some robolink impressions and applications from 2012:
An important, easily underestimated detail in the design of the pikchain® is the interface between the c-chain® and the slewing ring, or the rotary union. The c-chain® must be secured in such a manner that it does not bend or collapse at the point of directional rotation. igus® has designed a special component to address this issue. On the one hand, it gently guides the energy chain in the radius, and on the other, facilitates nearly friction-free rotation by using a PRT bearing from igus®, without generating significant torque. A hollow shaft then connects the slewing ring or the rotary union with this rotating bearing support.
As I already wrote in one of my earlier papers, the devil is truly in the details.
Back view PRT bearing