LNWR Dreadnought Class

The LNWR Dreadnought class was a class of 40 passenger three-cylinder compound 2-2-2-0 locomotives designed by F. W. Webb for the London and North Western Railway, and manufactured by them in their Crewe Works between 1884 and 1888. The railway also commissioned the Beyer, Peacock and Company to construct an additional locomotive of the design for the Pennsylvania Railroad.[1]

LNWR Dreadnought class
No. 507 Marchioness of Stafford
Type and origin
Power typeSteam
DesignerFrancis Webb
BuilderCrewe Works
Serial number2975–2804, 2886–2905, 3012–3021
Build date1884–1888
Total produced40
Specifications
Configuration:
​
 • Whyte2-2-2-0
 • UIC1AA n3v
Gauge4 ft 8+1⁄2 in (1,435 mm)
Leading dia.3 ft 6 in (1.067 m) + tyres
Driver dia.6 ft 0 in (1.829 m) + tyres
Wheelbase:
 • Engine		18 ft 1 in (5.51 m)
 • Leading8 ft 5 in (2.57 m)
 • Drivers9 ft 8 in (2.95 m)
Loco weight43 long tons (44 t)
Boiler:
​
 • Diameter4 ft 2 in (1.27 m)
 • Tube plates11 ft 0 in (3.35 m)
Boiler pressure175 lbf/in2 (1.21 MPa)
Heating surface1,401.5 sq ft (130.20 m2)
CylindersThree: two HP (outside), one LP (inside)
High-pressure cylinder14 in × 24 in (356 mm × 610 mm)
Low-pressure cylinder30 in × 24 in (762 mm × 610 mm)
Valve gearJoy, Slip-eccentric.
Career
OperatorsLondon and North Western Railway
ScrappedDecember 1903 – July 1905
DispositionAll scrapped

Design

The design featured a boiler pressed to 175 lbf/in2 (1.21 MPa) delivering saturated steam to two outside 14-inch (356 mm) high-pressure cylinders, which exhausted to one 30-inch (762 mm) low-pressure cylinder inside the frames. All three cylinders had a stroke of 24 inches (610 mm); the high-pressure cylinders drove the rear wheels, while the low-pressure drove the leading driving wheels. As the two pairs of driving wheels were not connected, the locomotives were "duplex drive" or "double-singles".

They were a development of Webb's Experiment class; they had larger boilers and smaller driving wheels, and while the Joy valve gear for the HP and LP cylinders could still be independently adjusted, it was now also possible to reverse both sets simultaneously. The inside valve gear was subsequently amended to the loose or slip-eccentric system, thus giving automatic reversal.[2]

Decline

When George Whale become chief mechanical engineer of the LNWR in 1903, he started a programme of eliminating Webb's over-complicated duplex compound locomotives. Consequently, the class was scrapped between December 1903, and July 1905, having been replaced by Whale's Experiment class.

References
  1. Nock, O. S., et al. Railways at the Turn of the Century, 1895-1905. Blandford P., 1969.
  2. Baxter 1979, pp. 194–195.
  3. Baxter 1979, p. 195.
  • Baxter, Bertram (1979). Baxter, David (ed.). British Locomotive Catalogue 1825–1923, Volume 2B: London and North Western Railway and its constituent companies. Ashbourne, Derbyshire: Moorland Publishing Company. ISBN 0-903485-84-2.
  • Morandière, Jules (1885). "Locomotive compound de M. Webb, modèle de 1884 pour trains rapides et lourds", Revue Générale des Chemins de fer et des Tramways, VII. Dunod éditeur, pp.75-79, fig. VI.
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