Lehigh Valley 4-8-2 "Mountain" Locomotives in the USA

The Lehigh Valley Railroad received six 3-cylinder "Mountain" type locomotive from the American Locomotive Company in 1923 and 1924. These locomotives were designated Class S-1 and were assigned road numbers 5000 through 5005. They had 25 x 28 cylinders, 69" drivers, a 200 psi boiler pressure, a tractive effort of 64,700 lbs and a weight of 369,000 pounds. Initially, all six of these new 4-8-2s were used for fast freight, but high maintenance cost soon had them working passenger service.

In 1939, the Lehigh Valley rebuilt all six of the Class S-1s. The three 25 x 28 cylinders were replaced with two 28 x 32 cylinders which reduced the tractive effort from 64,700 lbs to 61,811 lbs. The rebuilt locomotives weighed 370,000 pounds and were designated as Class S-2.

The Lehigh Valley retired the Class S-2s in 1948 and scrapped them shortly after.

Class Details by Steve Llanso of Sweat House Media

Class S-1 (Locobase 208)

Data from 1930 Locomotive Cyclopedia and LV 3 -1934 Locomotive Diagrams, the latter supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also Alfred W Bruce, The Steam Locomotive in America (New York: Bonanza Books, 1952), pp. 201-201, 210. (Thanks to Chris Hohl for pointing out the mixed valve gear.)

Locobase shows the prototype S-1 three-cylinder engine. The LV bought five more a year later from Alco-Brooks (works numbers 66102-66106 in December 1924.)

In 1939, the road rebuilt them at their Sayre, Pa shops as two-cylinder engines. Although they remained in service throughout World War Two, they were never very satisfactory.,

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID208
RailroadLehigh Valley (LV)
Number in Class6
Road Numbers5000-5005
Number Built6
Valve GearWalschaert & Gresley
Locomotive Length and Weight
Driver Wheelbase (ft / m)18.75 / 5.71
Engine Wheelbase (ft / m)41.17 / 12.55
Ratio of driving wheelbase to overall engine wheebase 0.46
Overall Wheelbase (engine & tender) (ft / m)77.67 / 23.67
Axle Loading (Maximum Weight per Axle) (lbs / kg)61,700 / 27,987
Weight on Drivers (lbs / kg)246,500 / 111,811
Engine Weight (lbs / kg)369,000 / 167,376
Tender Loaded Weight (lbs / kg)201,000 / 91,172
Total Engine and Tender Weight (lbs / kg)570,000 / 258,548
Tender Water Capacity (gals / ML)10,500 / 39.77
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)15 / 13.60
Minimum weight of rail (calculated) (lb/yd / kg/m)103 / 51.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)69 / 1753
Boiler Pressure (psi / kPa)200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)25" x 28" / 635x711 (3)
Tractive Effort (lbs / kg)64,674 / 29335.67
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.81
Heating Ability
Firebox Area (sq ft / m2)392 / 36.43
Grate Area (sq ft / m2)84.30 / 7.83
Evaporative Heating Surface (sq ft / m2)4729 / 439.50
Superheating Surface (sq ft / m2)1294 / 120.26
Combined Heating Surface (sq ft / m2)6023 / 559.76
Evaporative Heating Surface/Cylinder Volume198.18
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation16,860
Same as above plus superheater percentage20,401
Same as above but substitute firebox area for grate area94,864
Power L117,673
Power MT632.25

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