1. check with the tester: the main pin hole and the spring seat are used as the positioning test datum. The instrument is fixed on the two steel plate spring seat, and the two main pin holes are inserted into a test bar. The measuring head is in close contact with the inspection rod by the manipulating instrument. The position between the main pin hole and the steel plate spring seat and the two steel plate spring seat is reflected through the different scale, and the deformation position and the deformation degree are determined and determined. The specific methods and steps can be seen in the instruction manual. Place the front axle on the two V type iron on the flat plate, and the horizontal instrument is placed on the leaf spring seat. If the horizontal instrument is placed (vertical front axle), the bubble is not in the center position, which indicates that the front axis is distorted; for example, when the horizontal instrument is vertically placed, the bubble is not in the center position, then the front axis has a bending phenomenon. 2. test by the I-beam tester: this method can accurately measure the bending and distortion values of the front axle in the vertical plane and horizontal plane, and the accuracy can reach 5'. The tester is based on I-beam main pin hole, leaf spring seat and location hole. In the inspection, the front axle is fixed on the shelf, and the plate seat and the main pin hole are cleaned, and the two positioning pins are placed in the positioning hole of the steel plate seat. The base pad is placed on the plate seat plane and cooperated with the positioning hole. Place the tester on the pad and fix the locating mandrel in the main pin hole. Loosen the screws and rotate the handwheel so that the V shaped iron can be placed on the locating mandrel. Then the positioning pin of the V - shaped iron is tightened. The front axle should be corrected for its bending and twisting beyond the prescribed standard, and the correction of I-beam has two methods: heat correction and cold correction. The thermal correction is to first heat the deformed part to 500~600 degrees, then carry out pressure correction. This method can be used to correct large deformation without special equipment. But the heat school is operated by hand, the labor intensity is big, the repair quality is low, the metallographic organization of the heating part is easily changed, the mechanical property of the metal is affected, the strength of the beam is reduced, so it should be careful when heating. 3. use the special angle test: insert the test rod into the main pin hole, and put a special padding iron on the two steel plate spring seat. A special angle ruler is put on the cushion iron. The angle of the angle ruler should be adjusted and fixed in the range of the provisions of each type of vehicle. Then we can make the square rod stand upright and rely on the test bar, and then we can find out the result. If there is a gap at the upper end, it indicates that the front axle is bent downward, and the lower end has gaps, which indicates that the front axle is bent upwards. In addition, the coincidence of the angle between the square and the pad and the coincidence of the square and the test bar can also be used to judge whether the front axle is bent or distorted. 4. with the drawing line test: put the front axle in the horizontal position, draw the center line of the two steel plate spring, hang the heavy hammer on the two ends of the line, and make the line pass the center of the two main pin hole, and measure the distance between the plane and the line between the two plate spring seat with the ruler, and the difference between the two is the straightness of the beam. Pull the line to check whether the centerline of the two seats is on the same straight line. Then check whether the distance between the two positioning centers and the line is biased. If there is a deviation, the beam will be distorted. Check the distance between the inner end and the line on the main pin hole, and the two distance error indicates that the kingpin angle is not correct. The distance between the two steel plate spring seat and the fine line is measured with a ruler. If the center is not in the same line, it shows that the two ends of the front axis bend up and down, or bend forward and backward.