When I was a kid, I used to take things apart to see how they worked. I remember being fascinated at the tiny little gears that I found in the first watch that I opened.
Gears make things move, and are an indispensible part of any mechanical device, real or imagined.
Give yourself plenty of room to work. I started with a file that was 300 x 300 pixels. Before you begin working, take a look at your Style palette. To make your life easier while doing this tutorial, make sure this box is checked. This will keep your palette colors and styles from changing when you switch tools.