1937: The Public Debut of a New Class of Locomotives Built for Service in Scotland

March 4, 1937

After five weeks of crew training at a depot in the Scottish city of Glasgow, the prototype of the Class K4 locomotive of the London and North Eastern Railway (LNER) made its public debut as a self-propelled vehicle for passenger trains.

This prototype constituted what became a new class of 2-6-0 steam locomotives. In accordance with the steam locomotive classifications developed by mechanical engineer Frederick Methvan Whyte (1865-1941) in 1900, the designation 2-6-0 represents a wheel arrangement of two leading wheels on one axle, a total of six powered and coupled driving wheels on three axles, and no trailing wheels.

The Class K4 prototype No. 3441 — formally named Loch Long after a body of water in Scotland — had been designed by Nigel Gresley (1876-1941), who was LNER’s innovative and prolific chief mechanical engineer from 1923 until his death. Gresley envisioned this class of locomotives as an optimal one for the steep grades of LNER’s West Highland Line in Scotland.  

It soon became evident, however, that Loch Long’s steam pressure of 180 pounds per square inch (psi) — calculated in metric units as 1.24 megapascal (MPa) — did not result in any notable level of speed for this locomotive whenever it ascended the West Highland Line’s formidable inclines. In response to Loch Long’s initially sluggish performance, Gresley increased the steam pressure for this locomotive to 200 psi (1.38 MPa). This adjustment enabled Loch Long to more quickly haul 300-ton (272.2-metric ton) trains up difficult and daunting gradients. In addition, this locomotive was now able to achieve speeds of up to approximately 60 miles (97 kilometers) per hour on level ground.

The ultimately successful runs of Loch Long led to the construction of five more LNER K4 Class locomotives, all of which began operations between July 1938 and January 1939. The names of these locomotives were the Great Marquess (shown in the accompanying photo taken in 2011); Cameron of Lochiel; Lord of the Isles; MacCailin Mor; and MacLeod of MacLeod. This class of steam locomotives would remain in regular service until the 1960s.

Photo Credit: Andywebby (licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license at https://creativecommons.org/licenses/by-sa/3.0/deed.en)

For more information on the LNER K4 Class of locomotives, please check out https://preservedbritishsteamlocomotives.com/k4-61993-61998-2-6-0-lner-gresley/

Additional information on Nigel Gresley and the locomotives that he designed is available at https://en.wikipedia.org/wiki/Nigel_Gresley and https://gresley.org/gresley-locomotives/