Caledonian Railway 721 Dunalastair II Class
The Caledonian Railway Dunalastair II was the first development of McIntosh's celebrated Dunalastair 4-4-0 design, introduced in 1897 just one year after the original Dunalastair I had demonstrated the transformative effect of large-boiler design on Caledonian express performance. McIntosh moved quickly to capitalise on the success of the Dunalastair I by enlarging the boiler further and increasing the cylinder dimensions, producing a locomotive that was noticeably more powerful than the original class and capable of working the heaviest Caledonian express timings with a margin of power in hand.
The Dunalastair II retained the 6 ft 6 in coupled driving wheels and inside-cylinder layout of the original but specified a larger boiler with increased steam capacity, wider firebox, and cylinders of 19 in × 26 in compared to the Dunalastair I's 18½ in × 26 in. The boiler pressure was maintained at 175 psi. These relatively modest dimensional increases produced a locomotive that steamed more freely and sustained speed more easily on the West Coast main line grades, a performance advantage clearly perceptible to the drivers who worked both classes.
The Dunalastair II entered service in 1897 and joined the Dunalastair I fleet on the Caledonian's principal Anglo-Scottish expresses. The class attracted the same international attention as its predecessor: Belgian State Railways, which had already ordered Dunalastair I-type locomotives following their 1897 visit to Britain, also ordered examples to the Dunalastair II specification, confirming the Belgian railway authorities' view that McIntosh's large-boiler 4-4-0 represented the state of the art in express passenger traction.
The Dunalastair II was superseded in its turn by the Dunalastair III of 1899 and the IV of 1904, and the original examples were progressively displaced from the premier workings. None of the Dunalastair II class was preserved, making the entire original Dunalastair sequence — classes I through III — absent from the preservation record.
Design and development
McIntosh introduced the Dunalastair II at St Rollox in 1897 as an immediate enlargement of the successful Dunalastair I. Larger cylinders (19 in vs 18½ in bore), wider firebox, and increased boiler steam space gave a noticeably more powerful locomotive. Belgian State Railways, which had already ordered Dunalastair I-type locomotives, also ordered Dunalastair II examples, confirming international recognition of the design's excellence.
Service and withdrawals
Dunalastair IIs entered CR service in 1897 on the premier Anglo-Scottish expresses. Progressively superseded by the Dunalastair III (1899) and IV (1904). All withdrawn before the Grouping or in the early LMS era. None preserved.
Identification features
Inside-cylinder 4-4-0 with 6 ft 6 in coupled wheels, larger boiler than Dunalastair I.
Notable locomotives
- Various — none preserved
Allocations and regions
Polmadie (Glasgow), Carlisle Kingmoor, and Perth for principal Caledonian Anglo-Scottish express workings.
