... is composed of one base, four moving wheel, and 2pcs of wheel axles, 2 sets of motors. 2 ... sets of motors drive four wheel axles through the gear. It composes 4 wheel driving systems, in order to make ... hand, it can also drag on the plate wheel and mobile.The welding seam tracking devices are ... seam tracking device arc-guide frame , arc-guide wheel ,and gas cylinder .d. Electric control system electric ...