LNWR Dreadnought Class
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No. 507 Marchioness of Stafford
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| Type and origin | |
|---|---|
| Power type | Steam |
| Designer | F. W. Webb |
| Builder | Crewe Works |
| Serial number | 2975–2804, 2886–2905, 3012–3021 |
| Build date | 1884–1888 |
| Total produced | 40 |
| Specifications | |
|---|---|
| Configuration: |
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| • Whyte | 2-2-2-0 |
| • UIC | 1AA n3v |
| Gauge | 4 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) |
| • Leading | 8 ft 5 in (2.57 m) |
| • Drivers | 9 ft 8 in (2.95 m) |
| Loco weight | 43 long tons (44 t) |
| Boiler: |
|
| • Diameter | 4 ft 2 in (1.27 m) |
| • Tube plates | 11 ft 0 in (3.35 m) |
| Boiler pressure | 175 lbf/in2 (1.21 MPa) |
| Heating surface | 1,401.5 sq ft (130.20 m2) |
| Cylinders | Three: two HP (outside), one LP (inside) |
| High-pressure cylinder | 14 in × 24 in (356 mm × 610 mm) |
| Low-pressure cylinder | 30 in × 24 in (762 mm × 610 mm) |
| Valve gear | Joy |
| Career | |
|---|---|
| Operators | London and North Western Railway |
| Scrapped | December 1903 – July 1905 |
| Disposition | All scrapped |
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 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.
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.
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