How Trains Move From One Line to Another

The Institution of Railway Signal Engineers Inc Australasian Section Incorporated

A POINT OF PRINCIPLE How Trains Move from One Line to Another (And how the S&T Engineer becomes involved in the operation)

Richard Flinders MIRSE Product Line Manager Siemens Rail Automation

SUMMARY Some time ago the Australasian Committee decided that at least one paper a year would be presented to the Technical Meetings which covered basic principles. They were to be presentations that took a basic signalling/telecommunication subject and went through the principles of use and operation. They were to be aimed at younger members and those who had recently joined the profession. However it is to be hoped that maybe they also passed on some new information to older members as well. This paper is part of that series and looks at point operation (also known as switches, layouts and turnouts) and discusses some of the methods of moving points both mechanically and electrically. It also describes the various means of detecting that the points have moved to the required position and that they have been prevented from moving as a train passes over them. By necessity, some Civil Engineer’s terms will have to be used in this paper!

INTRODUCTION Very early on in the history and development of railways (Day 2 or even Day 1) it was recognised that a wagon (or rail truck) needed to be able to move to another line to allow others to pass. The very first attempts to create these points (or switches) were “Stub” switches which as the name implies were stub lengths of rail that could be moved such that the wheels of a wagon could take another direction. The ‘modern’ points however have their beginnings in a patent by Charles Fox of Derby, UK in 1832, about the time mechanisation of railways really began. From these pioneering beginnings we now have points that allow trains to diverge at over 200km/h! However, not in Australia…..Our railways are freight orientated and development in the Australasian market has been around reliable operation at 40Tonnes plus axle loads. The application may differ but the same principles still apply, along with the challenges of environment for many installations. INITIAL TERMINOLOGY

IRSE Convention – Launceston

It is very easy to become confused by the interlinking use of terms such as Switch, Point Blade, Points etc. The moving parts of the design being the Switch Blades, Point Blades etc. The terms do not easily adapt to specialist designs that still need to be operated, locked and detected. In order not to confuse the reader, now or later in general conversation with suppliers and specifiers From this point on I will refer to the total assembly of trackwork required to move a vehicle between tracks as a TURNOUT. This is the Civil Engineers term for a point assembly of varying designs in the Australasian market. However for those interfacing to trackwork plans please be aware that our Civil colleagues apply the term to the whole layout including the Frog. If this is a Swingnose version then it will need to be operated, locked and detected! POINT LAYOUT DEFINITIONS

DESIGN-SOME

USEFUL

The Signal Engineer does not require detailed knowledge of turnout design but some understanding of key parameters will allow more reliable scoping of operating and detection requirements. 19th July 2013

Richard Flinders MIRSE

A Point of Principle

and simple rotary or slide detector can be used to detect the blade position. There are many variants of lever available and specification generally follows the operator’s preferences. Some caution needs to be taken in detecting nonlocked lever operated turnouts as some of the older style mechanisms such as the Victorian WSa and Thornley lever are a spring toggle design and need careful adjustment if they are to reliably position the blade in a closed position repeatedly. USA imported levers, generally to relevant AREMA standards, offer a similar function with padlockable operating lever stands. These mechanisms, together with weighted levers can offer the advantage of trailability.

Fig 1 Common Parts of a Turnout NOTATION AREMA – American Railway Engineering and Maintenance-of-Way Association Blade/Switch – Moveable part of the turnout that guides the wheels to another track Detector – A device that senses the position of the blades FPL- Facing Point Lock Frog – Part of the Turnout which guides the wheels over the intersection of the rails LockBar – A bar that holds the blades in the correct position Normal/Reverse – Default position generally determined by the Designers as allowing passage of traffic on the most used route. Reverse is the opposite of Normal Spreader/Stretcher – Interconnecting bars between the blades Stockrail – Fixed rail of the turnout that the blade operates against Swing nose Crossing - Moveable Frog used to eliminate the gap at the intersection of rails MECHANISMS FOR OPERATING TURNOUTS In its simplest form, connecting a lever offering a mechanical advantage allowed quick and easy movement of the blades between the stockrails. It was necessary to ensure that not only did the required blade close against the stockrail but the opposite blade opened sufficiently to ensure the flange of the wheel did not strike it! This simple point lever still offers a cheap method of manual operation and is in use in sidings and often on lightly used rural lines, sometimes simply locked with a traffic keyed padlock. Hand Throw Levers The pioneers of turnout operation! Hand Throw Levers still have a place in turnout operation but this rarely concerns the Signal Engineer. Occasionally we are required to detect the position IRSE Technical Meeting – Launceston

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Fig 2 WSa Handthrow lever Also occasionally specified is non-powered facing point lock equipped hand throw levers. These are an escapement derived mechanism and offer an AREMA compliant facing point lock in the normal position only. Generally specified where security of lock is required e.g. Mainline facing turnouts for emergency sidings or occasional use traffic. Not trailable but they can replace the functions of some localised ground frame installations. Lever Frames Even in the 19th Century, automation was a popular efficiency improvement and rising wages led to the development of ‘consolidated’ point operation. Still manually operated but by a ‘Signalman’ in a centralised location. A maximum effective operating distance was around 300/350metres constrained by the effort required to pull or push the lever. There are still many lever frames in service but for the purpose of this paper I will limit discussion to small lever frames used generally for locking and operation of occasionally used sidings, generally known as Ground Frames/Switchlocks. Even now, the force required to operate these installations is testing the limits of modern OH&S regulations especially with the more modern, heavier, turnouts. th

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Richard Flinders MIRSE

A Point of Principle

Fig. 4 Air Operated Mechanism controlled by ‘E’ Valve-Sydney Metro Network 2. Air cylinder mounted in a similar location to a point machine driving a proprietary railhead locking mechanism, Spherolock, Claw Lock etc.

Fig 3 Ground Lever Frame-Wollongong NSW Powered Mechanisms There are three direct power sources used generally in the Australasian region. Electric, Hydraulic and Air, although all use electricity for the primary source! Air Mechanisms Air provides one of the most simplistic mechanical systems but is not commonly used. Restricted to Sydney and some smaller installations in Melbourne and Brisbane. Typically it becomes an attractive option in areas of high density as the high infrastructure costs of air compressors and conditioned reticulation systems needs to be amortised over a reasonable install base. It can also be found, typically overseas, in hump yards and areas that have very high traffic density and need less than two second point switching.

Fig 5. Air Operated Mechanism driving Claw LockSydney Metro Network Control of operation is interfaced from the signalling system by a Control Unit (Valve). Actually more than just a valve, this unit acts in some cases as a lock and has detection of air pressure contacts.

Within the Australasian market we find two types of operating mechanism; 1. Air cylinder operated escapement mechanism, generally mounted between the running rails and colloquially named 4 Foot Mechanism. Fig. 6 Typical Air Controller Circuit (Note Plunger and Pilot Valves)

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A Point of Principle

Hydraulic Mechanisms Hydraulic drives are popular overseas, particularly the UK and Europe. They have found some acceptance in Australasia but not universally. They consist of an electro-hydraulic power unit coupled to a double acting ram and connected to either a Network Rail Clamplock (Adelaide/Melbourne) or Claw/Spherolock Rail Lock mechanisms (Melbourne/Queensland).

used for many years. Particularly appropriate for our track conditions has been the ability to apply a closure force to the blade. This is sometimes used to ‘punch’ through maintenance or environment issues and ensure reliability.

Fig 8 AREMA Compliant Mechanism-Pilbara WA Railhead Lock Mechanisms (or Thrusters)

Fig 7 Hydraulic Drive-Melbourne Metro (No Locking) Starting to enter the Australasian market is a new generation of electro-hydraulic units from Europe. These units are offering low maintenance, sealed mechanisms often operating proprietary locking devices contained within a Tampable bearer. Electric Mechanisms Electro-mechanical mechanisms are used in the majority of installations. These can be split into two styles; Internal lock and thrusters.

By definition these mechanisms are a point machine without internal locking. This can cause some confusion amongst specifiers not familiar with the differences and it is often wise to use the term ‘Thruster’ to differentiate! Not necessarily tied to AREMA standards these machines may differ in their mounting requirements. All will have an operating stroke of at least 180mm to take account of the locking and unlocking requirements of a railhead lock mechanism. That is 125mm nominal blade movement and around 40mm of travel to operate the locking mechanism part of the travel. Detection is generally internal for lock & blade position. European designed machines often apply a secondary point lock via locking of the detection bars.

Internal Lock Mechanisms Within Australasia these mechanisms generally compliant to AREMA/BS standards;      

are

Operating Stroke 152mm (6 inch) Escapement Type operation Separate lock bar Lock resistance of 89kN (20,000lbs US) Standardised mounting position Closure force of 1720Kgs (3800lbs US)

There are a variety of mechanisms in service from various manufacturers with some having been in service for over 50 years! Suited to the style of turnouts and environment in Australasia these machines have generally been IRSE Technical Meeting – Launceston

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Fig 9 Thruster Mechanism operating Claw Lock Railhead Lock System-Salmon Gums WA

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Richard Flinders MIRSE

A Point of Principle

Failure and Emergency Working All operating mechanisms have some sort of hand operation in case of failure, and during Engineering works. Generally this falls into two forms; A fixed stroke operating lever for operating the turnout or a handcrank point on the mechanism. All will be protected from unauthorised operation by a padlock which will release a cover and either immediately open the internal motor power circuit or requires operation of lever or crank handle cover that carries this function. Generally it will also activate an indication circuit at the signallers’ position. Operation of the turnout will then be via a fixed stroke lever, restrained in lockable lever stands or insertion of crank handle. Crank handle operation was common over all of Australasia but in recent years there has been a move by railways to the fixed lever style operation. This has been driven by a reduction in operating staff in the field able to perform this function as well as OH&S requirements.

Australasian market generally followed the practises adopted by the Signal Engineer in the early stages of railway development. The background and experience of those Engineers having significant influence on future direction and leading to a multitude of differing standards and practise across the region. NSW, WA & Qld generally adopted British practise with Vic & SA following American practise. The major difference being American practise was to detect only the position of the Normal closed blade. The two standards that have influenced our region are;  USA (AREMA Standards)  UK (Network Rail formerly British Rail Standards) In practise the two offer similar settings of around 2-3mm for lock and 3-6mm for detection. The actual values determined by rail operators tend to be within these settings and influenced by the style of turnout adopted and it’s sensitivity to damage from the wheel flange when slightly open, generally known as ‘undercut’. European This is mentioned as a generic influence from both the adoption of railhead locking in the late 1950’s by Queensland Rail for trailable turnouts and also entry of European designed and manufactured mechanisms in the 1990’s and beyond.

LOCKING THE TURNOUT What are we Locking? The facing point lock is a device that locks the point blades in position to allow the safe movement of a train in a facing direction over the turnout. The closed blade is locked in a position against the stockrail and the open blade is restrained from closing the flange gap between the blade and the stockrail. In the majority of mechanisms this is achieved by actually preventing the movement of a locking bar connecting the two blades together. Effectively by inserting a plunger into a notch in this bar either between the rails of by extension of this bar into the point mechanism.

In particular the setting requirements for railhead locks which vary from those of internal mechanism locks. Whilst the specific settings of lock and detection clearance will still apply a railhead lock is generally set without any ‘pinch’ of the blade against the rail to ensure the lock releases easily. Some European machines also feature secondary hold of the detection rods. Introduced to allow emergency restraint of the blades in the case of component failure of railhead locks in period where steel technology was not as advanced. Every installation of locked turnouts will follow the basic principle or operation, irrespective of the type of mechanism or turnout;

Which Standard? Locking the blades in position for the passage of a train in either direction is not mandatory for all turnouts. The use of locking is defined by each rail authority and generally relates to the type of traffic and the permitted speed of trains in the facing move. Freight traffic being given more latitude but occasional passenger train movements may be allowed at speeds below 15km/h. It is a risk based scenario. Facing point locks (FPL) were adopted relatively early in the history of modern points due to some significant accidents overseas. Adoption by the IRSE Technical Meeting – Launceston

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Open the indication circuit Unlock the points Operate the points Lock the points Close the indication circuit (AREMA 12.2.1 & BS 581Pt. 3)

Internal Machine Locking Machines in use in the Australasian region follow the requirements of AREMA/British Standard for the internal lockbar, lock and interference. The th

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Richard Flinders MIRSE

A Point of Principle

track connections however can vary greatly in their design. It is important to ensure that locking design and the maintenance requirements are carefully considered. Not only the internal machine lock but connections to the turnout and including any Spreaders used to connect the blades together. As shown by the accidents at Potters Bar and Grayrigg in the UK show, (see References), failure to properly consider and maintain all the track connections can have severe consequences.

reasons such as assisting the movement of the blade.

Railhead Locking This is the term used to describe locking of the blades external to the operating mechanism. Within our region it will be either a claw type arm connected to the blade and locking by interference with a bracket connected to the stockrail. Alternatively, it may also be a proprietary ‘sliding dog’ type mechanism contained within a tube connected to both blades.

Fig. 11 Floating Spreader Claw Lock Layout-NSW

DETECTING THE TURNOUT Lock Detection We generally detect the insertion of the internal lock through the lockbar in internal lock machines and the operating bar position for the railhead locks. By inference we determine that the lock is correctly operated! It is therefore important to have confidence in the connections to these positions from the track. Blade Detection

Fig. 10 VAE Spherolock Point Lock MechanismDampier WA By locking the closed blade directly to the stockrail we remove the issues associated with connections to the lock. The open blade is generally constrained by the blade connected locking claw being ‘captured’ in a slot or notch of the fixed operating bar. Thus opening whilst the other blade closes. Railhead locking can be considered more sensitive in operation to track settings and deficiencies due mainly to independence of the blades. Because we are placing the mechanical lock actually on the rail we are subjecting it to the harsh track environment and together with the removal of spreaders making the blade a more flexible beam means track defects, condition and environment can affect the reliability. In certain cases to overcome and negate these forces for reliable operation specialised Spreaders have been fitted. To reduce roll of the blades, reduce the inherent blade closure force or other IRSE Technical Meeting – Launceston

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The purpose of blade detection is to know the position of the blades and to ensure that any movement of the closed blade open to a position where the wheel flange could split the turnout or the open blade could contact the wheel flange is detected. The older US standard, adopted in our region by railways following US practise, was to only detect the position of the normally closed blade. All Australasian railways have now moved to detecting both blades. However some legacy installations exist. Detector rodding is connected to the end of the blade or to a firmly bolted extension if clearance of bearers is an issue. The detector which can be part of the operating mechanism contains the switch operated by the rod position. Some detectors mount to the stockrail. In some cases with the thick web assymetric section of the blade it is permissible to detect the position of the blade at a distance from the toe per some European practise, often around 200300mm .

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A Point of Principle

the ‘Toe’ (that is the machine end and looking towards the diverging tracks and Frog), always apply. The signalling specification is then left or right hand dependant on location of the mechanism. The final part being which blade is normally closed…Left or right which may also be described as adjacent or opposite (referencing the closest blade to the mechanism). This information is still required for InBearer and 4 Foot mounted type drives as cabling entries and detection handing need to be specified to the supplier! (4Foot being the term adopted to define the space within the running rails of all gauge railways).

Fig. 12 Internal Point Machine Detection

Fig 14 Typical Handing Requirements Terminology

Fig. 13 Rail Mounted Point Blade Detector

Our ‘borrowing’ of names has led to some confusion over parts of a Turnout (Switch or Points!).

Supplementary Detection We may also need to know that there is sufficient clearance for the wheel flange through the turnout where the blades are flexible or may be subject to frictional resistance to movement. Whilst a loaded 40 tonne axle load minerals train will easily ‘push’ the blade out of the way, repeated actions could cause stressing or damage to the rail. In the case of higher speed light passenger traffic, it could cause rough riding or even allow the wheel to climb off the rail and create a derailment.

Definition Bearers Switch/Point Blade Toe Supplementary Drive Spreader

UK Variant Sleepers Blade Toe Backdrive

USA Variant Ties Switch Switch Point Helper

Stretcher

Gauge Rods

BASIC PRINCIPLES Conventional Style Turnouts

READING A TURNOUT….. One of the most common errors with specification of signalling product for a turnout is the handing. Whilst our Civil colleagues use the direction of diverge to indicate the ‘hand’, Signal Engineers use the placement of operating mechanism and normal position. (Our interest being which side of the track to run cabling and ensuring that detection circuits are correctly indicated)(See previous definitions of Normal and Reverse). The diagrams below can act as a reference for specification but the rule of ‘positioning oneself at IRSE Technical Meeting – Launceston

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I have generalised here and put all non-tangential turnouts into this category. Generally all AREMA compliant turnouts will be manufactured to have the unrestrained blade sit against the stockrail with an amount of force. They are designed to have both blades connected via a fixed spreader. This has the effect of ‘neutralising ‘the forces of the blades and allowing a relatively low force operating requirement. When this style of turnout is adapted to railhead locking there can be operating issues…. th

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Richard Flinders MIRSE

A Point of Principle

It is possible for our Civil colleagues to adjust the blades by ‘crowing’ them. That is a slight change to the geometry to reduce the amount of closure force, however this is not possible in all cases and therefore the free blades can exert a withdrawal force on the lock. (Blades are ‘’crowed’ that is bent using a device such as the one below in Fig 15. A slight change to the geometry of the blade can reduce, or increase the blades natural position against the stockrail and thus the force required to move and hold it.)

Fig 16 In Chairplate Switch (Blade) Roller We are dealing with application of a load to a cantilevered beam and with judicious use of point rollers to reduce the frictional load the longer turnouts with 1:20 and greater radii actually require less force to operate then a short blade! TURNOUTS Fig 15 Jim Crow Rail Bender

What exactly are these large track structures that we must operate and detect?

Tangential Geometry Turnouts

Some History

Unlike the conventional turnouts, these turnouts generally have a design of neutral or low closure force about the blade at the stockrail position. This means that they generally do not encounter the issues of operation when railhead locking is used.

The Technology behind turnouts changed little in nearly a century. It is still quite easy to find cast components of turnouts being reused in service with manufacture dates in excess of 50 years! These turnouts, generally derived from either US or UK practice were simple bolted heel designs that required little force to operate. The US standardised on layouts varying in switch length between 11 and 33 feet, (3.35 and 10 metres approx). This generally gave operating speed for trains diverging from 15-30mph, (3468km/h). Like many aspects of railway technology in Australasia, we acquired it when in the early 20th Century overseas Engineers were recruited to manage our mostly Government owned systems. They brought with them knowledge of the overseas standards and our local Engineers and Draftspersons adapted them to suit specific requirements. Government railways mostly used their own facilities to manufacture the turnouts using rail supplied from Australian Steel manufacturers to our own, (slightly different) design! There were a few local private suppliers who serviced private and specialist railways such as Sugar Mills etc. and supplemented the railways own capacity to supply. New Zealand appears to have differed by mostly importing its requirements from the UK as it did for most of its trackside signalling requirements.

All Australasia installed Tangential turnouts utilise a thick web blade so can look daunting when considering operation. However the newer designs are often supplied with point blade rollers specified and operation requires similar forces to conventionally bladed turnouts. (With heavier rail sizes the weight of the blade can affect movement due to friction therefore rollers in the plates work to let the blade roll and reduce this friction. They can be very effective in reducing the forces back to about the levels required for a fixed heel turnout).

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A Point of Principle

What Turnouts are Generally Installed in Australasia? These are split this into three groups for ease of explanation. Conventional I would describe conventional turnouts as those conforming to the ‘older’ design practises, By far the majority of turnouts in operation fall into this category. They may have a bolted or fixed heel block and may be of any Australian Standard rail section. However the installation of turnouts below 50Kg/m rail size is becoming rare in all jurisdictions.

vehicle ride qualities and reduced maintenance requirements. It is not the intention of this paper to expand on this development and further technical information is readily available via the internet or by asking our Civil colleagues. One issue of terminology again creeps in here…Whilst generally we have adopted the US practice of identifying turnouts by the angle of diverge, i.e. 1:12 etc. The European practice has generally been adopted for Tangential turnouts of using the radii of the described curve in metres i.e. 300metres. (Appendix 2)

Fig 18 Early Tangential Turnout Installation (Federation Square, Melbourne 1998) Specialised Designs Fig 17 Bolted Heel Turnout (Bunyip Victoria) Often these types of turnouts are installed for cost reasons or because of limited scope for track geometry changes, particularly within crowded urban rail reserves. Tangential Tangential turnouts have their development in European practice in the late 20th century. Generally, European railways were built for higher speeds and more intensive operation. This meant there was a desire to maintain higher speeds through diverging moves at turnouts. The development of Asymmetric rail sizes allowed railway companies to develop geometries of turnout that would if conventional rail was used for blade manufacture, result in very thin blade tips and premature wear. Initial Australasian take-up of this technology was driven by the entry into our region of European trackwork companies. Whilst our large heavy haul market with Greenfields sites allowed general adoption of this technology, our metro railway Civil Engineers also embraced it for its improved

IRSE Technical Meeting – Launceston

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Within this classification I will group the less commonly used designs. Swing Nose Crossings The point where the two wheel routes on a turnout cross is known as the Frog or sometimes in Australia; ‘V Rail or crossing”. This is generally a cast or fabricated assembly that has a ‘gap’ and permits the wheel to cross the opposite rail path. The actions of the wheel crossing this gap causes impact and consequently wear and noise. When axle loads increase with heavy haul applications the wear is accelerated and maintenance increases. Therefore moving the rail between the two paths and closing the gap becomes an attractive option. For noise reduction reasons in metro areas the same option is sometimes adopted, particularly in tunnels and underground areas. It is of interest to note that the first use of swing nose crossings were on high speed lines where trains often travelled at 300 km/h or more. The swing nose removed the gap that the wheel set had to negotiate thus offering both a quieter and smoother ride.

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A Point of Principle

Fig 19 Swing Nose Crossing (Pilbara WA) Dual Gauge Thankfully for the operating rodding designer, triple gauge turnouts are no longer used in Australasia. However there has been a large increase in Dual Gauge since standardisation of interstate network was commenced in the mid 1990’s. The term ‘Dual Gauge’ refers to a range of track specific items:    

Single Gauge Turnout (Only one gauge has a route option) Dual Gauge Turnout (Both gauges have a route option) Gauge Separator (The gauges no longer share a common rail) Common Rail Switch or Separator (The common rail of the track is swapped to the opposite side of the track or separated to independent rail…Most commonly used for platform clearance by ensuring that the common rail is on the platform edge at stations)

Fig 21 Non Powered Common Rail Switch-Guilford WA Wide to Gauge (Independent) This utilises a standard turnout but allows both blades to be operated independently. The purpose being to allow both blades to be moved to an open position thus derailing any vehicle that enters them in a facing move. Not commonly used in Australasia but a solution to protection of tracks where there is no room for a run off or catch point installation. Found in the Sydney area but little use elsewhere.

In Australia dual gauge consists of standard (1435mm) gauge sharing the trackbed with either narrow (1067mm) or broad (1600mm) gauge track.

Fig 22 Wide to Gauge Turnout (Note position of Blades) Photo: RailCorp Slips or Compound Turnouts Fig 20 Common Rail Separator-Roma St. Brisbane IRSE Technical Meeting – Launceston

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A Point of Principle

Stated simply…Where two tracks cross each other on a narrow angle forming a ‘X’ (Grade Crossing), the addition of points on one side (single) or both sides (double) forms a Slip or Compound. On double arrangements a single point operating mechanism is normally used to operate both sides of the points, therefore a Double Slip or Compound will have just two machines. Due to track geometry the two point ends will have slightly differing angles so the rodding tends to be more complicated and need care with setup. Although found in most States these were common in Victoria and South Australia where they were used to limit the distance required for turnouts caused by the geometry of the wider gauge. Still often installed around stabling yards or large station where the low movement speeds make them a space effective solution.

Due to space restraints the method of operation for 1435mm & 1600mm gauges will invariably be by an internal lock mechanism. Under some variants there is a requirement to detect the position of three blades and a common point lock. This is generally achieved by using the point mechanism internal functions and an additional external detector, often a rotary style. Using a single point operating mechanism requires a method of adjusting all three blades to ensure compliance with the locking requirements. An adjustment point needs to be made between the two gauge blades and this can be a challenge to fit on 1435mm and 1600mm gauges due to the limited clearance. K Crossings On 1067/1435mm dual gauge turnouts the point of the turnout rail crossing the adjacent gauge rail results in the necessity to use a moving K Crossing. Effectively two contra moving point blades. It is feasible to use two separate mechanisms but they are often both operated from a single mechanism to reduce overall cost. To achieve this however a certain amount of mechanical linkage is required!

Fig 23 Double Compound or Slip (Wellington NZ) TURNOUT OPERATION Swing Nose Crossings Consisting of a single blade that must be detected at each side of its stroke, generally a single detector bar is used in the mechanism. The conventional designs have a blade opening of around 65-70mm but the tangential designs have 110-120mm. It is therefore important to ensure that the correct mechanism is specified. The forces required to operate these can be higher due to the heavy short blades and they generally have a high centring bias that can put load on the lock. Both Internal lock and railhead lock mechanism are utilised but maintenance preference tends to be for internal lock due to the difficulty of accessing railhead lock mechanisms located under the rail.

Fig 24

K Crossing installation (Guildford WA)

Wide to Gauge The requirement to independently operate both blades has led to the use of railhead locking for this application. This installation generally requires a separate machine to independently operate and lock each blade. Therefore two point mechanisms will be fitted to the turnout, one on each side of the track! Whilst spreaders may be fitted for track geometry issues they will be of a ‘floating’ type and the lock spreader will be a split bar with each portion operated by a different machine. Supplementary Drives

Dual Gauge

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A Point of Principle

A blade can be likened to a cantilevered beam…When pushed at the free end it should ‘bend’ in a smooth curved fashion from its anchor point, (the Heel), to the toe, closed against the stockrail or open Short blades are stiffer and therefore mostly show this characteristic, however the longer blades are often too flexible and can ‘hog’ or bend along the length. We need to assist these blades by also pushing and pulling in the area where this happens. The exact position(s) is (are) determined by the designer together with the required movement. A supplementary drive and can be independently powered or ‘back-driven’ from the point operating mechanism. Within Australasia independently driven mechanisms have been limited to hydraulic power rams placed with either a separate power unit or a ‘feed’ from the main power pack. Back-driven drives are generally taken either from an extension of the operating bar or directly from the point mechanism drive bar. They can be a rodded or torque tube arrangement, (sometimes called a ‘Rotary Helper’). Most commonly a rodded style with a single or double drive. Double rodding offers some advantages against flexure of these longer rods and therefore can negate the requirement to detect a backdrive position but is more difficult to initially set-up, less tolerant of track geometry issues and generally will require the backdrive rod removed for machine tamping. Single rodding basically reverses the advantages and dis-advantages of the double rodding. Torque Tube arrangements are not common in Australasia. They require precise turnout installation and greater operating force due to the smaller mechanical advantage. They do offer a compact backdrive capable of placement within the four foot if required.

Fig 25 Torque Tube Backdrive

Fig. 26 Double Rod Backdrive

Fig. 27 Single Rod Backdrive

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InBearer Drives InBearer drives are another area where the name does not necessarily reflect the actual design. What is really required is a ‘Tampable Drive’. That is…..The ability to machine tamp (or pack), the turnout without removal or disturbance of the settings of the operating and detection rodding. This can be achieved by a dedicated drive mechanism inside a structural Bearer or by placing the operating mechanism and rodding outside of the Tampable area. There are several InBearer mechanisms offered In the Australasian market. These units replace a bearer in the turnout but do require some Civil design to ensure that the track loads are spread in accordance with the original turnout design. Tampable layouts can be applied to any mechanism by fitting it to hollow steel bearers and placing the operating and detection rodding inside the steel bearer. Again some civil design is required to ensure proper load placement.

Choice of design is often influenced by the type of operation and the preferences of maintenance staff who service the mechanisms in the field. We are now seeing an increased take up of InBearer but again the requirements of our Civil colleagues can often influence the acceptance and specification. It is also necessary to consider backdrives and point spreaders which also need to be placed out of the Tampable area. Spreaders can often be repositioned to sit above a bearer but below the railhead. Backdrives can be placed outside the Tampable area but with some constraints. The spacing between bearers and even the type of Tamping machine available all impact on choice. A variant of these currently not installed but offered by some European manufacturers are the ‘OnBearer’ Drive. These are ‘bolt on’ mechanisms that sit on the bearer between the rails. Mostly operated by remote hydraulic power packs.

There is no preferred option and the choice can be affected by many factors including; Feature

InBearer Drive

Type of Drive Mechanism

Proprietary self-contained. Often sealed to high level against ingress (IP67)

No. of Bearers

Mostly bearer.

Maintenance

Supplementary Drive

single

Mechanism may require removal for major maintenance Some Drives have no ability to offer backdrive take off. May require fitment of a 2nd unit

IRSE Technical Meeting – Launceston

Tampable Bearer Drive Ability to utilise existing drive mechanism with consequent benefits of spares and staff training. Usually double bearer assembly for machine support and adjustment access Uses existing maintenance procedures. Access can be better Ability to use conventional supplementary drives but does require an additional steel bearer to contain the operating spreader Page 13 of 15

Fig.27 InBearer (Tampable) Layout CONDITION MONITORING Condition monitoring has been a part of the trackwork environment since the start of railways. We now just do it differently! Where a Maintainer would visit turnouts on a very regular basis, sometimes daily we can utilise the advances in technology to monitor the reliability and safety of our turnouts. Whilst there are some intrusive monitoring systems that use load pins and sensors attached to machines and rail, the current trend is to use computing power to ‘learn and analyse’ the current/time curve of operation utilising a clamp sensor located in the control location. Each turnout is set up to the satisfaction of the Engineer and the operation is recorded as a reference curve. Deviation levels are set and warnings and alarms applied over those levels. th

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Richard Flinders MIRSE

A Point of Principle

Dictionary of Railway Track Terms-C.F. Schulte Caution needs to be applied to the information being obtained. They cannot substitute for inspection as they will not notify a broken spreader or loose detection bar unless the fault directly impacts on the load or time of operation. Condition monitoring and its purpose needs to be addressed in a separate paper.

British Standard BBS 581 (1950) Electrically Driven Point Mechanisms for Railways Public Transport VictoriaDefinitions V.1.0 (1999)

Track

Technical

Dept of Transport (UK)- Accident Report Grayrigg 23 February 2007

THE FUTURE? The current point operating mechanisms have served us very well in their basic form for around 80 years. They have suited our trackwork and environment. But as the computerisation of railway control accelerates it is likely that in some circumstances the humble point machine could be the only piece of signalling equipment in the field! What is the future design of point operating mechanisms? We are seeing some newer technology units starting to appear in our region. These have increased sealing (IP ratings), less intermediate maintenance requirements and inbuilt monitoring. However initial offerings appear to lack the redundancy of some existing installations. They also cannot remove the requirements of regular safety inspections. It is likely that in general freight and less populated areas we will see more solar and wind powered installations and entirely feasible for cabling to become wireless control. But will we move radically away from current technology? Vital solid state sensors monitoring blade and lock position, separate blade drive mechanisms, perhaps contained in a sealed bearer? This type of development will require large funding and perhaps these features will not suit the high capacity, high speed, European railways. Our operating practices have up to now been mainly influenced by US requirements. They show no short term intentions to develop alternates to the classic AREMA compliant mechanism and our market is too small for independent development. Do we stay with existing technology? Do we adopt the newer European technologies? Time will tell. ACKNOWLEDGEMENTS Alan Neirinkcx, Russel Freeman -RailCorp Haider Rivzi, Robin Stevens -Queensland Rail REFERENCES AREMA Communications & Signals Manual 2013

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RSSB (UK)- Accident Report Potters Bar 10 May 2002 The Protection of Facing Points-IRSE Paper presented by O.S. Nock February 1959 (IRSE Australasian Branch Archives) APPENDIX 1. AREMA Organisation (USA) AREMA has its roots in the formation of the Railway Signalling Club in Chicago in the 1880’s. Later becoming part of the Association of American Railroads (AAR). AAR, merged with other associations involved with complimentary railroad functions, (Track, Bridges & Structures etc.) in the late 1990’s to form a combined standards association generally adopted by most US railroads. 2. Definition of Turnout Curve There are two ways of describing curvature in common practice. In the US, a railway curve is described by the angle in degrees subtended by two radii, whose end points on the curve form a chord of 100 feet in length, i.e. 1:12. In other parts of the railway world, the length of the radius described above, measured in meters, describes the curve, i.e. 300metre THE AUTHOR Richard Flinders commenced an almost 30 year career in electromechanical signalling after spending around 10 years as a sea going marine engineer. Born in the UK, he joined the Merchant Navy after being persuaded by his father, a career Signal Maintainer, that a position with the railways held no future! After leaving the Merchant Navy he returned to College gaining a Higher National Diploma in Mechanical Engineering. He then returned to Australia permanently where he had spent much of his naval career. After a short period in the th

19 July 2013

Richard Flinders MIRSE

A Point of Principle

rolling stock side of railways, he joined Westinghouse Brake & Signal Co. Ltd. in Melbourne as Design Engineer. Early in his career with Westinghouse a decision was made to close the trackwork business in Brisbane and he was assigned to manage the completion of outstanding mechanical locking orders and transfer of IP to the Signal Division. This led to further demand and a 25 year+ involvement with turnout operation and track mounted equipment! In his role as Design Engineer, Richard has been involved in the development of new and updated signalling solutions for the Australasian market including the 84M series point machines. Richard held the position of Electro-Mechanical Engineering Manager with Westinghouse/InvensysRail for 13 years. In this role he was the Companies Design Authority for electro-mechanical product and application. He moved to his current role of Product Line Manager around 18 months ago and is responsible for customer technical issues, product scope and direction.

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