The Union Pacific Railroad ordered a single locomotive with a 4-12-2 wheel arrangement and the American Locomotive Company delivered it in March of 1926. This locomotive was the first locomotive built with this wheel arrangement and was given the name "Union Pacific" for the Railroad that first used this type of locomotive. It was designated as Class UP-1 and assigned road number 9000. It had 67" diameter drivers, three 27" diameter cylinders (two with 32" stroke and one with a 31' stroke), a 220 psi boiler pressure, it exerted 96,646 pounds of tractive effort and weighed 495,000 pounds. Later in 1926, fourteen more of these locomotives were delivered from ALCO and were designated as Class UP-2 and given road numbers 9001 through 9014. These locomotives were similar to number 9000.
In 1928, 1929 and 1930 a total of seventy-three more "Union Pacific" type locomotives were added to the UP roster. Class UP-3 included twenty-three locomotives, which were assigned road numbers 9015 through 9029 for those used on the UP and road numbers 9055 through 9062 were assigned to the eight locomotives that were used on the OWR&N. Twenty-five locomotives were designated as Class UP-4 and were assigned road numbers 9030 through 9054. The last group of twenty-five was designated as Class UP-5 and included 9078 through 9087 for those locomotives used on the UP and numbers 9500 through 9514 for the fifteen that were used on the OSL.
The American Locomotive Company built all eighty-eight of these fast freight locomotives for the Union Pacific Railroad. They were three-cylinder locomotives with the third cylinder located in the center of the steam chest. The third cylinder drove an eccentric in the axel of the second pair of drivers. The fourth set of drivers were flangeless, but it was later determined that this was not necessary and a small flange was added to these drivers. They were built to the same basic specifications as its first delivered "Union Pacific" type locomotive, number 9000. The UP ran the 4-12-2 "Union Pacific" locomotives at 50 mph hauling 120 car trains.
There is one surviving UP 4-12-2 "Union Pacific" type locomotive. It is number 9000 displayed at the Los Angeles County Fairplex in Pomona, CA
|Class||Qty.||UP Numbers||Road||Road Numbers||Year Built||Builder||Notes|
Brooks delivered 28 engines, Schenectady 50.
Valve motion had limited cutoff. The firebox's enormous heating surface included 62 sq ft (5.76 sq m) of arch tubes and a long combustion chamber. Alfred W Bruce,The Steam Locomotive in America - Its development in the twentieth century (New York: W W Norton, 1952), pp 302-303) observed that part of that combustion chamber was created by a low wall placed just behind the last driving axle. Thus the effective grate was reduced, but overall direct heating service was preserved.
The two outside cylinders had 32-in strokes; the inside cylinder was driven by Gresley conjugated gear and had a 31-in stroke. Notice the very rare instance of identical tube and flue diameters. Although the center motion gave some maintenance problems and the fixed wheelbase was the longest ever mounted, these "Union Pacifics" were considered a great success. Bruce notes with satisfaction that the locomotives had been delivered as "slow-speed units" with a restriction of 35-mph. "However," Bruce comments,"because of the long wheelbase the engines were very stable riding [sic], and speeds of 60 mph or over were very frequently reported." They also handled 2 % grades and 6-8 degree curves despite their extreme length.
No other railroads built such long-wheelbase engines, however. Another unusual note about this class was that the highest axle loading was found on the trailing truck under the firebox and not one of the driving axles.
Note on the cylinder and valve gear layout: Based on correspondence with John E Bush and examination of photos in the latter's book, Wes Barris (http://www.steamlocomotive.com/3cylinder/, viewed 30 March 2004) has concluded that the first axle was in fact not cranked. Instead, the spacing between the first two axles was 18" greater than was true of the other four. He notes that Barry Koeb, an R&LHS member responsible for the UP 9000 has been inside that engine's frame and saw no crank.
"The Cowboy" (email@example.com as of 30 March 2004) creates new files for the virtual railroad simulator Trainz Railroad Simulator 2004. In his notes on the UP 9000 series he adds quite a bit of additional information. The center cylinder and piston rod were raked at 8 degrees above the horizontal to clear the first axle. He adds: "This inclination resulted in a uneven positioning of the intervals for the 3 cylinders. When looking at the locomotive from the right side, the intervals are as follows rotating in a clockwise manner: 112 Degrees to the middle pin, then 128 Degrees to the left pin finally 120 degrees back to the right pin. This positioning gave the locomotive a very distinctive and uneven sounding exhaust."
TheCowboy says that the friction bearings in the Gresley gear wore quickly and that 8 of the class were converted to a "third-link" motion layout in which a second Walschaert gear was added to the right side. This additional link transmitted motion to the inside cylinder through a rocker arm. Later 9000s had roller bearings on their Gresley gear and were not so modified.
He also notes that the air compressors on the early 9000s, whose smokebox location gave the class such a distinctive look, were easier to maintain when they were moved to the sides of the boiler. The result gave rise to the name "Bald-Faced Nines".
|Specifications by Steve Llanso|
|Class||UP-1 to UP-5|
|Railroad||Union Pacific (UP)|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.59|
|Overall Wheelbase (engine & tender)||91.50'|
|Axle Loading (Maximum Weight per Axle)||60000 lbs|
|Weight on Drivers||354000 lbs|
|Engine Weight||496500 lbs|
|Tender Light Weight||310599 lbs|
|Total Engine and Tender Weight||807099 lbs|
|Tender Water Capacity||18000 gals|
|Tender Fuel Capacity (oil/coal)||22 tons|
|Minimum weight of rail (calculated) on which locomotive could run||98 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||220 psi|
|High Pressure Cylinders (dia x stroke)||27" x 32" (2)|
|Low Pressure Cylinders (dia x stroke)||27" x 31" (1)|
|Tractive Effort||96646 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||3.66|
|Firebox Area||591 sq. ft|
|Grate Area||108.25 sq. ft|
|Evaporative Heating Surface||5853 sq. ft|
|Superheating Surface||2560 sq. ft|
|Combined Heating Surface||8413 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||276.01|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||23815|
|Same as above plus superheater percentage||30960|
|Same as above but substitute firebox area for grate area||169026|