GNR Class H4

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GNR Class H4 LNER Class K3
K3 2-6-0 No. 1387 at York 1939
Type and origin Power type Steam Designer Nigel Gresley Builder Doncaster Works (30) Darlington Works (93) Armstrong Whitworth (40) Robert Stephenson & Co. (10) North British Locomotive Co. (20) Build date 1920–1937 Total produced 193
Specifications Configuration: ​  • Whyte 2-6-0 Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Driver dia. 5 ft 8 in (1.727 m) Loco weight 72.6 long tons (73.8 t; 81.3 short tons) Fuel type Coal Boiler pressure 180 psi (1.24 MPa) Cylinders Three Cylinder size 18.5 in × 26 in (470 mm × 660 mm) Valve gear Outside: Walschaerts Inside: Gresley conjugated
Performance figures Maximum speed 60 mph (97 km/h) (Modern mainline running) Tractive effort 30,030 lbf (133.6 kN)
Career Operators Great Northern Railway, London and North Eastern Railway, British Railways Class GNR: H4 LNER:K3 Power class BR: 5P6F Numbers LNER: 1800–1992 BR: 61800–61992 Nicknames Jazzers Withdrawn 1959–1962 Disposition All scrapped

The Great Northern Railway Class H4 (classified K3 by the LNER) was a class of 2-6-0 steam locomotive designed for mixed-traffic work.

The type was a more powerful development of the earlier H3 (LNER K2) class and was notable at the time, as the 6-foot-diameter (1.8 m) boilers were the largest fitted to any British locomotive to that date. After formation of the London and North Eastern Railway, the type became known as class K3 and was adopted as an LNER standard design. They got the nickname "Jazzers" after the rhythm of their exhaust beat and the unbalanced gyratory movement.^[1]