RAILWAY NEWS FROM AROUND THE PRESERVATION SCENE Not Your Average Tyre Change!! Heritage railway engineers at the South Devon Railway (SDR) know only too well that fitting heavy, new steel tyres to a steam locomotive is a lengthy and complex process, and it’s certainly nothing like the average tyre change at a garage which is usually done in minutes! So, in week one of the six-week long nationwide ‘Love Your Railway’ awareness campaign which started on the 26th July and whose first theme is ‘Heritage’ here’s how a steam railway tyre is changed in both words and pictures. Unlike your standard car tyre, these four to six feet diameter wheels take virtually a full day to fit each one and require the use of some heavy-duty, traditional engineering machinery. The SDR can also fit even bigger wheels well over six feet in diameter as well, and smaller ones too. Most steam locomotive have at least four large driving wheels, and often six, but sometimes eight, plus two or four wheels on ‘pony trucks’ at
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the front or back! The tyres are made from topquality steel sourced from South Africa, which means it can take six to nine months to get the different sizes ordered and shipped to the UK. In the attached pictures, the retyring process is shown whereby the engineers place the now machined steel tyre inside a gas-powered hearth. This heats up the metal tyre ring until it’s ‘cooked’ sufficiently so that it expands just enough to then drop the wheel centre into the middle of the tyre very carefully. The steel tyre then cools, causing it to shrink to fit the wheel centre tightly and it is then further secured by either using rivets; ‘double nip’ or Gibson ring methods later.
The enduring popularity of heritage railways and steam engines means the engineering team at Buckfastleigh in Devon, have been kept busy even throughout lockdown. Dick Wood, PR Manager for the South Devon Railway said: "The older, traditional steel railway wheels have a conventional tyre fitted in a similar way to a car. The tyre on the outside is the bit which wears out and eventually needs to be replaced. We take the new tyre and heat it steadily in a hearth to the right temperature and size so it expands, and then we can drop the wheel centre in snugly so that it shrinks to fit tightly onto the wheel centre as it cools. It’s a precision process with tolerances roughly the thickness of a human hair. Then, we finally secure the tyre to the wheel centre using different methods depending on the specification required by the owner.
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