This is a drivetrain that utilizes 4 CIM motors and a two-speed shifting gearbox. When the gearbox shifts into a low gear, the middle wheel shrinks in size by 1/8", allowing all 6 wheels to be in contact with the ground. The fact that the drivtrain has more torque in this gear means that it can turn itself easily, but other forces (ie other robots) can't. When it is in high gear, it grows an 1/8" to let only 4 of the 6 wheels touch the ground at any point in time. This "rock" in the drivetrain allows to to turn more easily as it has a higher speed in this gear. It is entirely shaft driven.