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January, 1921 2-inch steel cable, reeved in a double 4- part system, the cable ends passing over defiecting sheaves to the machin- ery house, where they are connected to separate drums geared to a standard power unit. The two main hoists will be so arranged that they may be coupled together for simultaneous use. The 40-ton auxiliary hoist block will be suspended from the trolley by eight parts of 134-inch steel cabie reeved in a double 4-part system. The two cables wiil be anchored to the inner end of the jib and, after reeving through the trolley and block, will pass around sheaves at the outer end of the jib and back to the auxiliary hoist mechanism, the ends being attached to two drums geared to a standard power unit, On account of the inclination of the jib, a greater amount of power is re- quired to move the trolley toward the outer end of the jib than in the re- verse direction. A double 2-part sys- ter of 134-inch cable will be used for - the outward travel and itwo 1-inch tail ropes will be provided. The two large ropes will be anchored at the outer end of the jib and lead around sheaves in the trolley, then around the end of the jib and back to the trolley mechan- ism, where they will be anchored to two large winding drums. The tail ropes will lead directly from the trol- ley to a drum of one-half the diameter of the Jarge ones thus compensating for the 2-part system on the outer end. All of the drums are geared to a stand- ard power unit, as in the case of the other mechanisms. The two independent power units for rotating the crane are located fat each side of the platform and each geared to one of the bevel pinions, which mesh with the gear ring alttached to the foundation. There is no mechanical con- nection between these two units, equali- zation of the rotating loads being pro- duced by the characteristics of the mo- tors, which holds them in electrical balance. In case of accident to either motor the other is capable of revoly- ing the crane at reduced spced. Lufing Done By Screws Luifing of the jib, up or down, will be accomplished by varying the dis- tance between the back-frame and the elbow of the jib. For this purpose. four large screws will be used, two having right hand and two left hand threads. These screws will be arranged in pairs at each side of the jib. one right hand and one left hand being placed end to end and coupled together at the center, the ends passing through nuts supported on trunnions in the back frame and the jib. These screws will be turned by gears attached to the center couplings. On accourt of THE MARINE REVIEW the extreme angle through which the jib is luffed, there is great variation in the distance between the nuts. In or- der to prevent underside deflections in the screws, when fully extended, a luffng strut will be introduced. This strut will be pin-connected to the jib at a point midway between the hinge- pins and the nuts, and its upper end will be supported on trunnions at the center of the screw coupling. In addi- 47 tion to supporting the screws, this strut forms aiso a support for the luffing mechanism, which will consist of two standard power units geared to the screw coupling. The screws will be 15 inches in diameter, of alloy steel, heat treated, and will have buttress threads 4 inches in pitch. The nuts will be over 4 feet in length, of manganese bronze, and will be supported in steel. trunnion castings, Laying Out Cant Plating Method Developed in Mold Loft of Large Eastern Shipyard BY WILLIAM ASHE NY system of development of plating is merely a method of laying down on a flat sur- face the outlines and connections of a plate. which is to be a: patt ol a curved surface, with sufficient ac- curacy, so that when the plate is laid- off from a mold made from the lines as laid down oh the flat surface, it will when bent tc the curved sur- face of which it is 'to torm a part, assume the outlines intended closely enough to make the rivet holes match, and permit it to be properly riveted in place. A good example to illus- trate the principles of any system of development is that of cant plating; - that is, the plating around the stern of the vessel over the cant framing. This is because the curvature is com- paratively so great and yet is such that it may readily be seen how the developed plates assume thé positions intended, Following is a brief description of the method of developing cant plating, which has been worked out in the mold loft of the Newport News Ship- building & Dry Dock Co., Newport News, Va.: Lines of the stern must be _ laid down on the mold loft floor in ,the usual way, profile, plan view and body plan, as shown in the accom- panying illustration, giving the lines of the cant framing in each view and also the buttock lines, usually for each 2 feet. The lines of the plating then are indicated in each view froin the shell plating plan, and the butts located. The first process in the development is to establish across the plating what is known as a "normal base line." This may be started in any convenient place. The method of constructing the nor- mai line is illustrated by an exagger- ated sketch in the accompanying fig- ure. As tthe buttocks are not exactly parallel to each other, this normal Proves Successful base line is an approxfmate line only and is obtained by establishing a point on any buttock, drawing a line from this point at right angles to the but- tock and marking its intersection on the next buttock. Another line then is drawn from the same point on the first buttock, at right angles to the second buttock, and its intersection with the second buttock marked. Since the two buttocks are not exactly parallel, this will establish on the second buttock two points a short dis-_ tance apart. A point then is marked on the second buttock, midway be, tween the above two points, and ig called the' "neutral point." -: Sitarting from this neutral point, ithe same pro- cess is repeated to the next buttock. The normal base line then is drawn from the starting point through the various neutral points established on the successive buttocks. Normal Base Taken In the cant plating as illustrated in the accompanying drawing, for in- stance, a normal base line is started on the center line near the knuckle in the plating, by laying a square--an ordinary carpenter's square or equi- valent device--with its corner on this point and one edge along the line of the plating at the center line, and marking on the No. 2 buttock the - point where the other edge of the square crosses it. The square then is laid with one edge on the No: 2 but- tock, and slid along until the other edge passes through the starting; point on the center line. The point at the corner of the square then is marked on the No. 2 butteck. This gives on the No. 2 buttock, two points a slight distance apart. A point is marked midway between them and this is the neutral point for the No. 2 but- tock. The corner of the square is then laid on this neutral point, with one