Union Pacific 4-10-2 (Southern Pacific or Overland) Type Locomotives

Class Details by Steve Llanso

Class FTT-1 (Locobase 289)

Data from tables in the 1930 Locomotive Cyclopedia, supplemented by the LA&SL 1 - 1928 Locomotive Diagram book (the Salt Lake Route) supplied in May 2005 by Allen Stanley from his extensive collection. (The 1930 Locomotive Cyclopedia was another source, but Locobase went with the railroad's data; the differences were not striking.)

The 8000 arrived in 1925, the 8800-8808 were delivered a year later.

By the Union Pacific's reckoning, these "Overlands" (others called them "Southern Pacifics") weren't particularly successful engines. Their three-cylinder layout - outside actuated by Walschaert, inside by Gresley conjugated valve gear - was mechanically complicated and the wheelbase was too rigid. The center cylinder inclined at 9 1/2 degrees to clear the first axle and drive the second. The outside cylinders drove the third axle. An unusual visual difference from many other locomotives was the straight bottom edge given to the smokebox, which allowed easier access to the third cylinder.

Yet, the even bigger 3-cylinder 4-12-2s from Alco dominated the prairies a few years later, which suggests that the Overlands suffered as much from being the pathfinders and a foreign road's design as anything else. See Locobase 288 for Alfred Bruce's assessment of the arrangement as it operated on the Espee.

They lasted on the LA&SL subsidiary until the late 1940s. In 1942, the class was "remodeled" from a 3-cylinder to a 2-cylinder type, these measuring 27" diameter by 32" stroke. For the result, see Locobase 13994.

Class FTT-1 - 2-cylinder (Locobase 13994)

Data from UP 11 - 1946 supplied in May 2005 by Allen Stanley from his extensive collection. See also the Challenger models account at http://www.railmodel.com/bulletins/chl/UP_4-10-2.htm and Wikipedia.

Locobase 289 describes these unusual freighters as they were delivered in their 3-cylinder configuration. Wikipedia quotes from James E Boynton's Three Barrels of Steam (Glenwood: Felton) on the problems presented by the floating bushings associated with the center cylinder.

Challenger notes that the 1942 program to remove the center cylinder and its Gresley conjugated link resulted in a noticeably large sand dome over the second and third axles and a fully round smokebox. A raised boiler pressure compensated to a large degree for the lost of cylinder volume.

Used in several regions, the class had joined the 9000s (3-cylinder 4-12-2) on the prairies in Kansas when they began retiring. Most had had the center driver replaced with a Boxpok main driver.

5094 and 5096 were the first to go out of service in 1948, followed by 5098-5099 in 1949. Then came a 5-year delay before 5095 was withdrawn in 1953 with the rest (5090-5093, 5097) retiring in 1954.


Specifications by Steve Llanso
ClassFTT-1FTT-1 - 2-cylinder
Locobase ID289 13994
RailroadUnion Pacific (UP)Union Pacific (UP)
CountryUSAUSA
Whyte4-10-24-10-2
Road Numbers8000, 8800-88085090-5099
GaugeStdStd
BuilderAlco-BrooksUP
Year19251942
Valve GearmixedWalschaert
Locomotive Length and Weight
Driver Wheelbase22.50'22.50'
Engine Wheelbase44.08'44.08'
Ratio of driving wheelbase to overall engine wheebase 0.51 0.51
Overall Wheelbase (engine & tender)82.42'84.77'
Axle Loading (Maximum Weight per Axle)60400 lbs60400 lbs
Weight on Drivers302000 lbs306900 lbs
Engine Weight404000 lbs405700 lbs
Tender Light Weight248600 lbs308916 lbs
Total Engine and Tender Weight652600 lbs714616 lbs
Tender Water Capacity12000 gals12000 gals
Tender Fuel Capacity (oil/coal)5200 gals5200 gals
Minimum weight of rail (calculated) on which locomotive could run101 lb/yard102 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter63"63"
Boiler Pressure210 psi230 psi
High Pressure Cylinders (dia x stroke)25" x 32" (2)27" x 32" (2)
Low Pressure Cylinders (dia x stroke)25" x 28" (1)
Tractive Effort81459 lbs72391 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.71 4.24
Heating Ability
Firebox Area357 sq. ft357 sq. ft
Grate Area84 sq. ft
Evaporative Heating Surface5489 sq. ft5461 sq. ft
Superheating Surface1375 sq. ft1375 sq. ft
Combined Heating Surface6864 sq. ft6836 sq. ft
Evaporative Heating Surface/Cylinder Volume301.92257.52
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation176400
Same as above plus superheater percentage211680
Same as above but substitute firebox area for grate area8996498532
Power L11657822345
Power MT605.10802.58

Photos

Reference

Credits

Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.