The reference for locomotives and railcars
Santa Fé classes 1157ff and 3300
United States | 1910 | 64 produced
Class 3300 with steel rings as a connection between the boiler halves
Class 3300 with steel rings as a connection between the boiler halves

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
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
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.

Variant1157, 1160117011583300
ManufacturerSanta FéBaldwin
Axle config2-6-6-2 (Mallet Mogul) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase57 ft 3 in56 ft 5 in
Fixed wheelbase13 ft 8 in
Total wheelbase89 ft 7 in89 ft 3 in
Service weight370,200 lbs359,000 lbs400,800 lbs
Adhesive weight304,300 lbs304,000 lbs290,000 lbs329,400 lbs
Total weight534,700 lbs545,000 lbs533,800 lbs586,200 lbs
Axle load54,700 lbs62,900 lbs
Water capacity9,000 us gal
Fuel capacity28,000 lbs (coal)24,000 lbs (coal)
Power sourcesteam
Estimated power2,600 hp (1,939 kW)2,750 hp (2,051 kW)3,200 hp (2,386 kW)3,175 hp (2,368 kW)
Optimal speed27 mph28 mph33 mph32 mph
Starting effort62,491 lbf
with start valve74,989 lbf
Power Plant
Driver diameter69 in
Boiler pressure220 psi
Expansion typecompound
Cylindersfour, HP: 24 x 28 in
and LP: 38 x 28 in
Grate area53.5 sq ft52.5 sq ft64.3 sq ft63.5 sq ft
Firebox area195 sq ft234 sq ft245 sq ft
Tube heating area3,748 sq ft4,860 sq ft5,237 sq ft5,162 sq ft
Evaporative heating area3,943 sq ft5,094 sq ft5,471 sq ft5,407 sq ft
Superheater area1,063 sq ft955 sq ft957 sq ft
Total heating area5,006 sq ft6,049 sq ft6,426 sq ft6,364 sq ft
Calculated Values
steam locomotive
flexible boiler
last changed: 03/2022

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