Simon,
What you say is partially true. However, if a modeler wants to run his train on a 2 rail scale track system, the 3 rail wheels with their large flanges and oversize width must be replaced or machined to a 2 rail scale profile or the locos will not go through scale switches without derailing. For most steam (and electric locos with quill drivers like the GG-1) this requires the use of a good metal lathe. Finding replacement scale drivers is not impossible but matching them up with the original model's crankpins, axles etc may be more difficult than just machining the original driver centers to accept scale tires.
Most diesels can be converted by using NWSL scale wheel sets insulated for 2 rail operation. In the case of battery power, insulation would not be necessary but I am not a big proponent of battery power at this time.
Joe Foehrkolb
