How to Rig a tank with reactive tracks and wheels.

I’m trying to learn how to Animate my various tanks for a scholarship entrance also just for the knowledge of how to do it to give my creations more life. Maybe make a short film or 2. There is an example file @ this link.

I want to know how he did it. I’ve tried downloading the file and dissecting it but I’m missing how it all works. I was wondering if anyone knows of a tutorial on how to do it like this. Or if you wouldn’t mind showing me. Thanks.

Also here’s some tanks. Just a few Examples :]