Normally, the railway crossings are such that the trains pass by in the same direction. Lesics has already released published a detailed Railswitch article how such a crossing works. However, what happens if the trains must cross each other by 90 degrees? The Diamond Crossing is an innovative junction design that allows two pairs of trains to pass by one another at a perfect 90 degrees alternately(Fig:1). This elegant design was developed by the Indian railways for the city of Nagpur.
Constructing diamond crossing
Let’s build a diamond crossing piece by piece. First, a pair of rails are installed in one direction. This will allow smooth passage of two trains at the same time in the X direction as shown in the fig:2.
Now, we have to design tracks in the Y direction. Obviously, we cannot use a single piece of rail here. Instead, we must add many pieces of rails between the X directional rails(Fig:3).
However, the main danger here is that when the train travels on the new tracks, it will get into an accident because of the flange. The flange will hit the X-direction rails(Fig:4). To know more about wheel flanges, check out the video, “How do Trains switch tracks?”
Clever railway engineers came up with an interesting idea: to utilise height difference. They lowered the height of the X directional rails you can see in the fig:5 below. This height is sufficient to let the flange of the wheel pass by.
However, we still have an issue when the train is travelling in the X direction. The flange bumps into these pieces of Y direction track. Now lets see how to solve this problem.
Fig: 6 – The flange hit to Y-track
How to prevent clash?
We can prevent this clash by providing sufficient clearance between the rails. The wheels will easily pass through this clearance while travelling in the X direction. However, there is an issue here. The rails’ wheels have a lateral play(Fig:7A). During the X movement, if the wheels are at one extreme end, they will again clash with Y direction tracks(Fig:7B). To ensure that such a movement is not allowed, let’s add our saviour rails: the guidance rails(Fig:7C). This will keep the train flanges on track while travelling in X direction.
The new track technology we developed seems perfect now. The track will allow the wheel movement both in X and Y directions. There is a good length of portion in the Y direction without any track. Because of this, there is a possibility of the wheels going in the wrong direction after crossing this region. To ensure this never happens, we must add guidance rails here as well.
Please note that when the trains enter this diamond crossing site, the guidance rails are curved inwards so as to direct the trains. However, the guidance rails in between the diamond crossing are not curved at all(Fig:9).
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