Walter Chalmers came from a North British Railway (NBR) background. His father was an NBR employee for 43 years including some time as an Assistant Locomotive Superintendent. Chalmers followed his father's example and started as an apprentice with the NBR at Cowlairs, and stayed until after Grouping (1923).
Chalmers reached the position of Chief Draughtsman in 1904, and became Chief Mechanical Engineer of the NBR in January 1920 after Reid retired. Unfortunately Grouping was on the horizon, resulting in a very short tenure for Chalmers. This was not helped by the NBR directors ruling out all locomotive development, because they did not wish to prejudice the building of new group standard types within the new railway company (LNER). Chalmers' tenure was also hampered by the creation of a new department that included the functions of the Locomotive Running Superintendent.
Therefore it is not surprising that this lack of scope and time, led to very few achievements. Chalmers' tenure at the NBR is noted for maintenance and rebuilding, including the final D31 rebuilds. Although it never passed beyond the drawing board, Chalmers did create a three cylinder 2-8-0 mineral design of note.
Chalmers retired in June 1924 after R.A. Thom became the Mechanical Engineer for the the entire Scottish Area of the LNER.