Rails are tilted inward at an angle of 1 in 20 to reduce wear and tear on the rails as well as on the tread of the wheels. As the pressure of the wheel acts near the inner edge of the rail, there is heavy wear and tear of the rail. Lateral bending stresses are also created due to eccentric loading of rails. Uneven loading on the sleepers is also likely to cause them damage. To reduce wear and tear as well as lateral stresses, rails are titled at a slope of 1 in 20, which is also the slope of the wheel cone. The rail is tilted by ‘adzing’ the wooden sleeper or by providing canted bearing plates.
The permanent way consists of rails, sleepers, the ballast, sleeper fittings, and the subgrade. The strength of each of these components is essential for the safe running of trains. The stresses developed in each component due to the movement of wheel loads should be within permissible limits as specified for different types of tracks. The concept of load distribution in a railway track is based on the elastic theory, but most of the equations used to calculate stresses in the different components lack a theoretical background. The coning of wheels helps reduce the wear and tear of the wheel flanges, providing a smooth ride. The ill effects of coning on horizontal curves are reduced by laying the rails at a slope of 1 in 20.
1. What do you understand by a railway track or a permanent way? Mention the requirements of an ideal permanent way.
2. What are the component parts of a permanent way?
3. Draw a typical cross section of a BG double track in embankment and show therein all the components of the track.
4. What is meant by ‘track modulus’? Indicate its usual range of values for a broad gauge track.
5. How is track modulus expressed? State the factors affecting it and give the values of at least one of these factors for the tracks in our country.
6. Draw a typical cross section of a permanent way. Explain briefly the functions of the various components of the railway track.
7. Discuss the necessity and effects of the coning of wheels.
8. What are the various types of stresses induced in a rail section? Explain briefly how these are evaluated.
9. Explain the following terms.
(a) Track modulus
(b) Coning of wheels
(c) Tilting of rails
(d) Permanent way