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.

Qty.ClassRoad NumbersYear BuiltBuilderNotes
15CSA-13800-38141936ALCO#1,2 & 3
19CSA-23815-38331937ALCO#9,4 & 5
6CSA-23834-38391937ALCO#6 &10
204664-33950-39691942ALCO
104664-43975-39841943ALCO#7
154664-43985-39991943ALCO
204664-53930-39491944ALCO#8

Notes
  1. Delivered with road numbers 3900-3914 and renumbered 3800-3814 in 1944.
  2. Numbers 3800-3814 were converted to burn oil in 1943.
  3. Numbers: 3801, 3802, 3804, 3807, 3809, 3810, 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 returned to the 3800 series numbers.
  4. Number 3815 was converted to burn oil in 1942.
  5. Numbers 3817 & 3818 were 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.
  6. Numbers 3834-3839 were delivered equipped for passenger service and were converted to burn oil on delivery in 1937.
  7. Numbers 3975-3984 were converted to burn oil and renumbered 3708-3717 in 1952.
  8. Numbers: 3930, 31, 32, 34, 37, 38, 43, & 44 were converted to burn oil and were renumbered 3700-3707 in 1952.
  9. Delivered with road numbers 3915-3933 and renumbered 3815-3833 in 1944.
  10. Delivered with road numbers 3934-3939 and renumbered 3834-3839 in 1944.

Specifications
 Class CSA-1Class 4664-3
Wheel Arrangement:4-6-6-44-6-6-4
Length:110' - 7"121' - 10"
Drivers:69" dia.69" dia.
Weight on Drivers:386,000 lbs404,000 lbs
Locomotive Weight:566,000 lbs627,000 lbs
Locomotive & Tender Weight:876,000 lbs975,500 lbs
Grate Area:108.2 sq ft132.3 sq ft
Cylinders (dia. x stroke):(4) 22" x 32"(4) 21" x 32"
Boiler Pressure:255 psi280 psi
Tractive Effort:97,300 lbs97,300 lbs
Tender Capacity:
Water:18,350 gals.25,000 gals.
Coal:22 tons28 tons

Union Pacific Challenger Weights
ClassWt. on DriversLocomotive WeightLocomotive & Tender
CSA-1386,000 lbs566,000 lbs876,000 lbs
CSA-2403,000 lbs582,000 lbs894,000 lbs
4664-3404,000 lbs627,000 lbs975,500 lbs
4664-4407,500 lbs633,500 lbs981,500 lbs
4664-5406,200 lbs634,500 lbs1,022,500 lbs

Photos

References

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