A completely axially symmetric vibraphone robot would be awesome. We decided to move away from a big row of keys and towards a round plate of keys. Here is a quick render of the key mounting structure and how it incorporates the ball retrieval and distribution system:
The large round plate is actually a 30-gon not a circle. It is inscribed in a 32″ circle, and is 1/4″ thick. There are 60 unique (thank you design tables!) plastic supports that slide onto notches in the aluminum. Each plastic support has to be unique because of the awkward hole spacing in the individual keys.
There are already notches in the plastic for clips that should hold it into the aluminum plate (aka “Megaplate”). However, depending on the design of the ball deployment mechanism, the retaining clips for the plastic plates should be incorporated into the support for the mechanism. Here is a close up of the plastic supports:
Finally, here is a close up of Mike Ornstein’s ball collection and sorting mechanism. It uses brushes from the bottom of doors to pull balls up an archimedes screw into a paintball-style hopper.