It’s easy to make a swerve drive, just build a pivoting wheel with a motor and you are done. Some issues around supplying power / control to the motor that is driving the wheel. To get around that you can build a Coaxial Swerve Drive. Both motors sit above the swerve wheel. Some form of gearing drives a shaft that goes down the pivot point to drive the wheel. A number of successful teams have Coaxial Swerve Drive, they are very nimble.
I came across this Lego swerve drive http://www.chiefdelphi.com/forums/showthread.php?threadid=137446 and thought it was pretty cool. I’m thinking of building one, but having a hard time with the upper support gear. I’m thinking of just drilling a hole in one of the large gears to pass the shaft through, but thought I’d throw it out here to see if anyone has any better ideas.
Orbit, one of the new 2015 HEXBUG VEX Robotics toys sets, contains some parts that will be useful for building a coaxial swerve out of standard VEX IQ parts. This set includes two different methods of transferring coaxial rotary motion, and would be useful for creating a coaxial swerve drive.
The first, is a new 36 Tooth Dog Gear, which has a center round hole in the 36 tooth gear. The other is a new XL Turntable Outer Housing and XL Turntable 36 Tooth Ring Gear Bushing; these can be assembled together into a turntable. A photo of these new parts is attached:
The 2015 HEXBUG VEX Robotics kits will be available in retail stores this fall.