The Santa Fe started in 1910 with one of the few attempts to develop a large mallet with large coupled wheels for use in front of passenger trains. The large wheel diameter resulted in a considerable overall length, which made special demands on flexibility in curves. Since the long boiler was an obstacle, the idea of a divided boiler came up.
Detail of the connection using steel rings
The locomotive with the number 1157 was assembled from the parts of two former Prairie locomotives (2-6-2), that now had the wheel arrangement 2-6-6-2. The greatest difficulty lay in connecting the two halves of the boiler in a flexible and tight manner. The water space between the two halves of the boiler was separated, while the hot smoke, complete with sparks and individual lumps of slag, passed from the rear to the front part of the boiler.
Class 1170 with ball joint
Locomotive Magazine, May 1911
The rear part of the boiler produced the steam and superheated it before it entered the rear high-pressure cylinders. The exhaust steam then entered the front part of the boiler where it was reheated and then sent to the front low pressure cylinders. The front part also served as a feedwater heater. The connection between the halves of the boiler was made by means of fifty steel rings nested alternately within each other. In operation, slag chunks often wedged themselves between the rings, which then burst in the next curve. This connection was adapted in later locomotives and a variant as a ball joint was also created.
Although it was not possible to find a completely satisfactory solution for the connection between the boiler halves, twelve more engines of this type were built in 1910 as classes 1158 and 1160. At the same time, 27 class 1170 units with a very long, one-piece boiler were built. Despite these circumstances, the Santa Fe had 24 examples of a heavier version with a two-piece boiler built in 1911. These were given the numbers from 3300 to 3323 and were thus referred to as Class 3300. Due to the continuing problems with these locomotives, they were later forced to either scrap them or dismantle them for the construction of Prairie locomotives as early as the 1920s.