GWR 4073 Class 4073 Caerphilly Castle

Specifications
Specifications
Configuration:;
• Whyte	4-6-0
Gauge	4 ft 8+1⁄2 in (1,435 mm)
Leading dia.	3 ft 2 in (0.965 m)
Driver dia.	6 ft 8+1⁄2 in (2.045 m)
Length	65 ft 2 in (19.86 m) over buffers
Width	8 ft 11 in (2.718 m)
Height	13 ft 1 in (3.988 m) (Cut back from 13 ft 4+1⁄2 in (4.077 m))
Loco weight	79 long tons 17 cwt (178,900 lb or 81.1 t); 89.4 short tons full
Tender weight	47 long tons 6 cwt (106,000 lb or 48.1 t); 53.0 short tons full
Fuel type	Coal
Fuel capacity	6 long tons 0 cwt (13,400 lb or 6.1 t); 6 long tons 0 hundredweight (6.10 t; 6.72 short tons)
Water cap.	4,000 imp gal (18,000 L; 4,800 US gal)
Firebox:
• Grate area	29.36 sq ft (2.728 m2)
Boiler	GWR Standard Number 8
Boiler pressure	225 lbf/in2 (1.55 MPa)
Heating surface:
• Firebox	162.7 sq ft (15.12 m2) (Collett); 163.5 sq ft (15.19 m2) (Hawksworth)
• Tubes	1,857.7 sq ft (172.59 m2) (Collett); 1,799.5 sq ft (167.18 m2) (Hawksworth)
Cylinders	Four (two inside, two outside)
Cylinder size	16 in × 26 in (406 mm × 660 mm)
Valve gear	Inside cylinders: Walschaerts; Outside cylinders: derived from inside cylinders via rocking bars.
Valve type	Piston valves
Train heating	Steam heating
Loco brake	Vacuum brake

Type and origin
Type and origin
Power type	Steam
Designer	Charles Collett
Builder	BR Swindon Works
Build date	1923

GWR 4073 Class 4073 *Caerphilly Castle*
GWR 4073 Class 4073 Caerphilly Castle
	Caerphilly Castle on static display in the STEAM museum in 2011. Note the GWR headboard for the Cheltenham Flyer.
Power type
Type and origin
Power type	Steam
Designer	Charles Collett
Builder	BR Swindon Works
Build date	1923
Configuration:;
Specifications
Configuration:;
• Whyte	4-6-0
Gauge	4 ft 8+1⁄2 in (1,435 mm)
Leading dia.	3 ft 2 in (0.965 m)
Driver dia.	6 ft 8+1⁄2 in (2.045 m)
Length	65 ft 2 in (19.86 m) over buffers
Width	8 ft 11 in (2.718 m)
Height	13 ft 1 in (3.988 m) (Cut back from 13 ft 4+1⁄2 in (4.077 m))
Loco weight	79 long tons 17 cwt (178,900 lb or 81.1 t); 89.4 short tons full
Tender weight	47 long tons 6 cwt (106,000 lb or 48.1 t); 53.0 short tons full
Fuel type	Coal
Fuel capacity	6 long tons 0 cwt (13,400 lb or 6.1 t); 6 long tons 0 hundredweight (6.10 t; 6.72 short tons)
Water cap.	4,000 imp gal (18,000 L; 4,800 US gal)
Firebox:
• Grate area	29.36 sq ft (2.728 m2)
Boiler	GWR Standard Number 8
Boiler pressure	225 lbf/in2 (1.55 MPa)
Heating surface:
• Firebox	162.7 sq ft (15.12 m2) (Collett); 163.5 sq ft (15.19 m2) (Hawksworth)
• Tubes	1,857.7 sq ft (172.59 m2) (Collett); 1,799.5 sq ft (167.18 m2) (Hawksworth)
Cylinders	Four (two inside, two outside)
Cylinder size	16 in × 26 in (406 mm × 660 mm)
Valve gear	Inside cylinders: Walschaerts; Outside cylinders: derived from inside cylinders via rocking bars.
Valve type	Piston valves
Train heating	Steam heating
Loco brake	Vacuum brake
Maximum speed
Performance figures
Maximum speed	45 mph (72 km/h) - (mainline, tender first) 75 mph (121 km/h) - (mainline, chimney first)
Tractive effort	31,625 lbf (140.68 kN)
Operators
Career
Operators	Great Western Railway; British Railways
Power class	GWR: D; BR: 7P
Axle load class	GWR: Red
Withdrawn	1960
Current owner	National Railway Museum
Disposition	Static display

GWR 4073 Castle class 4073 Caerphilly Castle is a steam locomotive completed in August 1923. It is a 4-6-0 standard gauge locomotive built to a design by Charles Collett, it was the first member of its class to be constructed. It operated on the British mainline from construction until the end of steam on Britain's railway network in 1960, after which it was preserved as part of the National Railway Museum's National Collection. As of March 2025, Caerphilly Castle is on static display at the Museum of the Great Western Railway in Swindon.

In 1924, Caerphilly Castle was displayed at the British Empire Exhibition alongside the LNER's Flying Scotsman, and was subsequently involved in comparative trials against the locomotive.