Re: Maximum grade for NG RR lines?

Randy,
Based on reading "Ghost Railroads of Kentucky" it would appear that Kentucky loggers preferred the Climax Locomotive.
Whether a Climax, Heisler or Shay locomotive, most grades would probably not have been more than 7% with occasional small stretches that could reach probably no more than 10-13% and I would expect these to be rare.
From what I have seen around the country on tourist lines, geared locos could work tonnage on 6-7% grades with little or no problems. Like mainline railroaders most loggers would prefer to keep the grades as low as possible in order to increase the tonnage that they could haul.