Originally Posted by r0sewhite
On the bottom side the motor shaft should be fixed with an aluminium ring with a grub screw (don't know the english word for it but I'm sure you have one). This ring keeps the shaft from being dragged out. Since the shaft diameter (inner diameter of the ring) is the only important size, I'm sure you will find a matching ring at your local hobby shop.
On the other hand you don't need this ring anymore if you reverse the motor because instead of this ring you will want to mount something like a prop spinner.
Yep, that was mentioned in manual
Btw, has anyone problems with shaft pull out during flight? I had 2 times (and I think that's enough), even when the bolts that hold shaft, are tightened at maximum.