Superheaters and Throttle Linkage

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On very early superheated locomotives, a damper inth e smokebox restricted the flow of furnace gases through the flues containing the superheater units when the throttle was closed.  The presence of this type of device is usually visible by way of a small pendulum-shaped counterweight that is located on the outside of the smokebox, near the front tube sheet on the engineer's side.  PRR used this device extensively.  It was also found on N&W's K2's as built, perhaps others. Its use was eventually discontinued, probably by the early 1920s.

Dave Stephenson