Tom, those are friction rollers, a type of clutch drive. They ride on the outside edge of the tapered slots in the slotted 'disc' next to them. In the forward push direction they ride up the inclines under centrifugal force and lock to the wheel's drive shaft so everything turns with the forward motion.
When you pull in reverse or stop pushing they are free to roll away from the shaft, which allows the fan axle to keep turning under inertia.
I would have expected to find a large fiber washer that presses against the clutch wheel to keep the rollers aligned with their inclines (?) and perhaps that's what we're seeing still on the left pressed-in axle bushing?
I hope you kept notes on the exact orientation of the parts, especially any spacer washers hidden in the old grease.
As for removing the fan, it is likely there is a cir-clip holding the screw shaft from backing out of the housing.
Highly recommend that you 'wash' the case and parts in a degreaser bath to clean away ALL the old grease and probably grit. Then it will be easier to determine what's holding the fan screw in place.
Be sure to replace with new lithium grease so the parts are well lubricated.
The small screw you removed is for setting the distance/depth of the fan on the screw shaft from the back plate so it does not contact the housing when reassembled. The fan is either seized from age or is in fact a screw on fan - I suspect there may even be a keyway.
But the screw shaft itself must be secured in place with a separate 'washer' or washers. As I say, probably a cir-clip.
Dave
