Adding some wheels
First, I'm going to create some small wheels at the bottom of the track, your track might not have these, but mine does!! Create your wheel, duplicate it once.
Now go to the animation menu>constraints>orientation constraint, click and then click on your first wheel (I changed the color of mine to orange). Select and rotate your small_wheel01, the other should follow. Now duplicate small_wheel02 as many times as you need to and link them all to position_icon.
Lets wire small_wheel01 to the position_icon. Select small_wheel01 go to the animation>wire parameters menu, now select rotation_Y, select position_icon >position_Y. In the dialog connect position_icon to small_wheel01. I used a simple minus Y_position divide by value, again use whatever value gives the best results. (mine was 5)
All that's left is to create is some bigger wheels, you can follow the same method I used (if you want) for doing this.:)
The only obvious thing is that this isn't setup for turning the tank. I'm still looking into a good solution for doing this, any ideas? If you do turn your tank, remember to set your coordinates to local, that way the tracks will still function properly. Any other questions feel free to email me. Have fun, and here's the file: