4-6-6-4

{{Short description|Articulated locomotive wheel arrangement}} {{Redirect|4664|the year|5th millennium|the number|4000 (number)}} [[File:Union Pacific Steam Locomotive 3814 fetter challenger.jpg|thumb|300x300px|Union Pacific Challenger No. 3814 was one of the first examples of a 4-6-6-4 locomotive]] In the [[Whyte notation]] for classifying steam locomotives by wheel arrangement, a '''4-6-6-4''' is a [[railroad]] [[steam locomotive]] that has four [[leading wheel]]s followed by two sets of six coupled [[driving wheel]]s and four [[trailing wheel]]s. 4-6-6-4s are commonly known as '''Challengers'''.<ref>{{Cite web|url=https://www.steamlocomotive.com/locobase.php?country=USA&wheel=4-6-6-4&railroad=up#341|title=Union Pacific 4-6-6-4 "Challenger" Locomotives in the USA|website=www.steamlocomotive.com|access-date=2019-05-08}}</ref>

A similar wheel arrangement exists for [[Garratt locomotive]]s, on which both engine units swivel, but is referred to as [[4-6-0+0-6-4]].

Other equivalent classifications are:<br /> [[UIC classification]]: '''2CC2''' (also known as German classification and [[Italian classification]])<br /> [[French classification]]: '''230+032'''<br /> [[Turkish classification]]: '''35+35'''<br /> [[Swiss classification]]: '''3/5+3/5'''

The [[UIC classification]] is refined to '''(2'C)C2'''' for simple [[articulated locomotive]]s.

Challengers were most common in the [[Union Pacific Railroad]], but many other railroads ordered them as well. The vast majority of these were built by the [[American Locomotive Company]], although the [[Baldwin Locomotive Works]] also built Challengers for two customers: the [[Denver and Rio Grande Western Railroad|Denver and Rio Grande Western]] and [[Western Maryland Railway]]. An expansion for the [[Union Pacific Challenger]] class was the [[Union Pacific Big Boy]] class, being a [[4-8-8-4]], instead of a 4-6-6-4.

Today, the only Challenger locomotives that survive were both owned by Union Pacific. One such locomotive, [[Union Pacific 3985]], was operated by the Union Pacific Railroad in [[Excursion train|excursion service]] from 1981 to 2010, when mechanical problems took it out of service. It was retired in January 2020 due to its poor mechanical condition<ref>{{Cite web|last=Keefe|first=Kevin|title=The Challenger at high tide|url=http://cs.trains.com/ctr/b/mileposts/archive/2020/01/17/the-challenger-at-high-tide.aspx|work=Classic Trains}}</ref> and subsequently donated to the Railroading Heritage of Midwest America, where it is now undergoing a second restoration.<ref>{{Cite web |title=Work begins on Union Pacific Challenger No. 3985 |url=https://www.trains.com/trn/news-reviews/news-wire/work-begins-on-union-pacific-challenger-no-3985/ |access-date=2023-01-07 |website=Trains |language=en-US}}</ref><ref>{{Cite web|title=Railroading Heritage of Midwest America - official website|url=https://rrhma.com/|publisher=Railroading Heritage of Midwest America|access-date=June 12, 2022|archive-url=https://web.archive.org/web/20220428204715/https://rrhma.com/|archive-date=April 28, 2022}}</ref><ref name="3985Donated">{{Cite web|last=Glischinski|first=Steve|date=April 28, 2022|title=Railroading Heritage of Midwest America, Union Pacific agree to donation of Challenger, other locomotives, cars|url=https://www.trains.com/trn/news-reviews/news-wire/railroading-heritage-of-midwest-america-union-pacific-agree-to-donation-of-challenger-other-locomotives-cars/|work=Trains|publisher=Kalmbach Media|access-date=June 12, 2022|archive-url=https://web.archive.org/web/20220428191606/https://www.trains.com/trn/news-reviews/news-wire/railroading-heritage-of-midwest-america-union-pacific-agree-to-donation-of-challenger-other-locomotives-cars/|archive-date=April 28, 2022}}</ref> The second example, [[Union Pacific 3977]] is on static display in Cody Park [[North Platte, Nebraska]].

Though originally intended for freight service, many units could be found for leading passenger consists as well.

==Roster of locomotives== Railroads that used the ''Challenger'' type locomotive include:

{| class="wikitable" |+ 4-6-6-4 construction roster ! Railroad (quantity) !! Class !! Road numbers !! Builder !! Build year !! Notes |- | rowspan=3 | [[Clinchfield Railroad]] (12 new, 6 secondhand) || E-1 || 650–657 || [[American Locomotive Company|ALCO]] || 1942–1943 ||Scrapped between 1953 and 1958 |- | E-2 || 660–663 || [[American Locomotive Company|ALCO]] || 1947 ||Scrapped between 1955 and 1959 |- | E-3 || 670–675 || [[American Locomotive Company|ALCO]] || 1943 || Ex-[[Denver and Rio Grande Western Railroad|D&RGW]], acquired 1947. Scrapped 1959 |- | [[Delaware and Hudson Railway]] (40) || J || 1500–1539 || ALCO || 1940–1946 ||Scrapped between 1951 and 1959 |- | rowspan=3 | [[Denver and Rio Grande Western Railroad]] (21) || L-105 || 3700–3709 || [[Baldwin Locomotive Works|Baldwin]] || 1938 |Scrapped between 1951 and 1956 |- | L-105 || 3710–3714 || Baldwin || 1942 ||Scrapped between 1951 and 1956 |- | L-97 || 3800–3805 || ALCO || 1943 || Diverted to the D&RGW from a UP order. To Clinchfield Railroad in 1947. Scrapped 1959 |- | [[Great Northern Railway (U.S.)|Great Northern Railway]] (2 secondhand) || Z-6 || 4000–4001 || ALCO || 1937 || Ex-[[Spokane, Portland and Seattle Railway|SP&S]] 903–904; sold back to SP&S March 1950 and July 1946 respectively. Scrapped between 1953 and 1957 |- | rowspan=3| [[Northern Pacific Railway]] (47) || Z-6 || 5100–5120 || ALCO || 1936–1937 ||Scrapped between 1950 and 1953 |- | Z-7 || 5121–5126 || ALCO || 1941 ||Scrapped between 1951 and 1954 |- | Z-8 || 5130–5149 || ALCO || 1943–1944 ||Scrapped between 1952 and 1957 |- | rowspan=2 | [[Spokane, Portland and Seattle Railway]] (8) || Z-6 || 900–905 || ALCO || 1937 || Identical to NP Z-6 class; 903–904 sold to GN January 1940; purchased back March 1950 and July 1946 respectively |- | Z-8 || 910–911 || ALCO || 1944 || Identical to NP Z-8 class |- | rowspan=5 | [[Union Pacific Railroad]] (105) || [[Union Pacific Challenger|CSA-1]] || 3900–3914 || ALCO || 1936 || To UP 3800–3814. Scrapped between 1957 and 1958 |- | [[Union Pacific Challenger|CSA-2]] || 3915–3939 || ALCO || 1937 || To UP 3815–3839. Scrapped 1958 |- | [[Union Pacific Challenger|4664-3]] || 3950–3969 || ALCO || 1942 ||Scrapped between 1958 and 1959 |- | [[Union Pacific Challenger|4664-4]] || 3975–3999 || ALCO || 1943 || No. 3977 and 3985 are preserved. |- | [[Union Pacific Challenger|4664-5]] || 3930–3949 || ALCO || 1944 ||Scrapped between 1957 and 1959 |- | [[Western Maryland Railway]] (12) || M-2 || 1201–1212 || Baldwin || 1940–1941 || These and the 15 units for the D&RGW were the only ones of this type made by Baldwin. Scrapped 1958 |- | [[Western Pacific Railroad]] (7) || M-100 || 401–407 || ALCO || 1938 ||Scrapped between 1953 and 1959 |}

==References== {{Reflist}}

== External links== * [https://web.archive.org/web/20051201200632/http://www.steamlocomotive.com/challenger/ The Challenger Type Locomotive] * [http://www.northeast.railfan.net/challenger.html The Union Pacific Challenger Roster] * [http://www.toytrains1.com/challenger.htm Web Site of ToyTrains1 4-6-6-4 Challenger Steam Locomotives]

[[Category:Whyte notation|66,4-6-6-4]]