POINTS & CROSSINGS

-Goutham Sarang-

Points and Crossings

To help transfer trains from one track to another

parallel, diverging, or converging

Necessary since wheels train wheels have inside flanges and,

hence require to navigate on rails

Points or switches – divert vehicles

Crossings – provide gaps in rails, for flanged wheels to roll

over them

A complete set of P&C, along with lead rails – a turnout

Terms

Turnout – arrangement of P&C with lead rails, to divert rolling

stock from one track to another Direction – Right Hand TO, Left Hand TO

Tongue rail/ Switch rail – a tapered movable rail, with high-

carbon or -manganese steel to withstand wear.

thicker end (heel) - attached to a running rail

Stock rail – the running rail against which a tongue rail

operates

Terms

Points/ Switches – A pair of tongue and stock rails

Crossing – device introduced at junction where two rails cross

each other to permit wheel flange to pass from one track to

another

Facing direction – from toe of switch towards crossing;

opposite is Trailing direction

Facing point of TO – where trains pass over switches first and

then crossing; vice versa is Trailing point of TO

Check rails – Extra rails bent at both ends and placed parallel

to running rails to guide and provide a path to wheel flanges

Throw of switch – distance by which tongue rails move

laterally at toe of switch, for movement of trains

Turnout

Working

Changing Track

Points or Switches

Stock rails, AB & CD

with medium-manganese steel

Tongue/switch rails, PQ & RS

with medium-manganese steel

Machined to a very thin section to

obtain a snug fit with the stock rail

Tapered end - toe

Thicker end - heel

A pair of heel blocks –

hold heel of tongue rails at standard

clearance or distance from stock rails

Points or Switches

Slide chairs/ Sliding plates support tongue rail and enable its movement towards or away from stock rail

Two or more stretcher bars connect both tongue rails close to toe, for holding them at a fixed distance

from each other

Switch tie plate/ gauge tie plate fix gauges and ensure correct gauge at the points

Types of Switches

Stud switch No separate tongue rail, instead some portion of track is moved

from one side to other side

Simplest type

No more in use in IR

Split switch consist of a pair of stock rails and a pair of tongue rails

Two types on the basis of fixation at heel

• loose heel type and fixed heel type

Two types based on toe

• undercut and overriding

Types of Switches

Loose heel or Articulated type

Tongue rail finishes at heel of switch for movement of free end of tongue rail

Fish plates holding tongue rail may be straight or slightly bent

Tongue rail - fastened to stock rail using a fishing fit block and four bolts

Fish bolts in lead rail - tightened, but kept loose or snug in tongue rail to

allow free movement of tongue

As discontinuity of track at heel is a weakness, NOT preferred

Fixed heel or Spring or Flexible type

Tongue rail not ending at heel of switch, but extends further and is

rigidly connected

Movement at toe of switch due to flexibility of tongue rail

Can be hand operated or by rod from a lever

Types of Switches

Undercut switch Foot of stock rail is planed to accommodate tongue rail

Becomes weak since a flange portion is cut out

Types of Switches

Overriding switch Separate rail sections of stock and tongue rails

Instead of cutting flange – heavy stock rail and lighter tongue rail

sections

Stock rail - full section; Tongue rail - planed to a 6mm (0.25")

thick edge

Tongue rail rides over flange of stock rail

Types of Switches

Overriding switch – Modified

Tongue rail - kept 6mm

higher than stock rail

from heel to point

towards toe where

planing starts

To eliminate possibility

of splitting due to any

false flange moving in

trailing direction

Crossing or Frog Device introduced at point where two gauge faces cross each

other to permit the flanges of a railway vehicle to pass from

one track to another

Gap - from throat to nose of crossing, over which flanged

wheel glides or jumps

Crossing or Frog

Trailing

Crossing or Frog

2 rails: point rail and splice rail machined to form a

nose Point rail ends at nose

Splice rail joins it a little behind the nose

Point rail should end in a point and be as thin as possible, but

would break off

Point rail - fine end slightly cut off to form a blunt nose, with a

thickness of 6mm

Toe of blunt nose - actual nose of crossing (ANC)

Theoretical point where gauge faces from both sides intersect -

theoretical nose of crossing (TNC)

Crossing angle – < b/w gauge faces of point and splice rails

Heel of crossing – line joins ends of point and splice rails

Crossing or Frog

2 wing rails: a right-hand and a left-hand - converge to

form a throat and diverge again on either side of nose Flared at ends to facilitate entry and exit of flanged wheel in the gap

Toe of crossing – line joins ends of wing rails

Throat – narrow space b/w 2 wing rails

A pair of check rails

Guide wheel flanges and

provide a path for them

Prevent them from moving

sideways

Otherwise may result in wheel

hitting nose of crossing as it

moves in facing direction

Types of Crossings

Acute angle crossing or ‘V’ crossing – intersection of

two gauge faces forms an acute angle When a right hand rail of one track crosses a left hand rail of

another track or vice versa

Unlike rail crossings

A and C

Types of Crossings

Obtuse or diamond crossing – intersection of two

gauge faces meet at an obtuse angle When a right hand or left hand rail crosses a similar rail

B and D

Types of Crossings

Square crossing – two tracks cross at right angles rarely used in actual practice

Number and Angle of Crossing

Crossing - designated either by angle b/w the gauge

faces or by number of crossing (N) N = Spread at leg of crossing ÷ Length of crossing from TNC

Design of Turnout – Terms

T – Toe of Switch L – Heel of Switch

E – TNC M – Point on Turnout at heel

Method I – Coles Method

Design of Turnout

T – Toe of Switch L – Heel of Switch

E’ – TNC M – Point on Turnout at heel

Method I – Coles Method

Design of Turnout

T – Toe of Switch B – Heel of Switch

H – Toe of Crossing

Method II – IRS Method