weld testing, grinding, including side and base grinding, may be carried out on the rail on the trailer frame.

After laying, the rails may be aligned as described above. The track laying method is particularly suitable for laying rail into a channel, whereby the wheels of the wheeled rail laying train may be guided in such channels.

The invention does not just relate to the individual components and methods discussed above, but also to combinations of the above components and methods. For a better understanding of the invention, the same will now be described, purely by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a rail stack using a rail stillage system according to an aspect of the invention; Figure 2 shows a rail lifting beam according to the invention;

Figure 3 shows a rail train unit according to the invention;

Figure 4 shows an alternative rail train unit according to the invention for supporting a single rail;

Figure 5 shows a rail train unit incorporating a tow hook according to the invention;

Figure 6 shows a rail end train unit according to the invention;

Figure 7 illustrates a complete assembled rail train assembly;

Figure 8 illustrates the mounting of a rail on the rail train of Figure 7;

Figure 9 illustrates positioning for welding; Figure 10 illustrates welding;

Figure 11 illustrates extending the rail from the rail train unit;

Figure 12 illustrates laying the rail in the track bed;

Figure 13 illustrates aligning the rail;

Figure 14 shows support units mounted on the track bed; Figure 15 is a longitudinal view illustrating aligning the rails; and

Figure 16 is a detailed view of part of Figure 15.

Like components given like reference numerals in the various figures.

Referring to Figure 1, there is shown a stack 2 of longitudinal rails 4 supported on a rail support system 6 including a base unit 8 and a plurality of intermediate units 10. The base unit 8 has a crossbeam 12 with opposed lower 14 and upper 16 surfaces and a plurality of pins 18 extending from the upper surface. The intermediate unit 10 again has upper and lower surfaces 14, 16 and a plurality of pins 18 extending from both upper and lower surfaces. As will be seen, the pins are spaced along the crossbeam.

In use, a plurality of base units 8 are placed longitudinally spaced along a horizontal support, for example, as illustrated, the track bed 90. A plurality of rails are then placed between the pins to form a first layer 22 of rails. Then, a corresponding plurality of intermediate units is placed, one above each of the base units, held in place by the pins 18 extending from the lower surface 14, and a first layer 22 is placed on the intermediate unit. This is repeated until all the rails required to be stored are included in the stack. The pins are spaced to provide both lateral stability of the stack and to ensure correct spacing for the lifting beam described below.

Referring to Figure 2, lifting beam 24 is a longitudinal lifting beam made up from a plurality of sections 26. The sections 26 are joined together to form the lifting beam by joint or support sections 28. Each support section 28 includes a pair of lateral plates 30 on either side of the lifting beam defining a pair of downwardly extending side members 32 which define a corresponding pair of through holes 34 through which a lifting pin 36 can pass. The support sections 28 are each welded onto one of the sections 26 and are fixed by means of nuts 38 and bolts 40 to the adjacent section to make the longitudinal beam 24. Some of the support sections 28 also include lifting points 42, including a pair of opposed holes 34 and a lifting bolt 36. These lifting points are used to support lifting ropes 44 or other lifting gear.

In use, the lifting beam is lowered onto a rail 4, for example in a stack 2 as shown in Figure 1. The side members 32 extend downwardly around the rail, and lifting bolts 36 are introduced under the rail to support the rail at a plurality of locations along the length. The rail 4 can then be lifted into place where required.

It will be noted that the rail support system illustrated in Figure 1 holds the rails off the ground in order that they can be lifted.

The sections 26 of the lifting beam are suitable for site assembly using the nuts and bolts 38, 40. The units support the rail under the rail foot (the underside of the rail) thereby avoiding any damage to the head (top) or the web (intermediate portion) of the rail. The units can pick up a rail from either side of a stack. The shape of the frame at the support sections 28 and in particular the side members 32 laterally around the rail hold the rail stable whilst the rail is being lifted.

Referring to Figure 3, an individual rail train unit will now be described. The rail train unit 72 has a frame 50 made up from a plurality of braces 52 and joints 54. The unit has a pair of laterally opposed wheels 56 fixed to the frame under corresponding rail supports 58. Each rail support includes a roller 60 mounted with its axis laterally so that it can roll longitudinally, and a pair of opposed guides 62. The frame includes a longitudinally extending member with a joint component 94 which is for cooperating with another joint component 96 on the other end of another rail train unit 72 to form an articulating joint (98, Figure 7), here a pin joint, to enable two rail train units 72 to be connected together. Referring to Figure 4, an alternative unit for a single rail includes a longitudinal frame 60, longitudinally spaced wheels 56 and respective rail supports 58, and guide wheels 66 laterally spaced from the longitudinal frame 60 to guide the train. The guide wheels 66 are arranged to be guided by an upstand 106 at the edge of the design of the concrete slab track bed, illustrated in section in Figure 15. As will be appreciated, the arrangement of the guide wheels 66 may be varied to suit the shape of the track bed. Figure 5 shows a rail train unit 74 having a tow point 64, here in the form of a tow ring, to allow a rail train to be towed.

Figure 6 shows an end unit which differs from the other units in that it is designed to support a rail extending in a cantilever fashion from the end unit. Again, a frame 50 is provided, but in this case the frame separates a pair of laterally spaced rail support units 70. Each rail support unit 70 includes, in the example, a pair of longitudinally spaced wheels 56 and a plurality of longitudinally spaced rail support units 58, each including a roller 60 and a pair of guides 62 as above. Note that the vertical position of the rollers 60 is adjustable. Figure 7 illustrates a complete rail train assembly 78 formed from a train of units 72 as shown in Figure 3 fixed to one another longitudinally by articulating joints 98 formed from joint components 94,96 on individual units 72. The articulated construction of the joints 98 of the assembly 78 permits greater flexibility and manoeuvrability and allows the assembly to be used for curved track beds. The wheels 56 of the assembly are located under the rollers 60 to support a rail mounted on the rollers 60 without requiring the frame 50 to support the load of the rail 4.

At the front end of the train 78 of units 72, a unit 74 having a tow point 64 is provided. At the other end of the chain, an end unit 76 as illustrated in Figure 6 is provided.

A rail laying train may also be formed from single rail carrying units, for example units as shown in Figure 4.' In use, referring to Figure 8, the assembly 78 is placed on the track bed. Where the track bed includes the channels of a slab rail system, the wheels 56 of the assembly may conveniently be guided within the channels. A rail 4 is lifted into position on the assembly 78 using rail lifting beam 24. It will be noted that an existing rail 4 is already present on the assembly. Referring to Figure 9, the new rail 4 is mounted with a 26mm gap to the existing rail already present on the assembly. Other spacings can be used if required.

A welding frame 80 (Figure 10), incorporating a welding jig 82 and crucible 84 are then mounted on the pair of rails and the crucible heated to join the existing rail to the new rail.

This is then repeated on the other side of the assembly for the other rail. Referring to Figure 11, the now welded rail is then lowered onto the track. This may in particular be done by dragging the train 78 forwards.

A shell and pad assembly 86 is introduced under the rail 4 as the rail is taken from the end unit 76 of the rail train assembly 78. As will be appreciated, in embodiments where, as in the example, the rail train assembly 78 carries a plurality of rails 4, each of these rails will extend from the end unit 76; the drawing only shows one rail, for clarity. The shell and pad assembly 86 includes an outer shell 142 and a-pad between shell 142 and rail 4 (see insert to Figure 11). Referring to Figure 12, the rail 4 and outer shell and pad assembly 86 are then lowered into channel 88 in concrete track beds 90.

The rail is now in place in the channel, and ready for alignment. The alignment will now be described in more detail with reference to Figures 13 to 16 since the alignment apparatus and method is a particularly important aspect of the invention. A plurality of support members 102 are fixed to the track bed 90 at regular intervals (in the example every 1.5m) with screws 104. The support members 102 include a vertical end clip 122, a substantially vertical plate 124 having an internal screw thread engaging screw 104, and a lateral joining plate 126 which has a top surface which is substantially horizontal. The joining plate 126 is wedge shaped (see Figure 16) to allow the top to be horizontal on a sloping edge of the track bed 90. A plurality of alignment supports 100 are fixed on respective laterally opposed pairs of support members 102, as can be seen in Figure 15. In alternative embodiments the supports may be mounted on a movable or motorized chassis.

Figure 15 illustrates one form of the track bed 90 with the channels 88 and shaped region 106 to which the support members 102 can be mounted. The system can also work with other forms of track bed. For example, if the support members 102 are absent the support may engage the top and side walls of the track bed 90 - this is particularly convenient if the top of the track bed is horizontal, though this is not essential. It will further be noted that Figure 15 shows three rails being aligned. The invention is not limited to two rail systems, as discussed above, but can also be due to systems having a vast different number of rails, for example three as shown.

The alignment support 100 includes a lateral support bar 108, extending laterally between the pair of support members 102. The support bar 108 is mounted on to the support members 102 by supports 110 mounted on bearings, in this case longitudinally oriented rollers 109. As will be seen the detailed view of Figure 16, a vertical adjustment screw 111 which is threaded into support bar 108 can be rotated to vertically adjust the position of the beam 108. An end extension 114 holds adjustment screw 116 for horizontally adjusting the position of 108. In each case, adjustment screws 111,116 thus constitute an adjustment mechanism that may be used to position the beam 108 with respect to the support members 102 and hence the track bed 90. The use of rollers allows the support beam to be moved laterally very easily, even when adjustment is carried out by a single operator.

Each rail is supported on each alignment support 108 by a clamp 112. The clamps 112 are considered to be inverted U-shaped clamps, although this is not intended to imply an exact U-shape. The clamps 112 also each include support hooks 113, for example, acting as fastenings to hold the rail 4 or its support or shell 86 or a suitable fastening arrangement as appropriate. In the disclosed embodiment, the support hooks are lifted from above on straps 134 threaded through a ratchet mechanism 120 having ratchet handle 136. The combination of hooks 113 and ratchet 120 enables the rail and its support system, if appropriate, to be lifted from the trackbed and held securely in the clamp 112, ready for the levelling and aligning process to be performed. The support hooks 113 are also designed to hold the rail or its support system securely in the clamp 112, which is shaped to ensure that the rail will be held at the correct inclination with respect to the alignment support beam 108. Each operation of ratchet handle 136 pulls the straps 134 by a fixed amount, in the example about 5mm. To allow the straps to be tensioned to a predetermined bias, and to allow for intermediate strap positions that might be between individual ratchet positions, spring 130 is provided to bias the ratchet to tension the straps 134 consistently.

The alignment support system thus allows both easy lifting of the rails using the ratchet mechanism 120 and also accurate positioning of the rails and support beam using screws 111,116. Moreover, a single operator can lift the rails 4 using the ratchet mechanism 120; The skilled person will be aware of many suitable ratchet mechanisms, not necessarily using straps or a handle, and so the ratchet mechanism and alternatives will not be described further.

In use, the adjustment screws 116, 111 are used to align, lift and incline the rails, and to provide an easy means of adjustment for both the vertical and the lateral positioning of the rails, for example to adjust the superelevation. Screw 118 adjusts the lateral positioning of the clamps with respect to one another to adjust the gauge.

Cam lever 132 ensures the rail head is tight to against the edge of the channel 88 in the track bed 90 on the gauge side.

In this way, it is possible to lay a slab track system to have rails of accurate height and position without needing to lay the track bed to the same accuracy as the rails. Moreover, the invention allows rails to be laid not merely in straight lengths but also in curves.

Once the rails are correctly aligned, cement-based grout is filled into the channels 88, in particular to cement the shell 86 in its now correctly aligned position in the track bed 90. Alternative fixing grouts or materials may be used if required. The rail is now held in place by the pad between the fixed shell and the rail 4.

It will be noted that by providing three clamps the alignment system shown may be used, not merely on two rail systems but also on three rail, dual gauge systems. There is no need to provide different alignment units depending on the for single and dual gauge systems. The invention may also be used on multi-rail systems having any number of rails 4, by providing an appropriate number of clamps. The system thus provides a track laying system that allows accurate alignment of rails, and is of particular application in slab rail systems.

It should be appreciated that the systems described in the specific embodiment are purely by way of example, and the systems are not exclusively designed for the specific system shown in WO99/63160. Some of the components are also suitable for other slab track systems, or conventional rail systems.

In alternative embodiments, a longer beam 108 may be used so that support bracket 102 may fit over the edges of the track bed.

Further, vertical support of the beam 108 can be assisted by providing vertical bolts through the frame, either to the concrete slab (if a cast slab is used) or directly off the rail foundation. Such vertical bolts may have wheels at their base to allow longitudinal motion, as shown dotted in Figure 15 and indicated by reference numeral 138.

Any of the adjusting mechanisms can be motorised or automated in combination with modern automatic servo control.

Several adjustment frames may be grouped on a moveable frame.

Claims

1. A rail alignment support for aligning rails with respect to a track bed comprising: a lateral support beam; a plurality of laterally spaced clamps fixed to the support beam for gripping a corresponding plurality of longitudinal rails from above; adjustable supports for supporting the support beam whilst allowing lateral and vertical motion of the support beam; and an adjustment mechanism for adjusting the position of the support beam laterally and vertically with respect to the track bed to align the rails.

2. A rail alignment support according to claim 1 wherein the laterally spaced clamps include a ratchet mechanism for raising the longitudinal rails and the adjustable supports include a fine adjustment mechanism for accurately positioning the adjustable supports and hence the support beam to accurately align the rails.

3. A rail alignment support according to claim 2, further comprising a spring between the ratchet mechanism and the support beam to bias the ratchet mechanism.

4. A rail adjustment support according to any preceding claim wherein the undersides of the adjustable supports include sliding bearings for allowing the adjustable supports to slide laterally with respect to the track bed.

5. A rail alignment support according to claim 4 wherein the sliding bearings include rollers.

6. A rail alignment support according to any preceding claim further comprising support members for fixing to the track bed and for carrying the adjustable supports.

7. A rail alignment support according to any preceding claim wherein each clamp further comprises a pair of laterally opposed support hooks for supporting a shell extending under the rail from one side of the rail to the other.

8. A rail laying equipment set including a rail alignment support according to any of claims 1 to 7 and a rail laying train assembly comprising: a train of rail laying trailer units fixed together longitudinally; a plurality of wheels under the train to support the assembly and allow wheeled motion a plurality of rollers for supporting at least one length of rail at a plurality of points spaced along the length of rail allowing the rail to be rolled longitudinally on the rollers; and a plurality of guides for laterally locating the at least one length of rail.

9. A method of aligning track using a rail alignment support having a plurality of laterally spaced clamps for gripping a corresponding plurality of longitudinal rails from above and adjustable supports for supporting the rail alignment supports, the method comprising: fixing the rail alignment support to a plurality of laterally spaced rails from above using the plurality of clamps; adjusting the adjustable supports to align the rail alignment support and hence the rails, and fixing the rails in place in their aligned position.

10. A method according to claim 9 including ratcheting the rail upwards using a ratchet mechanism before adjusting the adjustable supports.

11. A method according to claim 9 or 10 for aligning rails within channels of a slab track system, including supporting a shell extending under the rail within the channel, wherein the step of fixing the rails in place includes filling the gap between the shell and the inner side of the channel with fixing material.

12. A rail laying trailer unit comprising: a frame; at least two laterally spaced wheels on the underside of the frame for supporting the frame and allowing the frame to be wheeled longitudinally; and rail supports 'fixed to the frame above the laterally spaced wheels, each rail support including a pair of laterally opposed guides and a roller between the guides with its axis aligned laterally for supporting a rail whilst allowing longitudinal movement.

13. A rail laying trailer unit according to claim 12 further comprising a tow pin fixed to the frame for towing a set of linked rail laying trailer units as a rail laying train.

14. An end rail laying trailer unit comprising: a frame; a pair of laterally spaced rail support units for supporting a rail, each rail support unit including at least one wheel on the underside of the rail support unit; and a plurality of longitudinally spaced rollers having a laterally aligned roll axis for supporting the rail as it extends longitudinally from the end rail laying trailer unit.

15. A rail laying train assembly comprising: a train of rail laying trailer units fixed together longitudinally; a plurality of wheels under the train to support the assembly and allow wheeled motion a plurality of rollers for supporting at least one length of rail at a plurality of points spaced along the length of rail allowing the rail to be rolled longitudinally on the rollers; and a plurality of guides for laterally locating the at least one length of rail.

16. A rail laying train assembly according to claim 15 wherein the rail laying trailer units are connected together by articulated joints.

17. A rail laying train assembly according to claim 15 or 16 wherein the rail laying trailer units include a plurality of units according to claim 12 fixed together and wherein the unit at one end of the frame is an end rail laying trailer unit according to claim 14.

1 . A method of laying track, including: mounting a rail section on rollers on a wheeled rail laying train on a track bed; moving the wheeled rail laying train longitudinally with respect to the rail section to remove the wheeled rail laying train from under the rail section to lay the rail section on the track bed.

19. A method according to claim 18 further comprising mounting a further rail section on the wheeled^'rail laying train in alignment with the original rail section when part only of the original rail section is still on the wheeled rail laying train and welding the further rail section to the original section.