| LNWR Precursor Class (Whale) |
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| Type and origin |
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| Power type | Steam |
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| Designer | George Whale |
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| Builder | LNWR Crewe Works |
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| Serial number | 4415–4419, 4440–4504, 4510–4549, 4660–4679 |
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| Build date | 1904–1907 |
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| Total produced | 130 |
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| Specifications |
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Configuration:
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| • Whyte | 4-4-0 |
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| • UIC | 2′B n2 or 2′B h2 |
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| Gauge | 4 ft 8+1⁄2 in (1,435 mm) |
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| Driver dia. | 6 ft 9 in (2.057 m) |
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| Loco weight | 59.15 long tons (60.10 t) |
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| Boiler pressure | 175 psi (1.21 MPa) |
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| Cylinders | Two |
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| Cylinder size | 19 in × 26 in (483 mm × 660 mm) or 20+1⁄2 in × 26 in (521 mm × 660 mm) |
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| Valve gear | Joy |
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| Performance figures |
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| Tractive effort | 18,222 lbf (81.1 kN) or 20,640 lbf (91.8 kN) |
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The London and North Western Railway (LNWR) "Precursor" Class was a type of 4-4-0 ("American") steam locomotive designed by the company's Chief Mechanical Engineer, George Whale. Introduced in 1904, it should not be confused with the LNWR 2-4-0 "Precursor" Class of 1874 designed by Francis Webb, the last example of which was scrapped in 1895. In 1906, a 4-4-2T ("Atlantic") tank variant of Whale's engine, the "Precursor Tank" Class, also entered service.
