LNER Thompson Class A2/1

The London and North Eastern Railway (LNER) Thompson Class A2/1 was a class of 4-6-2 steam locomotives built at Darlington locomotive works during 1944. They were originally ordered as Class V2 locomotives, as designed by Sir Nigel Gresley, but were revised during construction into a 4-6-2 'Pacific' arrangement under the instruction of Edward Thompson.

Disambiguation: LNER Thompson Class A2

LNER Thompson Class A2/1
LNER Thompson A2/1 Pacific No. 60507 'Highland Chieftain' and train (right) waits for departure in August 1960.
Type and origin
Power typeSteam
DesignerEdward Thompson
BuilderDarlington Works
Build date1944
Total produced4
Specifications
Configuration:
​
 • Whyte4-6-2
Gauge4 ft 8 1⁄2 in (1,435 mm)
Driver dia.6 ft 2 in (1.880 m)
Loco weight98 long tons (100 t)
Boiler pressure225 psi (1.55 MPa)
CylindersThree
Cylinder size19 in × 26 in (483 mm × 660 mm)
Performance figures
Tractive effort36,385 lbf (161.85 kN)
Career
OperatorsLondon and North Eastern Railway
British Railways
ClassA2/1
Power class7P6F
NumbersLNER (1944): 3696-3699; LNER (from 1945): 507-510
BR: 60507-60510
LocaleEast Coast Main Line
Withdrawn1960–1961
DispositionAll scrapped

Background

At the time Edward Thompson succeeded Sir Nigel Gresley as Chief Mechanical Engineer of the LNER in April 1941, Darlington works was busy building Class V2 mixed traffic locomotives. Although the V2 class were competent and powerful locomotives, Thompson did not like this design as it required more servicing than his own mixed traffic B1 class 4-6-0. He also envisaged a time when the V2s would be replaced by his own design of 'Pacific' locomotives, but would not receive authority to build a new class during the war.[1] He therefore decided to build the final four V2 already authorised as experimental 'Pacific' locomotives along similar lines to his recently rebuilt A2/2 class. The revised design was authorised in August 1943 and the new locomotives built between May 1944 and January 1945.[2]

Design

The pony truck of the V2 class was replaced by Thompson's own design of bogie and they had an extended smokebox. They retained the same boiler as the V2 class although the pressure was increased to 225psi, giving an increased tractive effort of 36,390 lbf (161.87 kN). The firebox was also the same as the V2 although these were the first LNER locomotives to be fitted with a rocking grate and ashpan. Rather than have all three cylinders driving a single axle Thompson adopted divided drive with the middle cylinder driving the first pair of driving wheels and the outside cylinders the middle pair. Thompson also abandoned the Gresley conjugated valve gear and instead fitted independent sets of Walschaerts valve gear to each cylinder.

Performance

The four locomotives of this design performed adequately but proved to be under-boilered for their size and lacked adhesion. They were less problematic than the A2/2 class, but did not distinguish themselves.[3]

Accidents and incidents
No. 60508 Duke of Rothesay lying on its side, July 1948

On 17 July 1948, locomotive No. 60508 Duke of Rothesay was hauling a passenger train when it became derailed inside Barnet Tunnel, Hertfordshire due to a combination of faulty track and excessive speed. The whole train was subsequently derailed on points at New Southgate, London. One person was killed.[4]

Withdrawal

All four locomotives were withdrawn from stock in 1960/1.

YearQuantity in
service at
start of year		Quantity
withdrawn		Locomotive numbersNotes
19604360507/09–10
19611160508

Stock list
Original No.[5] LNER No. BR No. Name Entered stock Withdrawn Disposal Date
3696
507
60507
 Highland Chieftain 13 May 1944 12 December 1960 31 December 1960
3697
508
60508
Duke of Rothesay 30 June 1944 20 February 1961 February 28, 1961
3698
509
60509
 Waverley 30 November 1944 15 August 1960 31 August 1960
3699
510
60510
Robert the Bruce 15 January 1945 21 November 1960 30 November 1960

Models

Apple Green Engines produce a ready-to-run model of the A2/1 in 4 mm scale. PDK, Nucast, and DJH also produce 4 mm scale kits of the A2/1. Crownline have produced a 4 mm kit in the past, but this is no longer available.

References
  1. Boddy, Neve & Yeadon 1973, p. 143.
  2. Boddy, Neve & Yeadon 1973, p. 156.
  3. Allen 1962, p. 99.
  4. Hoole, Ken (1982). Trains in Trouble: Vol. 3. Redruth: Atlantic Books. p. 39. ISBN 0-906899-05-2.
  5. The ABC of L.N.E.R. Locomotives (Renumbering ed.). Ian Allan. 1946.
  • Allen, Cecil J. (1962). British Pacific Locomotives. London: Ian Allan.
  • Boddy, M. G.; Neve, E.; Yeadon, W. B. (April 1973). Fry, E. V. (ed.). Locomotives of the L.N.E.R., Part 2A: Tender Engines—Classes A1 to A10. Kenilworth: RCTS. ISBN 0-901115-25-8.
  • Yeadon, Willie (1991). Yeadon's Register of LNER Locomotives, volume 3: Raven, Thompson & Peppercorn Pacifics. Irwell Press.
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