![]() Aluminium is a highly reactive metal, looking to gain electrons. This process, as the name suggests, uses an exothermic oxidation-reduction reaction to create intense heat. That’s aluminothermic welding, using a material called thermite.’ But there’s a third type, which is very common – particularly on-site – because it’s easy to put together and doesn’t need expensive equipment. So, we use induction welding and flash butt welding, which are basically methods that use extreme heat and then smoosh the two rails together. ‘Rails don’t just float in midair,’ Gareth says. You need to consider all this before thinking about how to join the rails together in straight lines. ‘There’s a product called Zinoco, which contains zinc and is a sacrificial coating that goes around the foot of a steel rail to minimise the big corrosion effects.’ ‘So, you’ve got to have a rail that’s corrosion-proof,’ Gareth says. Typically, corrosion happens at the bottom, or foot, where salt and debris gather – particularly in areas such as level crossings, coastal routes or tunnels. ![]() The result is an incredibly hard-wearing alloy that’s also used to make the cables in suspension bridges.īut the contact point with the train at the top, or head, of the rail is only half the battle. This is created during the steel manufacture process, by slowly cooling the iron–carbon alloy to get alternating layers of different phases of steel. ‘The crystalline structure of the actual rail, particularly at the surface, has a major effect on its behaviour,’ Gareth says, ‘as well as the likelihood of fatigue happening, so you need a good understanding of the actual chemical makeup.’ In rails, the most common crystal structure used is pearlite. This makes choosing the right alloy of steel critical to a railway’s safety and long-term maintenance. And, indeed, you get the steel stretching out over huge distances, in a process called ratchetting.’ ‘You’ve got a huge amount of force going through an area about the size of a five pence piece all that weight of the train, but also dynamic forces as it goes over bumps and steering forces too. ‘The interface between the rail and the wheel is one of the most complex in engineering,’ explains railway engineer and writer Gareth Dennis. This means that, thanks to simple physics, a single person could move the entire, almost 100-tonne, Flying Scotsman with a single bar of metal. Staying on trackĪt its heart, a railway is an anti-friction device, with the contact point between the train and the track only about the size of a thumbnail. You can also get them up close with metal displacements by investigating the reactivity of different metals in a microscale practical. Today, science remains at the heart of every train journey – and some incredible chemistry is needed to keep things running on time.ĭemonstrate the explosive thermite reaction to excite learners about the possibilities that chemistry holds for solving everyday problems. And all these moving parts need oil, right? They started off using tallow – cow fat – but they swiftly moved on to using hydrocarbons (creosote from coal tar).’ By the 1960s, chemistry had become so integral to the rail network that it accounted for more than half the staff at the UK’s Railway Technical Centre in Derby.īut this was only the start. Steam engines basically run by boiling water and you must deal with impurities because, if the water foams, it starts to affect how the machine works. ‘The railways very swiftly employed metallurgists to figure out how long rails would last,’ Bob says, ‘and then they quickly went on to do other things, too. By 1864, less than eight years after the Bessemer process was discovered to mass-produce steel, the London and North Western Railway company employed a chemist to make improvements.īy the 1960s, chemistry had become so integral to the rail network that it accounted for more than half the staff at the UK’s Railway Technical Centre in Derby The wooden wheels soon evolved into wrought iron but, Bob says, they could very easily shatter, so steel became a priority for early railways – and with it came chemistry. ‘Railways go back to at least 1604 in the UK, when Huntingdon Beaumont built a wagonway with wooden wheels and wooden rails in Nottingham,’ explains Bob Gwynne, assistant curator at the National Railway Museum in York. ![]() But the railway network wasn’t built overnight and science has always been at the heart of its development. The UK’s rail network is a modern colossus, made up of almost 10,000 miles of track and more than 2500 stations, with passengers completing around 41.5 billion miles of journeys every year.
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