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 "Lehigh Valley Three-Cylinder Locomotive", Railway Age, Volume 76, No (14 June 1924), pp. 1585=1586; and 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, which is described in detail, including excellent diagrams, in the Railway Age article. The boilers held a great amount of evaporative and superheating areas, lots of firebox area, and a large grate.

Each of the three cylinders was fed through 11" (279 mm) piston valves. The right and center cylinder were cast together, the left cylinder was cast separately.

The LV bought five more a year later from Alco-Brooks (works numbers 66102-66106 in December 1924.)

In 1939, the road rebuilt the class at their Sayre, Pa shops as two 28 x 32 in cylinder engines. Although they remained in service throughout World War Two, the S-1s were never very satisfactory.,

The entire class was scrapped in December 1948.

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 wheelbase 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 / Liters/MT)15 / 14
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
Tubes (number - dia) (in / mm)230 - 2.25" / 57
Flues (number - dia) (in / mm)50 - 5.5" / 140
Flue/Tube length (ft / m)21 / 6.40
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 Volume198.20
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 L117,674
Power MT632.28

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