The reference for locomotives and railcars
Central Pacific “Mastodon” and class GE
Southern Pacific class TW-4
United States | 1882 | 21 produced
Drawing of the locomotive in its original condition by Richard Ward
Drawing of the locomotive in its original condition by Richard Ward

Although the Baltimore and Ohio had procured a locomotive with a 4-8-0 wheel arrangement in 1855 with the “Centipede”, the “Mastodon” was the first successful locomotive with this wheel arrangement. Completed in 1882, it was the heaviest locomotive in the world at the time. Shortly after its roll-out, test runs were undertaken in the Sierra Nevada with the locomotive number 229, during which, as expected, it performed significantly better than the existing Americans and Ten-Wheelers. When the operation was taken over by the Southern Pacific, it was renumbered 2925.

The shape of the boiler had some special features, including a firebox with a lower ceiling in the area of the driver's cab, which was around 13 feet long. The cylinders each had four slide valves, two of which were operated by one valve gear each. This type of cylinders was also inherited by “El Gobernator”, the even larger locomotive with 4-10-0 wheel arrangement.

Built by the Central Pacific workshops, number 229 was later sent to the Cooke Locomotive and Machine Works in New Jersey to set up series production. Depending on the source, 20 or 25 other machines were made, which had slightly larger cylinders. The first locomotive was later modernized and converted to oil firing, which probably also applies to the production locomotives. They were scrapped in June 1935.

VariantNo. 229GE
ManufacturerCentral PacificCooke
Axle config4-8-0 (Twelve-wheeler) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase24 ft 11 1/2 in23 ft 10 in
Fixed wheelbase15 ft 9 in13 ft 9 in
Total wheelbase53 ft 2 in47 ft 10 in
Service weight123,000 lbs144,100 lbs
Adhesive weight106,050 lbs114,000 lbs
Total weight186,000 lbs
Water capacity2,500 us gal
Fuel capacity10,700 lbs (wood)wood
Power sourcesteam
Estimated power600 hp (447 kW)750 hp (559 kW)
Optimal speed17 mph16 mph
Starting effort23,014 lbf29,143 lbf
Power Plant
Driver diameter54 in56 in
Boiler pressure135 psi160 psi
Expansion typesimple
Cylinderstwo, 19 x 30 intwo, 20 x 30 in
Grate area25.8 sq ft29.7 sq ft
Firebox area182 sq ft155 sq ft
Tube heating area1,173 sq ft1,883 sq ft
Evaporative heating area1,355 sq ft2,038 sq ft
Total heating area1,355 sq ft2,038 sq ft
Calculated Values
steam locomotive
last changed: 03/2022

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