Road turntable + Terence turntable help

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What does the circled gear do? Can I assume that the outside teeth turns Cranky? Is there something in the base that is a spring as something has to make it spin back. Have you looked at the other side turntable to see if its the same set up or possibly see whats powering a return spin? I really don't see anything in your picture that would be powering a retunn spin and isn't that the main problem?