4ft 6in Tank

The LNWR 4 ft 6 in Tank class was a series of 2-4-2 suburban tank locomotives designed by Francis Webb, Chief Mechanical Engineer of the London and North Western Railway from 1871 to 1903. Built at Crewe Works from 1879, they were intended for the LNWR's suburban and short-distance passenger services, particularly on the growing network of commuter services radiating from London Euston and Birmingham.

Webb specified the 2-4-2T wheel arrangement — two leading wheels, four coupled driving wheels, two trailing wheels — which gave better riding at speed than the older 0-4-2T or 0-6-0T configurations, while the side tanks provided adequate water capacity for suburban run-round distances without tendering. The 4 ft 6 in coupled wheel diameter was well matched to the frequent stop-and-start rhythms of suburban working, giving sufficient tractive effort at low speeds without sacrificing too much in terms of maximum speed on the slightly longer inter-suburban runs.

Webb was a prolific and controversial CME, capable of producing straightforward practical designs for everyday suburban work alongside the more ambitious — and often problematic — compound express locomotives that occupied much of his later career. The 4 ft 6 in tanks fell into the former category: workmanlike, reliable, and well-suited to their purpose. They worked LNWR suburban services for many years before being displaced by larger and more modern tank designs. None was preserved.