GWR 5101 Class

GWR 5101 Class

Preserved 5101 Class locomotive 4160 at Minehead, West Somerset Railway, painted in British Railways lined-green livery.

Type and origin Power type Steam Designer Charles Collett Builder GWR Swindon Works Build date 1929–1949 Total produced 140

Specifications Configuration 2-6-2T Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 2 in (0.965 m) Driver dia. 5 ft 8 in (1.727 m) Trailing dia. 3 ft 8 in (1.118 m) Length 41 ft (12.50 m) Loco weight 78.45 long tons (79.71 t; 87.86 short tons) Fuel type Coal Fuel capacity 4.0 long tons (4.1 t; 4.5 short tons) Water cap 2,000 imp gal (9,100 L; 2,400 US gal) Firebox:  • Firegrate area 20.35 sq ft (1.891 m2) Boiler GWR Number 2 Boiler pressure 200 psi (1,400 kPa) Heating surface:  • Tubes and flues 1,144.94 sq ft (106.368 m2)  • Firebox 121.8 sq ft (11.32 m2) Superheater: ​  • Heating area 82.2 sq ft (7.64 m2) Cylinders Two Cylinder size 18 in × 30 in (457 mm × 762 mm)

Performance figures Tractive effort 24,300 lbf (108 kN)

Career Class GWR 5101 Power class GWR D BR 4MT Axle load class GWR Blue Withdrawn December 1965 Disposition 8 preserved, 1 used for spares, 1 rebuilt to freelance; remainder scrapped

The GWR 5101 Class or Large Prairie was a class of 2-6-2T steam locomotives of the Great Western Railway.

The 5101 Class were medium-sized tank engines used for suburban and local passenger services all over the Great Western Railway system. The class was an updated version, by Collett, of Churchward's 1903 3100/5100 Class.

The original 40 members of the 3100 class were renumbered 5100 and 5111 to 5149 in 1927. The first batches of 5101s filled in the numbers 5101 to 5110 and extended the class from 5150 to 5189. They were little changed from the Churchward locomotives as they then were, but had an increased axle loading of 17 long tons 12 cwt (39,400 lb or 17.9 t); the maximum permitted for the ‘Blue’ route availability. Bunkers were of the standard Collett design with greater coal capacity. The 5100 number series was exhausted in 1934, and further new locomotives were numbered from 4100.

In 1938, the GWR began a modernisation programme to the earlier locomotives, rebuilding them to provide greater availability and more tractive effort. This would allow them to undertake their original mixed-traffic duties on a wider selection of routes, as well as banking. The 3100 class were to be rebuilt as the 3500 class, with Standard Class 4 boilers at 225psi replacing the original Standard Class 2 at 200psi, and using coupled wheels of 5 feet 3 inches diameter, which in combination took tractive effort up to 31,170 pounds. Only five engines were rebuilt pre the onset of World War II. The last of the large prairie locomotives constructed were 4140 to 4179, built to the last GWR design by British Railways at Swindon.

As both freight and passenger traffic on branch lines declined post-World War II with increasing volumes of private motor cars, and replacement on urban services by diesel-powered rail cars, the bulk of the class found itself allocated to various mainline support duties, mainly banking and piloting, often on the South Devon Banks on the Exeter to Plymouth Line, or around the Severn Tunnel on the South Wales Main Line.