Mount Washington Cog Railway #9 "Waumbek" comes off Long Trestle at 5300 MSL, clawing her way to Skyline Switch, just a couple of hundred yards ahead. There, the hard work will pretty much be done and the grade will ease considerably. Just beyond the train, is the west face of 5500 ft. Mt. Clay, which adjoins Mt. Washington to the north. Folks often ask about the source of the steam plume seen above the cab. This is called a side-stack exhaust. These cog locomotives don't have a conventional valve gear that would enable the Engineer to adjust the steam cutoff to the cylinders. Instead, a side-stack valve, controlled from the cab can allow exhaust steam to bypass its normal path to the smokebox, thereby reducing backpressure on the pistons when needed. When you see these locomotives on the steep grades, the side-stack exhaust is usually pouring out a pretty good plume....as you see here.
