When one track crosses an other at an angle, a diamonds is formed comprising of two acute and two obtuse crossings. When a vehicle passes over a diamond crossing, there is an inherent risk of derailment owing to a large unguided gap at the elbow of the obtuse crossing and due to the possibility of a wheel, particularly of a small diameter, being deflected to the wrong side of the nose. The position becomes worse, when the angle of intersection is very acute. In the Indian Railways, it has therefore been laid down that diamond crossing normally should not be flatter and less acute then 1 in 8 ½.
When two tracks cross one another at right angles, a square crossing is formed. Square crossings are generally avoided, since the gap in the running rail for wheel flanges, being opposite to each other, causes severe jolting to vehicles resulting in the rapid wear of the crossings and damage to rolling stock on account of the heavy impact.
Moveable Switch Diamond
Movable switch diamonds are used for flatter crossing angles i.e. 1 in 10 or 1 in 12, where normal crossing is not permitted as mentioned in
Diamond Crossings with slips
If track are to be so arranged that a train on one track may normally cross another track, but when required, may also be diverted to that track, an arrangement known as diamond crossing with slips is installed. This is made possible by the inclusion of two or four pairs of switches, with the connecting lead rails. When such diversion is permitted in one way the arrangement is known as single slips, and if it is permitted in both ways, the arrangement is known as double slip.
|Diamond Crossings with slips