Abstract: A self-propelled bogie or truck to automatically travel along guide tape attached to a floor surface has a base portion provided with plural non-driving wheels attached to a lower face thereof, an elevating plate moving vertically relative to the base portion, driving wheels attached to the elevating plate at levels of stable relative height positions, an electric motor attached to the base portion, a pressure rod adapted to vertically move when the motor rotates, and compression springs placed between the pressure rod and the elevating plate. When the driving wheels move to the upper storage position, the springs extend, however when the driving wheels move to the lower running position, the springs are compressed giving a ground contacting pressure to the driving wheels.