Ohio shaper disassembly

I am working on rehabbing an old and sadly neglected 16 inch ohio shaper. This poor machine was left outdoors for around 20 years and is surprisingly not all that bad off. I have had it inside the shop almost a year now, giving it a regular soak in kroil, and have thus far had less trouble getting it apart than I expected. I am now to the main shaft, bull gear and arm, and am stumped. The feed sprocket has no apparent keyway or setscrew, and its companion sprocket just slid off. The shaft is hollow for the stroke adjustment and I dont want to force anything or risk bending/ breaking components that will have to be fabricated. This machine is probably pre 1920. Is there anyone here who has removed these parts and can advise? Thus far there have been no nasty surprises and that in its self is kind of startling.