124 A TREATISE ON DREDGES AND DREDGING 



The hull is of steel, 175 ft. long, 38 ft. wide, and 8} ft. deep. 



The dredging pump is different from any other in the shape of the 

 casing and the runner. The runner has five blades 22 in. wide, 

 and is 7 ft. in diameter. The edges run close to the casing, but the 

 runner is not concentric with the casing, hence the outer ends of 

 the arms are nearer one side of the casing than the other, the widest 

 space being at the bottom, and the space being nearly cut off by a 

 projection in the casing at the upper side of the discharge opening. 

 The axis of the pump is parallel to the axis of the boat and lies over 

 the center line of the same. The shaft has one long bearing through 

 the aft side of the casting, and is provided with water bushing under 

 pressure to keep the sand out of the bearing. The sand pump is 

 driven by a vertical, inverted, two-crank, compound-condensing 

 engine, with cylinders 22 and 48 in. diameter and 24-in. stroke. It 

 is fitted with a piston and slide valve and has an adjustable cut off 

 for the piston valve. This engine was designed to develop 800 H.P. 

 at 140 revolutions per minute, with a boiler pressure at 160 Ibs. and 

 a vacuum of 25 in. 



The engine which drives the cutters is horizontal, two cylinder 

 and non-reversible, attached to a sliding steel frame, which moves 

 back and forth in guides as the cutter is raised or lowered. This is 

 necessary because the shaft which drives the sprocket chain is not 

 in the axis of motion on which the suction and cutter revolve. 

 The whole engine, with its frame, follows the motion of the shaft, 

 so that the gear and pinion are always engaged. To admit of this 

 motion, the steam pipes are provided with slip joints. The cylinders 

 of this engine are 12J in. in diameter and 15-in. stroke, with the loco- 

 motive type of slide valve. 



There are two winding drums located forward of the sand pump, 

 one on the starboard and the other on the port side of the hull. 

 These drums are provided with clutches and brakes, and are driven 

 by two independent double-cylinder, horizontal engines with cylinders 

 10X12 in. 



The ladder hoist for raising and lowering the suction, and the 

 spud hoist for raising the spud, each has drums 24x24 in. The 

 cables from these drums lead to the roof and thence out through 

 sheaves to the ladder and spud. These drums are operated by the 

 same engines that operate the winding drums. 



Steam is supplied by four Heine safety water-tube boilers rated 

 at 250 H.P. each. 



