The Guardian (And Evening Star, with which is incorporated the West Coast Times.) SATURDAY. JUNE 21st, 1924. AN ELECTRIC DREDGE.

Hokitika Guardian, 21 June 1924, Page 2

The Guardian (And Evening Star, with which is incorporated the West Coast Times.) SATURDAY. JUNE 21st, 1924. AN ELECTRIC DREDGE.

In order to carry on more rapidly anil at reduced cost the important work of keeping the channels of American liarhours al the rei|iiirod depth, the Corps of Engineers of the I’nited States Army which Ls responsible for this service, is reported to have <le-,igne<l four seagoing dretlees of a radically new ty 1 e. Thu dredges are elaime'J to 1.-c the first all-electric ships ever built, and electricity is used in them tor every possible purpose. Their power is venerated by internal-combustion oil engines resembling automobile engines on ;i large scale. Every movement of each ship is controlled from the pilot house, where the navigating officer personally stalls, stops, changes the speed and reverses the ship without signalling. to the engine-room. The entire midship section is occupied with two rows of hoppers, between which is a long well, in which is located the dredging mechanism. 'litis consists of a 2Gin. pipe, la loot long, supported in a frame of steel lattice work. One end of the pipe is connected through a flexible joint to the suction end •>! an 890 horse-power centrifugal pump, and the other end carries a heavy steel rs" ing which resembles a huge gridiron in shape and is called a “drag”. AMion dredging is to he done, the drag is lowered to the bottom, the pump is started, and the vessel is run slowly along the course to be dredged out. The drag acting like a great clnw, loosens the sand, which is sucked up by the dredge pump and discharged into

the hoppers. Where the bottom is too hard to be loosened by the drop, jets of water powerful enough to cut into almost any material except rock are forced out through the drag; The overall- length of each dredge is 2fiS feet o inches; beam -16 feet, depth 22 feet fi inches, and capacity of hoppers 1.2.70 cubic yards. Electricity drives the propellers, operates the dredge mechanism, opens and shuts the hopper floors, pumps water and fuel oil. compresses air for blowing the whistle, makes ice and maintains cold storage, heats all holds And living quarters, keeps the fu.-l oil at the proper temperature, ventilates every part of the vessel, runs the machine tool shops, raises and lowers the anchors, operates all winches and capstans, heats the water, does the steering, cooks the meals and lights the cigars, cigarettes and pipes. There are on each dredge .->!! electric motors. 100 electric heaters, 2.1 electric fans, and two electric ranges. These dredges are perhaps the first habitations of man where lire in some form or other is not needed. Electric power for all this apparatus is produced by three 1,000 h.p. Seymour for Diesel)- engines, each of which drives a 700 kilowatt generator in addition to which there are several auxiliary generating units. Two 800 h.p. motors each connected directly to a propeller form the actual propelling machinery of the dredge. The control of each of these motors is centred in a hand wheel in the pilot house. To start the propeller motors, the navigating officer merely turns these two wheels. As the wheels turn, tile speed of the motors increases until they come up to full speed at the extreme limit of the wheels motion. Turning the wheels in the reverse direction reduces the motors’ speed until they come to rest; then further rotation starts the motors in reverse, thus hacking the ship.