We have been trying to find a way to connect the mecanum wheel to the robot. After a bit of trial and error we were able to come up with this:
This uses clamps to clamp a pole in the middle then uses two more to solidly connect the pole to the wheel. On the other side, the one you can’t see, there is a gear in which the bigger gear will spin therefor spinning the pole along with the connected wheel. the pole that is clamped in the main gear is one that will fit in the servo in order to spin.
We will use a powerful DC motor to spin the wheel: