This is an N scale version using mostly balsa, miscellaneous dowels, and two tuna cans. All scales, (N, HO, OO, O) can be constructed using basic materials and common hardware store materials. To make life easier for the N scale version I used Plastruct railings and stairs. There are thirty heat exchanger tubes in the Heat Exchanger structure. Having a drill press that doubles as a lathe helped out. It's been a long time in the making. Now maybe I can get outside for some sunshine for a while before starting on the next project.