Large Omni Wheel

This is my design of Omni Wheel for robotics platform I'm working on (based on Mars Rover).
Omni Wheel as it's name suggest can move in pretty much any direciton. It can roll like a regular wheel forward, but can also slide sideways thanks to small rollers along it's perimeter.
In my case I needed to use omni wheel to overcome "scrub drag" during "skid steering" of 6 wheel platform. Here's a nice and easy to understand article: http://curriculum.vexrobotics.com/curriculum/drivetrain-design/drivetrain-terminology.html

Wheel is about 120mm in diameter and consists of multiple parts most of which can be 3D printed.
Hub is designed to fit 12mm hex shaft motor couplers (like ones used in "Wild Thumper" 6WD toy).
3D Printed Parts:
- First half rim with integrated hub (largest part)
- Second half rim
- Omni Rollers (18 per wheel)
- Rim cover (required to hold rollers in place).
I laser cut rim cover from 1/16" delryn (acetal) resin, however it should be easy to print one as well