Robot Wheel - compliant idler

This is a wheel for a lego-based robot.

The wheel has a compliant hub, giving the robot some suspension.

The robot was balanced on two main drive wheels and needed some wheels fore and aft to keep it level. But the floor wasn't flat, and when the robot went into a dip the drive wheels would come of the ground. A quick solution was needed that didn't involve rebuilding the robot to include suspension.

The springiness can be changed by changing the number of spokes, and how far they wrap around between the hub and the rim.

This replaced a stack of 3 of these: http://www.bricklink.com/catalogItem.asp?P=41531

Print it standing up on one end.