Union Pacific Challengers

The Union Pacific Railroad took delivery of the very first locomotive with the 4-6-6-4 wheel arrangement in 1936 when it received 15 of them from the American Locomotive Company. These newly named "Challengers" were designated Class CSA-1.

In 1937, another 25 ALCO-built "Challengers" were added to the roster. This group, designated Class CSA-2, was given road numbers 3915 through 3939. They were similar to the Class CSA-1s. Six of them, numbers 3934 through 3939, were equipped for passenger service.

In 1942, ALCO delivered 20 Class 4664-3 "Challengers" which were numbered 3950 through 3969. The tenders on these locomotives were larger than either of the CSA classes.

In 1943, another 25 Class 4664-4 "Challengers" came from ALCO and were numbered 3975 through 3999. This group was very similar to the Class 4664-3s except that each weighed 6,500 pounds more.

A final 20 ALCO-built "Challengers" arrived in 1944 giving the Union Pacific a total of 105 of the 4-6-6-4s. These locomotives designated Class 4664-5 were similar to the Class 4664-3s except for an additional 7,500 pounds in the total weight. They were numbered 3930 through 3949 which required that the Class CSA-1 and CSA-2 locomotives be renumbered into the 3800 series.

An article by King in "Trains" in the early 2000s stated that the later UP Challengers cost around $130,000.00.

There are two surviving Union Pacific Class 4664-4 "Challengers", number 3977 at Cody Park in North Platte, NE and number 3985 which is operational and used in excursion service by the Union Pacific.

UP 4-6-6-4 Roster
ClassQty.Road NumberLater NumbersYear Built Builder Notes
CSA-1153900-39143800-38141936ALCO1
CSA-2193915-39333815-38331937ALCO2
CSA-2 63934-39393834-38391937ALCO3
4664-3203950-39691942ALCO4
4664-4253975-39991943ALCO5
4664-5203930-39491944ALCO6

Notes
  1. Delivered with road numbers 3900-3914 and renumbered 3800-3814 in 1944. Converted to oil burners in 1943. Numbers 3801, 3802, 3804, 3807, 3809, 3811 & 3814 were converted to burn coal in 1950 and renumbered in the 3700 series and later that same year converted back to burn oil and retuned to the 3800 series numbers. Numbers 3800-3814 scrapped between 1956 and 1961.
  2. Delivered with road numbers 3915-3933 and renumbered 3815-3833 in 1944. Number 3915 converted to burn oil in 1942. Numbers 3817 & 3818 converted to burn coal in 1950 and renumbered in the 3700 series and later that same year converted back to burn oil and returned to the 3800 series numbers. Numbers 3815-3833 scrapped between 1956 and 1960.
  3. Delivered with road numbers 3934-3939 and renumbered 3834-3839 in 1944. Numbers 3934-3939 delivered equipped for passenger service and converted to burn oil in 1937. Numbers 3934-3939 scrapped between 1956 and 1960.
  4. Numbers 3950-3969 scrapped between 1956 and 1961.
  5. Numbers 3975-3984 converted to burn oil and renumbered 3708-3717 in 1952. Numbers 3975-3999 scrapped between 1959 and 1961.
  6. Numbers 3930-3932, 3934, 3937, 3938, 3943 & 3944 were converted to burn oil and renumbered 3700-3707 in 1952. All scrapped between 1952 and 1960.

Specifications:
ClassCSA-1CSA-2CSA-24664-34664-44664-5
Road Numbers:3900-39143915-39333934-39393950-39693975-39993930-3949
Wheel Arrangement:4-6-6-44-6-6-44-6-6-44-6-6-44-6-6-44-6-6-4
Length:110'-7 1/8"110'-7 1/8"110'-7 1/8"121'-10 7/8"121'-10 7/8"121'-10 7/8"
Drivers:69" dia.69" dia.69" dia.69" dia.69" dia.69" dia.
Weight on Drivers:386,000 lbs.403,000 lbs.404,400 lbs.404,000 lbs.407,500 lbs.406,200 lbs.
Total Locomotive Weight:566,000 lbs.582,000 lbs.584,000 lbs.627,000 lbs.633,500 lbs.634,500 lbs.
Locomotive & Tender Weight:876,000 lbs.892,000 lbs.894,000 lbs.1,063,500 lbs.1,070,000 lbs.1,071,000 lbs.
Grate Area:108.2 sq. ft.108.25 sq. ft.108.25 sq. ft.132.2 sq. ft.132.2 sq. ft.132.2 sq. ft.
Cylinders (dia. x stroke):(4) 22. x 32.(4) 22. x 32.(4) 22. x 32.(4) 21. x 32.(4) 21. x 32.(4) 21. x 32.
Boiler Pressure:255 psi255 psi255 psi280 psi280 psi280 psi
Tractive Effort:97,300 lbs.97,300 lbs.97,300 lbs.97,350 lbs.97,350 lbs.97,350 lbs.
Tender Capacity:
Water:18,350 gals.18,106 gals.18,106 gals.25,000 gals.25,000 gals.25,000 gals.
Coal:22 tons22 tons22 tons28 tons28 tons28 tons

Photos

References

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