WO2005003461A1

WO2005003461A1 - Displacement indicator apparatus

Info

Publication number: WO2005003461A1
Application number: PCT/GB2004/002892
Authority: WO
Inventors: Andrew Smith
Original assignee: Maws Precision Engineering Limited
Priority date: 2003-07-02
Filing date: 2004-07-02
Publication date: 2005-01-13
Also published as: GB2403541A; GB0315524D0

Abstract

The present application relates to apparatus suitable for providing an indication of the displacement of a railway tie. The apparatus comprises a mounting element (15) for mounting fixedly on the railway tie and an indicator member movable relative to the mounting element. The apparatus also includes retaining means (15,19) for retaining the indicator member in a displaced position relative to the mounting element. The application also relates to a method of inspecting a section of railway track.

Description

DISPLACEMENT INDICATOR APPARATUS The present invention relates generally to apparatus suitable for providing an indication of the displacement of a structural element. More particularly, the present invention relates to apparatus for providing an indication of the displacement of a railway tie (also known as a railway sleeper) . Railway tracks are generally supported by transversely extending railway ties. The railway ties may be made of timber or prestressed concrete beams and are typically supported in ballast made up of broken stone, gravel or other material. However, if the ballast is poorly compacted the railway ties may be displaced under load, for example when rolling stock passes over them. This displacement may result in deflection of the track (sometimes referred to as "bounce" but various other engineering terms colloquial to the railway industry and/or civil engineering and/or surveying fields or disciplines may equally be used to describe this characteristic) . In the case of "Concrete Slab Track" , such as "Stedef " and "Sonneville" track types, the railway ties are supported on a rubber pad/block which is supported by concrete. The rubber pad/block typically allows the railway ties each to be displaced vertically by a small amount to allow stresses to be dissipated. However, over time, the rubber pad/block for each railway tie may deteriorate and the amount of movement which occurs when rolling stock passes over the railway tie may increase. The amount of movement may eventually become greater than acceptable levels. Track deflection may be a factor in the derailment or rolling stock, broken rails, rail corrugation and other damage. The usable life of rail furniture (such as rail clips, DC rail and insulator, AC overhead lines and catenary) may also be reduced or stress-failures caused by deflection of the track. It may also cause "rough-ride" incidents and result in damage to rolling stock (such as suspension, DC shoes, AC pantograph etc) . Track-side buildings and stations may also be damaged due to impacted and/or airborne vibration. In order to counter the above problems, the rail industry performs regular inspections to check the track geometry. These inspections may be a visual inspection or they may be performed using electronic apparatus to measure the geometry of the tracks. However, these inspections are expensive and time consuming. Consequently, the inspections are usually only performed periodically, for example on a weekly basis. The cost of electronic apparatus to measure accurately the track geometry may also be prohibitive. The problems associated with identifying poorly supported railway ties using the above methods may be compounded where continuous welded railway tracks are used. These tracks may deflect under the load of passing rolling stock and then return to their original position, along with the supporting railway ties, once the load is removed. Thus, inspections performed when the track is not under load may fail to identify areas where the railway ties are poorly supported. An alternative approach adopted by the rail industry to identify areas of track subject to displacement under load has been to initiate non-permanent intrusive testing. However, this method of data collection is not permanently installed and such tests are only undertaken at sample spots, such as areas identified by train drivers as being particularly problematic . To address some of the above problems, specialist on- track inspection machines may be used. These machines are sufficiently large as to exert loading on the track similar to that experienced during normal operation. However, these machines are costly to purchase and maintain. Furthermore, special arrangements may have to be made to provide access to a section of potentially defective track. Delays may be caused while these inspections are performed. Thus, current inspection techniques are generally expensive. Furthermore, the inspection apparatus is not usually installed on a permanent basis and, consequently, the inspections need to be repeated on a regular basis. The present invention, at least in preferred embodiments, attempts to address at least some of the above problems. Viewed from a first aspect, the present invention provides apparatus suitable for providing an indication of the displacement of a railway tie, the apparatus comprising a mounting element for mounting on the railway tie and an indicator member movable relative to the mounting element, wherein retaining means are provided for retaining the indicator member in a displaced position relative to the mounting element. The displacement of a poorly supported railway tie will cause the indicator member to be displaced relative to the mounting element. Subsequently, even if the railway tie returns to its original position when the loading is removed from the railway track, the indicator member is retained in a displaced position relative to the mounting element. The mounting of the apparatus on the railway tie provides a datum for the indicator member and a visual inspection of the indicator member may provide an indication of the displacement of the railway tie. The retaining means provided in the apparatus may advantageously allow an indication of the maximum displacement of the railway tie during the time period between inspections to be determined. A positive indication of poorly supported railway ties may therefore be provided. If the apparatus shows that the displacement of the railway tie has been greater than a predetermined maximum, the required steps may be taken properly to support the railway tie. The apparatus is preferably permanently attached, in use, to the railway tie. Although the apparatus may be arranged to provide an indication of horizontal displacement of a railway tie, it is preferably used to provide an indication of vertical displacement. Preferably, the indicator member extends substantially vertically when the apparatus is installed. Although the indicator member may be rotatably mounted, it is preferably slidably mounted to allow axial displacement. The axial displacement of the indicator member allows for a relatively simple mechanism to be employed and provides a clearly visible and easily interpreted indication of the displacement of the railway tie. A scale may be provided on the mounting element to allow an indication of the displacement of the indicator member to be determined. Alternatively, a scale may be provided on the indicator member. The scale may be in centimetres and millimetres. The apparatus is preferably installed such that the indicator member is zeroed relative to the mounting element. This zeroing may be achieved, for example, by arranging the scale so that a marking provided thereon is flush with a mark on the mounting element or the top of the mounting element. Alternatively, the zeroing may be achieved by locating the indicator member in the mounting element so that the upper surfaces of both the indicator member and the mounting element are flush. The indicator member and/or the piston is/are preferably displaceable in first and second directions relative to the housing to facilitate more readily zeroing of the apparatus . The apparatus is preferably mounted on the end of the railway tie to provide readily comparable results. However, installation of the apparatus to the centre of the railway tie is considered equally effective and suitable. Alternatively, the apparatus may also be installed upon "track furniture" and fixed track-elements, not themselves railway ties for the purpose of providing an indication of displacement (for example, the apparatus installed upon railway points electrical switchgear or plant, which may itself be so connected upon or adjacent to railway ties within the track infrastructure) . To assist in the visual inspection of the displacement of the indicator member, the mounting element and the indicator member are preferably contrasting colours. Most preferably, the indicator member is orange or yellow in colour and the mounting element is black. The indicator member may contact the supporting ballast or another datum surface when the railway tie is displaced to effect displacement of the indicator member relative to the mounting element. Preferably, however, the apparatus further comprises a piston and the piston contacts the supporting ballast or datum surface to effect displacement of the indicator member. The piston may be provided with a foot portion to ensure a good contact with the surface of or anchorage within the ground or ballast. The length of the indicator member and/or the piston member may be adjustable to allow the apparatus to be calibrated. The adjustment may be made by displacing first and second components making up the indicator member and/or the piston member relative to each other. Alternatively, a portion of the indicator member and/or the piston member may be removed, for example by cutting or sawing. Preferably, however, a datum member is provided suitable for installation at a predetermined depth relative to the railway tie or mounting member. Installation of the datum member at a predetermined depth allows the apparatus to be zeroed without making the indicator member and/or the piston adjustable in length. The datum member is preferably conical in shape to allow it more readily to be introduced into the ballast. In a further embodiment , the datum member may be provided as a permanently-fixed, integral element of the indicator member or piston member in the form of a foot as previously described. The indicator member is preferably provided with a radial projection or flange suitable for engaging the mounting element to limit the relative displacement of the indicator member. Similarly, the piston may be provided with a radial projection or flange for engaging the mounting element also to limit the relative displacement of the piston. The mounting element is preferably a housing which extends around the indicator member. This arrangement advantageously protects the indicator member during general use and installation. The retaining means to prevent the indicator member returning to its original position may be effected simply by ensuring that the indicator member cannot move freely relative to the mounting element. For example, the indicator member may be a restricted fit in a channel defined in the mounting element. Alternatively, the indicator member or mounting element may be provided with a surface having a saw-tooth pattern for engaging an engagement member provided on the other of said indicator member or mounting element. The engagement member is preferably a flexible plastics member. Most preferably, however, a friction grommet (such as a rubber grommet) is provided in the mounting element to frictionally engage the indicator member. The friction grommet is preferably provided around the piston and retained in position in a channel in the mounting element. The mounting element is preferably provided with at least one hole to receive a mechanical fastener, such as a screw or a nail, to mount the apparatus on the railway tie. The mounting element may alternatively be adhesively attached to the railway tie. Preferably, the mounting element is provided with one or more adhesive pads. Of course, mechanical and adhesive means may be used in combination. The piston and/or indicator member may have any cross- sectional shape (i.e. square, triangular or hexagonal). Preferably, however, the piston and/or indicator member has a circular cross-section to allow a circular engagement member to be used. The present invention further extends to a railway tie in combination with apparatus described herein. The present invention also extends to a kit of parts for assembly into apparatus as described herein. Viewed from a further aspect, the present invention provides a method of inspecting a section of railway track supported on a plurality of railway ties, the method comprising the steps of: (a) installing apparatus as described herein on at least one of said railway ties; (b) allowing rolling stock to run along said section of railway track after said apparatus has been installed; and then (c) inspecting each device to determine if the indicator member has been displaced greater than a predetermined distance . The apparatus is preferably installed on a plurality of the railway ties. This allows the displacement of a plurality of railway ties along said section to be monitored simultaneously. The apparatus may be installed on each railway tie along said section of railway track. Alternatively, the apparatus may be installed, for example, on every second, third, fourth or fifth railway tie along said section of railway track. The section of railway track may extend over an area where problems are more likely to occur. For example, the method may be performed for a section of track having points or switches provided therein; or may be performed at a crossing. The apparatus is preferably permanently installed. The inspection of each device may be performed manually or automatically. Viewed from a further aspect, the present invention extends to a tool for installing apparatus as described herein. The tool comprises a tubular portion which, in use, extends round the apparatus, the tubular portion having an opening providing in the side thereof to allow the tool to be withdrawn from around the apparatus after it has been installed, wherein the said opening is at least partially closeable by a moveably mounted panel suitable for protecting the apparatus during installation. Although the tubular portion may have a clam-shell arrangement to create the desired opening, the panel is preferably rotatably mounted about the longitudinal axis of the tubular portion. A preferred arrangement of the tool retains the datum member so as at least partially to extend out of the tool in a predetermined position. This arrangement is particularly advantageous as the installation of the datum member at a predetermined depth may be performed with a high degree of accuracy and repeatability. Furthermore, in preferred arrangements whereby the datum member is conical in shape, the tool may more readily be introduced into the ballast. Viewed from a further aspect, the present invention relates to apparatus suitable for providing an indication of the displacement of a railway tie supported by ballast, the apparatus comprising a mounting element for mounting fixedly proximal to the railway tie, and an indicator member cooperable with the railway tie and movable relative to the mounting element, wherein retaining means are provided for retaining the indicator member in a displaced position relative to the mounting element. Viewed from a still further aspect the present invention relates to a method of inspecting a section of railway track supported on a plurality of railway ties, the method comprising the steps of: (a) installing a plurality of displacement indicator devices on said railway ties; (b) allowing rolling stock to run along said section of railway track after said displacement indicator devices have been installed; and then (c) inspecting each of said displacement indicator devices. Viewed from a still further aspect, the present invention provides a displacement measuring apparatus suitable for measuring the displacement of a structural element, the apparatus comprising a mounting element mountable on the structural element and an indicator member movable relative to the mounting element. Viewed from a yet still further aspect, the present invention provides a displacement measuring apparatus suitable for measuring the displacement of a structural element, the apparatus comprising a mounting element mountable proximal to the structural element and an indicator member cooperable with the structural element and movable relative to the mounting element . It will be appreciated that the preferred features outlined herein with regards to the embodiments suitable for mounting on a railway tie may equally be incorporated into the embodiments suitable for attachment to other structural elements. The structural element may be, for example, a railway tie or a pile for a bridge, pier or other structure. Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a cross-section front view of the measurement device in accordance with a first embodiment of the present invention; Figure 2 shows a front view of the measurement device shown in Figure 1 ; Figure 3 shows a front of the measurement device of Figure 1 with the indicator member in a displaced position; Figure 4 shows a side view of the measurement device of Figure 1 ,- Figure 5 shows a plan view of the measurement device of Figure 1 ; Figure 6 shows a cross-sectional front view of a second embodiment of a measurement device in accordance with the present invention; and Figures 7a and 7b show a fourth embodiment of the present invention for use on railway ties supported on flexible pads. A measurement device 1 for mounting on the end of a railway tie 2 in accordance with a first embodiment of the present invention is shown in Figure 1. The measurement device 1 comprises an indicator member 3 slidably mounted in a housing 5. A piston 9 is slidably mounted in the housing 5 below the indicator member 3. A conical ballast cone 11 is also provided for installation in the support ballast (not shown) for the railway tie 2. The indicator member 3, the housing 5, the piston 9 and the ballast cone 11 are all made of plastics material employing known techniques. The indicator member 3 is preferably a highly visible colour, such as orange. The housing 5 and the piston 9 are preferably a dark colour, such as black, to contrast with the indicator member 3. The indicator member 3 has a square transverse cross- section and a calibrated measurement scale 13 is provided on a front face thereof. Alternatively, the indicator member 3 may have a circular transverse cross-section. A first rubber friction grommet 15 is provided in a channel 17 defined by a first annular projection 16 provided on the inside of the housing 5. The first friction grommet 15 contacts the outer surface of the indicator member 3 to prevent the indicator member 3 moving under the force of gravity. The indicator member 3 is provided with a first flange 18 at its lower end which engages the first annular projection 16 to limit the displacement of the indicator member 3 and prevent it being displaced out of the housing 5. A second rubber friction grommet 19 is provided in a channel 21 defined by a second annular projection 20 provided on the inside of the housing 5. The second friction grommet 19 contacts the outer surface of the piston 9 to prevent the piston 9 moving under the force of gravity. The piston 9 is provided with a second flange 29 at its upper end which engages the second annular projection 20 to limit the displacement of the piston 9 and prevent it being displaced out of the housing 5. As shown in Figure 2, the housing 5 extends around the indicator member 3 to keep it clean and also to protect it from damage. The provision of first and second friction grommets 15, 19 also helps to prevent the ingress of dirt into the housing 5. The ballast datum cone 11 is installed at a predetermined depth below the upper surface of the railway tie 2 such that, when the bottom surface of the piston 9 rests on the datum cone 11 and the indicator member is in contact with the piston 9, the zero on the scale 13 is level with the upper edge of the housing 5. As shown in Figure 3, displacement of the piston 9 in an upwards direction relative to the housing 5 causes the indicator member 3 also to be displaced upwardly. Thus, when the railway tie 2 is displaced downwardly, the piston 9 contacts the datum cone 11 and is displaced upwardly relative to the housing 5 thereby also displacing the indicator member 3 upwardly relative to the housing 5. The extent of the displacement of the indicator member 3, and thus the railway tie 2, may be determined by reading the value on the calibrated scale 13 level with the upper edge of the housing 5 (approximately 15.5 cm in the example shown in Figure 3) . A side view of the measurement device 1 is shown in Figure 4. The housing 5 is provided with an integrally formed bracket 23 having holes 25 formed therein for receiving mechanical fastening means such as a nail or screw. The housing 5 is also provided with peel -off backing self-adhesive pads 27 which adhesively attach the housing 5 to the railway tie 2. Although the measurement device 1 may be reused, it is preferably permanently attached to the railway tie 2. A plan view of the measurement device 1 is shown in Figure 5. The installation of the measurement device will now be described. The installation may be performed manually employing a tool developed specifically for this purpose (not shown) . The tool comprises a light weight steel tube of larger diameter than the housing 5. The ballast cone 11 is displaced downwardly by the tool to allow the measurement device 1 more readily to be located in position. The measurement device 1 is located inside the tubular portion such that the bracket 23 extends through a first opening provided in the side thereof. When the bracket 23 contacts the upper surface of the railway tie 2, the ballast cone 11 is at the predetermined depth. A panel provided in the steel tube is then rotated to create a second opening in the side of the tubular portion proximal to the sleeper 2. The second opening is sized such that the tool may be withdrawn from around the measurement device 1 once it has been installed. The panel preferably rotates about the longitudinal axis of the tool such that half of the tube is effectively fitted inside the other half. Thus, the tool allows the measurement device 1 to be fixedly mounted on the sleeper 2 with the datum cone 11 located at a predetermined displacement below the upper surface of the sleeper 2. The installation process is repeated for each railway tie 2 provided in the railway. More preferably, a measurement device 1 is installed on each end of each railway tie 2. Although the tool described above is manually operated, it will be appreciated that the same principle could be applied to produce a mechanically operated/automatic tool installed upon existing on-track machines such as a "pandrol- clip machine" or "tamping machine" . The operation of the measurement device 1 in accordance with the present invention will now be described. When the measurement device 1 is initially installed on a railroad tie, the indicator member 3 is zeroed, as shown in Figure 1. In this zeroed position, the lower end of the piston 9 rests on the ballast cone 11. This zeroed position can be reset at any time, as may be required due to track maintenance works or reusing the measurement device 1 on another railway tie. Once installed, if the end of the railway tie 2 on which the measurement device is mounted is displaced in a downward direction, the piston 9 is displaced upwardly relative to the housing 5 by contacting the datum cone 11. The piston 9 cooperates with the indicator member 3 to displace it upwardly. The railway tie 2 may then return to its original position, for example by the spring action of the railway tracks, but the first and second friction grommets 15, 19 engage the sides of the indicator member 3 and the piston 9 respectively and prevent them from returning to their original positions. Thus, the indicator member 3 provides a visual indication of the displacement of the railway tie 2 under load, even if it subsequently returns to its original position. A track inspection may then be performed to check for railway ties 2 which have been displaced under load beyond a predetermined safety level. The indicator member 3 will clearly show which railway ties 2 are not properly supported by the ballast as they will show a greater displacement.

These track- side inspections may form part of a routine foot patrol . If the visual inspection of the measurement devices 1 highlight a railway tie 2 which has been displaced under load greater than a predetermined distance, the necessary steps may be taken to improve the ballast support for that railway tie 2. The ballast cone 11 may then be reinstalled at the desired depth and the indicator member 3 and the piston 9 reset to the zeroed position. If the measurement device 1 indicates that the displacement of the railway tie 2 under load is not sufficient to be of immediate concern, then ongoing monitoring for worsening of the situation can be undertaken. A second embodiment of the present invention is shown in Figure 6. The components of the second embodiment correspond generally to those of the first embodiment and like reference numerals have been used for like components. However, unlike the first embodiment, the housing 5 of the second embodiment of the measurement device 1 is not provided with first and second friction grommets 15, 19. Rather, the indicator member 3 is provided with first and second saw-tooth surfaces 31, 33. The housing 5 is provided with first and second pairs of flexible members 35, 37 which engage the saw-tooth surfaces 31, 33 to prevent the indicator member 3 returning to its zeroed position. In this embodiment, the indicator member 3 and the piston 9 are formed integrally so as to reduce the number of components required to make up the measurement device 1. A third embodiment of the present invention will now be described. This embodiment is also similar to the first embodiment and like reference numerals have again been used for like components. The main difference between the third embodiment and the first embodiment is that the indicator member 3 has a circular transverse cross-section. This arrangement is particularly advantageous as it allows the first and second friction grommets 15, 19 to be of standard circular design and ensures a good contact around the circumference of the indicator member 3. The housing 5 has also been modified in the third embodiment to reduce the amount of plastics material required. The housing 5 is produced from first and second components which clip together and retain the indicator member 3 and piston 9 in position. Advantageously, the measuring device 1 in accordance with the present invention is fully compatible with current and proposed on-track inspection machines and software and may therefore be read by a moving vehicle travelling along the railway track. In particular, the apparatus is particularly suitable for use with video surveying techniques and inspection procedures provided on on-track inspection machines and/or other rail -bound machinery, trains or other vehicles. These surveying techniques may be employed to monitor the measurement device 1 in accordance with the present invention at operational speeds of, for example, 200km/h. Moreover, the measuring device 1 does not interfere with any rail gauge or rolling stock clearance requirements, at least in preferred embodiments. The measurement device 1 also does not impinge upon the operation of rail -borne tamping machines or on-track machinery. The housing 5 may also be attached to sleepers of all types, materials and dimensions. Figures 7a and 7b show a fourth embodiment of the present invention for use on concrete railway ties supported on a micro-cellular support pad 41. The support pad 41 is itself retained in a recess 43 formed in a concrete bed 45. The components in this embodiment are similar to those outlined above and where appropriate like reference numerals have again been used for like components. In normal use, the support pad 41 allows the railway tie 2 to be displaced by a small amount. However, the structure of the support pad 41 may deteriorate over time and eventually the amount of displacement which occurs when rolling stock passes over the railway tie may exceed allowable levels. The same problems as outlined above will then also occur for these types of railway tracks as the railway tie 2 will be returned substantially to its original position by the railway track after the load is removed. As shown in Figure 7a , a measurement device 1 in accordance with the present invention is mounted on the railway tie 2. The indicator member 3 is initially zeroed (in a fully depressed position) with the base of the piston member 9 in contact with the surface of the concrete bed 45. Thus, the bed 45 provides a datum and a separate datum cone 11 is not required. The indicator member 3 may be zeroed by sawing off a portion of the piston member 9. The railway tie 2 may be displaced relative to the concrete bed 45 when rolling stock passes over it causing the support pad 41 to be compressed. The resilience of the railway track and the support pad 41 may, however, cause the railway tie to be returned to its original position. However, as shown in Figure 7b, the indicator member will remain in its displaced position and thereby provide an indication of the displacement of the railway tie relative to the concrete bed 45. Although the present invention has been described with reference to railway track applications, it will be appreciated that the device may be modified so as to be used in other roles where it is necessary to provide the visual indication of the displacement of a structural element, such as a pier pile. It will be appreciated also that the brackets 23 need not lie perpendicular to the longitudinal axis of the indicator member 3 but may lie parallel to this axis to facilitate use in other applications.

Claims

1. Apparatus suitable for providing an indication of the displacement of a railway tie, the apparatus comprising a mounting element for mounting fixedly on the railway tie and an indicator member movable relative to the mounting element, wherein retaining means are provided for retaining the indicator member in a displaced position relative to the mounting element.

2. Apparatus as claimed in claim 1, wherein the indicator member is slidable relative to the mounting element.

3. Apparatus as claimed in claim 1 or 2, wherein said indicator member is of adjustable length.

4. Apparatus as claimed in any one of claims 1, 2 or 3 further comprising a piston cooperable with said indicator member, whereby displacement of said piston displaces said indicator member.

5. Apparatus as claimed in claim 4, wherein said piston comprises a foot portion suitable for contacting the surface of ballast in which the railway tie is mounted.

6. Apparatus as claimed in claim 4 or 5, wherein said piston is of adjustable length.

7. Apparatus as claimed in any preceding claim, wherein said mounting element comprises a bracket for locating on an upper surface of the railway tie.

8. Apparatus as claimed in any preceding claim, wherein said mounting element is provided with at least one hole for receiving a mechanical fastener for fixedly mounting the apparatus on the railway tie.

9. Apparatus as claimed in any preceding claim, wherein said mounting element is provided with at least one adhesive pad for fixedly mounting the apparatus on a railway tie.

10. Apparatus as claimed in any preceding claim further comprising a datum member for locating below said indicator member .

11. Apparatus as claimed in claim 15, wherein said datum member is conical in shape.

12. Apparatus as claimed in claim 10 or 11, wherein said datum member has a recess formed in a surface thereof for receiving an end of the piston or indicator member.

13. Apparatus as claimed in any preceding claim, wherein the indicator member is provided with a scale.

14. Apparatus as claimed in any preceding claim, wherein said retaining means is at least one friction grommet.

15. Apparatus as claimed in claim 6, wherein the friction grommet is retained in position by the mounting element and extends around the indicator member.

16. Apparatus as claimed in any one of claims 1 to 13, wherein said retaining means comprises a saw-tooth surface provided on the indicator member or the mounting element and an engagement member provided on the other of said indicator member or mounting element for engaging said saw-tooth surface .

17. Apparatus as claimed in any preceding claim wherein, in use, said apparatus measures vertical displacement of the railway tie.

18. Apparatus as claimed in any preceding claim wherein the indicator member is substantially inflexible.

19 A railway tie in combination with apparatus as claimed in any preceding claim.

20. A kit of parts for assembling apparatus as claimed in any one of claims 1 to 18.

21. A method of inspecting a section of railway track supported on a plurality of railway ties, the method comprising the steps of: (a) installing apparatus as claimed in any one of claims 1 to

18 on at least one of said railway ties; (b) allowing rolling stock to run along said section of railway track after said apparatus has been installed; and then (c) inspecting each device to determine if the indicator member has been displaced greater than a predetermined distance .

22. A tool for installing apparatus as claimed in any one of claims 1 to 18, the tool comprising a tubular portion which, in use, extends around the apparatus, the tubular portion having an opening provided in the side thereof to allow the tool to be withdrawn from around the apparatus after it has been installed, wherein said opening is at least partially closable by a movably mounted panel suitable for protecting the apparatus during installation.

23. A tool as claimed in claim 22 wherein the panel is rotatably mounted.

24. Apparatus suitable for providing an indication of the displacement of a railway tie, the apparatus comprising a mounting element for mounting proximal to the railway tie, and an indicator member cooperable with the railway tie and movable relative to the mounting element, wherein retaining means are provided for retaining the indicator member in a displaced position relative to the mounting element.

25. A displacement measuring device suitable for measuring the displacement of a structural element, the device comprising a mounting element to be mounted on the structural element and an indicator member movable relative to the mounting element.

26. A displacement measuring device suitable for measuring the displacement of a structural element, the device comprising a mounting element to be mounted proximal to the structural element and an indicator member cooperable with the structural element and movable relative to the mounting element .

27. A displacement measuring device as claimed in claim 25 or 26 further comprising retaining means for retaining the indicator member in a displaced position relative to the mounting element .

28. A displacement measuring device as claimed in any one of claims 25, 26 or 27, further comprising a measurement scale.

29. A displacement measuring device as claimed in any one of claims 25 to 28, wherein the structural element is a railway tie, or a pile for a bridge, pier or other structure.

30. A measurement device substantially as herein described and with reference to Figures 1 to 5; or Figure 6.