The Pennsylvania Railroad's class I1ssteam locomotives were the largest class of 2-10-0 "Decapods" in the United States, with 598 built 1916-1923. They were the dominant freight locomotive on the system until World War II, and they remained in service until the end of PRR steam in 1957. Nicknames for the type included Decs and Hippos, the latter due to the large boiler. Unlike smaller 2-10-0s that preceded them, the I1s design was huge, taking advantage of the PRR's heavy trackage and high allowed axle load, with a wide, free-steaming boiler. Large cylinders enabled the I1s to apply that power to the rails. However, the large boiler limited the size of the driving wheels, which made it impossible to mount counterweights large enough to balance the piston thrusts. As a result, they were hard riding at anything but low speeds and prone to slipping, and not popular with crews. Their power was undeniable, with one author describing them as "the holy terror of the PRR". Subclass I1sa increased maximum steam cut-off to admit steam for 78% of the piston stroke, boosting low speed tractive effort from. There was no obvious external difference except for a revised builders' plate. I1s locomotives were converted to I1sa during major overhauls; eventually 489 were converted while 109 remained as built. In 1923 PRR put engine 4358 on the Altoona test plant. The tests below were all stoker fired.
In two hours at it consumed of coal and averaged of tractive effort at the driver rims, corresponding to 6.4% thermal efficiency.
In one hour at it consumed of coal and averaged tractive effort, or 7.1% efficiency.
At it consumed of coal and averaged TE, for 7.1% efficiency.
At at 50% cutoff it consumed of coal in 30 minutes averaging TE, for an efficiency of just under 5.4%.
Preservation
Of the nearly 600 class I1 locomotives built for the Pennsy, a sole example, #4483, survived the scrapper's torch. The locomotive was retired in August of 1957. Following then Chief of Motive PowerHal T. Cover's instructions, the railroad moved the engine to its roundhouse in Northumberland, PA, along with several other retired steam locomotives labeled for preservation. There the engine sat until 1963, when the PRR sold it to the Westinghouse Air Brake Company and moved the engine to Wilmerding, PA. WABCO had originally sought a railroad-themed display for its headquarters to commemorate its heritage of supplying air brakes to America's railroads. #4483 saw little maintenance during its life as a display piece for the company and its condition deteriorated significantly, although the boiler's asbestos cladding was removed. By 1982, the company had grown tired of the locomotive on its front lawn. The Western New York RailwayHistorical Society acquired #4483 and moved the engine to Hamburg, NY, where it resides today, receiving occasional maintenance. Currently, the organization hopes to move the locomotive to the Heritage Discovery Center in Buffalo, NY, where the engine will sit on public display protected from the elements.
