GAUGE, CONING & TILTING

Permanent Way

• Rail-road on which train runs

• Consists of 2 parallel RAILS placed at a

specified distance between them, &

FASTENED to SLEEPERS, which are

embedded in a layer of BALLAST of specified

thickness spread over the FORMATION.

Permanent Way - Requirement

• GAUGE: correct & uniform

• CROSS LEVELS: straight/curved sections

• ALIGNMENT: Straight & free of kinks

• GRADIENTS: Uniform & Gentle

Permanent Way - Requirement

• TRACK: resilient & elastic

• Drainage: stability, no water-logging

• Lateral Strength: shocks, vibrations

• Easy replacement of renewal of components

• Cost – minimum (construction operation &

maintenance)

Roadways vs. Railways

• Construction of route:

– RdW; suitable pavement of specified width provided with

shoulders on either side. 

– RLW: pair of steel rails which are laid parallel to each other

on sleepers at fixed distance apart. 

• Suitability to traffic: 

– In RdW, routes are meant for movement of different types,

of traffic such as buses, trucks, scooters, rickshaws,

cycles, pedestrians etc.

– RLW routes are meant only for movement of trains.

Roadways vs. Railways

• Width of right-of-way:

– RdW routes require MORE width of right-of-way.

– RLW routes require LESS width of right-of-way. 

• Starting and destinations: 

– In RdW, starting and destination points of traffic are

NOT FIXED.

– In RLW, starting and destination points of trains are

ALWAYS FIXED. 

Roadways vs. Railways

• Right of entry: 

– In RdW, it is free to all vehicles because their

movements are not according to any schedule.

– In RLW, it is not free to all railway vehicles

because their movements are always according

to schedule. 

• Strength of route: 

– In RdW it is LESS.

– In RLW tracks it is MORE. 

Roadways vs. Railways

• Elasticity: 

– RdW routes do not require an elastic structure since they

are not to withstand impacts of heavy wheel loads. 

– RLW routes require an elastic structure to withstand impact

of heavy wheel loads. 

• Gradients and curves: 

– In RdW, the routes can be constructed with steep

gradients & sharp curves. Thus, route length is LESS.

– In RLW, routes cannot be constructed with steep gradients

& flat curves. Thus, route length is MORE. 

Roadways vs. Railways

• Tractive resistance: 

– For RdW routes is high (5-6 times of railway).

– For RLW routes, it is low

• Load handling capacity: 

– For road vehicles, it is less & at low speeds.

– For RLW vehicles, it is more and at high speeds. 

Roadways vs. Railways• Requirement of turning devices: 

– In RdW , NO special turning devices are constructed for

turning vehicles on these routes.

– In RLW, special turning devices (points & crossings) are

constructed for turning vehicles on these routes. 

• Operational control devices: 

– In RdW , no special operational control devices in the form

of signaling and interlocking are required on these routes for

safe and efficient movement of vehicles.

– In RLW, these are REQUIRED for safe & efficient movements

of trains.

Roadways vs. Railways

• Suitability to transportation of people and goods:

– Suitable for SHORT DISTANCES (upto 500 km) is

convenient and cheap by roadway routes.

– Transport of people and heavy goods like raw materials,

coal, ores, etc. for LONG DISTANCE or manufacturing

concerns is convenient and cheap by railway routes. 

• Adaptability to type and size of goods: 

– All types and sizes of goods CANNOT BE HANDLED by

road vehicles.

– Almost all types and sizes of goods is handled by trains. 

Roadways vs. Railways• Suitability for hilly area: 

– RdW vehicles are MORE suitable for hilly area.

– Railway vehicles are LESS suitable for hilly area. 

• Employment potential:

– RdW have LESS employment potential.

– RLW  have HIGH employment potential. 

• Rate of accidents: – In roadways, the rate of accidents is HIGH.

– In railways, the rate of accidents is LESS. 

• Construction and maintenance cost: – Cost of roadway vehicles is LESS.

– In case of railway vehicles, the cost is MORE.

Gauge

• It is the minimum distance between 2 rails.

• Indian Railways (IR) measures gauge as clear minimum

distance between the running faces of the 2 rails.

Name of Gauge

Width (mm) Width (feet) Route Km % of Route km

Broad Gauge (BG)

1676 5’6” 40000 64

Metre Gauge (MG)

1000 3’3.37” 20000 31

Narrow Gauge (NG)

762 2’6” 4000 5

TOTAL 64000 100

Choice of Gauge

• Cost Consideration

• Traffic Consideration

• Physical Feature of Country – adopt steeper

gradient & sharper curves for a narrow gauge as

compared to a wider gauge.

Cost Consideration

• There is a marginal increase in cost of track if a

wider gauge is adopted

– Proportional increase in cost of land acquisition,

earthwork, rails, sleepers, ballast & other tracks.

– Cost of bridges, culverts & tunnels increases only

marginally due to wider gauge.

– Cost of constructing station buildings, platform, staff

quarters, level crossings, signals, etc.

– Cost of rolling stock is independent of the gauge for

carrying same volume of traffic.

Traffic Consideration

• Volume of traffic depends on Size of Wagons &

Speed & hauling capacity of trains

– Wider gauge carry larger wagons & coaches & hence

carry more traffic.

– Wider gauge have higher speeds.

– Type of traction & signalling equipment required are

independent of the gauge.

Coning of Wheels

Coning of Wheels

• Tread of wheels of a railway vehicle is not made flat, but

sloped like a cone in order to enable the vehicle to move

smoothly on curves & straight tracks.

• On Straight & level surface: Circumference of treads of

inner & outer wheels are equal.

• On curves, problem arises when outer wheel has to

negotiate more distance on the curve as compared to

inner wheels.

Coning of Wheels

• Due to action of centrifugal force on a curve, wheels tends

to move out.

• To avoid this, circumference of Tread of outer wheel is

made > inner wheel.

• This helps the outer wheel to travel a longer distance than

the inner wheel.

Coning of Wheels

• It helps to keep the vehicle centrally aligned on a

straight & level track.

• Slight irregularities in track do occur as a result of

moving loads & the vagaries of the weather.

Therefore wheels move from side to side &

therefore the vehicles sway.

• Due to Coning of Wheels, this side movement

results in the increase in tread circumference of

one wheel over the other.

Advantages of Coning of Wheel

• Controlling differential movement of Front & Rear Axles (which is caused due to rigidity of frame &

axle) thus acting as a balancing factor (on curves rear axle has the tendency to move towards inner rail)

• Smooth riding as it help vehicle to negotiate curves smoothly

• Reduces wear and tear of wheel flanges

• Approx. value of slip for BG is 0.029 m/degree of curve

Disadvantages of Coning of Wheel

• Pressure on Hz component of force near the INNER edge

of OUTER rail has a tendency to wear the rail quickly

• Hz component has to turn the rail outwards and hence the

gauge may be widened

• If no base plates are provided, sleepers under the outer

edge of the rail may be damaged

• In order to minimize the above disadvantages, Tilting of

Rails is done

Tilting of Rails

• Rails are tilted inwards at an angle of 1 in 20 to reduce wear & tear on

the rails & on the tread of the wheels.

• As the pressure of the wheel acts near the inner edge of the rail, there

is heavy wear & tear of the rail.

• Lateral bending stresses are created due to eccentric loading of rails.

• Uneven loading on sleepers damages them

• To reduce wear & tear and lateral stresses, rails are tilted at a slope of

1 in 20 (which is slope of wheel cone)

• Rail is tilted by ADZING the wooden sleepers or by providing canted

bearing plates.

Tilting of Rails

• Tilting of rails can be achieved by:–Adzing of Sleepers

–Use of Canted Base Plate

Tilting of Rails

• Advantages of Tilting Of Rails

– It maintains the gauge properly

– Wear at Rail Head is uniform

– It increases the life of sleepers and rails

Function of Rails

Function of Rails

• It provides a continuous & level surface for

movement of trains

• It provides a smooth & less friction pathway.

– Friction between the steel wheel & steel rail is about

1/5th of friction between pneumatic tyre & metalled road.

• It serves as a lateral guide for the wheels.

Function of Rails

• It bear the stresses developed due to vertical

loads transmitted to them

– through axles & wheels of rolling stock as well as

– due to braking & thermal forces.

• It transmits the load to a large area of the

formation through sleepers & the ballast.

Requirement of Rails

• Rail should have the most economical

section consistent with – Strength, Stiffness

& Durability.

• Centre of Gravity of rail section should

preferably be very close to the mid-height of

the rail so that the maximum tensile &

compressive stresses are equal.

Requirement of Rails

• Rail head: adequate DEPTH to allow for vertical

wear.

• Rail head: sufficiently WIDE so that it has a wider

running surface available & also has desired

lateral stiffness.

• Rail Web: sufficiently thick to withstand stresses

arising due to loads bone by it, after allowing for

normal corrosion.

Requirement of Rails

• Rail Foot: sufficient THICKNESS to withstand VR

& Hz forces after allowing for loss of corrosion.

• Fishing angle must ensure proper transmission

of loads from the rails to the fish plates.

• Rail Height: adequate so that rail has sufficient

vertical stiffness & strength as a beam.

SLEEPERS

Function of Sleepers

• Holds rails in their correct gauge &

alignment.

• Giving rails a firm & even support

• Transfers the load evenly from the rails to a

wider area of the ballast.

Function of Sleepers

• Acts as an elastic medium between rails &

ballast to absorb blows & vibrations caused

by moving loads

• Providing longitudinal & lateral stability to

the permanent way.

• Providing the means to rectify the track

geometry during their service life.

Requirement of Sleepers

• Initial & Maintenance cost: MINIMUM

• Weight: moderate so that it is convenient to

handle.

• Design of the sleeper & fastening should be such

that it is possible to fix & remove the rails easily.

• Sleeper should have sufficient bearing area so

that the ballast under it is not crushed.

• Sleeper should be able to maintain & adjust the

gauge properly.

Requirement of Sleepers

• Material of sleeper & its design should be such that it does

not break or get damaged during packing.

• Design of sleeper should be such that it is possible to have

track circuiting.

• Sleeper should be capable of resisting vibrations & shocks

caused by the passage of fast moving trains.

• Sleeper should be anti-sabotage & anti-theft features.

Ballast

Function of Ballast

• Provides a level & hard bed for sleepers to rest on.

• Holds the sleepers in position during the passage of trains.

• Transfers & distributes load from sleepers to a larger area of the

formation.

• Provides elasticity & resilience to the track for proper riding

comfort.

• Provides resistance to the track for longitudinal & lateral stability.

• Provides effective drainage to the track.

• Maintains the level & alignment of the track.

Requirement of Ballast

• Tough & wear resistant

• HARD: not get crushed under the moving loads.

• SHAPE: generally cubical with sharp edges.

• Non-porous & should not absorb water.

Requirement of Ballast

• Resist both attrition & abrasion.

• Durable & should not get pulverised or

disintegrated under adverse weather conditions.

• Allow for good drainage.

• Cheap & economical.

Creep in Rails

Creep in Rails

• It is defined as the longitudinal movement of rails

wrt sleepers in a track.

• Causes of creep:

– Closing of successive expansion spaces at rail joints in

the direction of creep and opening out of joints at the

point from where the creep starts.

– Marks on flanges and webs of rails made by scratching

as the rails slide.

Effects of Creep

• Sleepers move out of position leading to change in gauge

and alignment of the track.

• Rail joints are opened out of their limit & stresses are

developed in fish plates and bolts which leads to the

breakage of the bolts.

• Points and crossings get disturbed.

• Maintenance and replacement of tracks becomes difficult.

• Smashing of fish plates and bolts, bending of bars, kinks

at joints are other effects of creep.

Minor Causes of creep in rail

• Rails not properly fixed to sleepers

• Bad drainage of ballast

• Bad quality of sleepers used

• Improper consolidation of formation bed

• Gauge fixed too tight or too slack

• Rails fixed too tight to carry the traffic

• Incorrect adjustment of super elevation on outer rails at

curves

• Incorrect allowance for rails expansion

• Rail joints maintained in bad condition

Theories of Creep

• Wave Motion Theory

• Percussion Theory

• Drag Theory

CURVES

Radius or Degree of Curve

• A curve is defined by its – RADIUS or DEGREE.

• Degree of Curve (D) is the angle subtended by a

30.5m or 100ft CHORD at its centre.

• D = 1750/R (R in m)

• D = 5730/R (R in ft)

Relationship between Radius & Versine of Curve

• Versine is the perpendicular distance of the midpoint of a

chord from the arc of a circle.

• V = C*C/8R

• V = 12.5 C*C/R cm = 125 C*C/R mm

Degree of Curve with chord length of 11.8m or 62 ft

• D = 1750/R (put value of R=12.5 C*C/V)

• D = V cm

Elements of Circular Curve

• Angle of deflection + Angle of Intersection = 180o

• Tangent Length, OT1 = OT2 = R tan o/2

• Length of Long Chord = T1T2 = 2R Sin o/2

• Length of Curve = 2 pi R 00/360

Super elevation

• Super elevation or Cant (Ca): is the difference in height

between the OUTER & INNER rail of the curve.

• It is provided by gradually lifting the outer rail above the

level of the inner rail.

• Functions

– To ensure a better distribution of load on both rails.

– To reduce wear & tear of the rails & rolling stock

– To neutralize the effect of lateral forces

– To provide comfort to passengers.

Super elevation

• Equilibrium Speed: When speed of a vehicle negotiating a

curved track is such that the resultant force of WEIGHT of

vehicle & RADIAL acceleration is perpendicular to the plane

of rails, the vehicle is not subjected to any unbalanced radial

acceleration & is said to be in equilibrium.

• Maximum Permissible Speed: is the highest speed

permitted to a train on a curve taking into consideration –

Radius of Curvature, Actual Cant, Cant Deficiency, Cant

Excess & Length of Transition.

Super elevation

• Cant Deficiency (Cd): It occurs when a train travels

around a curve at a HIGHER than equilibrium

speed. It is the difference between the theoretical

cant required for such HIGH speeds & actual cant

provided.

• Cant Excess (Ce): It occurs when a train travels

around a curve at a LOWER than equilibrium

speed. It is the difference between the actual cant

provided & theoretical cant required for such LOW

speeds.

Super elevation

• Rate of Change of Cant or Cant Deficiency

– It is the rate at which cant deficiency increases

while passing over the transition curve, e.g., a

rate of 35mm/sec means that a vehicle will

experience a change in cant or cant deficiency of

35 mm in each sec of travel over the transition

when traveling at maximum permissible speed.

Super elevation

• Cant Gradient & Cant Deficiency Gradient

– It indicates increase or decrease in cant or

deficiency of cant in a given length of transition.

– A gradient of 1 in 1000 means a cant or a

deficiency of cant of 1mm is attained or lost in

every 1000mm of transition length.

Safe Speed on Curves

• Safe speed means a speed which protects a

carriage from the danger of overturning &

derailment & provides a certain margin of safety.

• For BG & MG

– Transitioned Curves, V1 = 4.4 (R – 70)1/2

– Non-transitioned Curves, V2 = 80% of V1

• V = 0.27 [(Ca + Cd) R]1/2

Transition Curve

• A TC smoothen the shift from straight line to the

curve.

• They are provided on either side of the circular

curve so that centrifugal force is built up gradually

as super elevation slowly runs out at a uniform

rate.

Transition Curve

• It decrease the radius of curvature gradually in a

planned way from infinity at straight line to

specified value of the radius of a circular curve in

order to help the vehicle negotiate the curve

smoothly.

• It helps in providing the gradual increase of the

super elevation starting from zero at straight line

to the desired super-elevation at the circular

curve.

Check Rail

• These are provided parallel to the inner rail on sharp curves

to reduce the lateral wear on the outer rail.

• They prevent the outer wheel flange from mounting the outer

rail & thus decrease the chances of derailment of vehicles.

• CR wear out quite fast but since, these are worn out rails,

further wear is objectionable.

• CR are provided on the gauge face side of inner rails on

curves sharper than 8 degree on BG, 10 Degree on MG & 14

degree on NG.

GRADIENTS

• These are provided to negotiate rise or fall in the level of

the railway track.

• In RISING gradient, track rises in the direction of

movement of traffic.

• In DOWN/FALLING gradient, track loses elevation in the

direction of movement of traffic.

• It is represented by the distance travelled for a a rise or fall

of 1 unit. Sometimes it is represented as % rise or fall.

• For e.g., if there is rise of 1m in 400m, the gradient is 1 in

400 or 0.25%.

Objective of Gradients

• To reach various stations at different

elevations

• To follow the natural contours of the ground

to the extent possible

• To reduce the cost of earthwork.

Types of Gradients

• Ruling G

• Pusher of Helper G

• Momentum G

• G in Station Yards

Ruling Gradients

• It is the steepest gradient that exists in a section.

• It determines the maximum load that can be hauled by a

locomotive on that section.

• Factors for deciding the RG

– Severity of G

– Length & position wrt G on both sides.

– Power of locomotive

• In Plain terrain: 1 in 150 to 1 in 250

• In Hilly Terrain: 1 in 100 to 1 in 150

• All other G in that section should be flatter than the RG.

Pusher of Helper Gradient

• When the gradient of ensuing section (in

hilly terrain) is so steep as to necessitate

the use of an extra engine for pushing the

train, it is known as P/H G.

• Here gradients steeper than RG are

provided to reduce the overall cost (length

of railway line).

Momentum Gradient

• MG is also steeper than RG.

• In valleys, a falling gradient is followed by a

rising gradient.

• During falling G, train gathers good speed or

momentum which gives additional kinetic

energy to the train & allows it to negotiate G

steeper than RG.

Gradient in Station Yards

• These are quite flat due to following reasons:

– It prevents the standing vehicles from rolling & moving

away from the yard due to combined effect of gravity &

strong winds.

– It reduces the additional resistive forces required to

start a locomotive.

– Max G: 1 in 400; Recommended G: 1 in 1000

Grade Compensation on Curves

• Curves provide extra resistance to movement of

trains.

• Hence, G are compensated to the following extent

on curves:

– On BG tracks: 0.04% per degree of curve or 70/R;

whichever is Minimum.

• G of a curved portion of section should be flatter

than RG because of extra resistance offered by the

curve.

THANK YOU !!!