LNER Gresley Classes A1 and A3

Specifications
Specifications
Configuration:;
• Whyte	4-6-2
• UIC	2′C1 h3
Gauge	4 ft 8+1⁄2 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)
Wheelbase	60 ft 10.6 in (18.56 m)
Length	70 ft 5 in (21.46 m)
Height	13 ft 1 in (3.99 m) (First 11 A1s were cut back from 13 ft 4 in (4.06 m))
Axle load	A1: 20 long tons (20.3 t; 22.4 short tons); A3: 22.05 long tons (22.4 t; 24.7 short tons)
Adhesive weight	A1: 60 long tons (61.0 t; 67.2 short tons)
Loco weight	A1: 91.35 long tons (92.82 t; 102.31 short tons)
Fuel type	Coal
Fuel capacity	8 long tons (8.1 t; 9.0 short tons)
Water cap.	5,000 imp gal (22,700 L; 6,000 US gal)
Firebox:
• Grate area	41.25 sq ft (3.832 m2)
Boiler pressure	A1: 180 psi (1.24 MPa); A3: 220 psi (1.52 MPa)
Heating surface:
• Firebox	215 sq ft (20.0 m2)
• Tubes	A1: 1,880 sq ft (175 m2); A3: 504 sq ft (46.8 m2)
• Flues	A1: 835 sq ft (77.6 m2); A3: 2,159 sq ft (200.6 m2)
Superheater:;
• Heating area	A1: 525 sq ft (48.8 m2); A3: 1,104 sq ft (102.6 m2)
Cylinders	Three
Cylinder size	18.25 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	Outside: Walschaerts; Inside: Gresley conjugated;
Valve type	Piston valves
Loco brake	Vacuum
Train brakes	Vacuum

Type and origin
Type and origin
Power type	Steam
Designer	Nigel Gresley
Builder	Doncaster Works (59); North British Locomotive Co. (20)
Build date	1922–1935
Total produced	A1: 52; A3: 51 rebuilt + 27 new (78)
Rebuild date	1928–1949
Number rebuilt	51

LNER Gresley Classes A1 and A3
LNER Gresley Classes A1 and A3
	Class A1 4474 Victor Wild at Kings Cross Station Yard
Power type
Type and origin
Power type	Steam
Designer	Nigel Gresley
Builder	Doncaster Works (59); North British Locomotive Co. (20)
Build date	1922–1935
Total produced	A1: 52; A3: 51 rebuilt + 27 new (78)
Rebuild date	1928–1949
Number rebuilt	51
Configuration:;
Specifications
Configuration:;
• Whyte	4-6-2
• UIC	2′C1 h3
Gauge	4 ft 8+1⁄2 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)
Wheelbase	60 ft 10.6 in (18.56 m)
Length	70 ft 5 in (21.46 m)
Height	13 ft 1 in (3.99 m) (First 11 A1s were cut back from 13 ft 4 in (4.06 m))
Axle load	A1: 20 long tons (20.3 t; 22.4 short tons); A3: 22.05 long tons (22.4 t; 24.7 short tons)
Adhesive weight	A1: 60 long tons (61.0 t; 67.2 short tons)
Loco weight	A1: 91.35 long tons (92.82 t; 102.31 short tons)
Fuel type	Coal
Fuel capacity	8 long tons (8.1 t; 9.0 short tons)
Water cap.	5,000 imp gal (22,700 L; 6,000 US gal)
Firebox:
• Grate area	41.25 sq ft (3.832 m2)
Boiler pressure	A1: 180 psi (1.24 MPa); A3: 220 psi (1.52 MPa)
Heating surface:
• Firebox	215 sq ft (20.0 m2)
• Tubes	A1: 1,880 sq ft (175 m2); A3: 504 sq ft (46.8 m2)
• Flues	A1: 835 sq ft (77.6 m2); A3: 2,159 sq ft (200.6 m2)
Superheater:;
• Heating area	A1: 525 sq ft (48.8 m2); A3: 1,104 sq ft (102.6 m2)
Cylinders	Three
Cylinder size	18.25 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	Outside: Walschaerts; Inside: Gresley conjugated;
Valve type	Piston valves
Loco brake	Vacuum
Train brakes	Vacuum
Tractive effort
Performance figures
Tractive effort	A1: 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)
Operators
Career
Operators	London and North Eastern Railway; British Railways
Power class	BR: 7P6F
Numbers	LNER (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 class	Route Availability: 9
Locale	East Coast Main Line
Withdrawn	1959–1966
Preserved	One: 4472
Disposition	One rebuilt as Thompson A1/1; one preserved, one boiler preserved, one tender preserved; remainder scrapped

The London and North Eastern Railway Gresley Classes A1 and A3 were 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley for passenger work. They were initially intended for use on the Great Northern Railway (GNR), but became a standard design on the London and North Eastern Railway after the amalgamation of 1923. The change in class designation from A1 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 and power. Eventually all but one of the A1 locomotives were rebuilt in this way, but no. 4470 was completely rebuilt as a 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.

Only one member of the class survives into preservation: 4472 Flying Scotsman, which is preserved in the National Railway Museum's National Collection.