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.
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 Then came a 5-year delay before 5095 was withdrawn in 1953 with the rest (5090-5093, 5097) retiring in 1954.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 of Sweat House Media|
|Class||FTT-1||FTT-1 - 2-cylinder|
|Railroad||Union Pacific (UP)||Union Pacific (UP)|
|Road Numbers||8000, 8800-8808||5090-5099|
|Locomotive Length and Weight|
|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 lbs||60400 lbs|
|Weight on Drivers||302000 lbs||306900 lbs|
|Engine Weight||404000 lbs||405700 lbs|
|Tender Light Weight||248600 lbs||308916 lbs|
|Total Engine and Tender Weight||652600 lbs||714616 lbs|
|Tender Water Capacity||12000 gals||12000 gals|
|Tender Fuel Capacity (oil/coal)||5200 gals||5200 gals|
|Minimum weight of rail (calculated) on which locomotive could run||101 lb/yard||102 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||210 psi||230 psi|
|High Pressure Cylinders (dia x stroke)||25" x 32"||27" x 32"|
|Low Pressure Cylinders (dia x stroke)||25" x 28" (1)|
|Tractive Effort||81459 lbs||72391 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||3.71||4.24|
|Firebox Area||357 sq. ft||357 sq. ft|
|Grate Area||84 sq. ft|
|Evaporative Heating Surface||5489 sq. ft||5461 sq. ft|
|Superheating Surface||1375 sq. ft||1375 sq. ft|
|Combined Heating Surface||6864 sq. ft||6836 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||301.92||257.52|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||17640||0|
|Same as above plus superheater percentage||21168||0|
|Same as above but substitute firebox area for grate area||89964||98532|