Abstract: A vehicle with a plurality of legs which selectively alternately support and advance the vehicle in horizontal straight line motion, each of the legs comprises a support member, and in one embodiment, a first gear nonrotatively affixed to the support member, a first link pivotally connected to the support member at one end thereof, a means for rotatably driving the link about the pivotal connection, an idler gear pivotally mounted to the first link intermediate the ends thereof and in driving engagement with the first gear, a second link pivotally connected at one end thereof to the first link at the second end thereof, the second link having a planet gear affixed thereto and engaging the idler gear, whereby when the first link is pivotally driven by the drive means through the idler gear and the planet gear produces angular motion of the second link about the pivotal connection between the links, the first link is constructed and arranged to limit the angular movement of said second link in either direction,