I consider mechanical repairs to be repairs that involve removing and replacing parts that are held on with screws or other fasteners. These are repairs that were anticipated by the company that built the model and can be made with common tools and no destructive disassembly. Most mechanical repairs can be made without damaging a painted locomotive. Examples of mechanical repairs would be replacing bent tender trucks or worn gearboxes.
Sometimes a particular mechanical part is too worn out to repair, and is no longer available from the manufacturer. In those cases we can install new parts from companies like North West Short Line and get your locomotive back on the tracks.