Test run of motor of bridge girder launcher: after finishing connecting wire of electrical system, firstly confirm whether motor turns correctly, remove linkage connection for multi-machine linkage drive system, then confirm the motor turning direction with inching. Rear support leg driving, rear support leg hydraulic system goes up to make the driving wheels suspend in the air. Lifting trolley driving and auxiliary support leg driving, firstly confirm the motor turning direction, then install drive chain After confirming turning direction of all motors, write down work current of each motor as test run of the machinery (current displayed on the frequency converter or clamp ammeter)