Class UP-1 to UP-5 (Locobase 290)

Brooks delivered 28 engines, Schenectady 50.

Valve motion had limited cutoff. The firebox's enormous heating surface included 62 sq ft of arch tubes and a long combustion chamber. Alfred Bruce (The Steam Locomotive in America, 1950, 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, 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" (permstev@cableone.net 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".