POINTS AND CROSSINGS 2.pptx

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POINTS AND CROSSINGS ---- CONTINUED RAILWAY TRAINING INSTITUTE CIVIL ENGINEERING AND ENVIRONMENTAL STUDIES SECTION

Transcript of POINTS AND CROSSINGS 2.pptx

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POINTS AND CROSSINGS---- CONTINUEDRAILWAY TRAINING INSTITUTECIVIL ENGINEERING AND ENVIRONMENTAL STUDIES SECTION

CROSSING LOOPSTURNOUT SELECTIONCOMMON TRACK CONNECTIONSSETTING OUT TURNOUTSSLEEPER ARRANGEMENTS IN TURN OUTSSWITCH LEVERSSWITCH DEFECTSFLANGE WAY LEARENCESCROSSING DEFECTS

TOPICSIn case a curve in main line is unavoidable the layout shall be properly calculated and designed to provide best combination of curves, the normal track spacing also increased for this purposeGenerally the limits for tracks spaced 16 and below shall be;Parallel loop on outside of the curveFor 1 in 12 & 1 in 16 turnouts -8Parallel loop on the inside of the curvefor a 1 in 12 turnout-3for a 1 in 16 turnout -6CROSSING LOOPSExcept for crossover tracks, gathering lines and turnouts from curves to parallel loops a minimum of 30 straight should separate the reverse curves(to avoid excess strain on central buffers)Reverse curves1 in 72- normal standard for sidings1 in 82- For use in turnouts from loops used by running trains and important sidings1 in 12- Normal standard for turnouts used by running trains . May also be used from inside of siding or curve in order to obtain suitable turnout curvature1 in 16 - Is a special turnout design for use only in special circumstances of main lines on curvesTURNOUT SELECTION

TURNOUT TO PARALLEL TRACKMinimum spacing is 14 0TURNOUT TO PARALLEL CURVED TRACKS-Dimensions must be calculated from the formulaDt= Ds + Dm From inside of curveDt = Ds Dm from outside of curveCROSSOVER TO PARALLEL TRACKS WITH DIFFERENT CROSSING NUMBER minimum spacing = 14 0Before laying crossover the two tracks should be slued to good alignment and uniform track spacingCOMMON TRACK CONNECTIONS

TURNOUT TO PARALLEL TRACK

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CROSSOVER TO PARALLEL TRACKS WITH DIFFERENT CROSSING NUMBERAdopted where track space is limited and speeds of trains using the crossover is lowSpacing is 14 0Before laying crossover the two tracks should be slued to good alignment and uniform track spacing

- - common track connections

SCISSORS CROSSOVERArrangement is the same as two simple crossovers with crossings of the same number and addition of a diamond Is an expensive arrangement and should only be provided where space prevents location of two separate simple crossoversMay only be used between parallel tracks which are straight - - common track connectionsA DIAMOND CROSSING

TANDEM TURNOUTIs only provided where space prevents the use of two simple turnouts butting on each otherSINGLE AND DOUBLE SLIPSThese are special layouts in which the switches and curved track are located within a flat diamond

- - common track connectionsDELTA POINT is denoted by a small triangular sign at the distance F from the theoretical nose of crossingAll turnouts should be set from the delta pointTo locate the delta point place a stake at half the track gauge opposite the theoretical nose of crossing in each of the two tracks, making the measurements square to the legs of the crossing and using small nails in the stakes for precise location

SETTING A TURNOUT FROM THE DELTA POINT

From the two nail dimension F is measured with two steel tapes and the delta point being the intersection of the two dimension FExtension of the line joining the delta point and the stakes opposite the nose of crossing will be parallel to the two legs of the crossing and the angle formed by these two lines will be equivalent to the angle of the crossing - -SETTING OUT FROM THE DELTA POINTEvery turnout has a type drawing indicating the number of sleepers for each panelPanel 2 which applies to switches and panel 4 crossing the sleeper spacing is fixed by the position of the slide chairs and crossing chairsPanel 1 and 5 the sleepers should be so arranged as to give close spacing at the rail jointsPanel 3 which covers the leads of the turnout the sleepers should be uniformly spaced regardless of the position of the rail jointsARRANGEMENT OF CROSSING SLEEPERSIn case of sleeper shortage the turnout may be laid with standard track sleepers up to the toe of crossing maintaining 10 gap for packingShould be placed side by side touching each other and square to the main trackInterlaced wood track sleepers

Must be used in all turnouts to prevent rails from cutting into the wood and gauge from spreadingBearing platestrack gauge in turnouts ;SwitchesNormal gauge 3 3/8Main track in leadCrossing (both tracks)Turnout track in lead widening by moving out the inside rail being run out over 3-4 sleepers to the heel of switch on one side and to the toe of crossing on the other side

GAUGEFor a turnout taking out from a curved track maintain gauge normal 50 in front of the stock rail and behind the crossing Exception of 1 in 6 turnouts due to sharp curve gauge over the switches, turnout curve and crossing should be widened by GAUGEShould be mounted on two long wood or steel sleepers each on one pieceMinimum clearance of switch lever in relation to track is 6 6(prevent falling door of livestock wagon from when unfastened from striking lever which may even cause switch to be thrown under train)SWITCH LEVERSCAST IRON TUMBLER LEVERThe box frame must be positioned such that the bell crank lever is at the centre of its travel when tongue rails are equidistant from the stock railsTo obtain full effect of cast iron counter weight to hold tongue rail to against stock rail Joint between pull rod and crank mustt clear lever box frame by 1Cast iron tumbler inside the box must not touch against narrow sides of the frame in either two positions of the tumbler

- - -SWITCH LEVERSSOULSBY LEVER it is a trailable lever having a spring which because it is arranged vertically does not close the switch with great forceRequires box to periodically be opened the cam and spring examined and adjusted and the box refilled with grease- - -SWITCH LEVERSTo install lever frame should be positioned such that the spring exerts equal pressure to the tongue rail in both positions adjustments being made by means of screw threads provided on the pull rod Lever may be used with any design of loose heel switches but only with light 60 R. BS flexible switches

SOULSBY LEVER

WILLIAMS TWO WAY TRAILABLE LEVERAre two makes Llewelyn Wynn- Williams ND Henry Williams having similar appearance and working principlesThe term two way denotes spring is arranged such that it will hold the switches closed in one direction or the other until they are moved by handle being moved- - -SWITCH LEVERSThe lever handle is still type (return to original position after operation) Box frame should be positioned such that the spring exerts equal pressure on tongue rails in both positions(crank in the frame should be in the half-way position when tongue rails are equidistant from the stock rails ) Most suitable in busy yards

WILLIAMS TWO WAY TRAILABLE LEVER

It is a through tie plate or a combined tie and slide chairs provided at the toe of the switch to resist thrust of wheel flanges and maintain correct track gaugeBend in the curve side stock railOne stock rail should be bend in order that track gauge ahead of toe of switch is exactBend done 6 in front of toe of switchGauge tie plateslength at which the front connecting rod fixes the clearance at toe of an open switch is known as throw (this rod must first be connected)Minimum throw = 4CONNECTING RODSLimits of gape;Interlocked switches 16Padlocked switches8Ordinary unlocked switches/16Gape over /16 may cause wheel to force its way into opening (serious accident)Gape at toe of switchExcessive wear and incorrect adjustment in locking assemblies Excessive wear in locking pinsIncorrect length of back connecting rodLoose connecting rods brackets and slide chair pinsLoose spikes fixing lever box frame to sleepersExcessive tightening of two front bolts in loose heel type joints

Common causes of gape

is a fitting comprising of a protector plate of manganese steel, a back plate and a washer plate each 9 long which are fixed to the stock rail with two bolts having lock washersfixed 2 in front of the toe of switchFunction is to draw wheels away from running face of the rail and so retard wear of the tongue rail at its thin endOnly required on the curved road (placed on RH stock rail for LH turnout and LH stock rail for RH turnout ) MUST NOT BE INSTALLED ON BOTH SIDE STOCK RAILSMACK SWITCH POINT PROTECTOROnce worn out can be reversed before replacementOnly protector plate is replacedNOTE; never fix the protector on worn out stock rail(table or side wear)Ensure bolts are fitted with lock washers and are always tightApply grease to face of protector to retard wearMACK SWITCH POINT PROTECTORWhere interlocked points are not provided switches in running lines shall be padlockedSafe way is to hold tongue rail to stock railPadlocked points

Minimum clearances required in check and wing rails opposite the nose of crossing to prevent the nose from being struck by wheel flange is controlled by wheel gauge and the max. and min. thickness of wheel flanges in relation to normal track gauge 3 3/Limiting clearance minimum= 1/Maximum clearance = 1/Flange way clearances in check and wing rails

Excess clearance may result from ;Widening of track gaugeLoose boltsDirt on the rubbing side of the rail head

- - Flange way clearanceReduced clearance is caused by;Wear in distance blocksWear in webs of railsIn Some cases due to flattening of head of running rail(Steel liners may be used between blocks to increase the clearance)NB : Flange way clearance must be kept clear of ballast and dirt

- - Flange way clearanceCaused by one or a combination of the following;Tight track gaugeExcessive check rail clearanceLoose bolts and chair fastenings especially at the throat causing wing rail to spread under wheel thrustNB: THIS A SERIOUS DEFECT AND SHOULD BE CORRECTED IMMEDIATELYIF NOSE IS BEING STRUCK BY WHEEL FLANGE

CROSSING, CHECK RAIL, CHECK RAIL CLEARENCE46STOCK RAIL: Excessive thinning of table due to wear or flattening causing matching tongue rail to break down at its thinned portionSide wear of gauge face causing TONGUE RAILSide wear or chipping at the thin end to an extend which may cause a wheel flange to force its way between the stock and tongue rail

SCRAPING LIMITSVERTICAL WEAR ON WING RAILS Grooving of the wing rail will determine when the crossing should be replacedRate of wear of wing rail after installation may be rapid and there after slowing downNB: the entire crossing unit (wings and vee) must be removed when the vertical depth of one or both wing rails measured at the rubbing edge and opposite the blunt nose of crossing reaches - - -SCRAPING LIMITSSIDE WEAR IN CHECK AND WING RAILWear on rubbing face to the extend which may causing the flange way clearance to exceed 1NOTE: Generally it is uneconomical or satisfactory to repair worn out crossings in the track and they must be sent to the permanent way depot for overhaulWith authority in situ welding may be carried out in large yards and ports- - -SCRAPING LIMITSAlways requisitioned as a single fish plate or a half set or a set stating symbols belowthe hand of fish plate is defined by looking rail joint from the lighter to heavier railJunction fish platesWhen installing junction fish platesrails selected should be of good shape on order to level up the rails as best as possibleRunning face of one rail should be true to running face of adjoining railSleepers at the joint must be brought closer to provide maximum supportWhere avoidable a junction joint should not be made directly onto a crossing or switch but rails of same section as the turnout should be interposed to save the joints of the expensive turnout joints from being battered

NOTE

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