Abstract: A polygonal chassis for a vehicle, having wheels or tracks, particularly intended for travel over rough terrain. The chassis preferably polygonal has peripheral members provided with journals for an inner or an outer train bearing and driving means. The chassis is made of sections joined by articulated flexible couplings in the corners of the perimeter of the frame. A second set of such couplings is provided optionally at the junction of a rigid brace with the frame. A first species of the invention teaches the use of rigid girders as the frame brace, with each girder connected with the outside of the frame by articulate couplings, or the girders are crossing each other and connect to the opposite periphery of the frame by articulate or flexible couplings and in the alternative a rigid bracing of inner longitudinal girders is joined by the same type of couplings to the opposite portions of the frame.