[Cory]

A big reason teams have been using 6 wheel drive lately is because they can drop the center wheel a very small amount, which will allow them to turn easily on the carpet, yet afford similar traction to a 4WD robot. This is because when the robot goes to turn it is essentially pivoting on two wheels, rather than trying to drag 4 wheels across the carpet. Turning issues and current draw are two big problems with 4WD and 6WD helps with that. One disadvantage is that it's heavier than a 4WD bot due to two extra wheels.

In all the 6WD bot's I've seen, all the wheels are driven, each side by one or more motors, and driven like a tank, in the same manner as a 4WD robot.

There are many teams who built similar drive systems last year, and some over the summer. Im sure they'd be more than willing to give you detailed information