body 1 moreover the forces applied to and by the right and left wheels 2 and 2 39 are uniform and equal in conventional systems for supporting a roller main body a hydraulic winch on an anchor vehicle is wound up or down in response to instructions from the operator of the roller vehicle 1 thereby changing the transverse position of the roller main body 1 therefore the wire is frequently too taut or too slack uniform roller pressurization is not possible due to the deflected loads to the right and left wheels 2 and 2 39 further there is a danger that the roller main body may slip or overturn due to incorrect or misunderstood instructions between the roller operator and the anchor vehicle operator fig3 shows an example of a unit for controlling the apparatus so the tension f 39 of the wire 13 will equal the force component f in this drawing solid lines represent hydraulic connections and broken lines represent electrical connections a voltage signal proportional to the inclination angle 0 is generated by the inclination angle sensor 17 on the roller vehicle this signal is amplified by a command signal converter 20 and output as a command signal to a proportional electromagnetic relief valve 22 this gives a constant proportional relation between the command signal and the hydraulic pressure which is supplied to a hydraulic motor 21 a variable hydraulic pump 23 is driven by a prime mover e to supply the.