page_title: SR USA class
section_title: Construction and adaptation
hierarchical_section_title: SR USA class / Construction and adaptation
context_page_description: The SR USA class were ex-United States Army Transportation Corps S100 Class steam locomotives purchased and adapted by the Southern Railway after the end of the Second World War to replace the LSWR B4 class then working in Southampton Docks. SR staff nicknamed them "Yank Tanks".
context_section_description: Following purchase, members of the class were fitted with steam heating, vacuum ejectors, sliding cab windows, additional lamp irons and new cylinder drain cocks. Further modifications became necessary once the locomotives started to enter traffic, including large roof-top ventilators, British-style regulators (as built they had US-style pull-out ones), three rectangular cab-front lookout windows, extended coal bunkers, separate steam and vacuum brake controls and wooden tip-up seats. This meant that it took until November 1947 for the entire class to be ready for work. Radio-telephones were later installed on the footplate to improve communication on the vast network of sidings at Southampton.
  The class was allocated the British Railways (BR) power classification 3F following nationalisation in 1948.
caption: Original drawings for the S100, dated 29 November 1941.
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