US Patent 7862131 Dual mode undercarriage for tracked vehicle

A vehicle with a frame connecting a driver wheel, an idler wheel and mid-roller wheels, an endless track belt being tensioned around the driver wheel and the idler wheel and being in contact with the mid-roller wheels on a lower run thereof, the mid-roller wheels being arranged in bogies, including a front bogie having a first pivot axis, a middle bogie and a rear bogie arranged in tandem having a second pivot axis, wherein the first pivot axis and said second pivot axis act as load transfer pivots.