Butte, Anaconda & Pacific 4-8-0 "Mastodon" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 23 (Locobase 11467)

Data from "Locomotive Building," The Railroad Gazette, Vol XXXVIII, No 24 (June 1905), p 205. See also the pamphlet that describes the BA & P's big push toward electrification among other such projects "Progress Made in Electrification of Railroads and the Economies Effected Thereby", Presented by the BLE and the BLFE, quoting among others, Railway Age articles from 1914, archived at []. (Many thanks to Dave Stephenson for pointing out the error in Locobase's sources that credited the BA&P with 4-10-0 locomotives.) Works numbers were 41223-41224 in January 1907.

The RA article of 25 December 1914, p. 1194, gives us an insight into how the Mastodons were used in order to contrast them to the greater power of the electrics:

"On October 10 a double-unit electric locomotive was put in the day freight service on the main line between East Anaconda and Rocker, a distance of 20.1 miles. The steam locomotive replaced in this instance was of the Mastodon type ... The standard train hauled on the trip west was 50 to 55 loaded ore cars weighing approximately 3,500 to 4,000 tons gross and the average running time of such trains where no stops were made was about l 1/2 hours, corresponding to an average speed of approximately 13.4 miles per hour."

How did the electrics compare?

"In the beginning the electric locomotive took only the standard train, but made the trip without stop in about one hour, corresponding to an average speed of 20 miles per hour. The ruling gradient on the westward trip is 0.3 per cent and about half the distance is down grade. On the 0.3 per cent grade with a 55-car train, the steam locomotive made about 7 miles per hour. The electric locomotives with similar train now make about 16 miles per hour on the same grade."

Note too: "The weight of the trains hauled by the electric locomotives on this run has been gradually increased up to 65 loaded ore cars averaging about 71 tons each, making the gross weight trailing about 4,620 tons. Adding 160 tons for the weight of the double-unit electric locomotives and 20 tons for the caboose makes a gross train weight of approximately 4,800 tons."

How about elsewhere on the BA& P?:

"The service on the Missoula Gulch line running between Rocker and Butte Hill yards was taken over for electrical operation on October 20. This line is 4.5 miles in length and the ruling gradient 2.5 per cent. The steam locomotives used on this line were of the Mastodon type ...Two complete crews had been required to handle this service during steam operation, averaging six trips per day each. A single crew with a double-unit electric locomotive has been doing this work successfully. Thirty-five to 45 loaded ore cars are taken down from Butte Hill yard to Rocker, and about an equal number of empties taken up. In addition to the empties, large quantities of timber and supplies for the mines are delivered over this line."

These two Twelve-wheelers were retired by 1917 and sold to the General Equipment Corporation.

Class 36 (Locobase 14417)

Data from "Schenectady Compound Mastodon Locomotive-Butte, Anaconda & Pacific Railway", Railway and Engineering Review (12 March 1898). Works numbers were 4594-4596.

These three Mastodons were based on the Northern Pacific's nearly identical X-class cross-compound engines (Locobase 929). The boiler had four fewer tubes, but all tubes were 11" longer, which resulted in more heating surface.

After the BA&P's electrification was completed in 1914, the class was idled until it was sold in 1917 to the Nashville, Chattanooga & St Louis as their class I1-44. They were renumbered 850-852 and simpled in 1920; see Locobase 14418.

The NC&StL operated the engines in transfer service or as heavy switchers for a decade or more, retiring the 852 in September 1926, the 850 in November 1927, and the 851 in May 1932.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID11467 14417
RailroadButte, Anaconda & PacificButte, Anaconda & Pacific
Number in Class23
Road Numbers23-2436-38/16-18
Number Built23
Valve GearStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)15.75 / 4.80
Engine Wheelbase (ft / m)26.75 / 8.15
Ratio of driving wheelbase to overall engine wheelbase 0.59
Overall Wheelbase (engine & tender) (ft / m)53.42 / 16.28
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)173,480 / 78,689154,000 / 69,853
Engine Weight (lbs / kg)212,740 / 96,497193,000 / 87,543
Tender Loaded Weight (lbs / kg)112,000112,000 / 50,802
Total Engine and Tender Weight (lbs / kg)324,740305,000 / 138,345
Tender Water Capacity (gals / ML)5500 / 20.834500 / 17.05
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)10 / 9 9.50 / 9
Minimum weight of rail (calculated) (lb/yd / kg/m)72 / 3664 / 32
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)56 / 142256 / 1422
Boiler Pressure (psi / kPa)210 / 14.50210 / 14.50
High Pressure Cylinders (dia x stroke) (in / mm)23" x 32" / 584x813 (1)23" x 32" / 584x813 (1)
Low Pressure Cylinders (dia x stroke) (in / mm)34" x 32" / 864x813 (1)34" x 32" / 864x813 (1)
Tractive Effort (lbs / kg)37,018 / 16791.1037,018 / 16791.10
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.69 4.16
Heating Ability
Tubes (number - dia) (in / mm)414 - 2.25" / 57328 - 2.25" / 57
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)15 / 4.5714 / 4.27
Firebox Area (sq ft / m2)206.51 / 19.19
Grate Area (sq ft / m2)34.75 / 3.2335 / 3.25
Evaporative Heating Surface (sq ft / m2)3380 / 314.132895 / 268.95
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)3380 / 314.132895 / 268.95
Evaporative Heating Surface/Cylinder Volume439.15376.14
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation72987350
Same as above plus superheater percentage72987350
Same as above but substitute firebox area for grate area43,367
Power L14579
Power MT262.21

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