page_title: Rigid-framed electric locomotive
section_title: (1′Co1′)+(1′Co1′)
hierarchical_section_title: Rigid-framed electric locomotive / (1′Co1′)+(1′Co1′)
caption_attribution_description: New York New Haven &amp; Hartford EP-2 running gear.
context_page_description: Rigid-framed electric locomotives were some of the first generations of electric locomotive design. When these began the traction motors of these early locomotives, particularly with AC motors, were too large and heavy to be mounted directly to the axles and so were carried on the frame. One of the initial simplest wheel arrangements for a mainline electric locomotive, from around 1900, was the 1′C1′ arrangement, in UIC classification.
  Some of these locomotives had their driving wheels coupled with coupling rods, as for steam locomotives. Others had individual motors for each axle, as would later become universal.
  By the middle of the century, the bogie arrangement for locomotives became more popular and rigid-framed locomotives are now rare, except for small shunters.
context_section_description: The American New Haven EP-2 of 1919–1927 combined two 1′Co1′ sub-frames beneath a single  boxcab body to make a (1′Co1′)+(1′Co1′) locomotive. As the two frames were articulated together and the body on top was not a structural component, this was a (1′Co1′)+(1′Co1′) rather than (1′Co1′)(1′Co1′); i.e. articulated in two units, rather than with bogies beneath a singe structure. At 2,000 hp, they were around the same power as a pair of the previous EP-1s, which had often worked in multiple, although also lighter and more stable at speed.
  The EP-1s had required conversion from a Bo'Bo' arrangement to (1′Bo)(Bo1′), in order to prevent oscillation or 'nosing' when running at speed. The same use of pony trucks was designed into the EP-2 from the outset. The central carrying axles were largely pointless though, having no guiding function. When additional locomotives, the EP-3 and then EP-4, were required in the 1930s, these used a (2′C)+(C2′) arrangement, with the carrying axles moved to the ends as twin-axle bogies.
caption: Frames and running gear of a New Haven EP-2 (1′Co1′)+(1′Co1′)
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