After reading Al Krug's great description of driving a 4-8-4 Northern ( http://krugtales.50megs.com/rrpictale/steam700/steam700a.htm ), I have one question. It seems that the loco's cab has a gauge the shows cyclinder back pressure which he used to determine when and by how much to reduce the cutoff. Could any of you loco drivers give an explanation of this gauge it to me?
Bob
Bob