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wise vessels. A chute extends from the warehouse into the hatch so that the maximum use is made of gravity in handling the flour. The Great Lakes Transit Co. un- loads freight from the deck houses on its freighters by chutes, while flour is handled through the side- ports with twin screw conveyors. At some terminals gravity roller con- veyors facilitate greatly the unload- ing of motor trucks. The seventh principle states that, “Productivity of equipment is in- ereased by providing good floors, automatic couplers, non-friction bear- ings, rubber tires and equipment best suited to conditions.”’ Good floors increase productivity of equipment by speeding movements of tractortrailer trains, crane trucks and other equipment. Speed of move- ment is reduced when the floors are in poor condition, or are constructed of unsuitable materials, both by the impossibility of moving fast, as well as delays caused by the necessity of stopping to readjust loads which have been jarred by the rough going. Automatic couplers reduce the terminal time of tractors by facili- tating greatly the coupling and. un- coupling of trailers, as well as speed- ing the switching of trailer trains. There is no logical argument against the provision of automatic couplers on all trailers. The addi- tional cost is offset quickly by the greater effectiveness of the opera- tion. The provision of non-friction bear- ings reduces the power—man or me- chanical—necessary to move a hand truck or trailer. Roller bearings should be standard equipment for the eargo blocks on ships. Tests have proved conclusively that rubber tires speed operations and re- duce costs. (See July 1932 issue MARINE REVIEW.) The eighth principle states that “The unit cost of transportation de- creases as the quantity to be trans- ported increases.’’ This is known generally as the law or principle of increasing returns. The economy of mechanical equip- ment increases as the volume of cargo to be handled increases. In every case there is a minimum point below which the mechanical equip- ment operates at a loss. Contrary to the opinion of some executives there is no fixed percentage of time which is a guide to economy of me- chanical equipment. Each case must be analyzed to determine the point at which mechanical equipment ceases to be profitable. Limiting Capacity The ninth principle is known as the principle of diminishing returns. It may be stated as, ‘‘The unit cost of transportation increases as the quantity to be transported exceeds the capacity of the plant.’’ A terminal which can _ handle 200,000 tons of cargo yearly is un- economical for handling 250,000 tons of cargo. The increased tonnage can be handled but not economically. This principle, like all principles, must not be applied blindly. In one case the capacity of the terminal was increased by piling bales of gunnies three high with trucks fitted with a special grab for this class of work. Frequently when a terminal be- comes congested, due to increased volume of cargo, it is possible to de- crease the congestion by providing mechanical equipment and modern- izing methods, the effect being to in- crease the capacity of the terminal. The tenth principle states that, “Productivity is increased by pro- © A sideport op- eration such as this is an ea- ample of the straight line movement principle of cargo handling ® © The economy of equipment is increased by de. signing it to perform more than one type of operation. This lift truck can be fitted with a crane attachment © MARINE REvieEw—December, 1934 viding working conditions suitable to the task.’’ Safe equipment and safe working conditions not only decrease insur- ance costs, but increase the produc- tivity of the operation. The studies which have been made of the rela- tionship of safety and productivity show that productivity is increased by providing high safety standards. Among these is the provision of ade- quate lighting. The eleventh principle, the. prin- ciple of stndardization, which is known as, ‘‘The determination of the best practice under any set of condi- tions is necessary to maximum profits.’ Determination of the one best way of handling flour, canned goods and other cargo on the terminal, and then make that one best way standard practice until experience, experiment or observation of other operations de- velop a better method. Versatility, Methods, Equipment The twelfth principle states that, “Economy in frieght handling is ob- tanied by providing equipment and methods which are capable of a vari- ety of uses.’’ For example, a lift truck which may be readily con- verted into a crane truck, or a news- print truck is more economical for some operations than a truck limited to use as a lift truck. Another example is found in the winch arrangement on ships. Re- gardless of the trade in which a ship is to operate, designers should, wherever other conditions permit, place winches close enough together, to be operated by one winch driver because in the life of the ship it is possible that she will operate in a trade where the practice is permit- ted . All equipment and methods shouid be made as flexible as practical to permit economical operation under changing conditions. Cargoes, ships and terminals change, and ships and terminal equipment should be plan- ned to permit handling of cargo un- der as great a variety of conditions as possible, because in the long run this results in the greatest economy. 29