Turnout is an arrangement of points and crossings with lead rails by which trains may be diverted from one track to another moving in the facing direction.A turnout is left handed or right handed as the train taking the turnout in the facing direction is diverted to the left or right of the main line.
Component parts of a turnout and their functions:
A pair of tongue rails:
The tongue rails along the stock rails in a turnout form a pair of points or switches. The tongue rails facilitate the diversion of a train from the main track to branch track.
A pair of Stock Rails:
They are the main rails to which the tongue rails fit closely. The stock rails help in the smooth working of tongue rails.
Two Check Rails:
Check rails are provided adjacent to the lead rails, one in main track and another in branch rack. These rails check the tendency of wheels to climb over the crossing.
Four Lead Rails:
Outer straight lead rail, outer curve lead rail, inner straight lead rail and inner curve lead rail are the four lead rails provided in a turnout. The function of these rails is to lead the track from heel of switches to the toe of the crossing.
A Vee Crossing:
A Vee Crossing is formed by two wing rails, a point rail, and a splice rail. It provides gaps between the rails so that wheel flanges pass through them without any obstruction.
Slide chairs are provided to support the tongue rail throughout their length and to allow lateral movement for changing of points.
Stretcher bar connects toes of both the tongue rails so that each tongue rail moves through the same distance while changing the points.
A pair of Heel Blocks:
These keep the heel ends of both the tongue rails a fixed distance from their respective stock rails.
Switch Tie Plate:
The function of switch tie plate is to hold the track rigidly to the definite gauge at the toe of switches. These are provided below the slide chairs.
Parts for operating points:
- Rods, cranks, levers, etc
- Locking system which includes locking box, lock bar, plunger bar etc.