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 or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or g ...

s built by the Pennsylvania Railroad. 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 Pennsylvania Railr ...

, which built the original

Pennsylvania Station Pennsylvania Station (often abbreviated Penn Station) is a name applied by the Pennsylvania Railroad (PRR) to several of its grand passenger terminals. Several are still in active use by Amtrak and other transportation services; others have been ...

New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...

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 North River Tunnels are a pair of rail tunnels that carry Amtrak and New Jersey Transit passenger lines under the Hudson River between Weehawken, New Jersey, and Pennsylvania Station in Manhattan, New York City, New York. Built between 1904 ...

. The Pennsylvania built a total of 66 locomotives in its Altoona Works; 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 ...

. With the arrival of the Class L5 locomotives in 1924, some DD1s moved to the Pennsylvania-owned Long Island Rail Road (LIRR), which had substantial electrified commuter rail operations. The conversion of the New York–

Philadelphia Philadelphia, often called Philly, is the List of municipalities in Pennsylvania#Municipalities, largest city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, the List of United States cities by population, sixth-largest city i ...

main line to

alternating current Alternating current (AC) is an electric current which 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 whic ...

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 The Railroad Museum of Pennsylvania is a railroad museum in Strasburg, Lancaster County, Pennsylvania. The museum is located on the east side of Strasburg along Pennsylvania Route 741. It is administered by the Pennsylvania Historical and Mus ...

and is listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic ...

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-headin ...

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 flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...

, 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 me ...

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 A jackshaft, also called a ''countershaft'', is a common mechanical design component used to transfer or synchronize rotational force in a machine. A jackshaft is often just a short stub with supporting bearings on the ends and two pulleys, gear ...

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 shunters, also have them. The coupling rods transfer t ...

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 railway ...

History

The first DD1-class of locomotives were introduced into regular passenger service on November 27, 1910 to operate in the

under the

Hudson River The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between N ...

. As steam locomotives were prohibited from entering the tunnels, the electric DD1 shuttled passengers from the Pennsylvania Railroad's Manhattan Transfer station in

and

. 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 Long Island Rail Road. 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. It developed as a linear village stretching about along the Great Conestoga Road, later known as the Strasburg Road.Susan M. Zacher, NRHP Nomination Form Strasburg/ref> The population ...

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

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