Download this handy PDF traction tire chart to determine what size traction tire your M.T.H. locomotive requires.
This document lists the recommended DC transformers for use with M.T.H. HO locomotives outfitted with Proto-Sound 3.0.
This document details the differences between the various sizes of Marklin C-Track HO Stud Rail curves. The chart includes a mm to inch comparison for each curve's radius.
This document details how to resolve a slipping drive train (the locomotive chuffs, but doesn't move) on the HO 4-8-2 Mohawk steam locomotive.