Pennsylvania Railroad class S2

Pennsylvania Railroad S2 class
PRR 6200 at Baldwin Locomotive Works c. 1944 (PRR promotional image)
Type and origin
Power typeSteam turbine
BuilderBaldwin Locomotive Works, Westinghouse Electric & Manufacturing Company
Order number70900
Serial number6200
Build date1944
Total produced1
Specifications
Configuration:
 • Whyte6-8-6
 • UIC3D3
Gauge4 ft 8+12 in (1,435 mm) standard gauge
Leading dia.36 in (914 mm)
Driver dia.68 in (1,727 mm)
Trailing dia.42 in (1,067 mm)
Wheelbase108 ft (32.92 m)
Length122 ft 7+14 in (37.37 m)
Height16 ft (4,877 mm)
Adhesive weight271,450 lb (123 tonnes)
Loco weight589,920 lb (268 tonnes)
Tender weight442,180 lb (201 tonnes)
Total weight1,032,100 lb (468 tonnes)
Tender type180-P-85 16-wheel tender (two 4-axle trucks)
Fuel typeBituminous coal
Water cap.19,500 gal
Tender cap.37 1/2 tonnes
Firebox:
 • Grate area120 sq ft (11 m2)
BoilerModified Belpaire type
102 in (2,591 mm) diameter (back)
Boiler pressure310 psi (2.1 MPa)
Feedwater heaterWorthington Corporation
Heating surface:
 • Tubes18 ft (5,486 mm)
Superheater:
 • TypeWorthington Type E single-loop
 • Heating area2,050 sq ft (190 m2)
TransmissionDirect geared turbine
Performance figures
Maximum speedAt least 110 mph (177 km/h)
Power outputForward turbine - 6,900 hp (5,150 kW), reverse turbine - 1,500 hp (1,120 kW)
Tractive effort65,000 lbf (289.13 kN)
Career
OperatorsPennsylvania Railroad
ClassS2
Number in class1
Numbers6200
Nicknames"The Big Whoosh"
DeliveredNovember 28, 1944
First runMarch 26, 1945
Last runJune 11, 1949
WithdrawnAugust 1949
DispositionScrapped May 29, 1952

The Pennsylvania Railroad's S2 class was a steam turbine locomotive designed and built in a collaborative effort by Baldwin Locomotive Works and Westinghouse Electric & Manufacturing Company, as an attempt to prolong the dominance of the steam locomotive by adapting technology that had been widely accepted in the marine industry. One was built, #6200, delivered in September 1944. The S2 was the sole example of the 6-8-6 wheel arrangement in the Whyte notation, with a six-wheel leading truck keeping the locomotive stable at speed, eight powered and coupled driving wheels, and a six-wheel trailing truck supporting the large firebox. The S2 used a direct-drive steam turbine provided by the Westinghouse Electric & Manufacturing Company, geared to the center pair of axles with the outer two axles connected by side rods; the fixed gear ratio was 18.5:1. Such design was to prevent energy loss and S2 achieved a mechanical efficiency of 97% which means only 3% of steam energy was lost within the propulsion equipment. The disadvantage of a direct-drive steam turbine was that the turbine could not operate at optimal speeds over the locomotive's entire speed range. The S2 was the largest, heaviest and fastest direct-drive turbine locomotive design ever built.