LB&SCR I3 class
class of 27 two-cylinder 4-4-2T locomotives
The LB&SCR I3 class was a class of 4-4-2 steam tank locomotives designed by D. E. Marsh for suburban passenger service on the London, Brighton and South Coast Railway.
History
After introducing two unsuccessful designs of 4-4-2 tank locomotive with the I1 and I2 classes, Douglas Earle Marsh learned a lesson and provided a new design with a far larger firebox. The new design was a tank version of Robert Billinton's successful B4 class tender locomotives. At the time of its introduction locomotive engineers were beginning to take an interest in superheating and Marsh therefore ordered two locomotives from Brighton railway works for comparative purposes, one with a traditional saturated boiler and one incorporating the Schmidt superheater. These were built in October 1907 and March 1908 respectively.
Several months of trials proved that both locomotives were performing well and reliably, but the LB&SCR Board of Directors were still not convinced that the extra building costs associated with superheating was matched by lower running costs. Marsh therefore built four more superheated locomotives and six without superheating, between February 1909 and March 1910. By mid 1910, there was sufficient operating data to convince the Directors and all after this date were superheated. Five more locomotives appeared in 1910.
Both varieties of the I3 class proved themselves to be excellent locomotives but the superheated versions were significantly cheaper to run on express trains, especially when compared with the B4 and H1 classes.
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This entry incorporates text from “LB&SCR I3 class” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.