Mecanum wheels are commonly used in robotics to achieve 3 degrees of motion from a drivetrain. They allow a robot to strafe from side to side in addition to normal tank drive motions. Similar to omni-wheels, mecanum wheels consist of multiple rollers around the circumference of the wheel, with each roller pitched at a 45 degree angle. My FTC team uses them, and one day I decided to challenge my CAD skills by designing my own 3d-printable version.

Here are the results.