The large center gear is hooked up to a windshield wiper motor. Here's video of it (sorry for the shakey cam) [nomedia="http://www.youtube.com/watch?v=LYeiXTbHbiM"]YouTube - Steampunk Bar[/nomedia]
The gears move a little too fast and it's kind of noisy. It's turning at 38rpm's with a 12V power supply. 5V should drop it to 15rpm and hopefully reduce the noise.