Why should there be a gap between the two railway tracks?
There are many ways of connecting rails to rails. The most traditional method will be about twenty meters of rail fixed on the sleeper, the rail between the joint (also known as joint). The British habit, the two tracks will have connections in the same place, but the United States will be placed in different places. The joint is joined with a fish plate. It is a steel plate about sixty cm long, with four or six steel bolts at each end and a small hole used to tie the rail. There is a gap between the rails, approximately 6mm wide, called the expansion joint. Make a small hole of rail fishplate steel bolt through the oval, so you can have a space to expand the rail in hot weather. This is very important for rails: if there is no room for expansion, the rails will have to withstand 1.6 tons of stress or tension whenever the temperature changes for a while. If a place has an annual maximum and minimum temperature difference of thirty degrees, this force can reach fifty tons. A rail may therefore become askew and affect vehicle safety.
Another relatively new way of connecting rails is the continuous welded rail (Continuous, Welded, Rail, CWR), also known as seamless rails or long welded rails. This method couples several kilometers of rails together to form a continuous line. Because there is no seam, the strength of the track increases, less maintenance is needed, and the vehicle runs more smoothly.The cost of welded rails is more expensive than that of a fish board. But because of the high strength, the vehicle can travel at a higher speed on the continuous welded track, and the friction force is reduced.
Although this can solve the problem of thermal expansion and contraction, but the "click, click" sound tracks left on some small joints to make trains passing. Unless the track is well maintained, the jointed track is not suitable for the high speed train; passengers may feel the traffic is unstable. Many railway developed countries still use this rail connection at low speed, non critical routes or side lines. Fish plates are also common in the absence of modern investment routes. Most of the routes in the United States belong to this category, and most of them still use wooden sleepers (sleepers). In addition, part of the reason is that the speed of American Railways is not high, and the prices of wood are also low.
