8 Requirements of the good ballast

Ideal ballast should possess the following characteristics. The following are the 8 Requirements of the good ballast:

1. It should be hard and tough.
2. It should not be brittle and porous.
3. It should have sufficient elasticity.
4. It should allow easy drainage with minimum leakage.
5. It should be wear-resistant and durable.
6. It should retain its position laterally and longitudinally under all conditions of traffic.
7. It should not produce any chemical action with rail and metal sleepers.
8. The materials should be easily workable.

Read Also:

 Function of Ballast

 Advantages & Disadvantages Of Gravel as Ballast

 Advantages And Disadvantages of Broken Bricks Ballast

Functions of Ballast

Ballast is the granular material placed and packed below and around the sleepers to transfer load from the sleepers to the formation. Ballast in railway tracks performs the following function:

1. It provides a suitable foundation for the sleepers.
2. It transfers and distributes loads from the sleepers over a larger area of the foundation. 
3. It holds the sleepers in the correct position and prevents their lateral and longitudinal movement due to dynamic loads.
4. It helps in maintaining the correct levels and alignment of a track.
5. It acts as an elastic medium and thereby increases the elasticity of the track.
6. It protects the top surface of the formation.
7. It improves the drainage facility of the track.

Read more:

Types of Rails

Functions of Rails

Coning of Wheels

The art of providing an outward slope of 1 in 20 to the treads of wheels of rolling stock is known as the coning of wheels.

The coning of wheels is provided to keep the vehicle in the central position with respect to the track and helps the vehicle to move smoothly on the straight and curved track.

In the case of a straight and level track (which is shown in Figure 1), the flanges of the wheels have an equal perimeter.

But in the case of a curved track, the situation will be different as shown in Figure 2. In this situation, the outer rail has to cover a greater distance than that of the inner rail. Also, due to the action of centrifugal force on a curve, the vehicle has a tendency to move out towards the outer rail.

To overcome this, the circumference of the flange of outer wheel is made greater than that of the inner wheel and this helps the outer wheel to travel a longer distance than the inner wheel.

The object of Providing Coning of Wheels

Coning of wheels is done to achieve the following object:
1. To reduce the wear and tear of the wheel flanges and rails.
2. To prevent lateral movement of trains.
3. To prevent the wheels from slipping to some extent.

Read more:

Hogged, Buckling, And Tilting of Rails

Creep of Rails

Hogged Rails

Due to the bettering action of wheels over the end of the rails, the rails get bent down and get deflected at the ends. These rails are called hogged rails.

This hogging of the rails at the ends is due to loose packing under the joints and/or loose fish plates. This defect causes rough riding. The following measures are taken to rectify the hogged rails

a. Cropping

In this method, the hogged ends are cut off and new holes are created in the rails for fixing the fish plate.

b. Replacing

In this method, the hogged rails are completely replaced by new rails. This method is very expensive.

C. Welding

In this method, the hogged rails are brought to the level by welding the deflected or worn-out ends.

D. De-hogging

In this method, the hogged ends of the rails are straightened by means of Jim screw or a de-hogging machine. This method is not so effective.

Buckling of Rails

Displacement of the track from its original position is known as buckling of rails.

Buckling of rails may take place due to the following reasons:
1. When the expansion gap is not sufficient.
2. When the bolt of fish plates are so tight that the rails are not allowed to expand.
3. Due to the presence of long welded rails on weak tracks.

Tilting of Rails

The art of placing the rails of a track at an inward slope of 1 in 20 is called tilting of rails. The main object of tilting of rails is to reduce the wear on inside edges of rails in a track. The required tilt is provided at rail seats in bearing plates, chairs and metal sleepers at the time of their casting.

The wooden sleepers, Which are used without bearing plates, are adzes to the required tilt of 1 in 20 at the rail seats.

Advantages of Tilting of Rails

1. The tilting of the rails enhances the life of both the sleepers and the rails.

2. The tilting of rails helps to hold the gauge in the correct position.

Read more:

Function of rails

Creep Of Rails