Racing Rings consists of three rods one each of copper, aluminum and PVC, Ring magnet is dropped down the PVC rod, it falls unobstructed, Two metal rods create an induced magnetic field to that adds resistance to the rings travel, metals are different, they fall at different rates
Air core solenoid, coils wound on a plastic tube with approximately 575 turns of copper wire, can carry a current of 5A continuously or 10A intermittently.