unit 2 revised

8/16/2019 Unit 2 Revised

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Sleepers

Introduction

Sleepers are the transverse ties that are laid to support the rails. They have an important role

in the track as they transmit the wheel load from the rails to the ballast. Several types of

sleepers are in use on Indian Railways. The characteristics of these sleepers and their suitability with respect to load conditions are described in this chapter.

Functions and Requirements of Sleepers

The main functions of sleepers are as follows.

1. Holding the rails in their correct gauge and alignment

2. iving a firm and even support to the rails

!. Transferring the load evenly from the rails to a wider area of the ballast

". #cting as an elastic medium between the rails and the ballast to absorb the blows and

vibrations caused by moving loads

$. %roviding longitudinal and lateral stability to the permanent way

&. %roviding the means to rectify the track geometry during their service life.'. To support the rails at proper level in straight tracks and at proper super elevation on

curves

#part from performing these functions the ideal sleeper should normally fulfil the following

re(uirements.

1. The initial as well as maintenance cost should be minimum.

2. The weight of the sleeper should be moderate so that it is convenient to handle.

!. The designs of the sleeper and the fastenings should be such that it is possible to fi)

and remove the rails easily.

". The sleeper should have sufficient bearing area so that the ballast under it is not

crushed.

$. The sleeper should be such that it is possible to maintain and ad*ust the gauge

properly.

&. The material of the sleeper and its design should be such that it does not break or get

damaged during packing.

'. The design of the sleeper should be such that it is possible to have track circuiting.

+. The sleeper should be capable of resisting vibrations and shocks caused by the

passage of fast moving trains.

,. The sleeper should have anti-sabotage and anti-theft features.

1. /ittings of the sleepers should be such that they can be easily ad*usted during

maintenance operations such as easy lifting0 packing0 removal and replacement.

Sleeper Density and Spacing of Sleepers

Sleeper density is the number of sleepers per rail length. It is specified as M x or N x0

where M or N is the length of the rail in metres and x is a number that varies according to

factors such as a3 a)le load and speed0 b3 type and section of rails0 c3 type and strength of

the sleepers0 d3 type of ballast and ballast cushion0 and e3 nature of formation. If the sleeper

density is M ' on a broad gauge route and the length of the rail is 1! m0 it means that 1! '

4 2 sleepers will be used per rail on that route. The number of sleepers in a track can also be

specified by indicating the number of sleepers per kilometre of the track. /or e)ample0 1$"

sleepers5km. This specification becomes more relevant particularly in cases where rails are

welded and the length of the rail does not have much bearing on the number of sleepers

re(uired. This system of specifying the number of sleepers per kilometre e)ists in manyforeign countries and is now being adopted by Indian Railways as well. The spacing of


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sleepers is fi)ed depending upon the sleeper density. Spacing is not kept uniform throughout

the rail length. It is closer near the *oints because of the weakness of the *oints and impact of

moving loads on them. There is0 however0 a limitation to the close spacing of the sleepers0 as

enough space is re(uired for working the beaters that are used to pack the *oint sleepers.

Types of sleepers

1. 6ooden sleepers

2. 7etal sleepers

a. 8ast iron sleepers

b. Steel Sleepers

!. 8oncrete sleepers

a. Reinforced concrete sleepers

b. %restressed concrete sleepers

Timber or wooden sleepers

Advantages

• 9asy to manufacture and handling.

• They have long life of 1-12 years depending upon the climate0 condition0 rain0

intensity0 nature of traffic0 (uality of wood etc

• ood insulators and hence good for track circuited railway tracks

• Suitable for salty regions and coastal areas

• They are not badly damaged in case of derailment

• They are not corroded

• Suitable for track circuited area.

• 8an be used with or without ballast.• Suitable for bridges0 %oints58rossings.

• Suitable for gauntleted track.

• #lignment can be easily corrected.

Disadvantages

1. :esser life compared to other sleepers.

2. :iable to damage by beater packing.

!. ;ifficult to maintain the gauge.

". Susceptible to fire ha of the track on Indian Railways is laid on steel sleepers. The increasing shortage

of timber in the country and other economical factors are mainly responsible for the use of

steel sleepers in India. Steel sleepers have the following main advantages5disadvantages over

wooden sleepers.

Advantages

• Have a useful life of 2-2$ years.

• /ree from decay and are not attacked by vermins

• 8onnection between rail and sleeper is stronger


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• 8onnection between rail and sleeper is simple

• 7ore attention is not re(uired after laying

• Having better lateral rigidity

• ood scrap value

• Suitable for high speeds and load

• 9asy to handle• ood resistance against creep

Disadvantages

• :iable to corrosion by moisture and should not because in salty regions

• =ad insulators and hence cannot be used in track circuited regions

• Should not be laid with all types of =allast

• ?ery costly

• 8an be badly damaged under derailments

• The rail seat is weaker

• @ot a good shock absorber as there is no cushion between rail foot and ballast

Cast iron Sleepers

Advantages

1. :ess corrosion

2. :ess probability of cracking at rail seat

!. 9asy to manufacture

". Higher scrap value

$. :ong life upto $-& years- High scrape value as they can be remolded

&. 8an be manufactured locally - %rovided sufficient bearing area

'. 7uch stronger at the rail seat - %revent and check creep of rail

+. They are not attacked by vermin

Disadvantages

1. auge maintenance is difficult as tie bars get bent

2. %rovides less lateral stability

!. Ansuitable for track-circuited lines

". @ot very suitable for mechanical maintenance and5or 7S% because of rounded bottom

$. Susceptible to breakage

&. They are prone to corrosion and cannot be used in salty formations and coastal areas -

@ot suitable for track circuited portions of railways

'. 8an badly damage under derailment

+. Re(uire a large number of fastening materials - ;ifficult to handle and may be easilydamaged - :ack of good shock absorber - They are e)pensive

,. @ot suitable for high speed route.

1. @ot fit for track circuited area.

Concrete Sleepers

These types of sleepers were promoted because of shortage of good wooden sleepers and

need for better design and economy of sleepers on sustainable basis.

These sleepers are mainly of two types

1. Reinforced cement concrete sleepers2. %re-stressed concrete sleepers


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9)periments have shown that concrete sleepers are idela material for sleeper for the

following reasons

1. They are made of a strong homogeneous material0 impervious to effect of moisture

and is unaffected by the chemical attack of atmospheric gases or sub Bsoil salts

2. It is easily moulded to si


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1. The tie bar is fastened to the plate by means of four standard cotters. Small variation

in gauge can be corrected by these four cotters

2. The shape of cast iron support is such as to give a stable base for the rail0 and high

lateral and longitudinal stability to the track

!. The sleeper may be used in sections of track in corrosive conditions such as saline

soil0 industrial waste etc". The bearing area is appro)imately e(ual to the effective bearing area of a wooden

sleeper

$. This sleeper forms the rigid track sub*ected to vibrations under moving loads without

any damage or absorption

&. The cantilever ends of the rails are long which lead to battering0 and ultimately

hogging of the rail end and deterioration of ballast under the *oint which finally need

the replacement of sleeper.

'. This type of sleeper is suitable for speeds upto 11 7%H

+. If used for tracks above speed of 11 kmph0 due to the shallow depth of the bowl0

packing becomes loose under vibrations at high speed

#s the sleeper does not have a flat bottom0 it is not (uite suitable for mechanical maintenancewith tie tamers.

1. The suitability of a 8ST-, sleeper on :ong 6elded Rails :6Rs30 particularly on the

breathing lengths0 is doubtful because of rigid fastenings and the inability of the

fastenings to hold the rail with a constant toe load.

2. The rail seat wears out (uickly causing the keys to come loose.

!. The sleeper has only limited longitudinal and lateral strength to hold :6Rs

particularly in the breathing length.

". ;ue to the use of less metal under rail seat0 the shocks and vibrations are directly

transmitted to the ballast0 resulting in poor retention of packing loose packing3 and

hence an increased fre(uency of attention.

Track /ittings and /astenings

Introduction

The purpose of providing fittings and fastenings in railway tracks is to hold the rails in their

proper position in order to ensure the smooth running of trains. These fittings and fastenings

are used for *oining rails together as well as fi)ing them to the sleepers0 and they serve their

purpose so well that the level0 alignment0 and gauge of the railway track are maintained


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within permissible limits even during the passage of trains. The important fittings commonly

used in a permanent way are the following

1. /ish plates

2. Spikes

!. =olts

". 8hairs$. =locks

&. eys

'. %lates

Fis! "latesis a metal bar that is bolted to the ends of two rails to join them together in atrack. The top and bottom edges are tapered inwards so the device wedges itself

between the top and bottom of the rail when it is bolted into place. The name Cfish

plateD derives from the fish-shaped section of this fitting. The function of a fish plate is to

hold two rails together in both the hori


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Spi#es

The re(uirements of a good spike are

1. /irst of all0 the spike should be strong enough to hold the rail in position and it should

have enough resistance against motion to retain its original position so that it does not

lead to creep

2. The spike should be as deep as possible0 for better holding power !. The spike should be easy in fi)ing and removal from the sleepers

". The spike should be cheap in cost

$. It should be capable of maintaining the gauge

Dog spi#es

/or holding the /./. Rails to a wooden sleeper0 dog spikes are commonly used. These are

simply stout nails to hold rail flanges with timber sleepers. The shape of head of spike

resembles with ear of the dog and hence its nomenclature as dog spike. The section of the

spike is s(uare-shape and bottom part is either pointed0blunt or chisel shaped. They arecheapest0 easy in fi)ing and removing from sleepers and maintain a better gauge than scre

spikes.

Screw spi#es

These are tapered screws with ? threads used to fasten the rails with timber sleepers. The

head is circular with s(uare pro*ection

Screw spike has double the holding power as that of dog spike an can also resist lateral thrust

in a better way as compared to dog spikes. However0 the screw spikes are costly and with that

their use0 the gauge maintenance become difficult

Round spi#es

Round spikes with a head either cylindrical or hemispherical are used for fi)ing chairs of

=.H. Rails to wooden sleepers for fi)ing slide chairs of points and crossings. These have a

blunt end and limited use

Standard spi#es

These are used for cast iron chairs only to fi) them with timber sleepers

$lastic spi#es

#ctually the main disadvantage with the dog head spikes is that due to wave motion the spike

comes out hence the fastening will get loose. To over come this disadvantage elastic spikes

are introduced which will absorb the wave motion without getting loose

Dog Spi#es

• It is used to hold flat footed rails to a wooden sleeper.

• The shape of the top head resembles that of a dog0 hence the name.

• The section of the spike is s(uare shaped and the bottom part is either pointed0 blunted

or chisel shaped.


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• They are cheap and easy to install0 but they move out of place due to wave motion0

resulting in creep.

SCR$% S"I&$

• These are tapered screws with ? threads used to fasten rails with timber sleepers.• The head is circular with a s(uare pro*ection.

• Screw spikes have more than double the holding power of dog spikes but they are

costly and maintenance is more difficult.


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'olts

1. ;og bolts0 where sleepers rest directly on a girder0 they are fastened to the top flange

of the girder by bolts called dog bolts

2. /ish bolt the fish bolts have to undergo shear due to heavy transverse stresses0 fish

bolts are made of medium or high carbon steel. Asually a bolt of 2.$ cm dia and 12.'

cm length is used. enerally the length of the bolt depends on the type of plate used.CI C!airs

• 8hairs are used for holding ;ouble Headed and =ull Headed rails.

• The rails are placed between the two *aws of a chair and pressed against the inner *aw

by inserting tapered keys.

• =.H. rails are supported on 8ast Iron 8hairs fi)ed to the sleepers by round spikes.

• In case of cast iron sleepers0 the chairs are casted together with the sleepers.

• In case of steel sleepers0 the chairs are welded to the steel sleepers.


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'loc#s

6hen two rails run very close as in case of check rails0 etc. small blocks are inserted in

between the two rails and bolted to maintain the re(uired distance or spacing.

=earing %lates

=earing %lates are rectangular plates of 7ild Steel or 8ast Iron that are used below /lat

/ooted rails to distribute the load on a larger area of the sleepers.Advantages of 'earing "lates

• They distribute the load coming from the rails to the sleepers over a larger area.

• They prevent the destruction of sleepers due to rubbing action of the rail.

• @o ad


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1. Trac# irregularities( if the track is not properly maintained due to irregularities0

additional resistance has to be overcome

2. Due to vertical movements( ;ue to improper *oints and poor maintenance of track0

vertical movements of wheels on rails occurs creating resistance

Atmosp!eric resistance

This is resistance which is developed on the ends and sides of the train when wind velocity isconsidered to be


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6hen a vehicle moves with speed0 a certain resistance develops0 as the vehicle has to move

forward against the wind. 6ind resistance consists of side resistance0 head resistance0 and tail

resistance0 but its e)act magnitude depends upon the si


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This type of ballast is normally used in yards and sidings or as the initial ballast in new

constructions since it is very cheap and easily available. It is harmful for steel sleepers and

fittings because of its corrosive action.

'ro#en stone ballast

This type of ballast is used the most on Indian Railways. # good stone ballast is generally procured from hard stones such as granite0 (uart


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track

• )ood packing „

material for 1!

sleepers

• Track cannot be

maintained to highstandards

tracks

7oorumballast

• 1heap, if locally

available

• revents water

from percolating

• rovides good

aesthetics

• 8ery soft and turns

into dust

• 7aintenance of

track the di9cult

• :uality of track

average

• ;sed as a sub6ballast

• !nitial ballast

for new

construction

1oal ash or

cinder

• oods andemergencies

• 2ot ?t for

high6speed

tracks

(roken stone

ballast• =ard and durable

when procured

from hard rocks

• )ood drainage

properties

• !s stable, and

resilient to the

track

•


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4 .1&W .+ N +W .& N +2 W

R 4 .11+"W

#ssuming total resistance 4 hauling power0

W M .11+" 4 1!.2 t

W= 111$ t2. Reduction in speed if the train has to run on an up gradient of 1in 2

En a gradient of 1 in 20 there will be an additional resistance due to gradient

e(ual to W M > of slope.

R 4 Resistance independent of speed resistance dependent on speed resistance due to

wind W M > of slope.

4 .1&W .+WV .&WV+W x slope

Substituting the value of w 4 111$ t and slope 4 152

4 .1& X 1115 .+ X 1115 X V .& X 1115 X V 2+W x 1/200

Since hauling power 4 total resistance0

1!.24.1& X 1115 .+ X 1115 X V .& X 1115 X V 2+W x 1/200?4"+.1!

Reduction in speed 4 + B "+.1! 4 !1.+' km5h 4 !2 km5h

!. #long with the gradient of 1in 2 if there is a curve of "K the reduction in speed is

calculated as

En a curve of "K on a rising gradient of 1 in 20 curve resistance will be e(ual to

R 44 .1&W .+WV .&WV+W x slope ." M degree of curve M 6

=. resistance due to curve is 4 ."M degree of curve M 63

4 .1& X 1115 .+ X 1115 X V .& X 1115 X V 2+W x 1/200+ ." M " M

W 4 .1&W

Hauling power of locomotive 4 total resistance. Therefore0

1!.2 4 .1&W .+WV .&WV 2 .$W .1&W

=y substituting the value of W 4 111$t in the e(uation and solving further0

V 4 "!.&+ km5h

/urther reduction in speed 4 "+.1! B "!.&+ 4 "."$ km5h. Therefore0

7a)imum permissible train load 4 111$ t

Reduction in speed due to rising gradient 4 !1.+' t

/urther reduction in speed due to curvature 4 "."$ km5h

8ompute the steepest gradient that a train of 2 wagons and a locomotive can negotiate given

the following data weight of each wagon 4 2 t0 weight of locomotive 4 1$ t0 tractive effortof locomotive 4 1$ t0 rolling resistance of locomotive 4 ! kg5t0 rolling resistance of wagon 4

2.$ kg5t0 speed of the train 4& km5h

Rolling resistance due to wagons 4 rolling resistance of wagon M weight of

wagon M number of wagons

4 2.$ M 2 M 2 4 1 kg 4 1 t

Rolling resistance due to locomotive

4 rolling resistance of locomotive M wt of locomotive

4 ! M 1$ 4 "$ kg 4 ."$ t

total rolling resistance 4 rolling resistance due to wagons rolling resistance

due to locomotive 4 1. ."$ t 4 1."$ ttotal weight of train 4 weight of all wagons wt of locomotive


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4 2 M 2 1$ 4 $$

total train resistance 4 rolling resistance resistance dependent on speed resistance due to

wind resistance due to gradient

4 1."$ .+WV .&WV 2 W 5 g

4 1."$ .+ M $$ M & .& M $$ M & $$5 g 3

4 1."$ 2.&" 1.1, $$5 g 3 4 $.2+ $$5 g 36here g is the gradient.

Tractive effort of locomotive 4 Total train resistance

1$ 4 $.2+ $$5 g 3

4 $&.$

4 15$& 4 1 in $&

Therefore0 the steepest gradient that the train will be able to negotiate is 1 in $&

unit 2 revised

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