LNER Class A4

Overview

Gresley introduced the Class A4 locomotives in 1935 to haul a new streamlined train called the Silver Jubilee to run between London King's Cross and Newcastle. The new service was named in celebration of the 25th year of King George V's reign.

During a visit to Germany in 1933, Gresley had been inspired by the high-speed streamlined "Flying Hamburger" diesel trains, and indeed the LNER had considered purchasing similar trains for use from London to Newcastle. However, the diesel units of the time did not have the desired passenger carrying capacity and the capital investment in the new technology was prohibitive.

Gresley was sure that steam could do the job equally well and with a decent fare-paying load behind the locomotive and so, following trials in 1935 with one of Gresley's A3 Pacifics No.2750 Papyrus, which recorded a new maximum of 108 mph (173.8 km/h) and completed the journey in under four hours, the LNER's Chief General Manager Ralph Wedgwood took the initiative, authorising Gresley to produce a streamlined development of the A3. Initially four locomotives were built, all with the word 'silver' as part of their names. The first was 2509 Silver Link, followed by 2510 Quicksilver, 2511 Silver King and 2512 Silver Fox. During a press run to publicise the service, Silver Link twice achieved a speed of 112.5 mph (181.1 km/h), breaking the British speed record and sustained an average of 100 mph (160.9 km/h), over a distance of 43 mi (69.2 km).

Following the commercial success of the Silver Jubilee train, other streamlined services were introduced: the Coronation (London-Edinburgh, July 1937) and the West Riding Limited (Bradford & Leeds-London & return, November 1937) for which more A4s were specially built.

Design

The A4 Pacifics were designed for high-speed passenger services. The application of internal streamlining to the steam circuit, higher boiler pressure and the extension of the firebox to form a combustion chamber all contributed to a more efficient locomotive than the A3; consumption of both coal and water were reduced. A further improvement to the design was the fitting of a Kylchap double-chimney first introduced on 4468 Mallard, built in March 1938. This device improved the capability of the locomotives further, and the final three locomotives of the class (4901 Capercaillie, 4902 Seagull and 4903 Peregrine) were fitted with the Kylchap exhaust from new. Eventually the rest of the class acquired it in the late 1950s.

This class was also noted for its streamlined design, which not only improved its aerodynamics, thus increasing its speed capabilities, but also created an updraught to lift smoke away from the driver's vision, a problem inherent in many steam locomotives particularly those operated with short cut off valve events, smoke deflectors being an alternative answer to the same problem. The distinctive design made it a particularly attractive subject for artists, photographers and film-makers. The A4 Class locomotives were known affectionately by train spotters as "streaks".

The streamlining side skirts (valances) that were designed by Oliver Bulleid to aerofoil shape, and fitted to all the A4 locomotives, were removed during the Second World War to improve access to the valve gear for maintenance and were not replaced.

This apart, the A4 was one of very few streamlined steam locomotive designs in the world to retain its casing throughout its existence. Many similar designs, including the contemporary Coronation class, had their streamlining removed or cancelled to cut costs, simplify maintenance and increase driver visibility.

World record

On 3 July 1938 4468 Mallard; the first of the class to enter service with the Kylchap exhaust, pulling six coaches and a dynamometer car, set a world speed record (indicated by the dynamometer) of 126 mph (202.8 km/h). However, Gresley never accepted this as the record-breaking maximum. He claimed this speed could only have been attained over a few yards, though he was comfortable that the German speed record of 124.5 mph (200.4 km/h) had been surpassed. Close analysis of the dynamometer roll (currently at the NRM) of the record run confirms that Mallard's speed did in fact exceed that of the German BR 05 002. The Mallard record reached its maximum speed on a downhill run and actually failed technically in due course, whereas 05 002's journey was on level grade and the engine did not yet seem to be at its limit. On the other hand, the German train was only four coaches long (197 tons), but Mallard's train was seven coaches (240 tons). One fact that is often ignored when considering rival claims is that Gresley and the LNER had just one serious attempt at the record, which was far from a perfect run with a 15 mph permanent way check just North of Grantham. Despite this a record was set. Gresley planned to have another attempt in September 1939, but this was prevented by the outbreak of World War II. Prior to the record run on 3 July 1938, it was calculated that 130 mph (210 km/h) was possible, and in fact Driver Duddington and LNER Inspector Sid Jenkins both said they might well have achieved this figure if they not had to slow for the Essendine junctions.

At the end of Mallard's record run, the middle big end (part of the motion for the inside cylinder) was found to have run hot (indicated by the bursting of a heat-sensitive "stink bomb" placed in the bearing for warning purposes), the bearing metal having melted, which meant that the locomotive had to stop at Peterborough rather than continue on to London. Deficiencies in the alignment of the Gresley-Holcroft derived motion meant that the inside cylinder of the A4 did more work at high speed than the two outside cylinders - indeed on at least one occasion this led to the middle big end wearing to such an extent that the increased piston travel knocked the ends off the middle cylinder - and this overloading was mostly responsible for the failure.

Performance in service

No other British steam locomotives have a longer or more consistent record of high speed running than the A4s. Instances of 100 mph running by them must exceed those of all other types combined, though 90 mph running was a relatively rare event with steam traction, much less 100 mph. It should also be remembered that A4s operated on the East Coast Main Line which has more opportunities for high speed running (particularly Stoke Bank) than any other in the UK.

In August 1936 the Silver Jubilee train on the descent of Stoke Bank headed by 2512 Silver Fox driven by George Henry Haygreen achieved a maximum of 113 mph (181.9 km/h), then the highest speed attained in Britain with an ordinary passenger train. The fastest recorded post-war speed with British steam was also recorded by an A4. This occurred on the 23 May 1959 on the Stephenson Locomotive Society Golden Jubilee special when 60007 Sir Nigel Gresley achieved 112 mph when hauling 400 tons down Stoke Bank. The driver, Bill Hoole, had hoped for an attempt to beat Mallard's record but Alan Pegler, who was on the footplate and mindful of the risks, told him to ease off.

Although A4s were primarily designed for high speed express work they were also capable of high power outputs. In 1940 4901 Capercaillie exerted 2200 drawbar horse power on the straight and level track north of York when hauling 21 coaches (730 tons gross) at an average of 75.9 mph for 25 miles. The highest recorded power output from an A4 was 2450 drawbar horsepower when Mallard herself was hauling 11 coaches (390 tons tare, 415 tons gross) up Stoke Bank at a sustained 80 mph in 1963. O.S. Nock thought this performance superior to Mallard's world record run in 1938. An A4 with the same load on a "good run" would be doing about 50 to 60 mph at the summit of Stoke Bank. On a run on 8 September 1961 Mallard had its train travelling at 78 mph. To put all this in perspective the highest possible drawbar horsepower from a Class 40 diesel (a class which was supposed to replace the A4s,) was 1450, though they could achieve this figure over long distances and with no effort from the crew.

Post-war history

Although newer Pacifics had been introduced since the war, and although the streamlined trains were never reinstated, the A4s continued on top link duties, notably on the London to Edinburgh services.

Improved methods of aligning the Gresley conjugated valve gear in the 1950s led to tighter tolerances for the bearings used within it and consequently to almost total eradication of the overloading of the middle cylinder. History repeated itself with the inside big end being replaced by one of the Great Western type, after which there was no more trouble, provided maintenance routines were respected.

The wholesale application of double Kylchap chimneys to the entire class was entirely due to the persistence of P. N. Townend, the Assistant Motive Power Superintendent at King's Cross from 1956. He at first met with considerable resistance from higher authority. When permission was eventually given, it was found that the economy obtained over the single chimney A4s was from six to seven pounds of coal per mile, which more than justified the expense of the conversion.

These improvements led to greatly increased availability.

Locomotive data

The first four locomotives included the word 'silver' in their names because they were intended to haul the 'Silver Jubilee' train. No 2512 Silver Fox of this batch carried a stainless-steel fox near the centre of the streamline casing on each side, made by the Sheffield steelmakers Samuel Fox and Company. The next batch of A4s were named after birds, particularly those that were fast flyers, Gresley being a keen bird-watcher. Five (4488–92) were named after British Empire countries to haul the new Anglo-Scottish 'Coronation' train; and two (4495/6), intended to haul the new 'West Riding Limited', received names connected to the wool trade: Golden Fleece and Golden Shuttle.

A4 No.4498 was the hundredth Gresley Pacific to be built and someone had the idea of naming it after the designer himself. This started a rash of renamings of other A4s, usually of directors of the LNER and many of the more obscure bird names (and a few of the better ones: Kestrel and Osprey for example) were exchanged for somewhat less inspiring names.

One locomotive was withdrawn after being damaged beyond repair in a German bombing raid on York on 29 April 1942 during World War II - No.4469 Sir Ralph Wedgwood, which at the time had been overhauled and was based at Gateshead. It was running local trains to run it in, and was stabled in York North Shed (now the National Railway Museum) where it suffered a direct hit. However, its tender survived and was later coupled to a Thompson A2/1.

The first five withdrawals, in December 1962, were 60014 Silver Link, 60028 Walter K. Whigham, 60003 Andrew K. McCosh, 60030 Golden Fleece and 60033 Seagull. The rest of the class was withdrawn between 1963 and 1966. The last six in service were: 60004 William Whitelaw, 60007 Sir Nigel Gresley, 60009 Union Of South Africa, 60019 Bittern, 60024 Kingfisher and 60034 Lord Faringdon. 60019 and 60024 were the last to be withdrawn, in September 1966.

Preservation

Six of the locomotives have been preserved, three of them thanks to the fact that they were assigned to sheds in Scotland after the closure of King's Cross shed (34A) to steam in 1964. Four A4s are in the UK and have run on the BR main lines at some point during their preservation career. Another two have been preserved in the USA and Canada, rather appropriately due to their names, and as such were gifted to these respected countries upon withdrawal by British Railways. Both North American-based A4s were moved to the National Railway Museum, York, in late 2012 on three-year loans as part of the NRM's 2013 celebrations of the 75th anniversary of Mallard breaking the world speed record for steam.

As of August 2016 only Union of South Africa is operational with a valid mainline certificate until 2019, 60007 Was withdrawn for overhaul on the 20th September 2015 and 4464 operated until the end of 2015 at the Watercress Line when it was withdrawn for its overhaul in Crewe.

Loco numbers in bold mean their current number.

In popular culture

A4s have appeared numerous times in popular culture, both during and after preservation. The class's first film appearance was 2509 Silver Link in the Will Hay film Oh, Mr. Porter, in which Hay accidentally ruins its naming ceremony. Post war, 60017 Silver Fox features heavily in the 1954 British Transport Film Elizabethan Express, which follows the revival of non-stop London to Edinburgh runs and features footage of the water trough and corridor tender in use. A few years later, the 1959 version of The Thirty-Nine Steps features colour photography of 60010 Dominion of Canada amongst others in their post-war British Railways Brunswick green livery. The scene crossing the Forth Railway Bridge was subsequently parodied in the 1961 film Carry on Regardless.

In The Railway Series books by the Rev. W Awdry, the 4468 Mallard is alluded to in the book Gordon the High Speed Engine by Christopher Awdry as one of Gordon's "Doncaster cousins" who did 126 miles an hour. Mallard appears as a character in the later book Thomas and the Great Railway Show. Mallard also features in the Peter's Railway book "Surprise Goods" by Christopher Vine, where she rescues a broken down freight train. The class was the basis for the character Spencer in the television series, Thomas and Friends.

A painting of 22 Mallard by Paul Gribble appears on the cover of the 1993 Blur album Modern Life is Rubbish.

A stylised A4 appeared in the opening title sequences for the original episodes of ITV's Poirot series.

The A4 is the basis for the Chuggington character Olwin. However, she lacks a tender.

Models

The distinctive shape of the A4 has made it an obvious choice for model manufacturers, with examples being made in the majority of the popular scales, including a wooden example for the Brio wooden railway. One of the first two Hornby Dublo locomotive models produced, in 1938, was an A4. In 1999 a 'Super Detail' Hornby A4 was released, later complimented by a budget 'Railroad' model Hornby also produced an 'OO'-scale live steam version in September 2003, that used an electrically-heated boiler to produce steam – not previously possible in such a small model. Trix produced an 'OO' scale model A4 from 1970; it was re-branded as a Liliput model in 1974 and survives to this day in modified form as a Bachmann model - Kader, Bachmann's parent company, had bought Liliput in 1993. Dapol currently produce several versions of the A4 class in N gauge and have also expanded their Black label range to include the A4 class as well.

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