Classic fan removal
Is that the Classic or Classic Omega? If it is the Classic, I think its armature may have a hole drilled through it that is used for fan removal. Look down through the vent in the motor housing and spin the impeller around. As you spin it, you may see the hole. You can take an ice pick, a thin punch pin, or something similar and put it down into the hole. That will bind the armature so you can spin the impeller off.