Last updated on August 21st, 2023 at 05:51 pm
The rolled steel sections laid end to end in two parallel lines over sleepers to form a railway track are known as rails. What is meant by rails. They work as continuous girders carrying axle loads of trains. Rails provide a hard and smooth surface for the movement of the train.
What is the function of rails:
d. To provide a hard, strong, and smooth surface for the movement of trains with minimum tractate resistance.
e. To bear the stress developed in the track due to heavy wheel loads, lateral and braking forces, and also due to variations of temperature.
f. To transmit the axle loads of trains to sleepers and consequently reducing pressure on ballast and formation.
Composition of rails steel: The composition of rail steel to be used in the manufacture of rail is given below:-
a. For ordinary rails: for these rails, high carbon steel having the following composition is used
Carbon – 0.55 to 0.68 %
Manganese Mn) – 0.65 to 0.90 %
Silicon (Si) – 0.55 to 0.3 %
Sulphur (s) – 0.05% or below
Phosphorus (P) -0.05% or below
b. For rails on points and crossing:- For these rails, medium carbons steel having the following composition is used:-
C. Carbon (C) -0.5 to 0.6 %
d. Manganese (Mn) -0.95 to 1.25 %
e. Silicon (si) -0.05 to 0.20 %
f. Sulphur (s) – 0.06% or below
g. Phosphorus (p) 0.06% or below
The rails used in the construction of railway track can be divided into the following three steps:
1. Double headed rails (D.H. rails)
2. Bull-headed rails (B.H. rails)
3. Flat footed rails (F.F. rails)
Bull headed rails: The rail sections, having their head of more dimensions than of their foot are known as Bull-headed rails.
The rails overcome the defect of double-headed rails. In these rails, metal in their foot is just sufficient to bear the stress caused by the moving wheel loads.
These rails also require chairs for holding them in position.
B.H. rails are commonly used in Indian railways, especially for constructing points and crossing.
- B.H. rails keep better alignment due to the provision of chairs for holding them in position.
- These rails facilities easy manufacturing of points and crossing
- These rails, with a larger bearing on sleepers due to provisions of chairs, provide longer life to wooden sleepers and also greater stability to the track.
- These rails can be removed and replaced quickly and hence, renewal to the track is easy.
- B.H. rails require costly fastening
- These rails are of less strength and stiffiness
- The track formed with these rails require more attention and thus involve more maintenance
TYPES OF RAILS – Double Headed, Bull Headed and Flat Footed Rails || Railway || Civil Engineering
What is Track Alignment? What are the requirements of a good alignment?
Track Alignment: It is the position and the direction given to the center lines of the railway track on the ground.
The vertical alignment includes changes in gradient and vertical curves. The horizontal alignment includes the straight path, its width, any deviations in width and curves.
Proper alignment of a new railway track is very essential as improper alignment would result in capital loss due to the higher initial cost of construction of recurring loSs in maintenance it is very difficult to change the alignment.
Requirement for a good Alignment
- The length of the track should be as short as possible
- The construction cost should be minimum
- The maintenance cost should be minimum
- The transport cost should be minimum
- It should have an easy gradient
- It should pass through aesthetic areas in view for a comfortable and pleasant railway journey
- It should connect important places
- It should pass through important cities and industrial areas.
What are the different type of survey to be carried out in case off new railway project? Explain traffic survey in detail.
The following four surveys should be conducted to fix the good alignment:
a) Traffic survey
b) Reconnaissance survey
c) Preliminary survey
d) Location survey
Traffic Survey: Before starting any big railway project the future earnings should be considered. The earning directly depends upon the traffic at present and traffic in the immediate future, both passengers and goods traffic.
To know the potential of available traffic in the route, a traffic survey is conducted. In the traffic survey the following information should be collected:
1) Population of the cities, towns, and villages lying within 15kms on both sides of the track
2) Approximate number of passengers who will use trains
3) Position of local industry
4) Future prospectus of development of industry and trade center
5) Jnature and volume of exports and imports center of their destination
6) Locations of railway stations to get more business
7) General character of land and communities
After collecting the above information, the cost of the railway per kilometer is calculated from the previous experience.
Then the approximate expenditure, the operating cost, and revenue earned is calculated.
In this type of survey the following maps are prepared for the study:
1. Topographical. maps
2. Agricultural maps
3. Industrial maps
What is coning of wheels? What are its advantages?
The art of providing an outwards slope of 1 in 20 to the treads of wheels of rolling stock is known as coning of wheels.
The wheels of rolling stock are provided with flanges on the inner side of rails forming the track.
The function of providing wheel flanges on the inner side is to prevent lateral slipping of the wheels over the rail in a track.
The distance (B) between the inner faces of the fiancé is kept somewhat less than the gauge. Distance ‘G’ so as to prevent to rubbing of the flange against the inner face of rails and causing were and tear of both the rails as well as of the wheels as illustrated in fig. 4.1.
If the threads of wheels are kept flat, there is the possibility of lateral movement of wheels axle by the distance equal to the distance between the runnings or inner face of the rails and the inner face of the flange.
Thus, the wheels will damage the inner faces of the rails. To check the lateral movement, which causes damage to the running or inner faces of rails and inc convenience to the passengers, and outwards slow of 1 in 20 is provided to the threads of the wheel, which is known as coning of wheels.
The main object of conning of wheels is to prevent lateral movement of trains.
On straight portions of the track, if the axle moves towards, one track rail, the diameter of the wheel rim over that rail increases, whereas it decreases over the opposite rail of the track, due to conning of wheels since both wheels are to cover the equal distance.
This prevents further lateral movement and the axle returns to its original position. Coning of wheels thus prevents the lateral movements and ensures smooth movements of trains without causing excessive wear of the inner faces of the rails and Inconvenience to passengers.
On curves, the outer wheels of the train have to travel a greater distance than the inner wheels. Under the effect of centrifugal forces, the axle moves towards the outer rail.
Due to the conning of wheels, the diameter of wheels on the outer rail increases, while on inner rails, it decreases as illustrated. This helps the outer wheels to cover a greater distance than the inner wheels without any slip.
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