Patent GB-732586-A (GB)
Title: Improvements in or relating to methods and apparatus for testing vehicle wheel alignment
IPC: G01B11/275
Filed: 1953-02-05
Abstract: 732,586. Alignment gauges for wheels of road vehicles. WILKERSON, E. D. Feb. 5, 1953, No. 3214/ 53. Class 106 (2). An apparatus for testing the alignment of vehicle wheels comprises two parts with means for attaching one to each of two vehicle wheels in planes parallel to the wheels, and deriving their sole support therefrom, there being a sighting device or means for projecting a line of light on one member co-operating with a target on the other member. Camber test. One post 31, Fig. 8, carries a sighting device 44 and the other post 32 carries a cylindrical target 60. With the sighting device 44 and the target 60 correctly positioned on their respective posts a reading of the target 60 through the sighting device 44 will give a measure of the camber of the left hand wheel. The fact that the target 60 is inclined slightly to the vertical does not cause any appreciable error in the reading. The target and the sighting device are then interchanged and the reading obtained is a measure of the camber of the right hand wheel. The sighting device 44 and the target 60 are each rotatable about their posts 31, 32 and supported thereon by adjustable collars 63. The target 60 may be illuminated from within. Toe-in test. The posts 31, 32, Fig. 15, extend horizontally and forwardly of the vehicle. The chart 60 is turned to present a " toe-out and toe-in " scale towards the sighting head 44 and the wheels are " cut " slightly to bring the line of sight to read 0 degrees on the chart. The sight head 44 and the chart tube 60 are then interchanged and the reading obtained is a measure of the toe-in of the wheel upon which the chart is supported. The wheels are then cut in the opposite direction until the reading is again 0 degrees after which the chart and the sighting head are again interchanged to determine the " toe-in " of the other wheel. Caster test. To test caster, which is the camber of the wheels when "cut" as in steering, the apparatus is as for the camber test except that the target 60 is turned to show a " caster " scale. The wheels are then cut, as in Fig. 10, causing them to rotate by a slight amount. A pendulum pointer 75, Fig. 11, is pivoted on each post 31, 32 at the wheel centres, and a protractor 77 under each pointer is so arranged that when a wheel is straight ahead, the pointer 75 indicates a central 0 degrees point. After the wheels are cut, the posts 31 and 32 extend angularly upwardly in opposite directions as shown in Figs. 10 and 11, due to the rotation of the wheels. The sighting head 44 on one post is used to view the target 60 on the other post. To bring cross-lines within the sighting head into alignment with the 0 degrees mark on the chart, an off-centre sight opening 57 is used in a disc that is turned until the cross-lines appear to cut said mark. The wheels are then cut in the opposite direction by the same angular amount and the caster read on the chart 60 after turning the sight head on its axis without changing the position of the sight opening .57. To test caster of the other wheel, the method is repeated with the target and sighting device arranged on opposite posts, and the angle of cut read from the protractor plate on the opposite side from that read in the first test. Rear axle wheel position test. To check the wheel base positions of the rear axle, Figs. 22 and 23, one of the posts 31 or 32 is secured in vertical position to one of the front wheels and the other post is secured in a horizontal position to the rear wheel on the same side. Perforations 85, Fig. 24, in the posts receive the shanks 86, Fig. 26, of two sighting pins 87 having tapered or pointed upper ends 88. A target 89 is mounted on the vertical post and bears a plurality of concentric circles, Fig. 24. The sighting pins 87 are checked for position by sighting them against the target, and if the rear axle is at right angles to the chassis the reading will be zero on the target. A check is then made on the two wheels on the opposite side of the car.