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. [1]

One of the most famous locomotives to be built at the PRR shops is Pennsylvania Railroad’s only member of the S1 class, #6100. It had a short but interesting life! It’s a story railfans still talk about. #6100 pulls out of Union Station in Chicago with the Manhattan Limited in February 1943.

The museum has on display a large and significant collection of Pennsylvania-related motive power and rolling stock spanning the years 1825 to the present. After WWII, in 1945, the PRR still operated more than 4000 steam locomotives.

Jul 5, 2018 · The PRR S1 was a unique duplex locomotive that utilized a 6-4-4-6 wheel arrangement. A six-wheel leading truck with 36 in (.91 m) wheels was positioned at the front of the engine.

Nov 17, 2020 · This photo shows the PRR's huge S1 6-4-4-6 locomotive under construction right here in Altoona at the Juniata Shops in 1939. Nicknamed "The Big Engine," the S1 was the longest reciprocating steam locomotive ever (just over 140 ft); …

Sep 3, 2010 · The PRR S1 class steam locomotive (nicknamed "The Big Engine") was an experimental locomotive that was the largest rigid frame passenger locomotive ever built. The streamlined Art Deco styled shell of the locomotive was designed by Raymond Loewy. The S1 was the only locomotive ever built to use a 6-4-4-6 wheel arrangement.

A long response in the Trainorders discussion of Caprotti valve gear include PRR engineer John Roller's method for dealing with wheel slip: " [H]e could control the PRR T1's slipperiness by letting the T1 boiler pressure come way down during station stops, helped by the injector.

The first experimental duplex on the PRR was the S1, a huge rigid frame duplex locomotive of the 6-4-4-6 wheel arrangement. This engine was over 146' long! This locomotive was built by the PRR at Altoona in 1939; it was hailed as the largest locomotive ever built.

AUGUST 1940: A view of the PRR S1 class steam locomotive (nicknamed 'The Big Engine' and designed by Raymond Loewy) on display at the 1939 New York World's Fair

Sep 23, 2018 · Instead of immediately pressing the S-1 into service, PRR sent it to the New York World’s Fair. As the highlight of a display of American railroading, the streamlined, bullet-shaped S-1 was placed on a set of rollers powered by the tractive force of the big engine.