Understanding Entry Angle in Curved Switches

Curved switches are important components in railway tracks, allowing trains to diverge from one track to another. They are different from straight switches because the turnout track curves away from the main track right from the point of switch.

A key characteristic of a curved switch is its geometry, which includes the entry angle. The entry angle refers to the angle formed by specific parts of the switch rails.

Let's analyze the definition based on the correct option provided:

• The entry angle in the case of Curved Switches is defined as the angle between the tongue rail and the gauge face of the stock rail.

The tongue rail is the movable rail that is pointed at one end and rests against the stock rail. The stock rail is the fixed rail of the main track. The gauge face is the inner face of the rail, which defines the track gauge.

Therefore, the angle formed at the very beginning of the switch, where the tongue rail starts to diverge from the stock rail, specifically between the tongue rail and the gauge face of the stock rail, is known as the entry angle.

Considering the options:

Option 1 describes an angle involving the outer face of the tongue rail and gauge face of the stock rail. This does not define the entry angle.

Option 2 describes an angle involving the outer face of the stock rail and gauge face of the tongue rail. This configuration does not represent the entry angle at the switch point.

Option 3 correctly identifies the entry angle as the angle between the tongue rail and the gauge face of the stock rail.

Option 4 describes an angle involving the tongue rail and outer face of the stock rail. This is not the standard definition of the entry angle.

Thus, the entry angle is precisely the angle formed between the tongue rail and the gauge face of the stock rail in a curved switch.