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~ 1901.] MARINE REVIEW. 21 Elevating Co.'s, under construction in Buffalo, the bins are simple cylin- drical tanks built of steel plates, and placed in rows with their bottoms at ground level. The grain is taken in from grain boats or cars by ma- chinery placed in a house at the end of the rows or groups of bins, and is sent to the bins by overhead conveyors which carry and drop it into any desired one. Beneath each row of bins is also a conveyor by which the grain is carried from any bin back to the working house, where it is elevated and shipped or restored as may be desired. The bins are roofed overhead, but the sides are not covered. In the Buffalo examples, the bins are of various sizes, but in those at Minneapolis they are all of about 50 ft. diameter and 100,000 bushels capacity each. In the Great Northern elevator of Buffalo, the circular bin system is quite differently treated. In it the bins are all supported on steel columns with their hopper bottoms at about the usual spouting height above the ground floor, and the elevator legs and working machinery, instead of being all at one end, is distributed throughout the house, and the grain is spouted from the bins to the boots, and from the heads to the bins as in ordinary elevators. There are thirty circular bins of about 39% ft. diameter, and 75,000 bushels capacity each, and in their interspaces are twenty-seven circular bins of about 15% ft. diameter and 12,000 bushels capacity. A number of the irregular shaped interspaces formed between the small and large cylinders, have been further utilized by connecting the cylinders by steel plates, thus making little bins of about 2,000 bushels capacity. The bins are housed around by steel framing and sheeting, and are surmounted by the usual upper stories and cupola for containing the elevator heads, spouting, weighing hoppers, etc. The elevator has a storage capacity of about 2,600,000 bushels, and is fitted for receiving from boats and for delivering to cars on tracks outside the house. In the elevator of the Buffalo Elevating Co. (practically the Lehigh Valley Railroad Co.), the round steel bin system is being skilfully used in still another way. It is yet in the early stages of construction, but it is intended to be a working and storage house for receiving from lake boats and delivering into canal boats and cars. The circular bins are supported on steel columns, with their bottoms at spouting height above the ground floor. They are 15% ft. in diameter by about 70 ft, high, and placed a foot apart, which gives circular bins of about 10,500 bushels capacity and interspaces of about 5,000 bushels capacity, which are utilized as bins. The third type of fireproof construction, or that in which the bins are of tiles, has thus far been used only for storage annexes, and the only examples seen are two in Minneapolis. In these the bins are circular, of 50 ft. diameter and 100,000 bushels capacity each. Their bottoms are at ground level, on concrete foundations, and they are filled and emptied by conveyors overhead and underneath. The walls of the bins are of spe- cially molded glazed hollow tiles laid in two thicknesses, with steel hoops built in to resist the internal pressure of the grain. Only the inside of the bins is used for storage; the interspaces are not utilized. Of the fourth, or concrete type, there is only one example, 'and that is an unfinished elevator at Duluth. The bins proper are being built of circular form, and in rows at about 4 ft..clear distance apart, with connect- ing walls to separate the interspaces, which are also intended to be utilized, are of about 30,000 bushels capacity each. The walls of the bins are of high class concrete, 12 in. thickness at the lower part and about 9 in. at top, and they are strengthened by steel hoops and diagonal wire lacing, built in. The bins are being roofed over, but they are to have no housing around them. It is obvious, on considering the main characteristics of the elevators described, that the new materials which have been adopted in order to make them fireproof have in great measure governed the larger features of the elevators as well as the details of construction. When wood alone was used the rectangular plank bin was so clearly the best that no other was used, and the limitations of the material and mode of construction practically limited the general arrangement to groups of rectangular bins of 15,000 bushels or less capacity each. Bins of such material and sizes have the advantage of suitability for the storage of grain of all sorts and conditions, and lots of all usual sizes; but being of inflammable material, the risk of fire made it prudent to keep the aggregate capacity of the group, or single elevator building to something like a million bushels. On the other hand, steel, the first and most generally adopted material for wholly fireproof elevators is best suited to the construction of bins of large size, of say 100,000 bushels capacity, and of circular shape, and being fireproof they may be safely grouped to give any required aggregate capacity. In early examples of steel elevators the bins were therefore made circular, chiefly of large capacities, and with bottoms at ground level, but this arrangement is unsuited to the storage of grain in small lots, and it involves the use of grain handling machinery of very limited capacity, and gives limited freedom in changing heated grain from bin to bin. Its main advantages are economy. of construc- tion and freedom from fire risk. An improvement in the cir- cular bin system which eliminates some of its most serious defects was that adopted in the Great Northern at Buffalo by raising the bot- toms of the bins to spouting height above the ground, putting small round bins in the spaces between the large and making bins of the re- maining interspaces, and by suitably increased working machinery of ordinary type. A still further and, for most conditions, the best develop- ment of the circular bin system, is that on the Buffalo Elevating Co.'s elevator, in which the bins are only about 11,000 bushels capacity, each with utilized interspaces of about half the capacity, and all at high level so as to be served by ordinary working machinery. While the circular bin system was being thus developed a more radical departure was made in the use of steel by discarding the circular bin altogether and reverting to square bins of moderate size, placed at high level, and served by ordi- nary machinery enclosed by steel housing, or in other words, in using steel in such a way as to make an enlarged and improved copy of the best features of wooden elevators, while avoiding their inflammability. A compromise type suited to certain requirements, and of moderate cost, is that of the Pioneer elevator in Minneapolis, in which there is a working house with square steel bins of convenient size, and an annex of large circular steel bins to make-up the total required storage capacity. The tile and concrete systems are obviously the outcome of efforts to ebtain suitable materials other than steel plates for the construction of incombustible bins. Thus far the bins under both systems have been only of large size and circular form and seated at ground level, and they have therefore the same limitations as to use as have steel bins of the same size and form. As regards the action of the various fireproof ma- terials upon the grain in contact with them and the sufficiency of the ma- terials to bear the strains of service, experience is short, but so far as it goes indicates that none of them do any harm whatever to the grain nor are they harmed by grain in any condition. It was at one time feared that steel bins might sweat or heat the grain, but nothing of the kind has taken place. For the resisting of load strains steel bins can of course be made of any required strength, and tile bins as built and used have proved to be of ample strength. Some of the newly built concrete bins at Duluth failed on a test made by filling an interspace with grain, but the failure has not deterred.the owners and builders from continuing the building of the other bins required to make up the full intended number. In applying the information thus set forth to the case of the proposed Montreal harbor elevators, the following are the main questions which arise and the ways in which, in my judgment, they should be met. The questions are, for convenience, worked out for one elevator of 1,000,000 bushels capacity, but the reasoning is applicable to other capacities and more elevators. 1. As to whether the elevator building be built of wood or of fire- proof materials. The question obviously touches both the owner and the user, and its solutions as regards both may be made on the following assumptions: A million bushel wooden elevator will cost, without wharf conveyors, say $300,000, and its insurance rate may be taken at about 2% per cent. One of fireproof materials will cost about $400,000, and on it there need be no insurance. The interest on first cost will be, say, 34% per cent. per annum, and alike for both kinds of elevators. An ele- vator like all other plant used in trade will soon become obsolete because of changing conditions, and must be practically rebuilt or replaced long before worn out. A renewal fund should therefore be set aside, which, at say 3% per cent. yearly compound interest, will provide for total renewa! in say twenty-five years. Such renewal fund will be equal to 2.9 per cent. per annum on the first cost. Maintenance and working expenses will about balance in the two kinds of buildings, and need not be taken into account. The average storage term of grain taken into the elevator for storage during navigation season, apart from that merely transhipped, may be taken at ten days; and the grain insurance rate for that term in a wooden elevator may be taken at 0.25 per cent. Probably no insurance need be carried on grain in fireproof elevator, but in case it should be required by banks making advances it would be about 0.05 per cent. For winter storage the term may be assumed at two months, for which the insurance rate would be about 0.75 per cent. in a wooden elevator, and 0.15 per cent. if demanded in a fireproof one. The owner's yearly investment and insurance expenses will then be: For a wooden elevator-- Interest, 31%4 per cent.; renewal fund, 2.9 per cent.; insurance, 2%4 per cent.; total, 8.9 per cent. on $800,000; first cost per an- MUM a a a Bate ee eee ae $26,700 For a fireproof elevator-- Interest, 8% per cent.; renewal fund, 2.9 per cent.; (insurance, none); total, 6.4 per cent. on $400,000; first cost............ 25,600 Difference per annum to owner in favor of fireproof elevator...... $ 1,100 The grain shippers' insurance charges will be: With a wooden elevator-- For summer, ten day. insurance.....(20.0. 6.450 ss 0.25 per cent. For winter, sixty day insurance. ...37 3.1.03 ...2...2 0.75 per cent. With a fireproof elevator-- For simmer, ten day insurance. ..2.........:....03. 0... 0.05 per cent. For, winter, sixty day insurance., .-..2.......:1:..5....... 0.15 per cent. The results of the estimates would, of course, be changed by change in the assumed data, but it is clear that a fireproof elevator could cost the commissioners no more per annum than would a wooden one, and that it would save to the shippers who store in it about four-fifths of their storage insurance. This conclusion is confirmed by the fact that almost all elevators built within the past two years are of fireproof material. I would therefore recommend that any elevator built by the commissioners for general use be made fireproof. 2. The chief requirements to which an elevator for the central part of the harbor should comply as regards its machinery and storage ar- rangements: It must, of course, be placed and equipped so as to take in grain from canal boats and cars, and to deliver to, say, four ships at any of ten berths, and also deliver to harbor lighters; and it should perform any or all operations separately or together. Grain shipments through Montreal are usually made up of small lots, whose identity must be pre- served and the elevator bins should therefore be of small size, say about 12,000 bushels capacity each. These conditions would, on the whole, be best fulfilled by an elevator resembling the Great Northern of Duluth in its main features but greatly reduced in size and modified in structural details. The bins should be built of steel. COMPASS PLATFORM TO BE INSULATED. . Rear Admiral Bradford, chief of the bureau of equipment, has re- ceived an interesting letter from Lieutenant-Commander F. M. Bost- wick, navigator of the Oregon, in which he describes the effect on the standard compass of a "ground" in the bridge electric circuit. While the Oregon was steaming up the China coast on course N. E. by N., the navigator reports that it suddenly became necessary to change the course about a point to the eastward by bridge and steering compasses, to make the allotted course by standard. Upon investigation it was found that the trouble lay with the standard compass. A time azimuth taken showed the deviation of the standard compass to be 10° and 4-100 min. east, the tabu- lated deviation being 1° and 4-100 min. Upon inquiry it was found that the bridge circuit had just been turned on, and later a "ground" was dis- covered. Experiments showed conclusively that the fault was due to this "oround." In order that this trouble may be avoided in the future, the secretary of the navy has authorized the chief of the bureau of con- struction and repair to inform the commandants of the navy yards and _ the superintending naval constructors that hereafter the platforms for car- rying the standard compass should, whenever practicable, be insulated from the structure of the ship by three-eighths of an inch of hard rubber fiber, and that the bolts securing platform stanchions to the structure should also be insulated by bushings and washers of the same material; also that all horizontal railings within 12 ft. of the compass should be made either of wood or Manila hemp rope.--Electrical World and Engi- neer. '