LNWR Whale Precursor Class

LNWR Precursor Class

No. 513, Precursor in photographic grey livery

Type and origin Power type Steam Designer George Whale Builder LNWR Crewe Works Serial number 4415–4419, 4440–4504, 4510–4549, 4660–4679 Build date 1904–1907 Total produced 130

Specifications Configuration 4-4-0 UIC class 2′B n2 or 2′B h2 Gauge 4 ft 8 1⁄2 in (1,435 mm) Driver dia. 6 ft 9 in (2.057 m) Loco weight 59.15 long tons (60.10 t) Boiler pressure 175 psi (1.21 MPa) Cylinders Two Cylinder size 19 in × 26 in (483 mm × 660 mm) or 20 1⁄2 in × 26 in (521 mm × 660 mm) Valve gear Joy

Performance figures Tractive effort 18,222 lbf (81.1 kN) or 20,640 lbf (91.8 kN)

Career Operators London and North Western Railway → London, Midland and Scottish Railway → British Railways Power class LMS: 2P, 3P Number in class 1 January 1923: 130 1 January 1948: 1 Withdrawn 1927–1949 Disposition All scrapped

The London and North Western Railway (LNWR) Precursor Class, the second to be known by that name, was a class of 4-4-0 steam locomotives.

The class were introduced by George Whale in 1904 and 130 examples were built by Crewe Works up to 1907. Their introduction allowed Whale to phase out his predecessor Francis Webb's unreliable compound locomotives. They were essentially a larger version of Webb's LNWR Improved Precedent Class. As built, they were saturated, though some were later superheated.

Whale's Experiment Class 4-6-0 were essentially an extended version built from 1905. An Atlantic tank engine version, Precursor Tank Class was also built from 1906. The Precursors were developed by Charles Bowen-Cooke into the superheated George the Fifth Class 4-4-0 (1910). The main visual difference was that the Precursors had separate splashers over each of the driving wheels while the Georges had combined splashers that covered both pairs.

The LNWR reused numbers and names from withdrawn locomotives, with the result that the numbering system was completely haphazard. Starting with the first of the class 513 Precursor in 1913, were given superheaters, the process continuing until just after grouping in 1923. Most of the superheated engines were also converted from having slide valves to piston valves.

This resulted in two main subclasses; saturated locomotives with 19 by 26 inches (480 mm × 660 mm) cylinders, and superheated locomotives with 20.5 by 26 inches (520 mm × 660 mm) cylinders. The LMS gave them the power classification 3P. The saturated engines were given the LMS numbers in the 5187–5266 series, though not all survived long enough to receive them. The superheated engines were given the LMS numbers 5270–5319 (5267–5269 were not used).