A high-speed magnetic trolley that utilizes an eddy current brake that may reduce the speed of a person in a harness traveling on a relatively steep zip line cable, making it possible to reach a landing brake at a reasonable speed and becomes easy to adjust an amount of braking force needed to reach a desired speed by taking off or adding more magnets without throwing one or more aluminum wheels out of balance. The high-speed magnetic trolley produce an eddy current that generates an opposing magnetic field, which then resists rotation of one or more aluminum wheels providing braking force.