[Sean Murphy]

With the combined stages, what constrains the intermediate pin assembly concentric? I could see if it's just the one stage there would be bearings on the output side, just like as pictured on the second stage output, but I don't see what holds the first stage output concentric. I suppose your eccentric input shaft might have a body that carries through, but that would complicate the shaft greatly and require a different "central" shaft for each stage configuration.

It's a cool design, thanks for sharing.