Showing how to create a representation of gears in 3D, Shawn Sheehan chooses the old school method of stacking layers to achieve a faked 3D look.
The value here not only are the expressions but also the workflow in which Shawn uses, creating the gears in Illustrator, and then bringing the vector gears into After Effects manipulating them with expressions.
In this tutorial, you will learn how to create 3D cartoon gears without using Ray-traced shape layer extrusions or the CINEWARE plug-in
Shawn shows how to create the gears in 3D, and shows how to drive the gear rotations and ratios properly using expressions in After Effects. Check out the tutorial for Creating Meshing 3D Gears with Expressions in After Effects here.