GCR Class 8B

GCR Class 8B LNER Class C4
Two LNER Class C4 (ex GCR Class 8B) on Retford shed in April 1947
Type and origin Power type Steam Designer John G. Robinson Builder Beyer, Peacock & Co. (7) North British Locomotive Company (12) Gorton Works (8) Build date 1903-1906 Total produced 27
Specifications Configuration: ​  • Whyte 4-4-2  • UIC 2′B1′ n2, later 2′B1′ h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) Leading dia. 3 ft 6 in (1.067 m) Driver dia. 6 ft 9 in (2.057 m) Trailing dia. 4 ft 3 in (1.295 m) Wheelbase 27 ft 9.5 in (8.5 m) Axle load 18.5 long tons (18.8 t) Loco weight 71.9 long tons (73.1 t) Tender weight 48.3 long tons (49.1 t) Total weight 120.2 long tons (122.1 t) Fuel type Coal Firebox:  • Firegrate area 26.24 sq ft (2.44 m2) Boiler 5 ft 0 in (1.5 m) Boiler pressure 180 psi (1.24 MPa) Heating surface 1,745 sq ft (162.1 m2)  • Tubes 885 sq ft (82.2 m2)  • Flues 464 sq ft (43.1 m2)  • Firebox 154 sq ft (14.3 m2) Superheater: ​  • Heating area 242 sq ft (22.5 m2) Cylinders Two, outside Cylinder size 19 in × 26 in (483 mm × 660 mm) (original engines) 19 in × 26 in (483 mm × 660 mm) (first rebuild) 21 in × 26 in (533 mm × 660 mm) (second rebuild) Valve gear Stephenson valve gear Valve type Slide (originally) Piston (later refits)
Performance figures Tractive effort 21,658 lbf (96.3 kN) @ 85% boiler pressure
Career Operators Great Central Railway → London & North Eastern Railway → British Railways Withdrawn 1939-1950 Disposition All scrapped

GCR Class 8B was a class of 25 two-cylinder steam locomotives of the 4-4-2 wheel arrangement built between 1903 and 1906 for the Great Central Railway.

Facing a potential rise in passenger traffic, the Great Central Railway placed an order for 2 pairs of different locomotives - one pair being the 4-6-0 GCR Class 8C, the other pair being this 4-4-2 locomotive. The two locomotives shared as many common components as possible to allow easy conversion of the 8Bs to the 4-6-0 configuration - and both designs borrowed heavily from John G. Robinson's earlier GCR Class 8.

However, due to a much smaller than anticipated traffic increase, no further Class 8Cs were built, and instead a further 25 Class 8Bs were ordered and built between 1904 and 1906 - built with larger fireboxes as there was no longer a need to convert the locomotives to a 4-6-0 configuration. In 1909 and 1910, the original locomotives also received this larger firebox.

Despite Robinson commencing the conversion to superheaters in 1912, the conversion was not actually completed until 1936. At the same time, any locomotive requiring cylinder replacement saw both larger cylinders and piston valves being fitted - 20 of the class would eventually receive this modification. From 1921, the Ramsbottom safety valves were phased out and removed, to be replaced by Ross pop safety valves.

Following a high-speed incident that caused severe damage to its frame and cylinders, No. 1090 was rebuilt with 3 simple expansion cylinders in 1908, as a comparison to the GCR Classes 8D and 8E. These cylinders had their Stephenson valve gear replaced with Walschaerts valve gear, which was the only application of this valve gear, excluding railcars, on a GCR locomotive. The experiment was reverted in 1922 when No. 1090 was rebuilt, with the original 2 cylinders and Stephenson valve gear being refitted.

Following the merger of the GCR into the London & North Eastern Railway, the class became known as the LNER Class C4. In 1925, several C4s were fitted with the LNER's trademark "Flowerpot" chimney, with one locomotive, No. 6085, also modified to fit the LNER composite gauge - a modification that the remainder of the class underwent between 1936 and 1939. In 1929, a further LNER classification change was made - the non-superheated locomotives were designated Class C4/1, those fitted with superheaters but still utilized slide valves Class C4/2, and those with both superheaters and piston valves became Class C4/3. By 1932, the re-gauged No. 6085 had been given the designation Class C4/4 - which became more populated as Class C4/3s were cut down. By 1939, all Class C4/1s and Class C4/3s had been redesignated as either Class C4/2s or Class C4/4s - by this time all locomotives were both superheated and had also been cut down to the LNER composite gauge.