What you're seeing is the view across the top of the pulley and tracking system!

The tail needed to have some form of sensory awareness, but multi-turn servos were too big and bulky to have a place in the gear box! Obviously, the solution was to build what was needed from scratch!

Reinventing the wheel as Mechanical Magnificus often likes to do, the surfaces of each micro-pulley was inscribed with an Archimedean spiral to transfer rotation to the sensor below via painstakingly crafted spur gears unlike any other.

Using spiral faces and custom spur gears over traditional worm gears saved half an inch on the final dimensions of the gear box!