4-6-4 Steam Locomotives in Great Britain

Class W1 (Locobase 3774)

Data from Richard Marsden, "The Gresley W1 4-6-4 "Hush-Hush" Locomotive" on his LNER Encyclopedia website at [], last accessed 4 November 2020. (Thanks to Patrick Shivley for his 17 May 2021 email commenting on the 4-6-2-2 proposed by Glover; see below.)

A Gresley original, this large passenger engine had a watertube boiler that probably contributed to its position as the only Hudson-type tender engine to run in Great Britain. Beginning in 1924, Gresley approached well-known ship boiler designer Yarrow & Company to combine their efforts to build a locomotive with a similar layout.

Marsden's detailed account includes his classic understatement: "Fitting a water-tube boiler into the restrictive British loading gauge was proving a problem." For example, the team adopted a 4-6-2 layout, but that left no room for the driver and fireman. Adding a trailing axle made room as did modifying tube lengths. Locobase suggests reading the LNER Encyclopedia to follow Gresley's exploration of the Gresley-Yarrow watertube boiler. (Hint: Look for the word(s) "leak" or "leaks". They turn up throughut the water-tube years.)

Introduced in 1928, the 10000 accumulated about 90,000 miles in service. Marsden sums up the result of this experiment: "On 13th October 1936, the water-tube boiler W1 made its last journey: from Darlington Works to Doncaster Works to be rebuilt with a conventional fire-tube boiler. Out of the 1,888 days since it was built, No. 10000 spent 1,105 days in Darlington Works."

Gresley rebuilt the four-cylinder engine in 1937 to the three-cylinder layout shown in this entry.

Glover (1967) commented that pedants would probably classify this engine as a 4-6-2-2 as each of the trailing axles was independently suspended. According to Glover, the forward non-powered axle had Cartazzi axle boxes for lateral movement and the after one was a Bissell truck.

Patrick Shivley's comment that the two axles were not independently suspended led Locobase to wonder if any other locomotive had ever been Whyte-classified using two numbers for the trailing non-powered axles. Finding none, he rules that Glover was mistaken: No matter how the trailing-truck's suspension was laid out, its position in the Whyte system was taken up by only one number-hence, 4-6-4.