Over the years, AFOLs have come up with lots of different ways to represent continuous tracks in micro. Most techniques involve stretching a tire, like this or this.
This tank by Fredoichi uses the narrow Technic link chain wrapped around a Technic liftarm.
The designers at LEGO came up with a simple solution for the micro crane in the 2010 City Advent Calendar, set 2824. They used a Technic liftarm.
Other micro vehicles in set 2824 include a bulldozer, a fire truck, an airplane, and a helicopter. See them all in this photo review.