{{Short description|Articulated steam locomotive with three sets of driving wheels}}{{Infobox locomotive | name = Erie Railroad Class P-1 Triplex Locomotive | powertype = | builder = Baldwin Locomotive Works | builddate = 1914–1916 | totalproduction = 3 | whytetype = 2-8-8-8-2 | gauge = | fleetnumbers = Erie Railroad ; 5014–5016 | retiredate = 1929–1933 | disposition = All three triplex locomotives scrapped by 1933 }}[[File:Erie Railroad - 2603 steam locomotive (Baldwin 2-8-8-8-2) (27197514215).jpg|thumb|300px|The Erie Class P-1 ''Matt H. Shay'' 2-8-8-8-2 Triplex locomotive]][[Image:ERIE 28882.jpg|thumb|300px|Baldwin Erie P1 5016 Triplex, an Erie Class P-1 locomotive, shown in Exeter, Pennsylvania]] [[Image:28884.jpg|thumb|300px|The only Class XA 2-8-8-8-4 triplex locomotive ever built, number 700, for the Virginian Railway, in 1916 during [[World War 1]]]]<!-- Please don’t remove these info boxes about these forgotten 1910’s steam locomotives it important information not vandalism I sorry if I sometimes delete stuff on Wikipedia --> {{Infobox locomotive | name = Virginian Railway Class Xa Triplex Locomotive | powertype = | builder = Baldwin Locomotive Works | builddate = 1916 | totalproduction = 1 | rebuilder = Virginian Railway and Baldwin Locomotive Works | rebuilddate = 1920 | numberrebuilt = 1 | whytetype = 2-8-8-8-4 | gauge = | operator = Virginian Railroad | fleetnumbers = Virginian Railway; 700 | retiredate = 1920 (rebuilt) 1953 (railroad service) | scrapdate = 1953 | disposition = Rebuilt and cut as 2 separate different steam locomotives a Virginian Railway Class AF 2-8-8-0 Articulated Mallet steam locomotive and a Virginian Railway Class MD 2-8-2 Mikado Steam Locomotive both locomotives operated by the Virginian Railway until they were scrapped in 1953 }}
A '''triplex locomotive''' was a [[steam locomotive]] that [[Divided drive (locomotive)|divided the driving force]] on its wheels by using three pairs of cylinders to drive three sets of [[driving wheel]]s. Any such locomotive will inevitably be [[articulated locomotive|articulated]]. All triplex locomotives built were of the [[Mallet locomotive|Mallet]] type, but with an extra set of [[driving wheels]] under the tender. The concept was extended to [[multiplex locomotive|locomotives with four, five or six sets of drive wheels]]. However, these locomotives were never built, except for one quadruplex locomotive in [[Belgium]].
==Erie and Virginian Triplex classes== [[Baldwin Locomotive Works]] built three 2-8-8-8-2 triplex locomotives for the [[Erie Railroad]] between 1914 and 1916 during [[World War 1]]. A '''2-8-8-8-2''' has two [[leading wheel]]s, three sets of eight [[driving wheel]]s, and two [[trailing wheel]]s. Because of its length, such a locomotive must be [[articulated locomotive|articulated]]. It is not longer than a normal articulated; the third set of drivers is located under the tender. All of the examples produced were a Triplex of the [[Mallet (locomotive)|Mallet]] type. The first was named ''Matt H. Shay'', after a beloved employee of that road.<ref name="Westing">{{citation | last = Westing | first = Frederick | year = 1966 | title = The locomotives that Baldwin built. Containing a complete facsimile of the original "History of the Baldwin Locomotive Works, 1831–1923" | publisher = Crown Publishing Group | isbn = 978-0-517-36167-2| lccn = 66025422|pages=124–125 }}</ref> These Triplexes were given the classification of '''P-1''' and they could reportedly pull 650 freight cars.<ref>{{cite news |title=A titan of the rails |url=https://archive.org/stream/independen79v80newy#page/n140/mode/1up |newspaper=The Independent |date=July 27, 1914 |access-date=July 24, 2012 }}</ref> The triplexes were primarily used as pushers on grades requiring helper locomotives. Slow moving, the triplexes were not considered highly successful, and no more were built for Erie. The Erie Railroad scrapped their Triplexes from 1929, 1931, and 1933.<ref name="Westing"/>
Other equivalent classifications are: :[[UIC classification]]: '''(1'D)D(D1')''' :[[AAR wheel arrangement|AAR classification]]: '''1-D-D-D-1''' :[[French classification]]: '''140+040+041''' :[[Turkish classification]]: '''45+44+45''' :[[Swiss classification]]: '''4/5+4/4+4/5'''
Another very similar designed triplex was built by Baldwin as a [[2-8-8-8-4]] for the [[Virginian Railway]], as No. 700, in 1916. This triplex was given classification of '''XA''', so named due to the experimental nature of the locomotive. The 2-8-8-8-4 was considered unsuccessful because it only made a maximum speed of {{cvt|3|-|5|mph|order=flip}} and had high maintenance costs. The XA was sent back to [[Baldwin Locomotive Works]] where it was taken apart in 1920 and converted into a [[2-8-8-0]] and a [[2-8-2]]. These two engines were in service until 1953.<ref>{{cite web |title=2-8-8-8-2/4 "Triplex" Locomotives in the USA |url=https://www.steamlocomotive.com/locobase.php?country=USA&wheel=Triplex&railroad=vgn|website=www.steamlocomotive.com}}</ref> Both of the two engines were scrapped when diesel locomotives were cheaper to operate after [[World War 2]].{{citation needed|date=April 2020}}
A 2-6-6-8-2 triplex design by ALCO was proposed to the Chesapeake & Ohio but was never built.
== Design == The triplex locomotives were of the Mallet type, but with an extra set of driving wheels under the tender. The centre set of cylinders received high-pressure steam. The exhaust from these was fed to the two other sets of cylinders.<ref name="Westing"/> The right cylinder exhausted into the front set of low pressure cylinders, and the left into the rear set; this is also why the high pressure cylinders are the same diameter as the low pressure cylinders, making the engine a 2 to 1 compound, whereas most Mallet locomotives have much smaller high pressure cylinders. The front set exhausted through the [[smokebox]] and the rear set exhausted first through a [[feedwater heater]] in the [[tender locomotive|tender]] and then through a large pipe directly to the outside, as can be seen in the photo. As only half of the exhaust steam went through the [[blastpipe|blast pipe]] in the smokebox, the draft in the firebox and the heating of the boiler was poor. Although the boiler was large in comparison with contemporary two-cylinder and four-cylinder locomotives, six large cylinders required more steam than even such a boiler could supply.<ref name="Westing"/>
The Erie locomotives always operated in compound mode and did not have "intercepting" valves that would have put full pressure on all six cylinders, yet the triplexes produced huge amounts of [[tractive effort]] that may have been the highest of any steam locomotives ever. Westing<ref name="Westing"/> gives a figure of {{convert|160000|lbf|kN|abbr=on}} in compound mode and seems to indicate that it was the largest tractive effort for any locomotives up to the mid-1910s. The [[Union Pacific Big Boy]]s built in the 1940s during [[World War 2]] did not exceed the Erie locomotives either, having only {{convert|135375|lbf|kN|abbr=on}}.
The triplexes could also be considered the largest [[tank locomotive]]s ever built, as the tender also had driving wheels and thus contributed to the traction.
The problem of diminishing adhesion of the tender unit as water and coal was used; was ''not'' a significant factor or design flaw, as the rear engine, as designed, was not to produce as much adhesion as the front and middle engines by adjusting the steam lap;<ref>Erie Power, Stauffer - Westing p. 208</ref> which compensated for the usage of coal and water. Even nearly empty, the rear engine produced equivalent amounts of tractive effort.
Also, pusher locomotives had frequent opportunities to take on additional fuel and water as they were not "line haul" assignments. Coaling facilities were close at Susquehanna, and Port Jervis.
== Usage == In all, only four triplex locomotives were built, and only in the United States. Because the [[tractive effort]] of the locomotives was so great that the couplings and frames of the cars could not withstand it,<ref name="steam"/> the triplex locomotives could only be used to [[Bank engine|bank]]<ref name="Westing"/> heavy trains up steep grades. Even with their huge boilers, the Erie locomotives could only produce enough steam to run at {{cvt|10|mph|order=flip}}, the Virginian only {{cvt|5|mph|order=flip}}.<ref name="steam"/> The reason for this was the poor performance of the boilers due to the lack of exhaust draught from the driving wheelset under the tender.<ref>{{cite journal |title=HO 2-8-8-8-2 Triplex |journal=Modèles Européens 2011 |page=11| editor=M.T.H. Electric Trains |location=Columbia (MD) |url=https://archive.org/details/manualzilla-id-6310498/page/11/mode/1up |access-date=23 October 2023 |language=fr}}</ref>
The Erie locomotives were used as helpers on the Susquehanna Hill also known as the [[Gulf Summit, New York|Gulf Summit]], near [[Deposit, New York]], on the [[Southern Tier Line]]. After 13 years they were replaced by 2-10-2s and retired.<ref name="steam"/> All Erie triplex locomotives had been scrapped by 1930, and none have survived. [[File:Virginian Railway Class AF -610.jpg|thumb|Virginian Railway Class AF]] The Virginian XA #700 [[2-8-8-8-4]] was unsuccessful. It was returned to Baldwin, where it was rebuilt into a Class MD [[2-8-2]], numbered 410, and a Class AF [[2-8-8-0]], numbered 610. A two-wheel trailing truck was later added, making it into a [[2-8-8-2]]. These two locomotives were operated until 1953.<ref name="steam">{{cite web |title=2-8-8-8-2/4 "Triplex" Steam Locomotives in the USA |url=https://www.steamlocomotive.com/locobase.php?country=USA&wheel=Triplex |archive-url= |archive-date= |access-date=10 October 2025 |website=steamlocomotive.com}}</ref>
== References == <references/>
== Patent == * {{patent|US|1629369|"Triple-expansion mallet locomotive." by [[Samuel M. Vauclain]] assigned to the [[Baldwin Locomotive Works]] filed on November 25, 1925}}
==External links== * {{cite web |title=2-8-8-8-2 Triplex Articulated Steam Locomotives & 2-8-8-8-4 Triplex Articulated Steam Locomotives |url=https://www.toytrains1.com/triplex.htm |website=Web Site of ToyTrains1 |access-date=2023-10-29}} Site about commercial model train triplex locomotives
{{Whyte types}}
[[Category:Steam locomotive types]] [[Category:2-8-8-8-2 locomotives]] [[Category:2-8-8-8-4 locomotives]] [[Category:Scrapped steam locomotives]]