I thought about adding also the motor controller, so you can just remove that element from your body and use that space for something else. Though it's not really needed to put the controller there if you what to use another type, or just want to place it with the rest of your electronics.
Also, as the motor controller supports two motors, you could place it in one of the tracks, and just send the power cables to the second motor. I'll show that later with pictures, so you know how to do that.
For each track you will need the following parts:
- 1 Yellow DC Gear Motor (like this one)
- 1 mini DC motor controller(like this)
- Some M3 wood screws (get them here) (I find them to work perfect with 3D printed stuff. I used 10 mm ones here, but I'd recommend getting a bunch of measures, because you'll use them for sure)
The main page for this project is in here my blog, were I'll be updating and linking related projects that use this thing
The design can be found in its thingiverse page