LMS Royal Scot Class

LMS Royal Scot Class

LMS Royal Scot class No. 6137 'Vesta', 1928.

Type and origin Power type Steam Designer Sir Henry Fowler rebuilt: Sir William Stanier Builder North British Locomotive Company (50) LMS, Derby Works (20) Order number LMS Lot 41 (50) and 73 (20) Serial number NBL: 23595–23644 Build date 1927, 1930 Total produced 70

Specifications Configuration 4-6-0 UIC class 2′C h3 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Leading dia. 3 ft 3 1⁄2 in (1.003 m) Driver dia. 6 ft 9 in (2.057 m) Loco weight 84.90 long tons (86.26 t; 95.09 short tons) Tender weight New: 42.70 long tons (43.39 t; 47.82 short tons) later: 54.65 long tons (55.53 t; 61.21 short tons) Water cap New: 3,500 imp gal (16,000 l; 4,200 US gal) later: 4,000 imp gal (18,000 l; 4,800 US gal) Tender cap New: 5.5 long tons (5.6 t; 6.2 short tons) later: 9 long tons (9.1 t; 10 short tons) Boiler G10¼S; rebuilt: 2A Boiler pressure 250 psi (1.72 MPa) superheated Cylinders Three Cylinder size 18 in × 26 in (457 mm × 660 mm) Valve gear Walschaerts Valve type Piston valves

Performance figures Tractive effort 33,150 lbf (147.46 kN)

Career Operators London, Midland and Scottish Railway → British Railways Power class 6P; reclassified 7P in 1951 Numbers LMS: 6100–6169 BR: 46100–46169 Axle load class BR: Route Availability 9 Disposition Two preserved; remainder scrapped

The London, Midland and Scottish Railway (LMS) Royal Scot Class is a class of 4-6-0 express passenger locomotive introduced in 1927. Originally having parallel boilers, all members were later rebuilt with tapered type 2A boilers, and were in effect two classes.

Until the mid-1920s, the LMS had followed the Midland Railway's small engine policy, which meant that it had no locomotives of sufficient power for its expresses on the West Coast Main Line. These trains were entrusted to pairs of LMS/MR Midland Compound 4-4-0s between Glasgow and Carnforth, and a 4-6-0 locomotive of the LNWR Claughton Class, piloted by an LNWR George V 4-4-0, southwards to Euston station .

The Operating and Motive Power Departments of the LMS were satisfied with the small engine policy. However, in 1926 the Chief Mechanical Engineer, Henry Fowler, began the design of a compound Pacific express locomotive. The management of the LMS, faced with disagreement between the CME and the other departments, obtained a loan of a GWR Castle class locomotive, Launceston Castle, which was operated for one month between Euston and Carlisle.

Following the success of the Castle 4-6-0 in working on the LMS, a decision was taken to cancel Fowler's Pacific project, and to replace it with a 4-6-0 with three cylinders and a simple-expansion steam circuit. Because there was an urgent need for new express locomotives the LMS placed an order with the North British Locomotive Company of Glasgow for 50 engines. The North British, with its extensive drawing office and two works, possessed sufficient capacity to expedite the order within a year. The Derby drawing office and North British staff collaborated in designing the class, with the latter producing the working drawings. Fowler took little part in the design process, which was carried out by Herbert Chambers, Chief Draughtsman at Derby, and his staff. The LMS requested a set of drawings of the Castle class from the GWR, but didn't receive them. Instead a set of drawings of the SR Lord Nelson Class were obtained, and used for the design of the firebox. The main features of the design followed existing Derby practice, with the cylinders and valve gear being derived from the Fowler 2-6-4T, also being designed at Derby at that time.