Rail Switches Carrying the Heavy Task of the trains’ Turning

In the kingdom of railways, where steel veins crisscross, switches are like invisible dancers, performing the precise art of track splitting in myriad postures. From the rough cast iron of the steam age to the intelligent alloys of the high-speed rail era, the morphological changes of these track joints inscribe the wisdom code of humanity’s conquest over geographical limitations.

The Evolution of Structure

In the 1830s, on the Stockton-Darlington Railway in Britain, the world’s first wooden switch, with its simple lever mechanism, opened the curtain on the diversion of tracks. Today, the switch family has evolved into dozens of forms, each a customized solution for specific transportation scenarios.

The single switch, as the basic form, with its “Y” shape, is like the enlightenment teacher of track splitting. On the arrival and departure lines of ordinary stations, this type of switch accounts for over 70% of the total.

The ingenious deflection of three steel rails enables trains to switch paths within 3 seconds. When two tracks need to diverge in opposite directions, the symmetrical beauty of the double turnout reveals its value – in the marshaling yard of Beijing’s Fengtai Station, the mirror-image arranged point systems guide thousands of carriages to precise diversion every day, with the synchronous operation of two switch machines having an error of no more than 1 millimeter.

Even more astonishing is the compact layout of the three-way turnout. In the tunnel of Hong Kong’s Prince Edward Station, this “one into three” design achieves the parallel and interlaced operation of three tracks within a space of less than 50 meters. Engineers use chrome-molybdenum alloy to cast elastic points. After enduring an average of 200 compressions and deformations daily, it still maintains a closure accuracy of 0.2 millimeters, a true spatial magic in track engineering.

The Material Evolution of Steel and Iron

Early cast iron switches often cracked within three months under the heavy pressure of steam locomotives. In 1893, Krupp’s high manganese steel switch (with a manganese content of 12%) emerged, with a wear resistance five times that of traditional materials, allowing the European railway network to expand wildly.

Modern high-speed rail switch points are forged from bainitic steel. This steel forms a feather-like crystal structure during quenching, achieving a hardness of HB380 while retaining toughness. Even when impacted by wheels traveling at 350 kilometers per hour a thousand times daily, it shows no signs of fatigue cracks for a decade. In the extreme cold of Siberia’s permafrost regions, switches cast from cold-resistant steel with a nickel content of 9% can maintain elasticity at -60°C, with their microscopic lattice structure resembling the needles of a pine tree, locking in the metal’s ductility.

Material innovations in special scenarios are even more ingenious. The aluminum alloy switches at Antarctic research stations weigh only one-third of the standard type, with a nano-ceramic coating on the surface that resists ice crystal erosion and reduces friction. The “invisible” switches on maglev lines use carbon fiber composite materials instead of steel, achieving contactless track switching through electromagnetic fields and eliminating mechanical wear.

 Intelligence and Function: The History of Functional Innovation

The functional evolution of switches is a microcosm of humanity’s push to break through speed and capacity limits. Ordinary switches are like the “basic cells” of the track system, meeting the conventional needs of speeds below 160 kilometers per hour. But when trains accelerate to 250 kilometers per hour, the movable heart rail switch becomes an inevitable choice – the precision fit between the V-shaped heart rail and the wing rail is as fine as 0.1 millimeters, equivalent to the gap between two human hairs, transforming the past violent jolts into the gentle ripples of a teacup when high-speed trains pass through.

In the field of heavy-haul railways, reinforced switches are rewriting the durability record. The manganese steel switch points on the Shuohuang Railway, after laser surface hardening, have a service life exceeding 300 million tons of traffic, equivalent to 300 ten-thousand-ton trains running non-stop for ten years. At the gauge conversion stations of the China-Europe Railway Express, the ingenious design of the gauge-changing turnouts is hidden: the sleepers that can slide laterally are equipped with a hydraulic positioning system, which can seamlessly switch between 1,435 mm and 1,520 mm gauges while the train is in motion, and the entire process is shorter than it takes to make a cup of tea.

In the intelligent era, turnouts have acquired the ability to “think.” The Beidou positioning turnouts on the Beijing-Zhangjiakou High-Speed Railway can start the switching procedure 30 seconds in advance based on the real-time position of the train; the shock-absorbing turnouts of Chengdu Metro have high-molecular damping materials embedded in the rail waist, reducing the noise of wheel-rail impact from 90 decibels to the library-level 62 decibels. These steel devices are evolving from executors to decision-makers, silently safeguarding the smooth flow of the rail arteries.

The Code of Numbers and Shapes

On the drawings of turnout designers, each parameter is a balance equation of force and beauty. The turnout number (such as No. 9 and No. 12) is actually the code of the switch angle; the larger the number, the longer the curve radius – the No. 42 large turnout on the main line of high-speed railways has a guide curve radius of 1,300 meters, equivalent to allowing the train to complete a graceful turn within the length of three football fields. The crossover turnout, this “railway overpass,” weaves eight directions of passage with four sets of switch rails at the cross intersection, with a structural complexity comparable to that of a watch movement.

The 14-millimeter gap setting between the guard rail and the basic rail is derived from the precise measurement of the wheel flange; the 35:1 slope ratio on the top surface of the switch rail embodies the practical wisdom of five generations of engineers. Under the lights of the Moscow Railway Museum, the century-long sequence from the wooden turnouts of 1825 to the modern digital models, each size change corresponds to a key breakthrough in transportation history.

When night falls, the searchlights of the Zhengzhou EMU Depot sweep over the turnout clusters arranged like strings of a piano, these steel joints are weaving the operation map for tomorrow’s high-speed railways. From the black smoke of steam locomotives to the blue light of maglev trains, the thousand-faceted evolution history of turnouts is actually the eternal journey of humanity to turn geographical barriers into thoroughfares – every precise track switch is continuing the magnificent poem of civilization crossing mountains and rivers.