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Conversion of Three Lake Freighters To Modern Self-Unloading Vessels three steamships DIAMOND ALKALI, THUNDER BAY QUARRIES and WM. T. Roperts, owned by the American Steamship Co., Boland & Cornelius, managers, Buffalo, is one of the out- standing examples of this type of work carried out in recent years. The conversion was done at the Lo- rain, O., plant of the American Ship Building Co., Cleveland. As this is written the work is nearly completed and delivery of all three vessels is ex- pected by April, about four months aft- er award of contract. In general, the conversion consists of hoppering the hold to serve two belt conveyors symmetrically arranged each side of the center line. These conveyors deliver to cross conveyors at the forward end, which, in turn, feed an inclined pan conveyor which carries the cargo to the deck, dis- charging on a boom conveyor. The boom can be swung over the ship’s side through a total are of 226 degrees. The most serious problem in the de- sign of a self-unloading vessel, wheth- er it be a conversion or a complete new ship, is to maintain the greatest possible cargo capacity. To insure the proper flow of material, all fore and aft plating has a slope of 35 de- grees and the athwartship plating slopes 60 degrees. This necessarily results in a loss of cubie and to mini- Tes conversion to self-unloaders of The author, E. B. Williams, is chief draftsman, hull: department, of The American Ship Building Co., Cleveland. Thunder Bay Quarries, one of three bulk cargo carriers converted to self-unloade 50 By E. B. Williams ~HE self-unloading vessel de- livers cargo on dock or to cars and receives payment for discharging as well as hauling. Such a vessel can serve any port or dock regardless of the lack or obsolescence of shore unloading equipment, thus greatly enlarging the range of employment. The system installed in these vessels is dependable. It will work with a minimum of upkeep expense and breakage of cargo. Cubic cap- acity has been maintained at a maximum consistent with the best possible efficiency of operation. Editor's Note mize this loss the hoppers are made as low as possible. In way of the con- veyors, the tank top was recessed to a point 30 inches above the base line. The upper part of the side tanks was cut away, allowing the hopper plating to extend to the shell. The resulting loss to the original capacity was ex- ceptionally low. The loss in midship MarRINE Review—April, 1932 area was 12 per cent and the overall loss in cubic capacity self-trimmed, 19 per cent. An important feature in the design of the conveying equipment is the pre- vention of breakage of the cargo. Par- ticular stress was laid on this point with the result that throughout the entire system there are no _ serious drops to cause breakage. Neverthe- less, a minimum clearance of 24 inches is maintained over the belts. The DiaAMOoND ALKALI and the THUNDER BAy QUARRIES are. sister ships, and the principal dimensions are 504 x 56 x 30 feet. The principal dimensions of the WM. T. ROBERTS are 504 x 54 x 30 feet. All three vessels were engaged in the bulk cargo trade on the Great Lakes. They are pow- ered with three-cylinder, triple expan- sion engines and Scotch boilers. The hatches are spaced 12 feet centers and number 30 in all. The throat openings of the hoppers are 4 feet 4 inches wide by 3 feet fore and aft and are spaced at 6-foot cen- ters. Hand operated gates of a uni- que design serve the hoppers. About two-thirds of the opening is closed by a sliding gate to which is attached a hinged plate which closes the remain- ing portion and also serves as an apron when the gate is open. This feature enabled the hoppers to be spaced more closely than on former vessels with a considerable capacity saving and at the same time prevents breakage by “laying” the material on rs by The American Ship Building Co.