The headstock is an integral welded component. The axis hole of the transmission sprocket is the positioning hole for installing the reducer or the blind shaft. There are holes for inserting chain hooks on the upper edges of the two sides of the head frame . There are on each side plate for mounting a gear unit φ200 and . 6 th φ26 holes. The Φ26 hole is a hole for installing the coupling bolt between the reducer and the head frame. Headstock fitted detachably fixed frame, derailleur (connected to the pin holder). The chain puller can force the scraper chain in motion to disengage the sprocket at the point where the sprocket runs away, to avoid accidents caused by " rolling chain " .