BAHIRDAR UNIVERSITY

INSTITUTE OF TECHNOLOGY

SCHOOL OF CIVIL & WATER RESOURCES

ENG.
RAILWAY ENGINEERING (CENG 4172)

CHAPTER 5 SWITCHES & TURNOUTS

Amdebrhan M.
(SWJU, P.R China )
(AAU/AAiT, Ethiopa)
anedebrha@gmail/yahoo.com
Feb. 2013
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CHAPTER 5 SWITCHES & TURNOUTS

5.1 the Switches and their function

5.2 types of switches
5.3 components of a single switch
5.4 Turnout
5.5 Railway Clearance

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 5.1 The Switches and their function

 Switches are of special importance for

railways, as they are the prerequisite for the
development of networks, i.e. for the branching
and joining of tracks
 The productivity and line speed of a railway
is essentially influenced by the number and
type of its switches

 The structure of a switch

is far more complicated and
expensive than that of the
track grid

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 Switches are structural elements requiring high
investment and large-scale maintenance, they can
severely hinder vehicle traffic
The purchase costs for one effective meter of a
switch (depending on the type of switch) are up to
four times higher than for one meter of track
 Switches must be arranged and designed in
such a way as to achieve a favorable lay out of the
line- from the point of view of the dynamics of
vehicle movement

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 These design decisions are very important, as high
dynamic forces might occur due to structural defects
which then lead to defective track position and early wear
 The same standard of maintenance has to be
achieved for switches and for track in order to
prevent switches from becoming sources of
disturbance.

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 Significant progress in the design of
traditional switches has been made during
the past decades. Nevertheless, the stress on
the structural elements of switches is much
higher than on track elements, as it is not
possible to avoid places of discontinuous
stress.
 Therefore, traditional switches can fulfill
their task only up to a certain speed and
stress level.
 New solutions have had to be found for the
geometry and structure of switches on which
trains pass at high speed and which are
subject to high stress
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 Switches enable vehicles to pass from one
track to another without interrupting their
run
 Crossing are the intersection of two tracks,
diamond crossings with slips make it possible
for vehicles to pass from one track to another
without interrupting their run at the point of
intersection
 The service life of a switch on wooden
sleepers is nowadays 20 years, on concrete
sleepers about 30 years

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 5.2 Main types of switches
The main types of switches:
crossings and diamond crossings with slips
split/single switches
symmetrical switches
three way switches

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Crossings

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 Diamond crossings with slip/Slip
switches

Schematic representation of a double

diamond crossing with slip, with blades
arranged within the diamond crossing

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Diamond crossings
Cross-over, double cross-over

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 5.3 Components of a single switch

Switch proper, frog and check/guard rails,

intermediate rails

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Switch proper: two Stock rails, two switch rails,
rail fastening and switch machine (switch
stand)
frog: frog centre, wing rails, appropriate rail
fastenings. Movable frog, rigid frog

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 5.4 Turnout

 Since the train usually needs to transfer

from one line to another, the turnout is set to
connect the lines

 Turnout is an important part of the rail, as

its large quantity, short life, limited speed and
low safety, it is called the three big weak links
with the curve and the joint.

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 Simple turnout
(1) constitution

the railroad switch, the frog and guard rail, the

pontes
frog

guard rail

railroad switch

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 the railroad switch: stock rail and switch rail
- to determine the opening direction of turnout
 the frog and guard rail: wing rail, guard rail and frog
- to ensure the safety
 the pontes: straight rail and curve rail
- to connect the line

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line A the railroad switch the pontes the frog and guard rail

stock rail switch rail curve rail guard rail

wing rail
frog
gap in the frog
switch line B

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(2) the railroad switch
1) function and constitution

function: to guide the direction

constitution: two stock rails, two switch rails,

some union pieces and switch equipment.

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2) stock rail

usually with a length of 12.5m or 25m

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Characteristic:
① main line is straight
② side line is curve
③ setting rail brace

main line

rail brace side line

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3) switch rail

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 (3) the frog and guard rail
consist of wing rail, guard rail, frog and some union
pieces frog

guard rail

railroad switch

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1) the frog

consist of wing rail and frog

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2) guard rail

guard rail guard rail

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3) movable frog

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 (4) the pontes

consist of straight rail and curve rail

line A the railroad switch the pontes the frog and guard rail

stock rail switch rail curve rail guard rail

wing rail
gap in the frog frog
switch line B

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 (5) size of frog

EF
N  ctg 
AE

the larger the size N is, the smaller the angle  it

could, and the faster the allowable speed is

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(6) others

right-turnout

left-turnout

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 Symmetrical turnout

Symmetrical turnout increase the radius of curve

rail, improve the speed and can shorten the length
of the station

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 Three-throw turnout

 It has three frogs and can lead to three directions

 It can decrease the use of land;

but the life of its switch rail is
short and it has gap in frog
without the guard rail.

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 Slip switch

 It can lead to four directions

 Though the connecting length is shorten, there
exists gap in frog without guard rail

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Special turnout

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Cross equipment

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 5.5 Railway clearance

1. Definition

To ensure the safety, all that buildings and

equipments close to the line, must be kept
their distance
There also have certain provisions for the
train

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2. types
(1) the locomotive clearance
(2) the structure approaching clearance
(3) the max limited clearance for out-of-gauge
freight
3. clearance diagram

datum line:
vertical: rail surface
horizontal: center line of track

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the structure approaching
clearance

the locomotive clearance

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 4. out-of-gauge freight
When any part of the freight is beyond the locomotive
clearance, it is called out-of-gauge freight.

according to the degree, it is divided into three levels:

level Ⅰ, level Ⅱ and level Ⅲ.

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The locomotive clearance should be widen while on curve.

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谢谢
Thanks!

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