Class X (Locobase 929)

Some data from Traite pratique de la machine locomotive ... By Maurice Demoulin, 1898

Librairie polytechnique, Baudry et Cie, p 404-405

These 12-wheelers were delivered as compounds in 1897 and intended, said Demoulin, for the Helena-Missoula section. This portion of the NP had a ruling grade of 2.2% that covered almost 17 miles. The writer noted a horsepower output of 1,300 continuous over a 3-hour period. Although regarded as mammoths of their day when they first appeared, this quartet would soon be outstripped in their dimensions on the NP by Schenectady-built Ten-wheelers (Locobase 9542).

Rebuilt 1917 with two 20" x 30" cylinders and a superheater, TE of 32,454. See Locobase 6561.

NB: The evaporative heating surface is an estimate calculated by adding the calculated tube heating surface to the reported firebox heating surface.

Class X - superheated (Locobase 6561)

Data from a 1944 Northern Pacific Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection. Locobase is intrigued by all this attention paid to a rarely used wheel arrangement: superheater, piston valves, new valve gear, new tubes and flues ... The later diagram describes the Xs as "switchers" and it's possible that they filled a key niche in short-haul freight.