Class R-1-b (Locobase 8122)
Data from NH 1962 St Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.
The United States Railroad Administration's Mountain design proved an excellent fit for the New Haven's fast freight requirements, so in addition to the 10 supplied during the USRA's administration, the railroad bought 39 more - 30 in 1920, 9 in 1924. Over time, the class (R-1, R-1-a, R-1-b) was updated with 95 sq ft of syphons and feedwater heaters. Maximum water evaporation rate was calculated at 56,555 lb/hour of which 22,825 lb/hour (40.4%) came from direct heating surfaces. As calculated by the New Haven, maximum steam consumption of 54,580 lb/hour yielded a 104% boiler factor.
To stave off the need to replace the class, the New Haven replaced the class's Southern valve gear with Baker gear in 1940 and fitted them with mechanical lubricators.
Thus equipped, all served the New Haven throughout World War II. Retirements occurred from the end of the war to the end of steam (1946-1951).
Class R-2a (Locobase 216)
This was a quirky mixture of new ideas and auxiliary equipment that in many cases was unsatisfactory. Specified by the New Haven's mechanical manager, WL Bean, the McClellon boiler had a water-tube firebox that leaked and let in cold air. Ultimately all New Haven engines originally delivered with the McClellon boiler had a conventional boiler fitted in 1929. Other problems included a balky DuPont-Simplex mechanical stoker (replaced by an HT-2 in the 1930s) and Southern valve gear replaced by Walschaerts or Baker gear. The design also came equipped with feedwater heater and a valve motion with limited cutoff.
The R-2s ran until 1949-1951.
Class R-3 (Locobase 217)
Boiler had feedwater heater. Unusual 3-cylinder variant of earlier R-2 that also came with the McClellon watertube firebox boiler design. Within a year they'd been reboilered. Note relatively small number of tubes and flues. Although the middle cylinder was a maintenance headache, financial stringency prevented conversion to a two-cylinder layout (as other railroads had done). They ran until 1949-1951.