This paper presents a grammar-based designer assistance tool for Epicyclic Gear Trains (EGTs) that helps designers generate concepts of EGT structures during conceptual design. The tool is comprised of three parts. The first is a grammar-based graph generation engine, the second is afunctional schematic sketching module and the third is a concept selection module.. Here we highlight the implementation of the first two modules. This is an initial exploration of using grammar-based generation routines to build an interactive designer assistance tool (DAT) for mechanism design.