Abstract: A drivable, steerable platform for a lawnmower and the like is disclosed in which a frame member is generally disposed in a frame member plane parallel to the terrain upon which the platform is to travel. Mounted on the frame member are at least three wheel assemblies. Each wheel assembly includes support structure rotatably connected to the frame member such that the support structure may endlessly rotate through an angle of 360.degree. about an axis substantially perpendicular to the frame member plane. A wheel member is rotatably mounted on each support structure such that the wheel members are disposed substantially parallel to each other and substantially perpendicular to the frame member plane. First drive structure is included to drive the wheel members. First steering structure is included to rotate the support structures, the wheel members being endlessly steerable through an angle of 360.degree..