{{Infobox locomotive |name = PRR D2 & D2a |powertype = Steam |image = PRR D2a 138.jpg |caption = Class B A #138 (later class D2a) |builder = PRR Altoona Works |builddate = 1868–1872 (D2);<br>1881–1882 (D2a) |totalproduction = 20 (D2); 45 (D2a) |whytetype = {{whyte|4-4-0}} |uicclass = 2′B |gauge = {{track gauge|ussg}} |leadingdiameter = {{convert|28|in|mm|0|abbr=on}} (D2)<ref name="dredge" /><br />{{convert|30|in|mm|0|abbr=on}} (D2a)<ref name="d2adiagram">{{cite web |title = Class D2 diagram |url = http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=d2a_oldba.gif&sel=ste&sz=sm&fr= |author = Pennsylvania Railroad |publisher = PRR.Railfan.net |accessdate = 2008-08-19}}</ref> |driverdiameter = {{convert|62|in|mm|0|abbr=on}} (D2)<ref name="dredge" /><br />{{convert|68|in|mm|0|abbr=on}} (D2a)<ref name="d2adiagram" /> |wheelbase = {{convert|22|ft|5+5/8|in|m|2|abbr=on}}<ref name="d2adiagram" /><ref name="diagram" /> |length = {{convert|54|ft|5.44|in|m|2|abbr=on}}<ref name="d2adiagram" /><ref name="diagram">{{cite web |title = Class D2a diagram |url = http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=d2.gif&sel=ste&sz=sm&fr= |author = Pennsylvania Railroad |publisher = PRR.Railfan.net |accessdate = 2008-08-19}}</ref> |width = {{convert|9|ft|0.94|in|m|2|abbr=on}}<ref name="d2adiagram" /><ref name="diagram" /> |height = {{convert|14|ft|8|in|m|2|abbr=on}} (D2)<ref name="diagram" /><br />{{convert|14|ft|11|in|m|2|abbr=on}} (D2a)<ref name="d2adiagram" /> |weightondrivers = {{convert|52500|lb|t|1|abbr=in}} (D2)<ref name="diagram" /><br />{{convert|53750|lb|t|1|abbr=in}} (D2a)<ref name="d2adiagram" /> |locoweight = {{convert|80500|lb|t|1|abbr=in}} (D2)<ref name="diagram" /><br />{{convert|82200|lb|t|1|abbr=in}} (D2a)<ref name="d2adiagram" /> |tenderweight = {{convert|51400|lb|t|1|abbr=in}} (D2 & D2a)<ref name="d2adiagram" /><ref name="diagram" /> |locotenderweight = {{convert|131900|lb|t|1|abbr=in}} (D2)<ref name="diagram" /><br />{{convert|133600|lb|t|1|abbr=in}}<ref name="d2adiagram" /> |tendertype = Eight-wheel with water scoop |fueltype = Soft coal |fuelcap = {{convert|8000|lb|t|1|abbr=in}}<ref name="diagram" /> |watercap = {{convert|2400|usgal|abbr=on}}<ref name="diagram" /> }} The Pennsylvania Railroad's steam locomotive class '''D2''' (formerly Class '''B''', pre-1895) comprised twenty {{whyte|4-4-0}} locomotives intended for mountain passenger helper service, constructed at the railroad's own Altoona Works (now owned by Norfolk Southern) during 1869–1880.<ref name="prr-roster">{{cite web |title = PRR Steam Roster |url = http://www.northeast.railfan.net/prr_steam2.html |work = Northeast Rails |accessdate = 2007-12-31 }}</ref> They were the second standardized class of locomotives on the railroad and shared many parts with other standard classes.<ref name="dredge">{{cite book |title = The Pennsylvania Railroad |first = James |last = Dredge |year = 1879 |publisher = Engineering magazine |location = London }}</ref>

This design differed from the Class A (later D1) mainly in its smaller drivers for greater tractive effort in mountainous terrain. Like all the early standardized 4-4-0s on the PRR, the Class B had a wagon-top boiler with steam dome and a firebox between the two driving axles.

In 1881, the PRR took the Class B design and modified it to produce more locomotives for express passenger service, with {{convert|68|in|mm|0|adj=on}} drivers like the earlier Class A. These new locomotives were designated '''Class B A''', and were classified as '''D2a''' in the post-1895 scheme; forty-five of them were constructed.<ref name="prr-roster" /><ref name="warner">{{cite book |title = Motive Power Development on the Pennsylvania Railroad System |first = Paul T. |last = Warner |year = 1924 |publisher = Baldwin Locomotive Works |location = Philadelphia }}</ref>

==References== <references /> {{Commons category|Pennsylvania Railroad D2}} {{PRR locomotives}}

{{DEFAULTSORT:Prr D02}} Category:4-4-0 locomotives D02 Category:Railway locomotives introduced in 1868 Category:Scrapped locomotives Category:Standard-gauge locomotives of the United States Category:Steam locomotives of the United States Category:2′B n2 locomotives