Tracked vehicles are uncommon in SketchyPhysics, but they do pop up from time to time. They are uncommon because they cause lag and are extremely difficult to make. They are also some of the most unstable models, because they produce so many bug splats.
However, due to the new animEnt feature of lazyscript, lagless tank tracks have been produced. This is done through rapidly hiding/unhiding certain groups within a component, and was first used by mr.k.