LNER Thompson Class A1/1
|LNER Thompson Class A1/1|
The single Thompson A1/1 Pacific 60113 Great Northern near Peterborough in 1959
|Gauge||4 ft 8 1⁄2 in (1,435 mm)|
|Driver diameter||6 ft 8 in (2.032 m)|
|Locomotive weight||101 long tons (103 t)|
|Boiler pressure||250 psi (1.72 MPa)|
|Cylinder size||19 in × 26 in (483 mm × 660 mm)|
|Tractive effort||37,400 lbf (166.36 kN)|
|Railroad(s)||London and North Eastern Railway
The London and North Eastern Railway (LNER) Thompson Class A1/1 was started in 1945 when a Gresley Class A1 (then reclassified A10) went into the works for rebuilding. Thompson had the intention of improving the A4 design, and drew up two modified Gresley 3-cylinder designs. These designs discarded the Gresley conjugated valve gear and had separate sets of Walschaerts valve gear for each cylinder. Due to space restrictions, the middle cylinder could not be parallel with the outside cylinders. One design had the middle cylinder forward of the outside cylinders, whilst the chosen design had the middle cylinder further back. Both designs used A4 boilers. The information in the infobox (right) is taken from Ian Allan ABC.
Great Northern (the very first Gresley Pacific) was chosen for this rebuilding, rather than being selected for future preservation. There has been much debate on the reason for this choice. Some state it as bad luck, whilst others clearly blame Thompson for letting his personal feelings towards Gresley cloud his judgement. It is known that the Chief Draughtsman and a number of high up officials within the LNER unsuccessfully tried to deter Thompson from rebuilding this engine.
Originally, the plan was to rebuild all of the remaining A1s that had not been converted to A3s but this never occurred. In the meantime, the remaining Gresley A1s (including, before its rebuild, Great Northern) were reclassified as A10s, to distinguish them from Thompson's planned rebuild. There were also plans for streamlining, but these were never acted upon.
Peppercorn Class A1
In October 1945, the order was given to construct sixteen new locomotives to the new A1 plan. These finally appeared during the tenure of Arthur Peppercorn, by which point the Thompson A1 design had evolved into the Peppercorn Class A1 Pacific design. In 1947 Great Northern, up to then the sole member of the class officially designated Class A1, was reclassified Class A1/1 in anticipation of these new Peppercorn A1s.
The A1/1 in service
In the first few years of service, the rebuilt Great Northern suffered a number of teething problems. These were fixed, but it never played a prominent role on the East Coast Main Line. Although it was occasionally allocated to Kings Cross, it spent much of its career based at Doncaster or Grantham. Great Northern was even allocated to be the Grantham pilot for a while during the mid-1950s.
Great Northern was renumbered No. 113 in Thompson's 1946 renumbering scheme. It then became No. 60113 during British Railways ownership.
60113 Great Northern was withdrawn on 19 November 1962 with a badly worn cylinder and was then broken up at Doncaster Works. An attempt to save the engine from the cutter's torch came to naught.
PDK Models produce a kit of the A1/1 for 4mm scale / OO gauge.
- Ian Allan ABC of British Railways Locomotives, summer 1961 edition, part 4, page 26
- 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. 231pp.
- Yeadon, Willie (1991). Yeadon's Register of LNER Locomotives, Vol. 3: Raven, Thompson and Peppercorn Pacifics.