Thanks, DaOld Man. I used the miter gears to keep the mechanism as thin as possible. I didn't have a lot of space in the cabinet. Unfortunately in terms of cost, it's one of the more parts. The software (both the menu for picking games and the procedure to run the motor) was written by myself. It's modeled on the original iPod interface - with simple lists that let you filter by different attributes. You can view games by system (or games across all systems), then alphabetically, by developer/publisher, by year, most recently played, favorites, random, or keyword search. I use MAME's rom metadata to decide if a game is vertical (or not) and run a simple routine to run the motor toward a specific angle until it's within a half-degree of the target. By "drive" do you mean the motor controller? If so, it's a Phidgets brand controller. I like it because it connects directly with USB and programming APIs for many, many languages are available.