The Pennsylvania Railroad DD1 was a class of boxcab

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 (electricity), battery or a supercapacitor. Locomotives with on-board fuelled prime mover (locomotive), ...

s built by the

Pennsylvania Railroad The Pennsylvania Railroad ( reporting mark PRR), legal name as 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. At its ...

. The locomotives were developed as part of the railroad's

New York Tunnel Extension The New York Tunnel Extension (also New York Improvement and Tunnel Extension) is a combination of railroad tunnels and approaches from New Jersey and Long Island to Pennsylvania Station in Midtown Manhattan. It was built by the Pennsylvania R ...

, which built the original Pennsylvania Station in

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

and linked it to

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

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 rel ...

; 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 the Sunnyside neighborhood of Queens in New York City. The yard is owned by Amtrak and is also used by New Jersey Transit. The Pennsylvania Railroad (PRR) complet ...

Queens, New York Queens is the largest by area of the Boroughs of New York City, five boroughs of New York City, coextensive with Queens County, in the U.S. state of New York (state), New York. Located near the western end of Long Island, it is bordered by the ...

. 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 , or LIRR, is a Rail transport, railroad 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 County on Long Islan ...

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

Philadelphia Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...

main line to

alternating current Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in w ...

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 Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in tracks, which usually consist of two parallel steel rails. Rail transport is one of the two primary means of land transport, next to ro ...

and is listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...

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 In railroad terminology, double heading indicates the use of two locomotives at the front of a train, each operated individually by its own crew. The practice of triple-heading involves the use of three locomotives. The practice of multi-headi ...

configuration. The PRR classed their 4-4-0 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 Direct current (DC) is one-directional electric current, flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor (material), conductor such as a wire, but can also flow throug ...

, commutating pole, electric motors within a

monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...

cab. The motors had a continuous

power rating In electrical engineering and mechanical engineering, the power rating of equipment is the highest power input allowed to flow through particular equipment. According to the particular discipline, the term ''power'' may refer to electrical or ...

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 rod A coupling rod or side rod connects the driving wheels of a locomotive. Steam locomotives in particular usually have them, but some diesel and electric locomotives, especially older ones and shunter locomotives, also have them. The coupling ro ...

s. The design of the DD1 served as a transition between

steam locomotives A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...

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

from a

third rail A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a track (r ...

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 The Hudson River, historically the North River, is a river that flows from north to south largely through eastern New York (state), New York state. It originates in the Adirondack Mountains at Henderson Lake (New York), Henderson Lake in the ...

. 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 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 re ...

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

Strasburg, Pennsylvania Strasburg is a borough in Lancaster County, Pennsylvania, United States. It developed as a linear village stretching approximately along the Great Conestoga Road, later known as the Strasburg Road.Susan M. Zacher, NRHP Nomination Form Stra ...

by the Pennsylvania's successor

Penn Central The Penn Central Transportation Company, commonly abbreviated to Penn Central, was an American class I railroad that operated from 1968 to 1976. Penn Central combined three traditional corporate rivals, the Pennsylvania, New York Central and the ...

, as part of a collection with twelve other historically significant locomotives. Both locomotives were jointly listed on the

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

* *

External links

LIRR Early Electric Engines (TrainsAreFun.com)
an

{{PRR locomotives 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 1910 Passenger locomotives