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Nanaimo73: You're talking about the drivers being quartered - in other words, the crankpins on one side being 90 degrees from those on the other. This is true of two-cylinder simple locomotives; three-cylinder engines had the three cranks 120 degrees apart (you only saw the outer ones; the middle one was, of course, between the frames). Most railroads had the crankpins on the right side leading; in other words, when the pins on the right side were on the front dead center, the left side was on the top quarter; the left side therefore followed the right. The PRR was the most notable exception to this rule; most of its engines used left hand lead. There was a factor in the counterbalancing of a steam locomotive called "dynamic augment". This is the effect of piston thrusts on one side of the locomotive on the balancing on the opposite side. A peculiarity of this factor caused the side that had the lead (on most locomotives, the right side) to tend to pound the rail more than the other side. Someone advanced the theory (since no one has put it into print as an actuality) that the PRR used left hand lead so that the left side would pound the rail more than the right side. Since the left side is the inside on multiple track, and the track structure is weaker on the outside, this would cause the hardest pounding to occur in the strongest area of the roadbed. PRR had more multiple track than most railroads. This may be all wet, but it was advanced as a theory a good many years ago. Old Timer
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