How to make a robust electrical slip ring

JimboZA:
You lost me 3 lines in 8)

square round

Dunno Jimbo.....that was the description of the door knob that Bunnings Warehouse uses.

I guess the 'square round' is another way of saying 'cylinderical' where the transition from the front surface of the knob to the side surface of the knob is at 90 degrees as in the corner of a square.