Can anyone shed light on the function of the steam exhaust pipe running toward the rear of the locomotive? Note: there are two pipes from this right rear cylinder, one to the smokebox for draft, and one that goes toward rear of locomotive in front of right rear driver. What is the function of this rearward facing steam exhaust pipe? Anyone with a blueprint, drawing, or photo of engine under construction may be able to determine where this pipe is going. Appreciate any ideas.