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Duplex Steam Locomotive / Steam discussion

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Quoth Overmod: "Opinion, likewise: the 'weak point' of the N&W J at high speed was lateral deflection of parts of the valve gear at high rpm, often encountered as a problem with 'conventional' piston-valve drives." Where did that opinion come from? The highest rotational speed credited to the J was undoubtedly the 115 MPH the 610 attained during tests on the PRR. This was just prior to the failure of the engine caused by the left valve freezing in its cage due to lubrication breakdown. If there was, as you opine, lateral deflection of the valve gear, it wasn't sufficient to cause problems at any RPM. When I worked at Shaffers Crossing 1959-1961 there was a Night Roundhouse Foreman there named Ed Payne. Payne had been on hand with the 610 during its tests on the PRR, and described the engine failure to me. He said that when the engine was brought back to Roanoke Shop and the valve heads removed, the valves and cages were discolored (yellow) and the conclusion was that something in the PRR's water treatment cut the lubrication of the valves. Bear in mind that the Js operated at 100 MPH every day (with, say, an inch or so of tire wear, that's 500+ RPM), but for relatively short distances. It was never necessary for the engine to be faster than it was; with the schedules and the territory on the N&W, speeds faster than that, sustained for long periods of time, were not necessary. But the 70" wheel produced a horsepower curve ideal for the N&W's topography and heavy passenger trains. The engine was capable of running track speed (curvature limits) UP any of N&W's mountains with any of the normal train consists. It was necessary for the J to start and accelerate these trains in difficult situations, on curves and grades, in all kinds of rail conditions - Northfork eastbound, on Elkhorn Mountain; Marion, Va. on the Bristol Line, Ada, W. Va., etc. There were sharp curves on Bluefield Mountain (Jug Neck) and Elkhorn (Bottom Creek Curve at Landgraff) where the J would have to accelerate its train back to track speed after a 25 MPH slowdown. The engine was never found wanting. I don't know enough about the Niagara and NYC's use of them to know what sustained speeds were expected of them. Did they operate at 100 MPH for miles on end? If such speeds were not expected of them, if NYC's 80 MPH limit was strictly enforced (or even with a 5 MPH tolerance), then one can ask the following questions: 1) Could the J have done everything expected of the Niagara on the NYC with NYC's traffic and topography? 2) Could the Niagara have done everything expected of the J on the N&W with N&W's traffic and topography? My feeling is that the answer to #1 is yes, and the answer to #2 is no. In other words, the J's 70" drivers would not be as much of a liability on the NYC as would the 79" drivers of the Niagara on the N&W. Old Timer
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