THE W1 (AND ONLY!)

摘要

In the earliest days of the steam locomotive, four wheels sufficed for the size and weight of very primitive machines. After all, the horses they replaced managed with only four legs! As time passed, larger and more powerful locos emerged, needing extra sets of wheels, until in 1908, the first British Pacific arrived on the scene - followed just four years later by a 4-6-4 tank engine design introduced by the London Tilbury & Southend Railway. Then, in 1929, Darlington Works constructed the first, and as it turned out, the only 4-6-4 tender engine to run in Britain. It was a highly experimental machine, the product of five years' development work by Nigel Gresley for the London & North Eastern Railway, and it entered traffic in June 1930 as a four-cylinder compound featuring a high-pressure (450psi) Yarrow marine water-tube boiler. Strictly speaking, its wheel arrangement could best be described as a 4-6-2-2, as the two rear axles were different in design - one of outside bearing type and the other inside bearing.