LNER Thompson Class A2/2

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LNER Thompson Class A2/2
King's Cross Station geograph-2261732-by-Ben-Brooksbank.jpg
No. 60503 'Lord President' at London King's Cross railway station in 1958
Type and origin
Power type Steam
Build date 1943-1944
Total produced 6
Specifications
Configuration 4-6-2
Gauge 4 ft 8 12 in (1,435 mm)
Driver diameter 6 ft 2 in (1.880 m)
Loco weight 101.5 long tons (103.1 t)
Boiler pressure 225 psi (1.55 MPa)
Cylinders Three
Cylinder size 20 in × 26 in (508 mm × 660 mm)
Performance figures
Tractive effort 40,320 lbf (179.35 kN)
Career
Operators London and North Eastern Railway
British Railways
Class A2/2
Power class 8P7F
Numbers LNER 501-506
BR 60501-60506
Disposition All scrapped

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’s P2 Class of 2-8-2 express passenger locomotives. The rebuilds were not particularly successful and all were withdrawn and scrapped between 1959 and 1961.

Background[edit]

On taking up office as Chief Mechanical Engineer of the London and North Eastern Railway in April 1941, Edward Thompson, proposed an unstreamlimed mixed traffic version of Sir Nigel Gresley’s A4 class pacifics with 6 ft 2 in (1.880 m) driving wheels, but new construction would not have been authorised at this time.[1] He therefore rebuilt the six of his predecessor P2 Class of 2-8-2 express passenger as pacific locomotives to try out his own thoughts on their design. The P2 Class 2-8-2 had been built between 1934 and 1936 for service between Edinburgh and Aberdeen and had proved to be powerful and capable locomotives. However, the long fixed wheelbase was not ideally suited to the winding route, giving rise to maintenance problems on both the track and the locomotives, notably failure of the crank axle.[2] However, O.S. Nock stated that the P2 class 'rode easily and elegantly around the sharpest curves.'[3] 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 is a chance to try out his own ideas of locomotive design[4]

Design[edit]

The pony truck and front coupled wheels of the original design were replaced by a newly designed bogie. The boiler barrel was shortened by 2 ft 0.25 in (0.616 m)and a new front end was designed with 20 in × 26 in (508 mm × 660 mm) cylinders. 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. However, In order to retain the original three connecting rods of the same length, the outside cylinders were set back behind the bogie, giving the locomotives an ungainly appearance.[5] Thompson also removed the Gresley conjugated valve gear and instead fitted independent sets of Walschaerts valve gear to each cylinder. The first locomotive to be rebuilt at Doncaster Works was No. 2005, Thane of Fife, which was 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.[6]

Performance[edit]

The new design steamed well and retained much of the Power of the P2's. The reduced weight meant they had a high power to weight ratio, and were good at hauling high speed expresses, although in the opinion of O.S. Nock they 'acquired a particularly bad reputation for wild and unsafe riding at high speed!'[7] However, there were other problems which prevented them from ever making an impact on the east coast main line. The first of these was a lack of adhesion causing wheel slip when starting which mean that they could not be used on the Edinburgh-Aberdeen line they had originally been built for. The second problem was that of reliability caused by their having been adapted from quite different locomotives. Both the A2/2 and the subsequent A2/3 suffered badly from frame movement, vibration and loose fittings. Using equal length connecting rods, as well as the divided drive meant that the centre cylinder was much further forward from the outside cylinders. During their lifetime in service Earl Marischal was the only A2/2 to cover over one million miles in service, 360,907 as a P2 and 673,947 as an A2/2. The information in the infobox (right) is taken from Ian Allan ABC.[8]

Withdrawal[edit]

No. 60505 'Thane of Fife' in York Locomotive Yard 26 May 1958.

Withdrawals from stock began in 1959 starting with 60505 Thane Of Fife on 10 November 1959. The next A2/2 to be withdrawn was Lord President on 27 November 1959. 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 1961.

Stock list[edit]

The LNER/BR stock list was as follows:

Original No.[9] LNER No.
(Intermediate No.)
BR No. Name Rebuild Date Withdrawn
2001
501
60501
Cock o' the North September 1944 February 1960
2002
502
60502
Earl Marischal June 1944 July 1961
2003
503
60503
Lord President December 1944 November 1959
2004
504
60504
Mons Meg November 1944 January 1961
2005
505
(994)
60505
Thane of Fife January 1943 November 1959
2006
506
60506
Wolf of Badenoch May 1944 April 1961

Models[edit]

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).

References[edit]

  1. ^ Boddy, Neve, & Yeadon, (1973). p. 143.
  2. ^ Boddy, Neve, & Yeadon, (1973). p. 143.
  3. ^ Nock (1983) p.111.
  4. ^ Allen (1962), p.96.
  5. ^ Allen (1962), p.97.
  6. ^ Boddy, Neve, & Yeadon, (1973). pp. 144 & 229.
  7. ^ Nock (1983) p.112.
  8. ^ Ian Allan ABC of British Railways Locomotives, summer 1961 edition, part 4, page 27
  9. ^ The ABC of L.N.E.R. LOCOMOTIVES (Renumbering Edition), Ian Allan, 1946
  • Allen, Cecil J. (1962). British Pacific Locomotives. London: Ian Allan. 
  • Nock, O.S. (1984). British Locomotives of the Twentieth Century Vol. 2 1930-1960. London: Book Club Associates. 
  • 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, W. B. (1991). Yeadon's Register of LNER Locomotives, volume 3: Raven, Thompson & Peppercorn Pacifics. Irwell Press. 

External links[edit]