LNER Class A4

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60027 Merlin at Dundee Tay Bridge, 1965, showing the corridor connection through the tender that allowed crews to be changed on Scotch expresses without stopping.

Another view of 60027 Merlin at Dundee Tay Bridge, 1965. The yellow cabside stripe indicates that she is prohibited from electrified West Coast Main Line south of Crewe, where she is out-of-gauge.

The London and North Eastern Railway Class A4 is a class of streamlined 4-6-2 steam locomotive, designed by Sir Nigel Gresley in 1935. One, 4468 Mallard, holds the record as the fastest steam locomotive in the world.

Overview

Sir Nigel Gresley introduced the LNER Class A4 locomotives in 1935 to pull a new train called the Silver Jubilee, between London King's Cross and Newcastle, in celebration of King George V's 25th year of reign.

During a visit to Germany in 1933, Gresley had been inspired by the steamlined "Flying Hamburger" diesel trains, and indeed the LNER had considered purchasing similar units for use from London to Newcastle. However, in 1935 one of Gresley's A3 Pacifics, No.2750 Papyrus achieved this journey in under four hours and LNER gave the green light for Gresley to produce a streamlined locomotive based on the A3. Initially, four locomotives were built, all with the 'silver' designation, the first being 2509 Silver Link. During a press run to publicise the service, this locomotive achieved a speed of 112.5 mph, breaking the British speed record.#redirect

Design

The A4 pacifics (with the 4-6-2 wheel arrangement) were designed for low consumption of coal and water on all kinds of services; passenger and freight. With the introduction of the double-exhaust Kylchap blastpipe, the consumption levels of the above dropped even more, gaining more revenue to their operators.

This class of locomotive was also noted for its streamlined design, which not only assisted in its aerodynamics, thus increasing its speed, but also created an updraught to lift smoke from the driver's vision, a problem inherent in the earlier A3 design.#redirect The distinctive design made it a particularly attractive subject for artists, photographers and filmmakers. The Class A4 locomotives were known affectionately by train spotters as "streaks".

The streamlining side skirts (valances) of all the A4 locomotives were removed later in their service life because they hindered maintenance access to the valve gear. The aerodynamic advantages of the streamlining were always debatable in any case, but were doubtless effective marketing for the LNER.

World Record

Plaque on Mallard in commemoration of breaking the world speed record of 125 mph.

On July 3 1938 4468 Mallard, newly fitted with the Kylchap exhaust, set a world speed record of 125 mph (201.2 km/h), pulling six cars plus a dynamometer car.

Although the dynamometer car indicated a top speed of 126 mph (202.8 km/h), Sir Nigel Gresley never accepted this speed as the record-breaking maximum. He claimed this speed could only have been attained over a few yards (metres). He was comfortable that the German speed record of 124.5 mph (200.4 km/h) had been surpassed.

The record attempt ended with the middle big end, the inside wheel connecting rod, running hot, which meant the locomotive had to stop at Peterborough rather than continue on to London. Inaccuracies in the machining and setup 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; this overloading was mostly responsible for the failure. However, given that the driving wheels went through 500 revolutions per minute at its full speed, this is perhaps forgivable.#redirect

Preservation

Preserved 4468 Mallard was returned to steam for the fiftieth anniversary of its record-breaking run in 1988.

60009 Union of South Africa.

A total of six A4s have survived to preservation, making them more numerous in preservation than any other LNER class. Two of these are in North America; 60010 Dominion of Canada in the Canadian Railway Museum and 60008 Dwight D Eisenhower in the American National Railroad Museum.

Numbers			Name	Current Location	Condition
Original	LNER 1946	BR
4464	19	60019	Bittern	Mid Hants Watercress Railway	Undergoing refurbishment to mainline condition
4468	22	60022	Mallard	National Railway Museum, York	Static display
4488	9	60009	Union of South Africa	Severn Valley Railway	Currently approved for mainline use
4489	10	60010	Dominion of Canada	Canadian Railway Museum	Static display
4496	8	60008	Dwight D Eisenhower	National Railroad Museum, Green Bay, Wisconsin	Static display
4498	7	60007	Sir Nigel Gresley	North Yorkshire Moors Railway	Undergoing refurbishment to mainline condition

In popular culture

The 1954 British Transport Film Elizabethan Express follows the post-war revival of non-stop London to Edinburgh runs. It stars A4 No.60017 Silver Fox, and features interesting footage of the water trough and corridor tender in use.

The 1959 version of The Thirty-Nine Steps features some wonderful colour photography of A4 No.60010 Dominion of Canada in the brunswick green livery.

Carry on Regardless of 1961 parodied this scene, briefly featuring another A4.

More recently, a stylised animated A4 is seen in the opening titles of the early David Suchet Poirot adaptations. This is undoubtedly based on the original art deco posters for the Silver Jubilee service.

A similar animated A4 was seen in the opening credits of the ITV programme The South Bank Show, in which it is seen at the head of a Pullman train racing beneath Marilyn Monroe's skirts. This appears to be inspired by an art deco poster for the Coronation Scot.

Two steam engines of this type, being Mallard and Spencer, have appeared in the Thomas the Tank Engine books and TV Series, originated by the Rev. W. Awdry.

The locomotive Silver Link appears in an early scene in the Will Hay film, Oh! Mr. Porter, in which Hay accidentally ruins its naming ceremony.

Other notable A4s

• LNER 4469 Sir Ralph Wedgwood
• LNER 2509 Silver Link

External links

• [LNER Encyclopedia Page covering the history and development of the LNER A4 Pacifics]
• [Detailed list of the names, numbers and production dates of LNER A4 locomotives]
• [Railuk database]
• [Screenshots from Elizabethan Express]

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