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Pennsylvania Railroad class S1
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Pennsylvania Railroad class S1
The PRR S1 class steam locomotive (nicknamed "The Big Engine") was a single experimental duplex locomotive of the Pennsylvania Railroad. It was designed to demonstrate the advantages of duplex drives espoused by Baldwin Chief Engineer Ralph P. Johnson. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy.
The S1 had a unique 6-4-4-6 wheel arrangement, meaning that it had two pairs of cylinders, each driving two pairs of driving wheels. To achieve stability at fast passenger train speeds (above 100 mph), articulation was not used. The S1 was completed on January 31, 1939, at Altoona shop, and was numbered 6100.
At 140 ft 2+1⁄2 in (42.74 m) overall, engine and tender, the S1 was the longest reciprocating steam locomotive ever; it also had the heaviest tender (451,840 lb (204.95 t)), highest tractive effort (76,403 lbf (339.86 kN)) of a passenger steam engine when built and the largest driving wheels (7 feet in diameter) ever used on a locomotive with more than three driving axles. The problem of wheel slippage, along with a wheelbase that was too long for many of the rail line's curves, limited the S1's usefulness. No further S1 models were built as focus shifted to the much smaller but more practical class T1 in June 1940. Design of the 4-4-4-4 T1 and the 6-4-4-6 S1 occurred concurrently, however, the S1 was the first produced.
As early as June 1936, the management of Pennsylvania Railroad decided to build a new passenger locomotive to replace its aging K4s locomotives. They also hoped that the new S1 steam locomotive would have a performance equal to their Pennsylvania Railroad class GG1 electric engine and would be capable of hauling a 1,000-ton passenger train at 100 mph. A conference was held between Baldwin Locomotive Works officials and W. F. Kiesel, J. V. B. Duer and W. R. Elsey for PRR, where PRR demanded a passenger locomotive to haul 15 standard cars at 100 mph (160 km/h) on level track between Paoli and Chicago. Baldwin presented several 4-8-4 and 4-4-4-4 designs made for other railroads. However, PRR rejected the 4-8-4 design in favor of a rigid frame duplex and asked Baldwin to consider the wheel arrangement 4-4-6-4. In July 1936, PRR requested Baldwin Locomotive Works to submit a design for a 4-8-4 engine capable of handling a 2,000-ton train between Colehour and Harsimus Cove.
Two months after the conference, Baldwin Locomotive Works officials presented four designs to PRR:
PRR chose the 4-4-4-4 and asked Baldwin to consider a passenger version with 6 ft 8 in (2.03 m) drivers and a freight version with 6 ft (1.8 m) drivers. However the cooperation between PRR and Baldwin, which proceeded without any official agreement or contract for developing the new duplex engine, didn't go smoothly. Ten months after the first conference (April 1937), PRR ended Baldwin Locomotive Work's consultation and assigned the task to a consortium of Baldwin, American Locomotive Company, and Lima Locomotive Works under a joint contract. T. W. Demarest headed the joint committee, General Superintendent of Motive Power in PRR's Western Region.
The members of the joint committee were:
On 28 April 1937, PRR's Board authorized $300,000 for this experimental high-speed passenger locomotive project. The design started with a 4-4-4-4 duplex.
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Pennsylvania Railroad class S1
The PRR S1 class steam locomotive (nicknamed "The Big Engine") was a single experimental duplex locomotive of the Pennsylvania Railroad. It was designed to demonstrate the advantages of duplex drives espoused by Baldwin Chief Engineer Ralph P. Johnson. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy.
The S1 had a unique 6-4-4-6 wheel arrangement, meaning that it had two pairs of cylinders, each driving two pairs of driving wheels. To achieve stability at fast passenger train speeds (above 100 mph), articulation was not used. The S1 was completed on January 31, 1939, at Altoona shop, and was numbered 6100.
At 140 ft 2+1⁄2 in (42.74 m) overall, engine and tender, the S1 was the longest reciprocating steam locomotive ever; it also had the heaviest tender (451,840 lb (204.95 t)), highest tractive effort (76,403 lbf (339.86 kN)) of a passenger steam engine when built and the largest driving wheels (7 feet in diameter) ever used on a locomotive with more than three driving axles. The problem of wheel slippage, along with a wheelbase that was too long for many of the rail line's curves, limited the S1's usefulness. No further S1 models were built as focus shifted to the much smaller but more practical class T1 in June 1940. Design of the 4-4-4-4 T1 and the 6-4-4-6 S1 occurred concurrently, however, the S1 was the first produced.
As early as June 1936, the management of Pennsylvania Railroad decided to build a new passenger locomotive to replace its aging K4s locomotives. They also hoped that the new S1 steam locomotive would have a performance equal to their Pennsylvania Railroad class GG1 electric engine and would be capable of hauling a 1,000-ton passenger train at 100 mph. A conference was held between Baldwin Locomotive Works officials and W. F. Kiesel, J. V. B. Duer and W. R. Elsey for PRR, where PRR demanded a passenger locomotive to haul 15 standard cars at 100 mph (160 km/h) on level track between Paoli and Chicago. Baldwin presented several 4-8-4 and 4-4-4-4 designs made for other railroads. However, PRR rejected the 4-8-4 design in favor of a rigid frame duplex and asked Baldwin to consider the wheel arrangement 4-4-6-4. In July 1936, PRR requested Baldwin Locomotive Works to submit a design for a 4-8-4 engine capable of handling a 2,000-ton train between Colehour and Harsimus Cove.
Two months after the conference, Baldwin Locomotive Works officials presented four designs to PRR:
PRR chose the 4-4-4-4 and asked Baldwin to consider a passenger version with 6 ft 8 in (2.03 m) drivers and a freight version with 6 ft (1.8 m) drivers. However the cooperation between PRR and Baldwin, which proceeded without any official agreement or contract for developing the new duplex engine, didn't go smoothly. Ten months after the first conference (April 1937), PRR ended Baldwin Locomotive Work's consultation and assigned the task to a consortium of Baldwin, American Locomotive Company, and Lima Locomotive Works under a joint contract. T. W. Demarest headed the joint committee, General Superintendent of Motive Power in PRR's Western Region.
The members of the joint committee were:
On 28 April 1937, PRR's Board authorized $300,000 for this experimental high-speed passenger locomotive project. The design started with a 4-4-4-4 duplex.
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