Class K-1 (Locobase 64)

Firebox had 119 sq of thermic syphons and arch tubes.

Data conflict in 1947 Locomotive Cyclopedia. Illustration has superheater area as 2,450 sq ft; table records smaller superheater of 1924 sq ft. Locobase had suspected that the area represented a superheater refit, but the later acquisition of the W&LE 10 - 1948 Locomotive Diagram book in May 2005 - supplied by Allen Stanley from his extensive collection -- prompted another thought. The Locomotive Cyclopedia illustration may have listed "equivalent superheater area" or some other enhanced superheater measurement designed to indicate the effect of superheating on the boiler's basic steaming ability.

In any event, Locobase decided to adopt the information shown on the diagram. This includes weights that reflect a rebuilding of the first 15 to the later standard. 6416-6432, delivered later, were only slightly heavier. Alco supplied the first 10 in a batch in 1937 (builder's numbers 68829-68838). Five more -- 6411-6415 -- arrived in 1939 (69121-69125) and 7 more in 1941 (69429-69435); these were road numbers 6411-6422. This sizable order of Berks was completed in 1942 with 10 more (70021-70030) finishing off the class.

The 2-8-4s also finished off the I-2 2-6-6-2 compound Mallets (see Locobase 7897).

These represented Superpower design at its peak - big boilers and grates, long-stroke cylinders, lots of superheat, and relatively tall drivers to deliver the freight at speeds only dreamt of 25 years earlier.