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"M4 MARINE REVIEW. a : ; end of the hull with all of its machinery upon it 2 feet in the water, which : DIPPER DREDGE PAN-AMERICAN. is equal to sustaining a weight upon the spuds of about 130 tons. When | the spuds are off the bottom the hull is "down by the head" several feet, - due to the great weight of the machinery on the front end. In other words no attempt has been made to distribute the weight upon the hull so that it will float on an even keel. In fact it would be a disadvantage to do SO, as the extra weight is needed at the forward end to hold the spuds down, and when the dredge is pinned up she is in the best position for work, The A-frame and boom are of steel, and are clearly shown in the view of the front end of the dredge. The A-frame is 53 feet high, and the beom is 53 feet long, and weighs 30 tons. The dipper handle is of wood, rein- A MAOHINE THAT IS CLAIMED TO BE THE LARGEST OF ITS KIND EVER CON- STRUOCTED--OF 12 TONS DIPPER CAPAOITY--OWNED BY HINGSTON & WOODS OF BUFFALO. Through the courtesy of the Engineering News of New York, the Review is enabled to present a complete description and a few very clear illustrations of the dipper dredge Pan-American, recently completed for Hingston & Woods of Buffalo, N. Y., for use on the great lakes. This is claimed to be the largest dredge "of its type ever constructed. It has ETS Tey a dipper with a capacity of 814 cubic . -yards or about 12 tons. While in- tended for service on the great lakes, the dimensions of the hull are such that the dredge can go through the ~ Welland and St. Lawrence canals, and can easily be fitted with tanks for salt water service. The hull and 'general arrangement of the dredge were planned by Mr. William _E, Hingston, and the machinery was designed and built by the Bucy- rus Co. of South Milwaukee, Wis. The Engineering News acknow- 'ledges indebtedness to Mr. Hings- 'ton and to Mr. A. W. Robinson, M. Am. Soc. C. E., chief engineer of the Bucyrus Co., for the information from which this description has _ been prepared. ~~ The hull is built of white oak and Oregon fir, and is 136 feet long, 42 feet 3 inches beam, and 13 feet 6 inches deep. There are four longi- tudinal steel trusses. Two of these '"aré-spaced 26 feet apart, or on the line of the'cabin work, and are each 119 feet long and 25 feet high. The total height from the keel to the 'tops of these trusses is 82 feet. The 'other two trusses are located at the sides and are each 119 feet long and '13 feet deep, or just the depth of the ~ hull. The sides of the hull are 8 _ Inches thick, and the bow is 12 _ inches thick. The bottom and sides _-are connected by 136 wrought-iron knees. Altogether, including the amaterial in the spuds, there entered Into. the construction of the hull 157,000 feet B. M. of fir, 70,000 feet B, M. of oak and 23,000 feet B. M. of pine, or a total of 250,000 feet B. M. of timber. There are four spuds, two at the bow, each 4 by 4 feet, made up of VIEW OF FRONT END OF DREDGE PAN-AMERICAN, SHOWING A-FRAME, BOOM AND DIPPER CONSTRUCTION, forced with steel plates, and, as already stated, it carries a dipper of 6% four 24 by 24 inches Oregon fir timbers, 50 feet. long, and two at the stern, _2 by 2 feet in size. The bow or forward spuds are raised and lowered by "power from the main engine by means of wire ropes. There is a large .Sheave on top of the spud and another fitted in a slot through the spud about 12 feet from its lower end. There are two ropes to each spud, both connected to opposite ends of one drum, and the ends of the rope are _ attached to a fixed point outside the spud, and provided with means for adjustment. The rope passing around the sheave near the lower end of .the spud serves to raise it, and the other rope passing over the top of cubic yards capacity and weighing 16 tons. As the dipper is operated by wire rope, single whip, it is expected that the dredge will work very rapidly. She is guaranteed, in fact, to make a full revolution with a load from water 25 feet deep every 40 seconds, which is a capacity »f from 5,000 to 6,000 cubic yards per ten-hour day. Perhaps the most distinguishing feature of the dredge is the use of the single-part wire-rope hoist instead of the chain hoist for the dipper. The reason for this innovation, as stated by the builders, is as follows. As dipper dredges increase in size a hoisting chain that will withstand the necessary strain becomes ex- VIEW OF 18 BY 24-INOH DOUBLE HOISTING ENGINE--DREDGE PAN-AMERIOAN. pen' serves to force it down with great force and thus "pin up" the redge. ~ It will easily be seen that with dredges of the dipper type it is very necessary to pin them up securely, so that a considerable portion of the 'weight of the hull at the forward end rests upon the spud upon the bot- tom, in order to hold the dredge against the digging thrust of the dipper. The "pinning up" power of the Pan-American is easily able to lift the ceedingly heavy, and it is also neces- sary to run it at great speed in order to make time. This necessitates a great waste of power and wear and tear of the chain and sheaves. A hoisting chain, to do the work of this great dredge, would be three parts 244 inches in diameter and 275 feet long, and would weigh about ten tons. It would require four sheaves, which should not be less than 6 feet in diameter, and would probably weigh about two_ toms each, or a total of eight tons. It will readily be seen that the friction and wear and tear on this chain wou be enormous, and the horse powef required to move it would be con- siderable. Moreover, when such 4 chain breaks, as it sometimes does without notice, it is a serious task to SNS fish it up again. So much for the = disadvantages of the chain hoist for very large dredges. Attempts have been made to substitute wire rope for chain by us- ing three parts of rope and binding them around the sheaves in the usual way, but this method has not been altogether satisfactory, as the frequent bending and friction of the ropes against each other caused them soon to wear out. In 1890 Mr. John Kennedy, chief engineer of the harbor commissioners of Montreal, introduced the first wire rope dredge for large and heavy work on the single rope plan. This dredge was designed for digging hard material, such as shale rock, ete., in 40 feet of water, and had a direct pull 0