LNER 0-6-2 Locomotives in Great_Britain

Class N7/3 (Locobase 20988)

Data from Richard Marsden, "The Hill N7 (GER Class L77) 0-6-2T Locomotives" in his LNER Encyclopedia at [], last accessed 28 February 2022.

Locobase 20987 covers the first 80 N7/1s and N7/2s built for the LNER in 1923-1926 after the Grouped railway adopted the original N7 design described in Locobase 20531. Much was kept, including the "cramped" location between the frames for the constant-lead radial gear, 9" (177 mm) long-travel piston valves, driver diameter, and general layout.

A big change was the adoption of the LNER's Diagram 101 round-topped boiler, although the actual difference in heating surface areas came to very little. Doncaster supplied 32 and William Beardmore 20 (works numbers 305-324).

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Class N7GE, N7/1, N7/2 (Locobase 20987)

Data from "New Suburban Tank Locomotives, London & North Eastern Ry - Great Eastern Section ", Locomotive Magazine, Volume XXX [30], No 377 (15 January 1924), p. 1; and Richard Marsden, "The Hill N7 (GER Class L77) 0-6-2T Locomotives" in his LNER Encyclopedia at [], last accessed 28 February 2022.

In 1915, the Great Central Railway, later one of the LNER's constituent railways, introduced the 0-6-2T wheel arrangement to serve its overmatched suburban traffic. One of the two prototypes used a saturated boiler, the other, described in Locobase 20531, was fitted with a 12-element Robinson superheater. Like both prototypes, 9" (177 mm) piston valves supplied steam to the cylinders and the boiler was mated to a Belpaire firebox.

Masden writes that the N7 design "impressed the LNER and it was adopted as a Group Standard to complement Gresley's N2 0-6-2T design." The big railway especially liked the small drivers, which encouraged rapid acceleration between "closely-positioned" stations. Because they were delegated to serving LNER suburban routes such as the Metropolitan City Widened Lines in the the south, Marsden adds, they were set up for left-hand drive and sported lower boiler and cab mountings.

Given the size of the LNER group, this was quite an endorsement and the railway would build or order 112 engines between 1925 and 1928. Of these, Gorton Works built the first 50, which retained the Belpaire firebox and 9" piston valves actuated by short-travel, constant-lead radial gear.. Robert Stephenson & Company produced the next 80, which introduced long-travel valves.

Short- or long-travel, the layout of the Walschaert gear "proved to be problematic," writes Marsden, because of its "cramped location" inside the frame.. His summary notes ". The cramped location resulted in less than ideal linkages and heavy forces acting on parts of the gear. The combination lever pins experienced heavy wear, and the anchor bracket bolts often failed." And the long-travel gear suffered bent valve spindles and the stress sometimes broke anchor brackets.

Former Great Eastern drivers now piloting N7s for the LNER's GE Section continued the practice of coasting "with the engine coasting in full gear followed by a sudden change in cut-off at speed ...complete failure in the valve motion" often followed. A GE Section advisory suggesting coasting at half cutoff reduced but didn't completely fix the problem.

Locobase 20988 describes the last 32 "round topped" N7s. 19 of the N7/GEs and 18 of the N7/1s eventually received those boilers as well.