TIG's idea worked perfectly. Why didn't I think of that before?!
Here is a screenshot of my design showing the internal gear:

Now all I need to do is figure out this animation thing, and I will be able to show you how this contraption works!

Awesome! Thanks for all the input guys. I will give TIG's solution a try first, and post up my results if you are interested!

I need some help modeling an internal tooth gear. I found this one in the 3D Warehouse, but am finding it difficult to adjust it to suit my needs.
I found and downloaded the Involute Gear plugin which was extremely helpful in creating the other four small gears I needed. As far as I can tell, this plugin does not create internal gears.
Let me know if I should provide more info about my design, or clarification of my question.
Any guidance would be very much appreciated!