[Jared]

Cool! I'm planning to do the same thing on my 25B when I get back to it. I have a shaper I plan to use to cut the gear teeth- after I get it running, that is. How will you cut the teeth?

I don't think the center shaft does anything to keep the house centered on the swing circle; the hook rollers do that. As far as I know, it is just a way to transmit power down to the tracks. I wouldn't get too worried about building that part into your machine. Before hook rollers came along, cranes had upper and lower rollers to support the weight of the house and the center shaft did double duty as power transmission and keeping the house from falling off the circle and my understanding is it was nothing but trouble.