The Pennsylvania Railroad DD1 was a class of

boxcab A boxcab, in railroad terminology, is a locomotive in which the machinery and crew areas are enclosed in a box-like superstructure (from boxcar). It is a term mostly used in North America while in Victoria (Australia), such locomotives have been ...

electric locomotive An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or gas ...

s built by the

Pennsylvania Railroad The Pennsylvania Railroad (reporting mark PRR), legal name The Pennsylvania Railroad Company also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was named ...

. The locomotives were developed as part of the railroad's New York Tunnel Extension, which built the original Pennsylvania Station in

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

and linked it to

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

via the North River Tunnels. The Pennsylvania built a total of 66 locomotives in its

Altoona Works Altoona Works (also known as Altoona Terminal) is a large railroad industrial complex in Altoona, Pennsylvania. It was built between 1850 and 1925 by the Pennsylvania Railroad (PRR), to supply the railroad with locomotives, railroad cars and relat ...

; they operated in semi-permanently coupled pairs. Westinghouse supplied the electrical equipment. The first locomotives entered service in 1910, with the opening of Pennsylvania Station. They operated between Manhattan Transfer and Pennsylvania Station, and from there to the coach yards at

Sunnyside Yard Sunnyside Yard is a large coach yard, a railroad yard for passenger cars, in Sunnyside, Queens in New York City. Description The yard is owned by Amtrak and is also used by New Jersey Transit. The shared tracks of the Long Island Rail Road (LIR ...

Queens, New York Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long I ...

. With the arrival of the Class L5 locomotives in 1924, some DD1s moved to the Pennsylvania-owned

Long Island Rail Road The Long Island Rail Road , often abbreviated as the LIRR, is a commuter rail system in the southeastern part of the U.S. state of New York (state), New York, stretching from Manhattan to the eastern tip of Suffolk County, New York, Suffolk Co ...

(LIRR), which had substantial electrified commuter rail operations. The conversion of the New York– Philadelphia

main line Mainline, ''Main line'', or ''Main Line'' may refer to: Transportation Railway * Main line (railway), the principal artery of a railway system * Main line railway preservation, the practice of operating preserved trains on an operational railw ...

to alternating current in the 1930s saw the remainder of the DD1s scrapped or transferred to the LIRR. One pair, Nos. 3936 and 3937, is preserved at the Railroad Museum of Pennsylvania and is listed on the National Register of Historic Places.

Design

Each semi-permanently coupled pair had a length of and weighed . DD1-class locomotives were nearly always operated as a pair—never individually and rarely as two pairs in a double-heading configuration. The PRR classed their

4-4-0 4-4-0 is a locomotive type with a classification that uses the Whyte notation for the classification of steam locomotives by wheel arrangement and represents the arrangement: four leading wheels on two axles (usually in a leading bogie), four po ...

locomotives as class D, and the DD1 was essentially two 4-4-0 locomotives coupled back to back, resulting in the new class, DD. Each pair was assigned a single "Electrified Zone Number" (EZN); the EZN simplified train dispatching for each pair of DD1s while their original individual serial numbers were used for the mechanical records of the locomotives. Each locomotive had its own Westinghouse 315-A, direct current, commutating pole, electric motors within a monocoque cab. The motors had a continuous power rating of at , and could produce up to at for no more than an hour. Their top speed was , but PRR/LIRR timetables had a speed limit of . The motors were connected to the two drivers via a jackshaft and coupling rods. The design of the DD1 served as a transition between steam locomotives and modern electric locomotives. Despite their ungainly appearance, DD1s ran "quietly and smoothly...with no appreciable rod clanking", and had a very low maintenance cost. DD1 locomotives operated off 650 volt direct current from a third rail.

History

The first DD1-class of locomotives were introduced into regular passenger service on November 27, 1910 to operate in the North River Tunnels under the Hudson River. As steam locomotives were prohibited from entering the tunnels, the electric DD1 shuttled passengers from the Pennsylvania Railroad's Manhattan Transfer station in

and Pennsylvania Station in

. A total of 66 locomotives were constructed by the Pennsylvania Railroad's Juniata Shops in Altoona starting in 1909; 3936 and 3937 were put into service in 1911. As the new L5s were being introduced in 1924, most DD1s were transferred to the

. Both 3936 and 3937 were shifted from mainline passenger duty, and hauled the empty passenger trains from Pennsylvania Station to

. The Long Island Rail Road scrapped most of its DD1s from 1949 to 1951, and only two pairs remained in 1962. By 1978, Nos. 3936 and 3937 comprised the last existing DD1 and were donated to the Railroad Museum of Pennsylvania in Strasburg, Pennsylvania by the Pennsylvania's successor Penn Central, as part of a collection with twelve other historically-significant locomotives. Both locomotives were jointly listed on the National Register of Historic Places on December 17, 1979.

Gallery

Image:PRR DD1 running gear.jpg, Running gear and electrical equipment Image:PRR DD1 side drawing.jpg, Side-view drawing Image:RRMOP 3936.JPG, The surviving DD1 3936 and 3937

Footnotes

References

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External links

LIRR Early Electric Engines (TrainsAreFun.com)
an

2-Bo-Bo-2 locomotives DD1 600 V DC locomotives Electric locomotives of the United States Standard gauge locomotives of the United States Railway locomotives introduced in 1911 {{US-train-stub Passenger locomotives