Union Pacific Challenger

For the Union Pacific passenger train, see Challenger (train).

Union Pacific Challenger
Union Pacific 3985 runs through Alton, Iowa, on October 1, 2008
Type and origin Power type Steam Designer CSA Class : Arthur H. Fetter 4664 Class : Otto Jabelmann Builder American Locomotive Company (ALCO) Build date 1936–1944 Total produced 105 + (6 Denver & Rio Grande Western)
Specifications Configuration: ​  • Whyte 4-6-6-4  • UIC (2′C)C2′ h4 Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Driver dia. 69 in (1,753 mm) Wheelbase 60 ft 4+1⁄2 in (18.402 m) Engine 121 ft 10+7⁄8 in (37.157 m) Engine + tender Adhesive weight 404,000 lb (183,251 kg) Loco weight 4664 3/4 : 627,900 lb (284,800 kg) 4664 5 : 634,500 lb (287,800 kg) CSA 1/2 : 566,950 lb (257,160 kg) Tender weight 446,000 lb (202,000 kg) Total weight 1,073,900 lb (487,100 kg) Fuel type Coal, oil Fuel capacity 32 short tons (29 t; 29 long tons) 6,450 US gal (24,400 L; 5,370 imp gal) UP3985 Water cap. 25,000 US gal (95,000 L; 21,000 imp gal) Firebox: ​  • Grate area 4664 Class : 132 sq ft (12 m2) (grate removed in 1990) CSA 1/2 = 108.25 sq ft (10 m2) Boiler 94 in (2,400 mm) Boiler pressure 4664 3/4/5 : 280 lbf/in2 (1.93 MPa) CSA 1/2 : 255 lbf/in2 (1.76 MPa) Heating surface: ​  • Firebox 4664 3/4 : 602 sq ft (55.9 m2) 4664 5 : 602 sq ft (55.9 m2) CSA 1/2 = 548 sq ft (50.9 m2)  • Tubes 527 sq ft (49.0 m2)  • Flues 3,687 sq ft (342.5 m2)  • Total surface 4,795 sq ft (445.5 m2) Superheater: ​  • Heating area 2,162 sq ft (200.9 m2) Cylinders Four Cylinder size 4664 3/4/5 : 21 in × 32 in (533 mm × 813 mm) CSA 1/2 : 22 in × 32 in (559 mm × 813 mm)
Performance figures Maximum speed 70 mph (110 km/h) Tractive effort 4664 3/4/5 : 97,352 lbf (433.04 kN) CSA 1/2 : 97,305 lbf (432.83 kN) Factor of adh. 4664 3/4/5 : 4.15 CSA 1/2 : 4.11
Career Operators Union Pacific Railroad Class CSA-1, CSA-2, 4664-3, 4664-4, 4664-5 Preserved Two (Nos. 3985 and 3977) Restored No. 3985; April 1981 Disposition No. 3985 awaiting restoration, No. 3977 on display, remainder scrapped

The Union Pacific Challengers are a type of simple articulated 4-6-6-4 steam locomotive built by American Locomotive Company (ALCO) from 1936 to 1944 and operated by the Union Pacific Railroad until the late 1950s.

A total of 105 Challengers were built in five classes. They were nearly 122 ft (37 m) long and weighed 537 short tons (487 tonnes). They operated over most of the Union Pacific system, primarily in freight service, but a few were assigned to the Portland Rose and other passenger trains. Their design and operating experience shaped the design of the Big Boy locomotive type, which in turn shaped the design of the last three orders of Challengers.

Two Union Pacific Challengers survive. The most notable is Union Pacific No. 3985, which was restored by the Union Pacific in 1981, then operated in excursion service as part of its heritage fleet program. Mechanical problems forced it out of service in October 2010; it was retired in January 2020 after the restoration of the 4-8-8-4 Big Boy 4014 and eventually donated to the Railroading Heritage of Midwest America in 2022. These were later sold to Clinchfield Railroad in 1947 and were renumbered as 670-675, where they formed the Clinchfield's Class E-3.

Preservation

Only two Challengers survive, both from the 4664-4 order built in 1943. No. 3977 is on static display in North Platte, Nebraska. No. 3985 was restored to operating condition by Union Pacific in 1981 and used in excursion service until mechanical problems sent it back into storage in October 2010. It was officially retired in January 2020 and is stored in Cheyenne, Wyoming, but has since been acquired by the Railroading Heritage of Midwest America (RRHMA), who have plans to restore the locomotive to operation once again.

Surviving Challenger locomotives

Type	Number	Image	Date built	Serial number	Location	Coordinates	Notes
4664-4	3977		June 1943	70160	Cody Park, North Platte, Nebraska	41.147853°N 100.753113°W / 41.147853; -100.753113 (Challenger 3977)	Displayed next to EMD DDA40X #6922. Painted in two-tone gray passenger scheme.
4664-4	3985		July 1943	70174	Union Pacific Railroad, Cheyenne, Wyoming	41°7′46.9308″N 104°48′49.1688″W	No. 3985 was restored in 1981 and used by Union Pacific on excursions until October 14, 2010, when mechanical problems forced it from service. It was officially retired in January 2020. The locomotive's tender, No. 25-C-311, has since April 2019 been assigned to the restored Big Boy, No. 4014. In 2022, No. 3985 was donated to the RRHMA, with plans to restore the locomotive to operation.

See also

• Union Pacific Big Boy
• Union Pacific FEF Series

Bibliography

• Drury, George (2015). Guide to North American Steam Locomotives (2nd ed.). Kalmbach Publishing. ISBN 978-1-62700-259-2.
• Solomon, Brian (2009). Alco Locomotives (1st ed.). Voyageur Press. ISBN 978-0-7603-3338-9.

Further reading

• Ehernberger, James L. (1993). Union Pacific Steam Challenger Portraits (1st ed.). Challenger Press. ASIN B000TXFDIC.
• Kratville, William W. (1980). The Challenger Locomotives (1st ed.). Kratville Publications. ASIN B0006E9WN6.

External links

• Union Pacific Steam Shop Information on locomotives and excursion schedules.
• UP 3985 Challenger, Steam Locomotive - photos and additional information