Here is a link from a Google search for railroad log loading. This link will take you to another forum and in that link is a similar question which will take you to another forum with a fairly up to date photo of loading logs using a grapple that is mounted on a log trailer truck.
http://www.railroad.net/forums//viewtopic.php?f=53&t=42052I do know there are scale model log loaders on trailer trucks and a log loader that looks like a modified bucket loader. Check Walther's for log loader or do a Google search for ho scale log loader.
Rich