LNER Gresley Classes A1 and A3

LNER Gresley Classes A1 and A3[1]
Class A1 4474 Victor Wild at Kings Cross Station Yard
Type and origin
Power typeSteam
DesignerNigel Gresley
BuilderDoncaster Works (59)
North British Locomotive Co. (20)
Build date1922–1935
Total producedA1: 52
A3: 51 rebuilt + 27 new (78)
Rebuild date1928–1949
Number rebuilt51
Specifications
Configuration:
 • Whyte4-6-2
 • UIC2′C1 h3
Gauge4 ft 8+12 in (1,435 mm) standard gauge
Leading dia.3 ft 2 in (0.965 m)
Driver dia.6 ft 8 in (2.032 m)
Trailing dia.3 ft 8 in (1.118 m)
Wheelbase60 ft 10.6 in (18.56 m)
Length70 ft 5 in (21.46 m)
Height13 ft 1 in (3.99 m) (First 11 A1s were cut back from 13 ft 4 in (4.06 m))
Axle loadA1: 20 long tons (20.3 t; 22.4 short tons)
A3: 22.05 long tons (22.4 t; 24.7 short tons)
Adhesive weightA1: 60 long tons (61.0 t; 67.2 short tons)
Loco weightA1: 91.35 long tons (92.82 t; 102.31 short tons)
Fuel typeCoal
Fuel capacity8 long tons (8.1 t; 9.0 short tons)
Water cap.5,000 imp gal (22,700 L; 6,000 US gal)
Firebox:
 • Grate area41.25 sq ft (3.832 m2)
Boiler pressureA1: 180 psi (1.24 MPa)
A3: 220 psi (1.52 MPa)
Heating surface:
 • Firebox215 sq ft (20.0 m2)
 • TubesA1: 1,880 sq ft (175 m2)
A3: 504 sq ft (46.8 m2)
 • FluesA1: 835 sq ft (77.6 m2)
A3: 2,159 sq ft (200.6 m2)
Superheater:
 • Heating areaA1: 525 sq ft (48.8 m2)
A3: 1,104 sq ft (102.6 m2)
CylindersThree
Cylinder size18.25 in × 26 in (464 mm × 660 mm) (A3)
19 in × 26 in (483 mm × 660 mm) (A3)
20 in × 26 in (508 mm × 660 mm) (A1/A3)
Valve gear
Valve typePiston valves
Loco brakeVacuum
Train brakesVacuum
Performance figures
Tractive effortA1: 29,835 lbf (132.71 kN)
A3: 30,362 lbf (135.06 kN) (18.5×26 cylinders)
32,910 lbf (146.39 kN) (19×26 cylinders)
36,465 lbf (162.20 kN) (20×26 cylinders)
Career
OperatorsLondon and North Eastern Railway
British Railways
Power classBR: 7P6F
NumbersLNER (until 1945/46): 2543–2582, 2595–2599, 2743–2752, 2795–2797, 4470–4481, 2500–2508;
LNER (from 1945/46); 35–112;
BR: 60035–60112
Axle load classRoute Availability: 9
LocaleEast Coast Main Line
Withdrawn1959–1966
PreservedOne: 4472
DispositionOne rebuilt as Thompson A1/1; one preserved, one boiler preserved; remainder scrapped

The London and North Eastern Railway Gresley Classes A1 and A3 locomotives represented two distinct stages in the history of the British 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley. They were designed for main line passenger services and later express passenger services, initially on the Great Northern Railway (GNR), a constituent company of the London and North Eastern Railway after the amalgamation of 1923, for which they became a standard design. The change in class designation to A3 reflected the fitting to the same chassis of a higher pressure boiler with a greater superheating surface and a small reduction in cylinder diameter, leading to an increase in locomotive weight. Eventually all of the A1 locomotives were rebuilt, most to A3 specifications, but no. 4470 was completely rebuilt as Class A1/1.

The names for the locomotives came from a variety of sources. The first, Great Northern, was named after its parent company. Others were given the names of high-ranking railway officials, but most were given the names of famous racehorses. One was named after the company's most famous long-distance passenger train, the Flying Scotsman. Flying Scotsman is the sole member of the class to be preserved.

  1. ^ Herring (2000), pp. 106–107.