the additional power supply being supplied mechanically

Full Title

Steering non-deflectable wheels; Steering endless tracks or the like > by differentially driving ground-engaging elements on opposite vehicle sides > by means of a single main power source > using gearings with differential power outputs on opposite sides, e.g. twin-differential or epicyclic gears > differential power outputs being effected by additional power supply to one side, e.g. power originating from secondary power source > the additional power supply being supplied mechanically