A friction wheel drive for an internal combustion engine's a unit belt drive for a secondary unit includes a control system, a friction wheel that engages frictionally with an outer side of a belt in a wrap-around portion of a drive wheel of the internal combustion engine and that is controlled by the control system to engage or disengage frictionally with a drive wheel of the secondary unit, and a guidance system having an arc section for guiding the movement of the friction wheel with the control system. The arc section is arranged equidistant from the axis of rotation of the drive or driven wheel relative to the driven wheel to the outside of the belt in the wrap-around portion for turning the secondary unit on and off.