What is measured in electrogastrography

In order to install a heavy cutterhead upon a box hole boring machine, within the confined working space available in underground mining operations, the cutterhead is placed upon a wheeled dolly having a central opening through which the attachment stem of the cutterhead depends downwardly, a temporary bridge including a pair of rails is rested upon the top of the machine frame, and the dolly with cutterhead supported thereon is moved along the bridge to a position where the cutterhead can be attached to the machine. The vertical drive of the machine is then utilized to lift the cutterhead, and the dolly and temporary bridge are removed.