LNER Thompson Class A2/2. The London and North Eastern Railway Class A2/2 was a class of six 4-6-2 steam locomotives rebuilt by Edward Thompson in 1943 and 1944 from his predecessor Sir Nigel Gresley's P2 Class of 2-8-2 express passenger locomotives. The rebuilds improved reliability and reduced maintenance, but also suffered from a variety of issues during service, and all were withdrawn and scrapped between 1959 and 1961.

Background
On taking up office as chief mechanical engineer of the London and North Eastern Railway in April 1941, Edward Thompson inherited a railway with many aging locomotives, most dating from the pre-grouping era, struggling against wartime material and manpower shortages and skyrocketing passenger and freight traffic demands. 

Nigel Gresley's Class P2 were a class of 6 non-identical, highly powerful and capable locomotives which had poor availability and required high maintenance. The engines suffered from hot axle boxes, an issue found at Vitry, rapid wear in journals and connecting rods from working on the Edinburgh to Aberdeen mainline and fractured joints in steam pipes. Their large grate also consumed 75-90 lbs of coal per mile, requiring an almost superhuman effort on the part of the fireman. In 1935, Oliver Bulleid asked for Teddy Windle to go to Cowlairs to inspect No. 2001 Cock o' the North, which has a cracked pony truck, as well as Dundee to inspect No. 2002 Earl Marischal. Crank axle failures were commonplace with the class of engines, with one such accident happened to No. 2005 Thane of Fife on 18 July 1939, with another following in No. 2004 Mons Meg on 27 May 1942 and No. 2003 Lord President on 29 July 1944. Suggestions for other failures also exist but were not confirmed by surviving records.

Contrarily, O. S. Nock stated that the P2 class rode easily and elegantly around the sharpest curves.' In either event, rather than transfer the locomotives to other duties on the East Coast Main Line south of Newcastle, where this would have been less of a problem, Thompson saw this as a chance to try out his own ideas of locomotive design.

It is also said that he proposed an unstreamlined mixed traffic version of Nigel Gresley's A4 Class Pacifics with  driving wheels, but new construction would not have been authorised at this time, and he therefore rebuilt the six Class P2 express passenger locomotives as Pacific locomotives to try out his own thoughts on their design.

Design
In place of the maintenance heavy Gresley conjugated valve gear was three cylinders of independent Walschaerts valve gear. The cylinders had their bore reduced to 20 in and diameter enlarged to 10 in with separate castings, compared to the monobloc casting for Gresley's conjugated valve gear. However, wartime economies meant all three short connecting rods were retained, requiring the outside cylinders to be moved back and the middle cylinder to drive the leading axle, adopting divided drive. The extended look was not seen commonly on the LNER, and was considered ungainly.

The pony truck and front coupled wheels of the original design were replaced by a newly designed bogie to Thompson's side support pattern design. The locomotives retained their eight wheeled tenders, and were fitted with a Kylchap exhaust. The boiler barrel was shortened and pressure increased from  to . These changes gave a tractive effort of .

The first locomotive to be rebuilt at Doncaster Works was No. 2005, Thane of Fife, as it had the lowest annual mileage and was reputedly the worst of the P2s, ordered in October 1942 and completed in January 1943. After trials the remaining five P2 locomotives were ordered to be rebuilt in September 1943 and they all appeared in traffic during 1944.

Performance
The first rebuild, No. 2005 Thane of Fife emerged partway through 1943 and achieved 45,732 miles by the end of the year, significantly outperforming the P2s. Arthur Peppercorn presented the board with a report on the operation of the rebuilt locomotive with great praise, and the board approved the rebuilding for the remaining five members. The rebuilds would become some of the best performing locomotives with high mileage and availability.

Claims that the locomotives were unable to continue to be used on the Edinburgh-Aberdeen mainline due to their reduced adhesion are unfounded, as it is said in the LNER Board Notes "The converted engine (No. 2005 Thane of Fife) has been in service for some time, and has proved entirely satisfactory in that it has not only been able to handle loads at least equal to the stipulated maximum load of the P2 class, on the Edinburgh and Aberdeen section, but it has also been remarkably free from mechanical troubles so that it has been consistently available for traffic."

A set of comparison trials were undertaken during May and June 1945, the first comparing the A1/1 with an A4 and the second comparing an A4, the converted A2/1 and A2/2 on identical express passenger and freight duties, overseen by Arthur Peppercorn and Bert Spencer. Representing the classes in the second trials were A4 No. 2512 Silver Fox, A2/1 No. 3697 Duke of Rothsay and A2/2 No. 2003 Lord President. During the trials, the A4 performed the best on the express passenger service, while the A2/1 performed best on the freight services, with the A2/2 being in third place on both trials. Locomotive Running Superintendent George Musgrave commented that "During the trials, the A2/1 and A2/2 Class engines did not have to be worked to their full capacity. It was considered by the Locomotive Inspector that they both worked the freight easier than the A4."

Cecil J. Allen acknowledges the design with a log of a run behind No. 60502 Earl Marischal with a 220 ton gross load train, achieving a speed of 95 mph, possibly the highest recorded speed by a  driving wheel locomotive.

However, the engines had a high power to weight ratio and led to being extremely prone to slipping and were "light on their feet", limiting their haulage capacity and did not fully realize their theoretical power, although coal consumption was reduced and reliability improved. The divided drive design worked well, although the frame required modifications due to flexing and stress damage from the stretched design. During retirement, Thompson came to believe that the divided drive was not ideal and the solution adopted by Peppercorn and his team was better. According to O.S. Nock, they "acquired a particularly bad reputation for wild and unsafe riding at high speed!" 

In addition, due to prejudice against the rebuilt locomotives, especially in Scottish depots, by 1949 the engines were sent south of the Border with three stationed at York and three at Peterborough New England shed. During their lifetime in service Earl Marischal was the only A2/2 to cover over one million miles, 360,907 as a P2 and 673,947 as an A2/2.

Withdrawal 

Withdrawals from stock began in 1959 starting with 60505 Thane of Fife on 10 November that year. The next A2/2 to be withdrawn was 60503 Lord President on 27 November. 60501 Cock o' the North was withdrawn in 1960, while 60504 and 60506 were withdrawn in 1961, with 60502 the last member of the class withdrawn on 3 July that year.

Stock list 

The LNER/BR stock list was as follows:

Accidents
 On 16 March 1951, No. 60501 Cock o' the North was involved in an accident shortly after departing Doncaster railway station on the 10:04 Doncaster to King's Cross. The cause was found to be poor maintenance of the crossover.

Models

Apple Green Engines produce a ready-to-run model of the A2/2 in 4 mm scale. PDK, DJH, and Millholme sell 4 mm scale kits of the A2/2. Crownline have also produced a 4 mm scale kit in the past, but this is no longer available.

DJH also sell a kit of the A2/2 for O gauge (7 mm scale).

Hornby announced that they will produce a number of A2/2 models for their 2020 range, these becoming available in 2021.
The initial releases included:

R3830 - 60501 'Cock o' the North' in BR green with early emblem

R3831 - 60505 'Thane of Fife' in BR green with late crest

R3977 - 60502 'Earl Marischal' in BR green with late crest

Each release included variations based on prototype allocations and modifications through the life of the class (boiler types and fittings).

Notes

References

External links 

 The Thompson A2/2 Pacifics LNER Encyclopedia

A2 2
4-6-2 locomotives
Railway locomotives introduced in 1943
Scrapped locomotives
Standard gauge steam locomotives of Great Britain
2′C1′ h3 locomotives
Rebuilt locomotives
Passenger locomotives