Volume Eleven - Pre-Victorian to the Present Day - some more aspects - The Steam Navvy and the Dock Extension of 1883 . . .

At the front end rises a wrought-iron tower carrying the top pivot of a crane jib, the lower pivot resting on girders fixed to the main frame. The jib may be said to be of twin construction, being composed of two sides which are united only at the post and at the outer end or point ; between them therefore is a long slot, in which swings an arm of adjustable length, depending from a fulcrum fixed on the upper member of the jib ; and at the base of the post is a circular platform, on which a man stands to regulate by means of a hand wheel the “ reach ” or length of radius of the arm. The scoop or bucket is fixed at the lower end of the arm, and is raised or lowered by the main chain passing over the extremity of the jib.

Handling. The whole of the movements are controlled by two men, called the " driver " and the " wheelman.” The driver raises the scoop while making its cut, swings it round into position for discharging ; then he moves it back again and lowers it. The wheelman regulates the depth of cut, releases the scoop from the face of the bank, and opens the door or bottom for discharging its contents.

Supposing the navvy to be in position, the mode of working is as follows. The bucket having been lowered till its arm is vertical, as shown by the dotted lines at A in the elevation, Fig. 1, the wheelman regulates the length of the arm by means of his hand wheel, so that the cutting edge of the bucket shall get its proper grip of the soil. The driver throws the main chain drum into gear, and the scoop is dragged forwards and upwards by the chain into the position B, describing a circular arc of about 80 deg.

By the time it reaches the top it is fully loaded, and the driver throwing the drum out of gear, holds it with a foot brake ; at the same instant the wheelman by easing his foot brake allows the bucket to fall back to C, clearing itself from the face of the bank. The driver next swings the jib round till the bucket is over the wagon, when the wheelman releases the latch by means of a cord, and the door falling open, the contents instantly drop through.

The driver then swings the jib back again, and at the same time lets go the foot brake of the chain drum, thus causing the bucket to descend through a sort of spiral course, until he brings it up sharply by the brake again when in position D. The wheelman at the same moment adjusts the fall by means of his brake, so as to lower the bucket to A again, with just the right reach of arm for the next cut.