u2032 applied to the centring bars 18 and 18 u2032 is equal to the inside track of the wheels of the corresponding axle of the vehicle at this point the motor vehicle wheel supporting means 58 and 59 extended as described above and pressed against the tyres so as to clamp the wheels 22 22 u2032 23 and 23 u2032 and prevent them moving on their resting surface are lifted by the rising of the frames 8 to avoid transferring a vehicle whose mass is too great unacceptable for example on the handling platform the system shown in fig1 is used to limit the amount of mass that can be lifted by limiting the force transmissible through the chain 14 on the output shaft 39 of the lifting speed reducer 12 the toothed wheel 13 which passes the torque of the speed reducer 12 to the chain 24 is housed by the friction rings 40 between a hub and an axially movable anchor 41 pressed via the spring 42 by a disc 43 which compresses the spring 42 by a controlled amount adjusted by means of the screw 44 depending on the force exerted by the spring 42 and the coefficient of friction of the friction rings 40 the toothed wheel 13 can transmit a variable force to the chain 14 to limit how much mass can be raised once the vehicle is raised the carriage can transfer it to the handling platform the job of the sensor 38 is to detect the presence or absence of the motor vehicle on the carriage since the position of the wheels 22 and 22 u2032 of the front axle of the motor vehicle is stationary on the carriage the.