secondary shaft

The spokes are inserted through the center of a sliding block and the sliding block slides along the spokes radially. The secondary shaft and the sliding block are connected by a chain bar.

Tesla's invention is, in essence, a rotating transformer. Its primary windings reside in a stationary steel casing (the stator) and and secondary conductors are attached to an inner shaft (the rotor).

Think of it as a rotating transformer, with the primary windings residing in a stationary casing (stator) and the secondary conductors attached to an inner shaft (rotor).