Buenos Aires Pacific 4-6-2 Locomotives in Argentina

Class Details by Steve Llanso of Sweat House Media

Class 1501 Class (Locobase 2583)

Data from "4-6-2 Passenger Locomotive, Buenos Ayres & Pacific Ry.", The Locomotive, Volume XVI [16] (15 June 1910), p. 118-119; and "'Express" Passenger Locomotive for the Buenos Ayres[sic] & Pacific Railway Co.", North British Locomotive Company-Glasgow", Franco-British Exhibition, Machinery Hall, Building No 48 (White City, Shepherds Bush, London: 1908). Works numbers were 18745-18756 in 1909, 19034, and 19360-19370 in 1911.

These were relatively small Pacifics with small drivers for express service. Hollingsworth (1982) notes that because of its weak financial condition, these were the last express passenger locomotives ordered by the BAP before it was nationalized 38 years later. They were hulking engines with collared smokeboxes and block Belpaire fireboxes. In their original green livery they looked quite colorful, but in the General San Martin National Railroad days after 1948, they took on a dusty black pall that lasted until their retirement in the 1960s.

[], a Spanish-language website with code for a train simulator, says there were 18 of this class and that they were the first of the wheel arrangement to be brought to Argentina. The writer notes that while European Pacifics had grate areas of at least 3.7 sq meters (39.8 sq ft), this class got by with 2.5 sq meters. The steam space above the tubes was unusually large to reduce the foaming that operation at higher altitude could induce and that would reduce the amount of steam actually entering the cylinders. The design's piston valves served superheated steam to the cylinders.

They entered service pulling trains such as El Cuyano and El Internacional out of Buenos Aires toward Mendoz and San Juan. El Internacional later scaled the Andes to terminate at Santiago, Chile. In 1934, 8 of the class were converted to oil-fired fireboxes.

Class Class 21 (Locobase 4297)

Data provided by Carlos Alberto Fern+ndez Priotti in Bryan Attewell ([] Steam Locomotive simulator program (December 2000).

Attewell comments that it's interesting to compare Argentine Pacifics with their British contemporaries. Taking this engine, for example, you see one that adopted the cylinder size and number, the boiler size and relatively meager superheat, but used a much larger grate.

Principal Dimensions by Steve Llanso of Sweat House Media

Class1501 ClassClass 21
Locobase ID2583 4297
RailroadBuenos Aires Pacific (BAP)Buenos Aires Pacific (BAP)
Number in Class1812
Road Numbers1501-15242101-2112
Number Built1812
BuilderNorth BritishArmstrong Whitworth
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.17 / 3.71
Engine Wheelbase (ft / m)34.58 / 10.54
Ratio of driving wheelbase to overall engine wheelbase 0.35
Overall Wheelbase (engine & tender) (ft / m)65.19 / 19.87
Axle Loading (Maximum Weight per Axle) (lbs / kg)40,000 / 18,144
Weight on Drivers (lbs / kg)117,600 / 53,343120,960 / 54,867
Engine Weight (lbs / kg)181,216 / 82,198
Tender Loaded Weight (lbs / kg)141,820 / 64,329
Total Engine and Tender Weight (lbs / kg)323,036 / 146,527
Tender Water Capacity (gals / ML)6605 / 25.025847 / 22.15
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)2350 / 8894.8013.20 / 12
Minimum weight of rail (calculated) (lb/yd / kg/m)65 / 32.5067 / 33.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)67 / 170271 / 1803
Boiler Pressure (psi / kPa)150 / 10.30194.40 / 13.40
High Pressure Cylinders (dia x stroke) (in / mm)21" x 26" / 533x66018" x 26" / 457x660 (3)
Tractive Effort (lbs / kg)21,820 / 9897.4029,408 / 13339.26
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.39 4.11
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)12.37 / 3.7718 / 5.49
Firebox Area (sq ft / m2)156 / 14.49
Grate Area (sq ft / m2)27 / 2.5142.20 / 3.92
Evaporative Heating Surface (sq ft / m2)1601 / 148.742103 / 195.45
Superheating Surface (sq ft / m2)431 / 40.04286 / 26.58
Combined Heating Surface (sq ft / m2)2032 / 188.782389 / 222.03
Evaporative Heating Surface/Cylinder Volume153.60183.09
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation40508204
Same as above plus superheater percentage49019188
Same as above but substitute firebox area for grate area28,314
Power L110,060
Power MT565.78

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