NBR 224 and 420 Classes

NBR 224 and 420 Classes
224 Class, as built
Type and origin Power type Steam Designer Thomas Wheatley Builder NBR, Cowlairs Build date 1871 (224 Class); 1873 (420 Class) Total produced 2 (224 Class); 4 (420 Class)
Specifications Configuration: ​  • Whyte 4-4-0 Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 2 ft 9 in (840 mm) (224 Class) 3 ft 4 in (1,020 mm) (420 Class) Driver dia. 6 ft 6 in (1,980 mm) Wheelbase 20 ft 3+3⁄8 in (6,182 mm) (224 Class) Adhesive weight 24.45 long tons (24.84 t) (224 Class) Loco weight 38 long tons (39 t) (224 Class) 37.75 long tons (38.36 t) (420 Class) Fuel type Coal Water cap. 1,652 imp gal (7,510 L) Firebox: ​  • Grate area 15.75 sq ft (1.463 m2) (224 Class) Heating surface: ​  • Firebox 87 sq ft (8.1 m2) (224 Class)  • Tubes 894 sq ft (83.1 m2) (224 Class)  • Total surface 981 sq ft (91.1 m2) (224 Class) Cylinders Two, inside Cylinder size 17 in × 24 in (432 mm × 610 mm)
Career Operators North British Railway Numbers 224, 264, 420–3 Withdrawn 1914–19 Disposition All scrapped
[1][2][3]

The NBR 224 and 420 Classes consisted of six steam locomotives of the 4-4-0 wheel arrangement built by the North British Railway (NBR) in 1871 and 1873. No. 224 had three claims to fame: it was the first inside-cylinder 4-4-0 engine to run in Great Britain;^[4] it was the locomotive involved in the Tay Bridge disaster;^[5] and after rebuilding in 1885, it was the only compound-expansion locomotive on the NBR, and one of just three tandem compounds in Britain.^[6]

Intended for express passenger trains on the Edinburgh–Glasgow, Edinburgh–Carlisle, and Burntisland–Dundee routes, they handled these well. When trains from London to Edinburgh began to be forwarded via Carlisle over the NBR in mid-1876, these heavier trains were beyond the locomotives' capabilities, and they had to be removed from front-line service on the Carlisle line. Rebuilt between 1885 and 1897, they remained in service until 1914–19.