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10 some of the advantages of this method points out that nonfree-flowing materials can be handled whereas only free-flow- ing materials are now handled; the cen- ter of gravity is lowered permitting in- stallation without the question of stability being introduced. The unloading speed tuns up to 500 tons an hour, on the Fontana, the largest installation, the scraper making a round trip a minute. Two men unload a steamer, one to each tunnel, so that each has his tunnel in full view. Leathem D. Smith, president of the Leathem D. Smith Dock Co. Stur- geon Bay, Wis., designed and patented this subcargo unloading apparatus. The problem came to his attention because of hits active connection with the busi- ness of stone quarrying which led to his entrance into the lake transportation field in order to obtain wider and more cer- tain distribution of his stone. His Stur- geon Bay plent, during the war, engaged in ship construction work for the govern- ment and is now equipped for ship build- ing and repairing. This training in both the stone trade and in vessel design and construction well fitted Mr. Smith for study and solution of the problem of unloading bulk freight from the holds of vessels. This equipment has been designed and installed up until this time in two stand- ard sizes. In the smaller ships of 2000 MARINE REVIEW to 3000 tons deadweight with cargo holds up to 150 feet in length, bottom- less drag scrapers of 4 cubic yard ca- pacity are used in the two longitudinal subcargo tunnels. These scrapers are each handled by double drum _ steam koists having a line pull of 16,000 pounds on the load cable and about 8000 pounds on the back haul cable . The hoists are placed at the forward end of the ship on the tank top along- side the foot of the scraper incline. By this arrangement, the bucket operation at all times is visible to the operator. The scraper is pulled back in the tunnel by the back haul cable which leads to the after end of the ship under side or center cargo drain slopes. The cable comes up the tunnel and is rove through an overhead trolley on an I-beam through a sheave on the back of the scraper and dead-ended on the trolley. This reave of cable lifts the returning light scraper up over the cargo which flows into the tunnel from both sides. Slacking the back haul cable lowers the scraper on to the material. The load cable then pulls the scraper forward and shoves the material up the scraper in- cline into the hopper which feeds the in- clined belt conveyor. In connection with the 4-yard scrapers, a 40-inch inclined troughing conveyor belt and a 36-inch swinging boom con- veyor are used. This size installation January, 1925 has given an actual average rate of un- loading of coal and stone of 300 tons an hour. In the larger type of ships, ranging from 3000 to 6000 tons deadweight ca- pacity with cargo holds from 150 to 250 teet in length, scraper buckets of 8 cubic yards capacity are used. These are the largest ever built and will hold 10 tons of stone or 6 tons of coal. This requires a cable line pull of 25,000 pounds and about 10,000 pounds on the back haul cable. The speed of the loaded scraper runs from 200 to 250 feet per minute and the maximum back haul speed from 400 to 500 feet per minute. The same arrangement of equipment is used in both sizes of unloading rigs. With the 8-yard scrapers, a 54-inch incline con- veyor belt and a 48-inch boom belt is used, The average stone and coal unloading rate of these ships is 500 tons an hour, the doubled capacity of scrapers being partially offset by the longer average haul of the materials in the tunnels. The maximum unloading rate has been found in service to be double the aver- age rate. The swinging doors installed in the tunnel side openings permit selective un- loading of cargo from various compart- ments as desired. Many special features, of design in parts of the equipment have been worked COMPLETE TUNNEL CROSS SECTION ON STEAMER FONTANA ‘