Arica La Paz / Arica-La Paz Articulated Locomotives in Chile

Class Details by Steve Llanso of Sweat House Media

Class 17 (Locobase 20840)

Data from "The Hanomag Journal", Railway and Locomotive Engineering, Volume XXVII [27] , No 1 (January 1914), pp.39-40 ; and Martin Coombs, Chilean steam locomotive list, Part 3, Metre gauge locomotives, 2016, p 17, downloaded from [], last accessed 8 April 2022. Works numbers were 6776-6779 in 1913.

Coombs contributed the somewhat cheeky comment that the 17 "disgraced itself on an opening day train." As the Mallet climbed up the line, it stalled at km 49 (MP 30.5) because it had melted its firebox's firebars.

At the other end of this quartet's career, Coombs reported the 20 as still in service in 1955.

See Locobase 10993 for details on theA-LP's challenging profile and operating conditions.

Class 24 (Locobase 10993)

Data from Record of Recent Construction #91 (Baldwin Locomotive Works, 1918), p.18-19. See also DeGolyer, Volume 66, pp. 390+. Works numbers were 48195-48196 in March 1918 and 48219 in April.

Arica is a Chilean port and La Paz the capital of landlocked Bolivia. This narrow-gauge line scaled the Andes at altitudes as great as 14,000 ft (4,267 m) above sea level.

Special Agent Frederic M Halsey reported in 1918 in Special agents series, Issue 169 - Investments in Latin America and the British West Indies (Washington, DC: United States. Bureau of Manufactures, United States. Bureau of Foreign and Domestic Commerce, 1918) on the route this railroad had to take:

"The Arica-La Paz Railway extends from the Chilean port of Arica to La Paz, Bolivia, and is the shortest route between the latter city and the coast. The main route from La Paz to Arica is 281 miles, comparing with 534 miles La Paz to Mollendo (Peruvian Corporation route) and 718 miles to Antofagasta (Antofagasta & Bolivia Railway). The highest altitude (13,986 feet) is reached near the Bolivian boundary. A total of 28 miles of rack rail is in use, the maximum gradient being 6 per cent. There are no tunnels on the Bolivian section although several are found in the Chilean section. The run from the Chilean-Bolivian boundary to La Paz is 150 miles, including 6 miles of the Guaqui-La Paz Railway from Alto de La Paz to the city."

Such were the conditions that awaited this trio of articulateds. The class was designed to a metric axle loading limit of 12 tonnes on a railway with a maximum cut of 147 feet (44.8 m) and a minimum curve radius of 100 metres (328 feet) or 17 1/2 degrees. At the time of the order, the Arica a La Paz operated some Henschel-built Mallets that they reported slipped "very badly." The specs included the instruction that "we are to do what we can to prevent this on these locomotives." As they would operate on the rack section, although without engaging the rack itself, clearances had to ensure that the underparts of the engine cleared the rack when the locomotive was steaming.

Already equipped with a large grate, the 24s had a Gaines wall and brick arch that turned the front part of the firebox into a combustion chamber. All cylinders were fed by piston valves; 9" (229 mm) valves supplied the HP cylinders, 11" (279 mm) valves worked with the LP cylinders. Baldwin further notes that both the pilot and the rail guard at the tender end had "...exceptionally strong bracing, in order to knock off any rocks which may happen to fall on the track."

In 1942, the three engines went to Chile's FC Estado as 3525, 3626, and one more, possibly 3628.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID20840 10993
RailroadArica-La PazArica La Paz
Number in Class43
Road Numbers17-20/20-2324-26
Number Built43
Valve GearHeusingerWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m) 8.60 8.50 / 2.59
Engine Wheelbase (ft / m)2524.42 / 7.44
Ratio of driving wheelbase to overall engine wheelbase 0.34 0.35
Overall Wheelbase (engine & tender) (ft / m)44.8850.37 / 15.35
Axle Loading (Maximum Weight per Axle) (lbs / kg)26,450 / 11,998
Weight on Drivers (lbs / kg)137,987 / 62,590150,000 / 68,039
Engine Weight (lbs / kg)137,987 / 62,590150,000 / 68,039
Tender Loaded Weight (lbs / kg)52,99980,000 / 36,287
Total Engine and Tender Weight (lbs / kg)190,986 / 62,590230,000 / 104,326
Tender Water Capacity (gals / ML)21994000 / 15.15
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)12006 / 6
Minimum weight of rail (calculated) (lb/yd / kg/m)38 / 1942 / 21
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)43.50 / 110543.50 / 1105
Boiler Pressure (psi / kPa)203.10 / 14200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)15.75" x 21.65" / 400x55016" x 22" / 406x559
Low Pressure Cylinders (dia x stroke) (in / mm)24.02" x 21.65" / 610x55025" x 22" / 635x559
Tractive Effort (lbs / kg)29,810 / 13521.6031,229 / 14165.25
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.63 4.80
Heating Ability
Tubes (number - dia) (in / mm)105 - 2" / 51
Flues (number - dia) (in / mm)18 - 5.5" / 140
Flue/Tube length (ft / m)16.83 / 5.13
Firebox Area (sq ft / m2)134 / 12.45
Grate Area (sq ft / m2)30.14 / 2.8031.30 / 2.91
Evaporative Heating Surface (sq ft / m2)1991 / 1851479 / 137.45
Superheating Surface (sq ft / m2)363 / 33.74
Combined Heating Surface (sq ft / m2)1991 / 1851842 / 171.19
Evaporative Heating Surface/Cylinder Volume407.83288.89
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation61216260
Same as above plus superheater percentage61217512
Same as above but substitute firebox area for grate area32,160
Power L16283
Power MT554.07

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