View source for Pennsylvania Railroad class DD1

{{Short description|Class of 66 (33 pairs) of American 2′B+B2′ electric locomotives}}
{{Infobox locomotive
| name = PRR DD1
| powertype = Electric
| image            = PRR DD1.jpg
| imagesize = 280px
| caption = 
| builder = [[Altoona Works]]
| builddate = 1910–1911
| totalproduction = 66 (in 33 [[married pair]]s)
| whytetype = {{Whyte|4-4-0+0-4-4|OE}}
| aarwheels = 2-B+B-2
| uicclass = 2′B+B2′
| gauge = {{track gauge|ussg|allk=on}}
| leadingdiameter = {{convert|36|in|mm|0|abbr=on}}
| driverdiameter = {{convert|72|in|mm|0|abbr=on}}
| wheelbase = {{convert|7|ft|5|in|m|2|abbr=on}} between driving axles
| length = {{convert|64|ft|11|in|m|2|abbr=on}}
| width = {{convert|9|ft|1|in|m|2|abbr=on}}
| height = {{convert|14|ft|8|in|m|2|abbr=on}}
| locoweight = {{convert|313000|lb|kg t|sigfig=4|abbr=in}}
| weightondrivers = {{convert|199000|lb|kg t|sigfig=4|abbr=in}}
| electricsystem = 650&nbsp;[[volt|V]]&nbsp;[[direct current|DC]] [[Third rail]]
| collectionmethod = [[Contact shoe]]
| transmission = [[Resistor#Grid resistor|Resistance]] controlled DC current supplied to DC motors connected to the axles through [[Jackshaft (locomotive)|Jackshaft]] and [[coupling rod|side rods]]
| tractionmotors = 2 × 315-A {{convert|2000|hp|abbr=on}}
| maxspeed = {{convert|85|mph|km/h|abbr=on}} 
| poweroutput = {{convert|1580|hp|kW|lk=on|abbr=on}} continuous
| tractiveeffort = {{convert|55500|lbf|kN|lk=on|abbr=on}}
}}
The '''Pennsylvania Railroad DD1''' was a class of [[boxcab]] [[electric locomotive]]s built by the [[Pennsylvania Railroad]]. The locomotives were developed as part of the railroad's [[New York Tunnel Extension]], which built the original [[Pennsylvania Station (1910–1963)|Pennsylvania Station]] in [[New York City]] and linked it to [[New Jersey]] via the [[North River Tunnels]]. The Pennsylvania built a total of 66 locomotives in its [[Altoona Works]]; they operated in semi-permanently coupled pairs. [[Westinghouse Electric Corporation|Westinghouse]] supplied the electrical equipment.

The first locomotives entered service in 1910, with the opening of Pennsylvania Station. They operated between [[Manhattan Transfer station|Manhattan Transfer]] and Pennsylvania Station, and from there to the coach yards at [[Sunnyside Yard]] in [[Queens, New York]]. With the arrival of the [[Pennsylvania Railroad class L5|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]] [[Northeast Corridor|main line]] to [[Amtrak's 25 Hz traction power system|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 {{Convert|64|ft|11|in|m|1}} and weighed {{Convert|313000|lb|kg|-3}}.{{Sfn|Hart|Zacher|1978|loc=sec. 7, p. 4}} DD1-class locomotives were nearly always operated as a pair&mdash;never individually and rarely as two pairs in a [[double-heading]] 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. {{Sfn|Staufer|Pennypacker|1962|p=249}} 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.{{Sfn|Staufer|Pennypacker|1962|p=249}}

Each locomotive had its own [[Westinghouse Electric (1886)|Westinghouse]] 315-A, [[direct current]], commutating pole, electric motors within a [[monocoque]] cab. The motors had a continuous [[power rating]] of {{Convert|1580|hp|kW|-1}} at {{Convert|58|mph|km/h|0}}, and could produce up to {{Convert|2130|hp|kW|-1}} at {{Convert|38|mph|km/h|0}} for no more than an hour.{{Sfn|Staufer|Pennypacker|1962|p=249}} Their top speed was {{Convert|85|mph|km/h|0}}, but PRR/LIRR timetables had a speed limit of {{Convert|65|mph|km/h|0}}. The motors were connected to the two {{Convert|72|in|mm|adj=on|0}} [[driving wheel|driver]]s via a [[jackshaft]] and [[coupling rod]]s. The design of the DD1 served as a transition between [[steam locomotives]] and modern electric locomotives.{{sfn|Hart|Zacher|1978|loc=sec. 7, p. 4}} Despite their ungainly appearance, DD1s ran "quietly and smoothly...with no appreciable rod clanking", and had a very low maintenance cost.{{sfn|Staufer|Pennypacker|1962|p=249}} DD1 locomotives operated off 650&nbsp;volt [[direct current]] from a [[third rail]].

== History ==
The first DD1-class of locomotives were introduced into regular passenger service on November&nbsp;27, 1910 to operate in the [[North River Tunnels]] under the [[Hudson River]].{{sfn|Staufer|Pennypacker|1962|p=249}} As steam locomotives were prohibited from entering the tunnels, the electric DD1 shuttled passengers from the Pennsylvania Railroad's [[Manhattan Transfer (PRR station)|Manhattan Transfer]] station in [[New Jersey]] and [[Pennsylvania Station (New York City)|Pennsylvania Station]] in [[New York City]].

A total of 66&nbsp;locomotives were constructed by the Pennsylvania Railroad's [[Altoona Works|Juniata Shops]] in [[Altoona, Pennsylvania|Altoona]] starting in 1909; 3936 and 3937 were put into service in 1911. As the new [[PRR L5|L5]]s 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 [[Sunnyside Yard]]. 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 Transportation Company|Penn Central]], as part of a collection with twelve other historically significant locomotives.{{sfn|Hart|Zacher|1978|loc=sec. 7, p. 1}}<ref>{{cite web |title=Motive Power Roster |publisher=[[Railroad Museum of Pennsylvania]] |url=http://www.rrmuseumpa.org/about/roster/locomotiveroster.pdf |access-date=October 20, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130703151453/http://www.rrmuseumpa.org/about/roster/locomotiveroster.pdf |archive-date=July 3, 2013 }}</ref> Both locomotives were jointly listed on the [[National Register of Historic Places]] on December 17, 1979.<ref name="focus">{{cite web |title=NPS Focus |work=National Register of Historic Places |url=http://nrhp.focus.nps.gov |publisher=[[National Park Service]] |access-date=October 20, 2013}}</ref>

==Gallery==
<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
</gallery>

==See also==
* [[PRR locomotive classification]]

==Footnotes==
{{reflist}}

==References==
* {{Staufer-Pennsy}}
* {{Cite web |last1=Hart |first1=George M |last2=Zacher |first2=Susan M |title=Pennsylvania Railroad Rolling Stock Thematic Resource |work=National Register of Historic Places Inventory&mdash;Nomination Form |date=March 1978 |url={{NRHP url|id=64000729}} |access-date=October 20, 2013 }}

== Further reading ==
* {{cite book | last=Bezilla | first=Michael | title=Electric traction on the Pennsylvania Railroad, 1895-1968 | publisher=[[Pennsylvania State University Press]] | location=University Park, Pennsylvania | date=1980 | isbn=978-0-271-00241-5 }}
* {{Cudahy-Hudson}}
* {{Middleton-PRR-Under-Wire}}
* {{cite magazine | last=Westing | first=Frederick | title=The Locomotive That Made Penn Station Possible | magazine=[[Trains (magazine)|Trains]] | volume=16 | issue=12 | date=October 1956 | issn=0041-0934 | pages=28–38 }}

==External links==
*[http://www.trainsarefun.com/lirr/early-electric-engines/earlylirr-electric-engines.htm LIRR Early Electric Engines (TrainsAreFun.com)]
*[http://www.newdavesrailpix.com/lirr/htm/usr_h_lirr_nonpass_344_westendmorrisparkshop_1950s_bmjt_002.htm Long Island Rail Road DD1-344] and [http://www.newdavesrailpix.com/lirr/htm/usr_h_lirr_nonpass_348_morrispark_1950s_jmjt_003.htm 348 at Morris Park Shops (New Dave's Rail Pix)]

{{commons category|PRR DD1}}
{{PRR locomotives}}

[[Category:2-Bo-Bo-2 locomotives]]
[[Category:Pennsylvania Railroad locomotives|DD1]]
[[Category:600 V DC locomotives]]
[[Category:Electric locomotives of the United States]]
[[Category:Standard gauge locomotives of the United States]]
[[Category:Railway locomotives introduced in 1911]]
[[Category:Passenger locomotives]]