page_title: Duplex locomotive
hierarchical_section_title: Duplex locomotive
caption_attribution_description: English: Detail of the cylinders and driving wheels of Pennsylvania Railroad S1 6-4-4-6 steam locomotive at the New York World's Fair, July 15, 1939. LOC call number LC-G613-35558.
context_page_description: A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive. The concept was first used in France in 1863, but was particularly developed in the early 1930s by the Baldwin Locomotive Works, the largest commercial builder of steam locomotives in North America, under the supervision of its then chief engineer, Ralph P. Johnson.
  Prior to this, the term duplex locomotive was sometimes applied to articulated locomotives in general.
context_section_description: A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive. The concept was first used in France in 1863, but was particularly developed in the early 1930s by the Baldwin Locomotive Works, the largest commercial builder of steam locomotives in North America, under the supervision of its then chief engineer, Ralph P. Johnson.
  Prior to this, the term duplex locomotive was sometimes applied to articulated locomotives in general.
caption: Closeup of the second set of cylinders on the PRR S1.
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