Clamp it in a vice as hard as you can, then put a piece of scaffold pole on the crank to undo it. If you don't want to damage the sprocket then put a piece of old chain around it before putting in the vice. Is that the same idea to get a screw on bash ring off..... i have tensile cranks with a duel bash. tryed to get it off with a whain whip, but the whip snapped!! vice idea sound good.