2. Introduction
Turnout is the simplest combination of points and crossings which
enables one track either a branch line or a siding, to take off from
another track. So the object of turnout is to provide facilities for safe
movement of trains in either direction on both the tracks.
The assembly of various components which enables trains to move
from one track to any other track either parallel to or diverging from
track, is called a turnout or point and crossing.
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3. Turnout
The combination of points and crossing of a railway track, is called a turn
out.
According to the direction of diversion, turnouts are classified as under:-
Left hand turn out: The turnout which diverts the train to the left, is called
a left hand turnout.
Right hand turnout: The turnout which diverts the train to the right, is
called a right hand turnout
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6. Component Parts of a Turnout
• A pair of tongue rails
• A pair of stock rails
• Two check rails
• Four lead rails
• A vee crossing
• Slide chairs
• Stretcher bar
• A pair of heel blocks
• Switch tie plate or gauge
• Parts for operating points- Rods, cranks,levers etc
• Locking system which includes locking box, lock bar, plunger
bar etc
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7. Important Terms Used
• Facing Direction: If someone stands at toe of switch and looks
towards the crossing, then the direction is called “Facing Direction”
• Trailing Direction: If someone stands at the crossing and looks
towards the switches then the direction is called “Trailing Direction”
• Facing Points of Turnouts:When a train travels from the switch to
the frog, the points are known as facing points of turnouts.
• Trailing Points of Turnouts:When a train travels in the direction
from the crossing to the switches, the points are known as trailing
points or trailing turnouts.
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8. Turnout are basically consists of two main parts
Points
Crossings
Components of Points
Stock rail: The rails of the main line track against which tongue rails
snugly fit, are called stock rail
Tongue rail: The tapered rails whose thicker ends known as heel are fixed
to the main track and thinner ends known as toe of the switch to obtain a
snug fit with the respective stock rails, are called tongue rails, switch rails
or point rails
Switch: A stock rail and its respective tongue rails form a switch. A set
switch is known as points which divert the trains from one track to another.
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9. Heel block: The block which connects the heel of the tongue rail to the
stock rail, with a ordinary fish plate and bolts, is called the heel block.
Sliding plate: The metal plates which are provided for supporting and
sliding the tongue rail to obtain snug fit against the stock rail is called the
sliding plates.
Stretcher bar: Two or three bars which are used to connect the ends of the
tongue rail at the toe to ensure the movement of the tongues through the
same distance, are called the stretcher bar.
Point rod: The rod which moves the points by operating a point leaver, is
called the point rod.
Throw of switch: The distance through the tongue moves laterally at the
toe of the switch for movement of trains is known as throw of switch.
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11. Components of crossings
The arrangement of rails which provided to enable the flanges of wheels
to cross the rail, of other track is called crossing.
Crossing lead rail: The heels of tongue rail are connected to the crossing with
two rails one straight rail and other curved rail. These two rails are called
crossing lead rail.
Point rail: The rail of the V-shaped portion of the crossing i.e. frog, which ends
the nose of crossing, is called point rail.
Splice rail: The rail of V-shaped portion of the crossing i.e. frog, which ends a
little behind the nose of crossing is called splice rail.
Wing rail: The two bent up rails of the crossing which are connected to the
ends of the crossing lead rails( one straight and one curve rail) are called the
wing rails.
Toe of crossing: The line joining the joints of the rail of the crossing assembly
with the end of crossing lead rails, is called the toe of crossing.
Heels of crossing: The line which joins the ends of the point rail and splice rail
of the crossing, is called the heel of the crossing.
Throat: the narrowest space between the two wing rails of a crossing is called
the throat of the crossing.
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14. Check Rail: It is the rail length provided on the opposite side of crossing to
check the tendency of wheel to climb over the crossing
Crossing angle: The angle between the gauge of the rail and splice rail, is
called the crossing angle(α). The size of the crossing is designated by its
crossing angle.
Theoretical nose of crossing(T.N.C): The point of intersection of the gauge of
the point rail and splice rail of a crossing, is called the theoretical nose of
crossing. It is slightly away from the actual nose of the crossing.
Actual nose of crossing(A.N.C): The ends of the point rail in the gap of the
crossing is called actual nose of crossing.
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15. Working Principle of Turnout
Referring to the previous figure, a turnout provides facilities for safe
turning of vehicles from track to another. One turnout provides
facilities for turning of vehicles from one direction only and not from
both the directions of the straight path or route as in the case of roads.
A turnout works with the combination of points and crossings. This
consists of mainly a pair of points or switches, four lead rails(2-straight
and 2-curved lead rails), two check rails and a crossing
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16. Types of Turnouts
There are different types of turnouts designed to fit particular
trackwork situations. And they are-
Conventional :The diverging route curves away from a tangent
(straight) track. Left- or right-hand designation is the direction of
diversion when looking at the turnout from the switch-point end. On
main lines the straight leg should be the main route, if possible.
Curved :Both routes curve in the same direction, but with different
radii. Left- or right-hand designation is the direction of curvature
when looking at the turnout from the switch-point end. Curved
turnouts can save space in some trackwork situations like yard leads.
Equipment will track better on the larger radius leg, which should be
the main route
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17. Conclusion
In a developing country like India, the contribution of railway
transport towards the economic growth is immense at other modes of
transport ie roadways, airways ,inland waterways etc are not available
at reasonable rates and in sizeable quantity to cope up with quantum of
traffic.
In order to move the traffic efficiently, it is felt that the speed of the rail
transport shall be augmented. Turnout , an essential feature of the
track structure for diversion of traffic from one road to another, poses
at present a tricky problem in the context of achieving reasonably high
speed over the turnout.
Turnouts are an essential feature of trackwork but can be trouble
makers if not done right
Turnout points are hinged rails that move back and forth(left & right)
and guide the train’s wheels throughout the turnout’s frog to either the
straight leg of the turnout or through the curved leg of the turnout.
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18. Reference
A text book of Railway Engineering-By S.C. Saxena and S.P. Arora
www.wikipedia.com
www.modelrectifier.com
Transportation Engineering II: Railways-By Dr. Charisma Choudhury
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