Apparatus for determining the relationship of vehicle thrust line, and body center line for use in wheel alignment

Apparatus for use in determining the relationship between a vehicle's thrust line and its body center line wherein said vehicle has at least one steerable wheel spaced longitudinally from a pair of laterally spaced nonsteerable wheels and comprising:

• movable light source means located independently of and remote from said vehicle for establishing a pair of parallel reference light beams extending from a position located forwardly of said steerable wheel and directed rearwardly alongside and spaced outwardly from said nonsteerable wheels and wherein said light beams are spaced apart in parallel planes sufficient to permit said vehicle to be positioned substantially midway therebetween;
• means for determining the thrust line of a said vehicle including a pair of sensor means each adapted to be mounted to one of said nonsteerable wheels and being positioned outwardly therefrom to intercept one of said reference beams, each said sensor means including detector means responsive to a said light beam for providing an output indication indicative of the location at which the beam impinges upon the detector means, and measurement means associated with both of said detector means for providing a measured output representative of the vehicle's thrust line location, and
• means for determining the vehicle's body center line, including a pair of forward body side targets each having an aperture therein and adapted to be removably mounted to like body side locations on opposite sides of the vehicle, the body targets being positioned outwardly from the vehicle's body sides by like amounts to permit the reference light beams to pass therethrough and a pair of rear targets adapted to be removably mounted to like body side locations on opposite sides of the vehicle but longitudinally spaced along and rearwardly from said front targets and being spaced outwardly from the vehicle's body sides by like amounts sufficient to intercept the light beams whereby to the extent that said movable light source must be displaced in a transverse direction from its thrust line determining position in order for the light beams to impinge at like locations on the rear body side targets is representative of the variance between body center line and the thrust line.