[EricH]

A "jump" drive, as I recall, switches between two drive systems. The most common are the "octocanum" or "butterfly" drivetrains, which switch between a traction wheel and a mecanum wheel, or occasionally an omni wheel.

Just to give a little more detail into swerve or crab drive, there are a number of different subtypes, but in the interest of simplicity: the robot can go in any direction without turning. Some internal wheel-turning configurations can turn the robot, some cannot. Some require lots of chain, some do not.

And, to elaborate on West Coast Drive (WCD): A "true" WCD is 6WD, dropped center wheel directly driven from a 2-speed gearbox on each side, with chain runs to the outer wheels, and all wheels cantilevered outside of the frame. They've been used for over 10 years, and have been very effective the whole time. There are a number of variations and tweaks; the most common is to move the wheels inside of the frame and use chain drive on all of them. 8-wheeled WCDs have been cropping up as well.