1-1/2 inch per foot taper reamers exist and are commonly used with ball joint (front end) installation. It creates a nearly "self-locking" taper. I say nearly as unlike a morse taper (5/8" per foot) 1-1/2 inch/foot is "more removable."
Holding your fan perpendicular to the axis of cut will be the challenge. My 20" Flather lathe (1873) comes to mind.
Joe K