Steam goes back on track

It was not the most auspicious of birthdays for the Flying Scotsman, 75 years old in February. Number 4472, the most famous, best loved, and most travelled steam locomotive spent the day in pieces at the Southall Depot in west London in a workshop leased from Railtrack. It has been there since businessman Dr Tony […]

It was not the most auspicious of birthdays for the Flying Scotsman, 75 years old in February. Number 4472, the most famous, best loved, and most travelled steam locomotive spent the day in pieces at the Southall Depot in west London in a workshop leased from Railtrack. It has been there since businessman Dr Tony Marchington paid Sir William McAlpine £1.25m for it in 1996.

Today marks the 70th anniversary of the Flying Scotsman’s 392-mile run between London’s Kings Cross and Edinburgh, which set a world record for the longest non-stop rail journey. In a 1988/89 Australian tour it set another world steam record for endurance, which it retains, with a 422-mile non-stop journey in New South Wales.

The Flying Scotsman was withdrawn by British Rail in 1963 after 40 years’ service (the year of the Beeching report on rail cuts), then bought by Alan Pegler of Eastern Region, who is now Honorary President of the Flying Scotsman Association. In 1969, when BR first banned steam, he took it to the US to promote British business. The Scotsman returned in 1972 and was bought by McAlpine.

Today the outlook is good for this grande dame of the tracks who, since 1923, has been painted apple green (its original Great Northern Railway livery), British Rail dark blue, Brunswick green and wartime black, had one then two chimneys and other refinements to the thermodynamic design to improve performance, and clocked up more than 2.5 million miles in three continents.

Rivalry between east and west coast train operators drove its development. In gleaming livery at the 1924 Empire Exhibition in Wembley it stood alongside Pendennis Castle owned by Great Western Railway. A board proclaimed Pendennis to be the most powerful express passenger locomotive in Britain. It was, with a smaller but more efficient conical ‘Swindon’ boiler designed by GW Churchward.

By then GNR and other rail companies had merged to form the London and North Eastern Railway, the main east coast train operator.

In trials that same year two Castles, Pendennis and Caldicot, beat the LNER’s Pacific A1s Flying Fox and Victor Wild on runs between Leeds and Plymouth. The 80-ton four-cylinder Castles were faster and used less coal than the early A1Pacifics. With their 4 6 2 wheel arrangement (four-wheel bogey, six driving wheels, two under the driver’s cab) the Pacifics were a 92-ton three-cylinder stroke engine replacement for H A Ivatt’s smaller Atlantics, which were struggling to pull the longer, heavier passenger trains as rail became more popular.

The Flying Scotsman, which started as a Pacific A1 type locomotive, was the third to be built according to the new design of LNER chief engineer Nigel (later Sir Nigel) Gresley.

Developing 12.3bar steam pressure, the A1 boiler was no match for the smaller Swindon boiler rated at 15.4bar. Tractive effort, the key figure, is measured by a formula based on boiler pressure, cylinder diameter, piston stroke and wheel diameter. Both the A1s and Castles had 6ft 8in wheels. But the A1s produced a tractive effort of 29,875 lb compared with the Castles’ 31,625 lb, putting the A1s at a 5.5% disadvantage.

With improvements to the steam passage design, longer valve travels and, later, new 15bar boilers, the A1s including the Flying Scotsman were reclassified as A3s. To improve boiler steaming capability and cylinder exhaust the new generation of more powerful Pacific A4 locomotives were fitted with the Kylchap double chimney/double exhaust arrangement patented by Finnish engineer Kylala and French engineer Chapelon. Poorer quality coal and declining footplate skills made fuel-efficiency a byword even then.

Famous names belong to the Pacific A4 group. Mallard, now in the National Railway Museum in York, retains the world steam locomotive speed record of 126mph, grabbed from the Flying Scotsman in 1938.

But the Flying Scotsman was the first to ‘do the ton’ in 1934 in an authenticated test run between Leeds and Kings Cross. It reached 100mph on the Stoke Bank, downhill between Grantham and Peterborough. Its performance had been measured with calibrated instruments by ministry officials who were more interested in safety issues such as braking capacity, than speed.

Gresley’s best-known innnovation is the corridor tender which made non-stop journeys possible by allowing the two-man crew of driver and fireman to crawl from the train along a narrow passage in the tender to the driver’s cab.

Next year the Flying Scotsman, its £0.25m overhaul complete and supervised by project chief engineer Roland Kennington, will come close to fulfilling Gresley’s design intent. A new air-braking system is compatible with modern trains.

With a brand new central cylinder the original was cracked beyond repair because of a design weakness on linkages which meant it did more work than the other two cylinders and boiler refurbished by welding body TWI, Number 4472 should get its seven-year boiler ticket.

Project manager David Ward, who was director of British Rail special passenger services until 1994, confirms: ‘Flying Scotsman is being restored as near as possible to a new engine.’ Hauling steam trains on Railtrack and the private networks, it will cost around £250,000 a year to maintain. Ward does not rule out work in mainland Europe.