GB1391312A - Apparatus for measuring road vehilce geometry - Google Patents

Abstract

1391312 Wheel geometry measurement POLYPRODUKTE AG 6 Oct 1972 [7 Oct 1971] 46187/72 Heading G 1A Apparatus for measuring toe-in and castor angle of the wheels of a road vehicle comprises four measuring blocks 1-4 provided with movable sensing elements 6-9 to be placed in contact with measuring discs 14-17 connected to the car wheels 10-13, means on the sensing elements to provide a number of pulses proportional to the distance moved from the blocks and means to calculate a measure of the inclination of the vehicle axis 19 to the apparatus axis 18 and to correct therefore in the measurement of toe-in using further movable elements and displacement encoders on the movable sensing elements. As shown the displacement encoder comprises photoelectric devices 31-34 and rods carrying notches 27-30 and the calculations are performed by stepping motors. With switches 37 and 38 set as shown the rods 8 and 9 are moved out to contact the front wheels 12, 13 and the corresponding pulses are fed to stepping motors 41, 42 driving differential 43. Switches 37, 38 are switched and the process is repeated using rods 6, 7 against rear wheels 10, 11. The rotation of differential 43 is proportional to 20 and 21 and to the angle between lines 18 and 19 and is transmitted to driv wheel 45 by belt 44 as a correcting factor. Drive wheel 45 is connected to differentials 47, 48, which differentials are also connected to stepping motors 64, 65 respectively. To measure toe-in, rods 57, 57a, horizontally spaced from fixed rods 56, 56a on the movable sensing elements are moved to contact the wheel and the displacement pulses from encoders 58, 60 and 59, 61 are fed to stepping motors 65, 64, the toe-in for each wheel being indicated by pointers 71, 72 on belts 66, 67 driven by differentials 47, 48. Camber is measured using a second movable rod and encoder vertically spaced from the fixed rod on the moving sensing element and the alignment correction is not needed. The result may be printed on a strip chart by an electromagnetically actuated hammer mounted on belts 66, 67. In an alternative embodiment, Fig. 3 (not shown), the correction is made without the need for switches 37, 38 by using more stepping motors and differentials and a toe-in reading is provided for each wheel.