how trains move from one line to another

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The Inst itution of Railway Signal Engineers Inc Aust ralasian 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)

IRSE Convention – Launceston 19th

July 2013

Richard Flinders MIRSEProduct Line Manager

Siemens Rail Automation

SUMMARY

Some time ago the Australasian Committee decided that at least one paper a year would be presented to theTechnical Meetings which covered basic principles. They were to be presentations that took a basicsignalling/telecommunication subject and went through the principles of use and operation. They were to beaimed at younger members and those who had recently joined the profession. However it is to be hoped thatmaybe they also passed on some new information to older members as well. This paper is part of that seriesand looks at point operation (also known as switches, layouts and turnouts) and discusses some of themethods of moving points both mechanically and electrically. It also describes the various means of detectingthat the points have moved to the required position and that they have been prevented from moving as a trainpasses 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 recognisedthat a wagon (or rail truck) needed to be able tomove to another line to allow others to pass. Thevery first attempts to create these points (or switches) were “Stub” switches which as the nameimplies were stub lengths of rail that could bemoved such that the wheels of a wagon could takeanother 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 pioneeringbeginnings we now have points that allow trains todiverge at over 200km/h! However, not in Australia…..Our railways are freight orientated anddevelopment in the Australasian market has beenaround reliable operation at 40Tonnes plus axleloads.The application may differ but the same principlesstill apply, along with the challenges of environment for many installations.

INITIAL TERMINOLOGY

It is very easy to become confused by theinterlinking use of terms such as Switch, PointBlade, Points etc. The moving parts of the designbeing the Switch Blades, Point Blades etc. Theterms do not easily adapt to specialist designs thatstill need to be operated, locked and detected.

In order not to confuse the reader, now or later ingeneral conversation with suppliers and specifiersFrom this point on I will refer to the total assemblyof trackwork required to move a vehicle betweentracks as a TURNOUT. This is the Civil Engineers

term for a point assembly of varying designs in the Australasian market. However for those interfacingto trackwork plans please be aware that our Civilcolleagues apply the term to the whole layoutincluding the Frog. If this is a Swingnose versionthen it will need to be operated, locked anddetected!

POINT LAYOUT DESIGN-SOME USEFULDEFINITIONS

The Signal Engineer does not require detailedknowledge of turnout design but some

understanding of key parameters will allow morereliable scoping of operating and detectionrequirements.



Richard Flinders MIRSE A Point of Principle

IRSE Technical Meeting – Launceston of 15 19th

July 2013

Fig 1 Common Parts of a Turnout

NOTATION

AREMA – American Railway Engineering andMaintenance-of-Way AssociationBlade/Switch – Moveable part of the turnout thatguides the wheels to another trackDetector – A device that senses the position of the bladesFPL- Facing Point LockFrog – Part of the Turnout which guides thewheels over the intersection of the railsLockBar – A bar that holds the blades in thecorrect positionNormal/Reverse – Default position generallydetermined by the Designers as allowing passage

of traffic on the most used route. Reverse is theopposite of NormalSpreader/Stretcher – Interconnecting bars

between the bladesStockrail – Fixed rail of the turnout that the bladeoperates againstSwing nose Crossing - Moveable Frog used toeliminate the gap at the intersection of rails

MECHANISMS FOR OPERATING TURNOUTS

In its simplest form, connecting a lever offering amechanical advantage allowed quick and easymovement of the blades between the stockrails. Itwas necessary to ensure that not only did therequired blade close against the stockrail but theopposite blade opened sufficiently to ensure theflange of the wheel did not strike it!This simple point lever still offers a cheap methodof manual operation and is in use in sidings andoften on lightly used rural lines, sometimes simplylocked with a traffic keyed padlock.

Hand Throw Levers

The pioneers of turnout operation! Hand ThrowLevers still have a place in turnout operation butthis rarely concerns the Signal Engineer.Occasionally we are required to detect the position

and simple rotary or slide detector can be used todetect the blade position. There are many variantsof lever available and specification generallyfollows the operator’s preferences.Some caution needs to be taken in detecting non-locked lever operated turnouts as some of the

older style mechanisms such as the Victorian WSa

and Thornley lever are a spring toggle design andneed careful adjustment if they are to reliablyposition the blade in a closed position repeatedly.USA imported levers, generally to relevant AREMAstandards, offer a similar function with padlockableoperating lever stands.These mechanisms, together with weighted leverscan offer the advantage of trailability.

Fig 2 WSa

Handthrow lever

Also occasionally specified is non-powered facingpoint lock equipped hand throw levers. These arean escapement derived mechanism and offer an AREMA compliant facing point lock in the normalposition only.Generally specified where security of lock isrequired e.g. Mainline facing turnouts for emergency sidings or occasional use traffic. Nottrailable but they can replace the functions of some localised ground frame installations.

Lever Frames

Even in the 19

th

Century, automation was apopular efficiency improvement and rising wagesled to the development of ‘consolidated’ pointoperation. Still manually operated but by a‘Signalman’ in a centralised location. A maximumeffective operating distance was around300/350metres constrained by the effort requiredto pull or push the lever.There are still many lever frames in service but for the purpose of this paper I will limit discussion tosmall lever frames used generally for locking andoperation of occasionally used sidings, generallyknown as Ground Frames/Switchlocks. Even now,

the force required to operate these installations istesting the limits of modern OH&S regulationsespecially with the more modern, heavier,turnouts.





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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 mechanicalsystems but is not commonly used. Restricted toSydney and some smaller installations inMelbourne and Brisbane.Typically it becomes an attractive option in areasof high density as the high infrastructure costs of air compressors and conditioned reticulation

systems needs to be amortised over a reasonableinstall base.It can also be found, typically overseas, in humpyards and areas that have very high traffic densityand need less than two second point switching.

Within the Australasian market we find two typesof operating mechanism;

1. Air cylinder operated escapementmechanism, generally mounted betweenthe running rails and colloquially named 4Foot Mechanism.

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 proprietaryrailhead locking mechanism, Spherolock,Claw Lock etc.

Fig 5. Air Operated Mechanism driving Claw Lock-Sydney Metro Network

Control of operation is interfaced from thesignalling system by a Control Unit (Valve). Actually more than just a valve, this unit acts insome cases as a lock and has detection of air pressure contacts.

Fig. 6 Typical Air Controller Circuit (Note Plunger and Pilot Valves)





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Hydraulic Mechanisms

Hydraulic drives are popular overseas, particularlythe UK and Europe. They have found someacceptance in Australasia but not universally.

They consist of an electro-hydraulic power unitcoupled to a double acting ram and connected toeither a Network Rail Clamplock(Adelaide/Melbourne) or Claw/Spherolock RailLock mechanisms (Melbourne/Queensland).

Fig 7 Hydraulic Drive-Melbourne Metro (NoLocking)

Starting to enter the Australasian market is a newgeneration of electro-hydraulic units from Europe.

These units are offering low maintenance, sealedmechanisms often operating proprietary lockingdevices contained within a Tampable bearer.

Electric Mechanisms

Electro-mechanical mechanisms are used in themajority of installations.

These can be split into two styles; Internal lockand thrusters.

Internal Lock Mechanisms

Within Australasia these mechanisms aregenerally compliant to AREMA/BS standards;

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 inservice for over 50 years!Suited to the style of turnouts and environment in Australasia these machines have generally been

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

Fig 8 AREMA Compliant Mechanism-Pilbara WA

Railhead Lock Mechanisms (or Thrusters)

By definition these mechanisms are a pointmachine without internal locking. This can causesome confusion amongst specifiers not familiar with the differences and it is often wise to use theterm ‘Thruster’ to differentiate!

Not necessarily tied to AREMA standards these

machines may differ in their mountingrequirements. All will have an operating stroke of at least 180mmto take account of the locking and unlockingrequirements of a railhead lock mechanism. Thatis 125mm nominal blade movement and around40mm of travel to operate the locking mechanismpart of the travel.Detection is generally internal for lock & bladeposition. European designed machines often applya secondary point lock via locking of the detectionbars.

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





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Failure and Emergency Working

All operating mechanisms have some sort of handoperation in case of failure, and duringEngineering works.Generally this falls into two forms;

A fixed stroke operating lever for operating theturnout or a handcrank point on the mechanism.

All will be protected from unauthorised operationby a padlock which will release a cover and either immediately open the internal motor power circuitor requires operation of lever or crank handlecover that carries this function. Generally it willalso activate an indication circuit at the signallers’position.

Operation of the turnout will then be via a fixedstroke 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 amove by railways to the fixed lever style operation.This has been driven by a reduction in operatingstaff in the field able to perform this function aswell as OH&S requirements.

LOCKING THE TURNOUT

What are we Locking?

The facing point lock is a device that locks thepoint blades in position to allow the safemovement of a train in a facing direction over theturnout.

The closed blade is locked in a position againstthe stockrail and the open blade is restrained fromclosing the flange gap between the blade and thestockrail.In the majority of mechanisms this is achieved byactually preventing the movement of a locking bar connecting the two blades together. Effectively byinserting a plunger into a notch in this bar either

between the rails of by extension of this bar intothe point mechanism.

Which Standard?

Locking the blades in position for the passage of atrain in either direction is not mandatory for allturnouts. The use of locking is defined by each railauthority and generally relates to the type of trafficand the permitted speed of trains in the facingmove. Freight traffic being given more latitude butoccasional passenger train movements may beallowed at speeds below 15km/h. It is a risk based

scenario.Facing point locks (FPL) were adopted relativelyearly in the history of modern points due to somesignificant accidents overseas. Adoption by the

Australasian market generally followed thepractises adopted by the Signal Engineer in theearly stages of railway development. Thebackground and experience of those Engineershaving significant influence on future direction andleading to a multitude of differing standards and

practise across the region.NSW, WA & Qld generally adopted British practisewith Vic & SA following American practise. Themajor difference being American practise was todetect only the position of the Normal closedblade.The two standards that have influenced our regionare;

USA (AREMA Standards)

UK (Network Rail formerly British RailStandards)

In practise the two offer similar settings of around2-3mm for lock and 3-6mm for detection.

The actual values determined by rail operatorstend to be within these settings and influenced bythe style of turnout adopted and it’s sensitivity todamage from the wheel flange when slightly open,generally known as ‘undercut’.

European

This is mentioned as a generic influence from boththe adoption of railhead locking in the late 1950’sby Queensland Rail for trailable turnouts and alsoentry of European designed and manufacturedmechanisms in the 1990’s and beyond.

In particular the setting requirements for railheadlocks which vary from those of internal mechanismlocks. Whilst the specific settings of lock anddetection clearance will still apply a railhead lock isgenerally set without any ‘pinch’ of the bladeagainst the rail to ensure the lock releases easily.Some European machines also feature secondaryhold of the detection rods. Introduced to allowemergency restraint of the blades in the case of component failure of railhead locks in periodwhere steel technology was not as advanced.

Every installation of locked turnouts will follow thebasic principle or operation, irrespective of thetype of mechanism or turnout;

Open the indication circuitUnlock the pointsOperate the pointsLock the pointsClose the indication circuit(AREMA 12.2.1 & BS 581Pt. 3)

Internal Machine Locking

Machines in use in the Australasian region followthe requirements of AREMA/British Standard for the internal lockbar, lock and interference. The





July 2013

track connections however can vary greatly in their design.It is important to ensure that locking design andthe maintenance requirements are carefullyconsidered. Not only the internal machine lock butconnections to the turnout and including any

Spreaders used to connect the blades together. Asshown by the accidents at Potters Bar andGrayrigg in the UK show, (see References), failureto properly consider and maintain all the trackconnections can have severe consequences.

Railhead Locking

This is the term used to describe locking of theblades external to the operating mechanism.Within our region it will be either a claw type armconnected to the blade and locking by interferencewith a bracket connected to the stockrail.

Alternatively, it may also be a proprietary ‘slidingdog’ type mechanism contained within a tubeconnected to both blades.

Fig. 10 VAE Spherolock Point Lock Mechanism-Dampier WA

By locking the closed blade directly to the stockrailwe remove the issues associated with connectionsto the lock. The open blade is generally

constrained by the blade connected locking clawbeing ‘captured’ in a slot or notch of the fixedoperating bar. Thus opening whilst the other bladecloses.Railhead locking can be considered more sensitivein operation to track settings and deficiencies duemainly to independence of the blades.Because we are placing the mechanical lockactually on the rail we are subjecting it to the harshtrack environment and together with the removal of spreaders making the blade a more flexible beammeans track defects, condition and environmentcan affect the reliability.

In certain cases to overcome and negate theseforces for reliable operation specialised Spreadershave been fitted. To reduce roll of the blades,reduce the inherent blade closure force or other

reasons such as assisting the movement of theblade.

Fig. 11 Floating Spreader Claw Lock Layout-NSW

DETECTING THE TURNOUT

Lock Detection

We generally detect the insertion of the internallock through the lockbar in internal lock machinesand the operating bar position for the railheadlocks. By inference we determine that the lock iscorrectly operated!

It is therefore important to have confidence in theconnections to these positions from the track.

Blade Detection

The purpose of blade detection is to know theposition of the blades and to ensure that anymovement of the closed blade open to a positionwhere the wheel flange could split the turnout or the open blade could contact the wheel flange isdetected.The older US standard, adopted in our region byrailways following US practise, was to only detect

the position of the normally closed blade. All Australasian railways have now moved todetecting both blades. However some legacyinstallations exist.Detector rodding is connected to the end of theblade or to a firmly bolted extension if clearance of bearers is an issue. The detector which can bepart of the operating mechanism contains theswitch operated by the rod position. Somedetectors mount to the stockrail.In some cases with the thick web assymetricsection of the blade it is permissible to detect theposition of the blade at a distance from the toe per

some European practise, often around 200-300mm .





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Fig. 12 Internal Point Machine Detection

Fig. 13 Rail Mounted Point Blade Detector

Supplementary Detection

We may also need to know that there is sufficientclearance for the wheel flange through the turnoutwhere the blades are flexible or may be subject tofrictional resistance to movement.Whilst a loaded 40 tonne axle load minerals trainwill easily ‘push’ the blade out of the way, repeatedactions could cause stressing or damage to therail. In the case of higher speed light passenger traffic, it could cause rough riding or even allow thewheel to climb off the rail and create a derailment.

READING A TURNOUT…..

One of the most common errors with specificationof signalling product for a turnout is the handing.Whilst our Civil colleagues use the direction of diverge to indicate the ‘hand’, Signal Engineersuse the placement of operating mechanism andnormal position. (Our interest being which side of the track to run cabling and ensuring that detection

circuits are correctly indicated)(See previousdefinitions of Normal and Reverse).

The diagrams below can act as a reference for specification but the rule of ‘positioning oneself at

the ‘Toe’ (that is the machine end and lookingtowards the diverging tracks and Frog), alwaysapply. The signalling specification is then left or right hand dependant on location of themechanism.The final part being which blade is normally

closed…Left or right which may also be describedas adjacent or opposite (referencing the closestblade to the mechanism).This information is still required for InBearer and 4Foot mounted type drives as cabling entries anddetection handing need to be specified to thesupplier! (4Foot being the term adopted to definethe space within the running rails of all gaugerailways).

Fig 14 Typical Handing Requirements

Terminology

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

Definition UK Variant USA Variant

Bearers Sleepers Ties

Switch/Point Blade Blade Switch

Toe Toe Switch Point

SupplementaryDrive

Backdrive Helper

Spreader Stretcher Gauge Rods

BASIC PRINCIPLES

Conventional Style Turnouts

I have generalised here and put all non-tangentialturnouts into this category.Generally all AREMA compliant turnouts will bemanufactured to have the unrestrained blade sitagainst the stockrail with an amount of force.They are designed to have both blades connectedvia a fixed spreader. This has the effect of ‘neutralising ‘the forces of the blades and allowinga relatively low force operating requirement.

When this style of turnout is adapted to railheadlocking there can be operating issues….





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It is possible for our Civil colleagues to adjust theblades by ‘crowing’ them. That is a slight changeto the geometry to reduce the amount of closureforce, however this is not possible in all cases andtherefore the free blades can exert a withdrawalforce on the lock.

(Blades are ‘’crowed’ that is bent using a devicesuch as the one below in Fig 15. A slight changeto the geometry of the blade can reduce, or increase the blades natural position against thestockrail and thus the force required to move andhold it.)

Fig 15 Jim Crow Rail Bender

Tangential Geometry Turnouts

Unlike the conventional turnouts, these turnoutsgenerally have a design of neutral or low closureforce about the blade at the stockrail position. Thismeans that they generally do not encounter theissues of operation when railhead locking is used.

All Australasia installed Tangential turnouts uti lisea thick web blade so can look daunting whenconsidering operation. However the newer designsare often supplied with point blade rollers specifiedand operation requires similar forces toconventionally bladed turnouts. (With heavier railsizes the weight of the blade can affect movementdue to friction therefore rollers in the plates work tolet the blade roll and reduce this friction. They canbe very effective in reducing the forces back toabout the levels required for a fixed heel turnout).

Fig 16 In Chairplate Switch (Blade) Roller

We are dealing with application of a load to a

cantilevered beam and with judicious use of pointrollers to reduce the frictional load the longer turnouts with 1:20 and greater radii actually requireless force to operate then a short blade!

TURNOUTS

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

Some History

The Technology behind turnouts changed little in

nearly a century. It is still quite easy to find castcomponents of turnouts being reused in servicewith manufacture dates in excess of 50 years!These turnouts, generally derived from either USor UK practice were simple bolted heel designsthat required little force to operate.The US standardised on layouts varying in switchlength between 11 and 33 feet, (3.35 and 10metres approx). This generally gave operatingspeed for trains diverging from 15-30mph, (34-68km/h).Like many aspects of railway technology in Australasia, we acquired it when in the early 20

th

Century overseas Engineers were recruited tomanage our mostly Government owned systems.They brought with them knowledge of theoverseas standards and our local Engineers andDraftspersons adapted them to suit specificrequirements.Government railways mostly used their ownfacilities to manufacture the turnouts using railsupplied from Australian Steel manufacturers toour own, (slightly different) design!There were a few local private suppliers whoserviced private and specialist railways such asSugar Mills etc. and supplemented the railways

own capacity to supply.New Zealand appears to have differed by mostlyimporting its requirements from the UK as it did for most of its trackside signalling requirements.





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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 thoseconforming to the ‘older’ design practises, By far the majority of turnouts in operation fall into thiscategory. They may have a bolted or fixed heelblock and may be of any Australian Standard railsection. However the installation of turnouts below50Kg/m rail size is becoming rare in all jurisdictions.

Fig 17 Bolted Heel Turnout (Bunyip Victoria)

Often these types of turnouts are installed for costreasons or because of limited scope for trackgeometry changes, particularly within crowdedurban rail reserves.

Tangential

Tangential turnouts have their development in

European practice in the late 20

th

century.Generally, European railways were built for higher speeds and more intensive operation. This meantthere was a desire to maintain higher speedsthrough diverging moves at turnouts. Thedevelopment of Asymmetric rail sizes allowedrailway companies to develop geometries of turnout that would if conventional rail was used for blade manufacture, result in very thin blade tipsand premature wear.Initial Australasian take-up of this technology wasdriven by the entry into our region of Europeantrackwork companies. Whilst our large heavy haul

market with Greenfields sites allowed generaladoption of this technology, our metro railway CivilEngineers also embraced it for its improved

vehicle ride qualities and reduced maintenancerequirements.It is not the intention of this paper to expand onthis development and further technical informationis readily available via the internet or by asking our Civil colleagues.

One issue of terminology again creeps inhere…Whilst generally we have adopted the USpractice of identifying turnouts by the angle of diverge, i.e. 1:12 etc. The European practice hasgenerally 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

Within this classification I will group the lesscommonly used designs.

Swing Nose Crossings

The point where the two wheel routes on a turnoutcross is known as the Frog or sometimes in Australia; ‘V Rail or crossing”. This is generally acast or fabricated assembly that has a ‘gap’ andpermits the wheel to cross the opposite rail path.

The actions of the wheel crossing this gap causesimpact and consequently wear and noise.When axle loads increase with heavy haulapplications the wear is accelerated andmaintenance increases. Therefore moving the railbetween the two paths and closing the gapbecomes an attractive option.For noise reduction reasons in metro areas thesame option is sometimes adopted, particularly intunnels and underground areas.It is of interest to note that the first use of swingnose crossings were on high speed lines wheretrains often travelled at 300 km/h or more. The

swing nose removed the gap that the wheel sethad to negotiate thus offering both a quieter andsmoother ride.





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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 largeincrease in Dual Gauge since standardisation of interstate network was commenced in the mid1990’s.The term ‘Dual Gauge’ refers to a range of trackspecific items:

Single Gauge Turnout (Only one gaugehas 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 (Thecommon rail of the track is swapped to theopposite side of the track or separated toindependent rail…Most commonly usedfor platform clearance by ensuring that thecommon rail is on the platform edge atstations)

In Australia dual gauge consists of standard(1435mm) gauge sharing the trackbed with either

narrow (1067mm) or broad (1600mm) gauge track.

Fig 20 Common Rail Separator-Roma St. Brisbane

Fig 21 Non Powered Common Rail Switch-GuilfordWA

Wide to Gauge (Independent)

This utilises a standard turnout but allows bothblades to be operated independently. The purposebeing to allow both blades to be moved to an openposition thus derailing any vehicle that enters themin a facing move.

Not commonly used in Australasia but a solution toprotection of tracks where there is no room for arun off or catch point installation. Found in theSydney area but little use elsewhere.

Fig 22 Wide to Gauge Turnout (Note position of

Blades) Photo: RailCorp

Slips or Compound Turnouts





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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 bothsides (double) forms a Slip or Compound.On double arrangements a single point operatingmechanism is normally used to operate both sides

of the points, therefore a Double Slip or Compound will have just two machines. Due totrack geometry the two point ends will have slightlydiffering angles so the rodding tends to be morecomplicated and need care with setup.

Although found in most States these werecommon in Victoria and South Australia wherethey were used to limit the distance required for turnouts caused by the geometry of the wider gauge.Still often installed around stabling yards or largestation where the low movement speeds make

them a space effective solution.

Fig 23 Double Compound or Slip (Wellington NZ)

TURNOUT OPERATION

Swing Nose Crossings

Consisting of a single blade that must be detectedat 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 have110-120mm. It is therefore important to ensurethat the correct mechanism is specified.The forces required to operate these can be higher due to the heavy short blades and they generallyhave a high centring bias that can put load on thelock.Both Internal lock and railhead lock mechanismare utilised but maintenance preference tends tobe for internal lock due to the difficulty of accessing railhead lock mechanisms located

under the rail.

Dual Gauge

Due to space restraints the method of operationfor 1435mm & 1600mm gauges will invariably beby an internal lock mechanism.Under some variants there is a requirement todetect the position of three blades and a commonpoint lock. This is generally achieved by using the

point mechanism internal functions and anadditional external detector, often a rotary style.Using a single point operating mechanism requiresa method of adjusting all three blades to ensurecompliance with the locking requirements. Anadjustment point needs to be made between thetwo gauge blades and this can be a challenge to fiton 1435mm and 1600mm gauges due to thelimited clearance.

K Crossings

On 1067/1435mm dual gauge turnouts the point of

the turnout rail crossing the adjacent gauge railresults in the necessity to use a moving KCrossing. Effectively two contra moving pointblades.It is feasible to use two separate mechanisms butthey are often both operated from a singlemechanism to reduce overall cost. To achieve thishowever a certain amount of mechanical linkage isrequired!

Fig 24 K Crossing installation (Guildford WA)

Wide to Gauge

The requirement to independently operate bothblades has led to the use of railhead locking for this application.This installation generally requires a separatemachine to independently operate and lock eachblade. Therefore two point mechanisms will befitted to the turnout, one on each side of the track!Whilst spreaders may be fitted for track geometryissues they will be of a ‘floating’ type and the lockspreader will be a split bar with each portionoperated by a different machine.

Supplementary Drives





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A blade can be likened to a cantileveredbeam…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 thestockrail or openShort blades are stiffer and therefore mostly show

this characteristic, however the longer blades areoften too flexible and can ‘hog’ or bend along thelength. We need to assist these blades by alsopushing and pulling in the area where thishappens. The exact position(s) is (are) determinedby the designer together with the requiredmovement. A supplementary drive and can be independentlypowered or ‘back-driven’ from the point operatingmechanism.

Within Australasia independently drivenmechanisms 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 froman extension of the operating bar or directly fromthe point mechanism drive bar. They can be arodded or torque tube arrangement, (sometimescalled a ‘Rotary Helper’). Most commonly a roddedstyle with a single or double drive.Double rodding offers some advantages againstflexure of these longer rods and therefore cannegate the requirement to detect a backdriveposition but is more difficult to initially set-up, less

tolerant of track geometry issues and generally willrequire the backdrive rod removed for machinetamping.Single rodding basically reverses the advantagesand dis-advantages of the double rodding.Torque Tube arrangements are not common in Australasia. They require precise turnoutinstallation and greater operating force due to thesmaller mechanical advantage. They do offer acompact backdrive capable of placement withinthe 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 namedoes not necessarily reflect the actual design.What is really required is a ‘Tampable Drive’. Thatis…..The ability to machine tamp (or pack), the

turnout without removal or disturbance of thesettings of the operating and detection rodding.

This can be achieved by a dedicated drivemechanism inside a structural Bearer or by placingthe operating mechanism and rodding outside of the Tampable area.

There are several InBearer mechanisms offered Inthe Australasian market.These units replace a bearer in the turnout but dorequire some Civil design to ensure that the trackloads are spread in accordance with the original

turnout design.Tampable layouts can be applied to anymechanism by fitting it to hollow steel bearers andplacing the operating and detection rodding insidethe steel bearer. Again some civil design isrequired to ensure proper load placement.

There is no preferred option and the choice can beaffected by many factors including;

Feature InBearer Drive TampableBearer Drive

Type of Drive

Mechanism

Proprietary

self-contained.Often sealed tohigh levelagainst ingress(IP67)

Ability to utilise

existing drivemechanismwithconsequentbenefits of spares andstaff training.

No. of Bearers Mostly singlebearer.

Usually doublebearer assembly for machinesupport and

adjustmentaccess

Maintenance Mechanismmay requireremoval for major maintenance

Uses existingmaintenanceprocedures. Access can bebetter

SupplementaryDrive

Some Driveshave no abilityto offer backdrive takeoff. Mayrequire fitmentof a 2nd unit

Ability to useconventionalsupplementarydrives but doesrequire anadditional steelbearer tocontain theoperatingspreader

Choice of design is often influenced by the type of operation and the preferences of maintenancestaff who service the mechanisms in the field.

We are now seeing an increased take up of

InBearer but again the requirements of our Civilcolleagues can often influence the acceptance andspecification.It is also necessary to consider backdrives andpoint spreaders which also need to be placed outof the Tampable area.Spreaders can often be repositioned to sit above abearer but below the railhead. Backdrives can beplaced outside the Tampable area but with someconstraints.The spacing between bearers and even the type of Tamping machine available all impact on choice.

A variant of these currently not installed butoffered by some European manufacturers are the‘OnBearer’ Drive. These are ‘bolt on’mechanisms that sit on the bearer between therails. Mostly operated by remote hydraulic power packs.

Fig.27 InBearer (Tampable) Layout

CONDITION MONITORING

Condition monitoring has been a part of thetrackwork environment since the start of railways.We now just do it differently!Where a Maintainer would visit turnouts on a veryregular basis, sometimes daily we can utilise theadvances in technology to monitor the reliabilityand safety of our turnouts.Whilst there are some intrusive monitoringsystems that use load pins and sensors attachedto machines and rail, the current trend is to usecomputing power to ‘learn and analyse’ thecurrent/time curve of operation utilising a clampsensor located in the control location.

Each turnout is set up to the satisfaction of theEngineer and the operation is recorded as areference curve. Deviation levels are set andwarnings and alarms applied over those levels.





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Caution needs to be applied to the informationbeing obtained. They cannot substitute for inspection as they will not notify a broken spreader or loose detection bar unless the fault directlyimpacts on the load or time of operation.

Condition monitoring and its purpose needs to beaddressed in a separate paper.

THE FUTURE?

The current point operating mechanisms haveserved us very well in their basic form for around80 years. They have suited our trackwork andenvironment.But as the computerisation of railway controlaccelerates it is likely that in some circumstancesthe humble point machine could be the only piece

of signalling equipment in the field!What is the future design of point operatingmechanisms? We are seeing some newer technology units starting to appear in our region.These have increased sealing (IP ratings), lessintermediate maintenance requirements and inbuiltmonitoring. However initial offerings appear to lackthe redundancy of some existing installations.They also cannot remove the requirements of regular safety inspections.

It is likely that in general freight and less populatedareas we will see more solar and wind powered

installations and entirely feasible for cabling tobecome wireless control. But will we moveradically away from current technology?Vital solid state sensors monitoring blade and lockposition, separate blade drive mechanisms,perhaps contained in a sealed bearer?

This type of development will require large fundingand perhaps these features will not suit the highcapacity, high speed, European railways. Our operating practices have up to now been mainlyinfluenced by US requirements. They show noshort 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 adoptthe newer European technologies? Time will tell.

ACKNOWLEDGEMENTS

Alan Neirinkcx, Russel Freeman -RailCorp

Haider Rivzi, Robin Stevens -Queensland Rail

REFERENCES

AREMA Communications & Signals Manual 2013

Dictionary of Railway Track Terms-C.F. Schulte

British Standard BBS 581 (1950) ElectricallyDriven Point Mechanisms for Railways

Public Transport Victoria- Track Technical

Definitions V.1.0 (1999)

Dept of Transport (UK)- Accident Report Grayrigg23 February 2007

RSSB (UK)- Accident Report Potters Bar 10 May2002

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 theRailway Signalling Club in Chicago in the1880’s. Later becoming part of the Associationof American Railroads (AAR). AAR, merged with other associations involvedwith complimentary railroad functions, (Track,Bridges & Structures etc.) in the late 1990’s toform a combined standards associationgenerally adopted by most US railroads.

2. Defini tion of Turnout CurveThere are two ways of describing curvature incommon practice. In the US, a railway curve isdescribed by the angle in degrees subtended bytwo radii, whose end points on the curve form achord of 100 feet in length, i.e. 1:12. In other partsof the railway world, the length of the radiusdescribed above, measured in meters,describes the curve, i.e. 300metre

THE AUTHOR

Richard Flinders

commenced an almost 30year career in electro-mechanical signallingafter spending around 10years as a sea goingmarine engineer.Born in the UK, he joinedthe Merchant Navy after being persuaded by hisfather, a career SignalMaintainer, that a position

with the railways held no future! After leaving the Merchant Navy he returned to

College gaining a Higher National Diploma inMechanical Engineering. He then returned to Australia permanently where he had spent muchof his naval career. After a short period in the





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rolling stock side of railways, he joinedWestinghouse Brake & Signal Co. Ltd. inMelbourne as Design Engineer.Early in his career with Westinghouse a decisionwas made to close the trackwork business inBrisbane and he was assigned to manage the

completion of outstanding mechanical lockingorders and transfer of IP to the Signal Division.This led to further demand and a 25 year+involvement with turnout operation and trackmounted equipment!In his role as Design Engineer, Richard has beeninvolved in the development of new and updatedsignalling solutions for the Australasian marketincluding the 84M series point machines.Richard held the position of Electro-MechanicalEngineering Manager withWestinghouse/InvensysRail for 13 years. In thisrole he was the Companies Design Authority for

electro-mechanical product and application.He moved to his current role of Product LineManager around 18 months ago and isresponsible for customer technical issues, productscope and direction.

how trains move from one line to another

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