Modern Mechanism, Appleton's Cyclopedia of Applied Mechanics, 1892
APPLETON"S DICTIONARY OF ENGINEERING, published in 1851, was the first work in which were gathered, in cyclopedic form, descriptions of the products of American industry. It served the best purpose of such a publication, in that it crystallized existing knowledge into concrete shape, digested it, and so rendered it easily available to the busy mechanic and engineer. thirty years afterward - so great had been the advances due to American invention in every department of the mechanic arts - it was found that, to bring the work abreast of the time, its complete reconstruction was necessary. As a result, appears Appleton's Cyclopedia of Applied Mechanics, in which of the older publication nothing remained save the small proportion which was valuable in point of historical interest, or which dealt with subjects still instructive when brought into contrast with later achievements. No work of a technical character so signally and so quickly demonstrated its own usefulness. It became at once the recognized standard of American mechanical practice. It found its way into the workshops and the manufactures and the technical schools all over the land. It has borne a prominent part in the education of the American mechanic as he is today; and, more than any other literary production, it has helped him toward the pre-eminence which he has attained. But modern progress in all the great fields of invention and discovery is moving with a constantly accelerating speed. In the bending of that great force of Nature which we call "electricity" to human needs, advances are becoming almost a matter of hours. A decade of such onward motion calls for a new record - a new crystallization of the results - and a new effort to bring them in the same tried and assimilable form to those who constitute "the hands of the nation." Hence the present volume. It is not a revision. It is a new book, dealing solely with the principal and most useful advances of the past ten years; and it is therefore issued under a new name which exactly describes its contents - Modern Mechanism. It does not supersede the Cyclopedia of Mechanics, but adds to it. A word, in conclusion, as to how the book has been made. Countless letters and circulars asking information on mechanical topics have been sent to manufacturers and engineers throughout the country. A large collection, not merely of trade literature but of valuable suggestions, has thus been gathered; and this has been supplemented by the best papers which have appeared in American and foreign periodicals and in the transactions of engineering societies. The great mass of accumulated material, carefully digested, has been untrusted to eminent experts on each subject, and by them has been winnowed and selected in the light of their special knowledge and judgment. The result is now submitted to the higher adjudication of the master mechanics of the United States.
ELEVATORS. Part III, GRAIN ELEVATORS - The elevator known as elevators A and B, belonging to the Armour Elevator Co., of Chicago, Ill., and receiving grain from the St. Paul road, is the largest elevator in the world under a single roof. Elevator D, and its annex, belong to the Armour Company, surpass it in capacity of 2,500,000 bushels, can unload 500 cars per day, and deliver 100,000 bushels per hour to cars and boats. Cars enough to keep it at work for four days can be accommodated in the great yard annexed to it. The building proper is 550 feet long and 1,200 horse power is employed in driving the elevator belts. The general features of its construction are the following: It comprises a main building surmounted by what is termed the cupola. The main driving engine is situated on about the ground level, at one end of the building. Along the top of the cupola a counter shaft, the full length of the building is carried. This is driven by the engine. The main belt is of India rubber and canvas, 8 ply in thickness and 60 inches wide. This runs very nearly vertically from the engine driving pulley to the pulley on the counter shaft 150 feet above it. All along the counter shafts are the driving pulleys for working the 28 elevator belts. These belts are made also of India rubber belting, and carry steel buckets riveted at regular intervals along their outside face. As the belt travels up on one side it carries up full buckets. At the top these pass over the driving pulley and are emptied as they turn over, and then they descend empty on the other side of the belt. From the point of delivery of the belt the grain passes by gravity through inclined chutes to the main body of the elevator, and is directed by one or the other chutes to any desired point. The grain from the elevating belt falls into the mouth of a chute which rotates on a vertical axis, whose prolongation would pass through its receiving end or mouth. thus, when swung around on its pivot, its receiving mouth remains unchanged in position. The open ends of a number of chutes leading to the garners corresponding to respective bins below are arranges in a circle around the revolving chute or "revolver." Each is numbered in accordance with the bin it leads to. The revolver can be swung so as to connect with any one of these. In this way one elevator is made to feed a number of bins. Below the chutes on the next floor are what are known, and have just been referred to, as garners. These are simply square bins holding 1,000 bushels each. Immediately under each is a platform scale, with its bin of the same size as the garner above it, and receiving grain from the garner when desired. Here the grain is weighted. The garner, it will be seen, can receive grain during the operations of weighting and discharging the weighting bin, and when the latter is emptied can at once refill it. From each weighting bin the grain is delivered into the bins and pockets the completely fill most of the height of the main building. These range in size from 500 to 7,000 bushels capacity, so as to suit every requirement. Much of the grain received is simply graded, and an equivalent weight of grain of the same grade is delivered when called for. Other grain is to be received with its "identity preserved." In this case the specific grain, and no other, must be delivered on call. The great variety in size of bins adapts the elevator to this work. The garners, weighting bins, and storage bins have sloping bottoms, so that no grain lodges in them. As inclination of 6 inches in a foot is sufficient to insure this. Grain is weighted when received and when delivered. Each weighting operation involves the elevation of the grain from the lower floor, where the bins deliver it clear to the top of the building, for delivery through the revolver and fixed chute to the proper scale. Transfer elevators are employed to effect the transfer of grain from one bin to another. These elevate it so that it can descend through inclined chutes in the desired direction. If the chute does not carry it far enough, one or more additional elevators and chutes are called into requisition. One function of the elevator is the cleaning of grain. Some of the bins, termed cleaning bins, are equipped with winnowing fans for blowing out dust and chaff, and with screens through which the grain has to pass. The latter removes the coarser particles. The winnowed and sifted grain then falls into the bin. The bins all terminate some distance above the ground level. A train of cars has ample head room below them. From the level of the bottom of the bins to the weighting floor the entire area is devoted to the honeycomb of bins, except the few small trunks through which the elevator belts travel, or through which grain descends from one tier of bins to the tier below. A space at one end is also free for the great driving belt to travel in. The elevator belts descend into hoppers below the ground surface, into which grain to be delivered. At intervals along the platforms the bottom floor are trap doors giving access to these hoppers. Grain does not remain in these hopers; it is at once cleaned. To deliver the grain from the cars into the elevator hopers thereis used a scaping shovel about 3 feet square to whic a rope is attached. The rope leads to a steam apparatus, by which it is taken in at the proper time, as if on a windlass. The operator draws the shovel back into the car of grain, and holds it nearly vertical and pressed down into the grain. The rope drawn along the shovel with the grain in front of it, and a number of bushels are delivered at each stroke. In this way a couple of men can vary quickly empty a car. The movements of the shovels succeed one another with sufficient rapidity to keep the men in active movement. One of the features of this elevator is the use of the electric light, which is arranged to light the interior of cars, so that night work can be carried on. In the recent heavy grain deliveries it was found neccessary to work day and night. The portion of such elevators containing the bins is built without framing. Planks are laid flatwise upon each other and spiked through to the layer below. In this way the outer walls and the bin divisions are built up, giving immense strength and power to resist lateral thrust. A usual timber for the sides is 2 x 8 inch spruce, giving 8 inch walls, and for the bins 2 x 6 inch is often employed. The Armour elevator contains over 8,000,000 feet of wood, and about 4,000 kegs of nails were used in its construction. The main building is bricked in out side of the timber walls, and the roof and cupola walls are covered with tin. It was erected between June 1887, and March, 1888, being put in operation on the last named date. It cost about $600.000.
MILL, GRAIN: see Milling - Machines, Grain. MILLING - MACHINES, GRAIN. A very advanced step has been taken in the last twelve years by the introduction of rolls for grinding grain. This has led to a radical change of systems of milling. The old process of low grinding in which the wheat was reduced to flour by buhr stones at one operation, and the more advanced "new process" system, have both given way to the Hungarian or high grinding system, in which the production and treatment of middlings are the essential features, as also the production of as little flour at the early operations in the wheat as possible. The present systems of milling have for their object the separation of the bran from the flour producing portions of the wheat berry by gradual reduction, using chilled iron and porcelain rolls in place of buhr stones. The rolls have proved a powerful factor in the radical change of systems, though the purifier must receive proper recognition of its importance as a milling appliance, while the various improved sifting and cleaning devices growing out of the employment of the high grinding system all contribute to make the latter pre-eminent as a method of producing a quality of flour to meet the exacting demands of the day, and to do this profitably commercially. It is well to note that the so-called "new process" system, used in America prior to the introduction of rolls, may be considered a process intermediate between low milling and the Hungarian system of high milling. It no doubt had great influence in preparing the way for the introduction of rolls, and hastened the development of the purifier, especially in America. It is stated that rolls were used as early as 1820, but it was twenty years later before they attracted much attention. The noted Pesth mill was the first to use rolls alone for the reduction of wheat. For over forty years, previous to the general change from stones to rolls, this famous mill had been in prosperous condition; and, while it stood as a prominent illustration of what rolls could do, millers generally were not inclined to the idea that the system there used could be advantageously employed on any other than the hard wheats used in that locality. Experiment and enterprise have, however, brought about the almost universal use of rolls for the various reductions, and the corresponding abandonment of the time honored millstone. The introduction of rolls gave rise to the more scientific phase of milling. With a more general knowledge of the physical structure of the wheat berry came a better understanding of what was necessary to be done to properly separate the bran and germ from the flour producing portions. The system of low grinding made the elimination of these portions impossible, since the fine, branny particles became inseparably mixed the flour, as did also the crease dirt held in the wheat berry. The Austro-Hungarian or high grinding system provides for their separation at stages of reduction, thus making it possible to produce a clear sharp flour. Gradual reduction, where buhr stones are used, is attended with the same trouble as low grinding, though in a far less degree. The fine branny particles and some crease dirt become mixed with the flour, due to the more or less tearing action of the surface of the stone on the bran, especially with hard wheats, and subsequent treatment by reel and purifier falls to remove them. With proper treatment of the wheat by rolls the fine, branny particles and crease dirt, so objectionable when obtained in the early stages of reduction, are almost if not wholly avoided, the middlings obtained are clean and sharp, the bran large and flaky, and the flour preserving the natural sweetness of the germ. A great impetus was given to roller milling by the introduction, in 1874, of the Wegmann roller mill, in which rolls of porcelain were used. These mills were introduced into England in the fall of 1876, and into the United States the spring of the following year, by Mr. Oscar Oexle, of Augsburg, Bavaria. The essential features of this roller mill that found ready acceptance with millers were: the squeezing action of the rolls, the character of the roller surface, the different speed of the rolls, and the use of the springs to keep the rolls up to their work. Soft iron, stone, chilled iron, and steel rolls had previously been used, and, it was claimed, did not possess a uniform porous surface. Close upon the introduction of the porcelain roll came the more extended use of corrugated chilled iron rolls, especially for the earlier operation upon the wheat berry, technically known as break rolls. Smooth rolls had for some time been used for flattening the germ, and, indeed, for crushing wheat, while the middlings were usually treated on stones. In the early part of 1878 great interest was aroused in roller milling, especially in America. The work done by rolls began to be appreciated. Since 1878 there has been a gradual conversion from stones to rolls. This period has been marked not alone by the introduction of rolls, but by the practical application of principles and appliances suggested by the process employed in the treatment of the products coming from the rolls. The period is also marked by the refined mechanical construction of the various appliances now used. Rolls. - Rolls are now made almost exclusively of chilled iron, with either smooth or corrugated surface, according to the nature of the work they have to do. The peculiar gritty surface of porcelain rolls renders them well suited for the reduction of purified middlings, but their lack of durability as compared with the chilled iron has led to a preference for the latter. Smooth rolls are generally delivered to the buyer with polished surface, but attain a dulled surface after being in use a short time. They then give the best results. This is due to the increased friction between the particles of material operated upon and the surface of the rolls. It should be understood that, as this friction is increased, the pressure required for reduction is decreased. Prof. Kick gives the coefficients of friction for polished chilled rolls on hard semolina dressed over No. 7 silk as 0-213; that for fine dull surface, 0-287; and for rolls that have been in use, 0-325. On No. 2 middlings the coefficients are given as 0-195, 0-268, and 0-306 respectively. Porcelain rolls give a coefficient of 0-404 for fine semolina, and 0-364 for No. 2 middlings. Prof. Kick also states that the whiteness of flour obtained with porcelain rolls is due to the greater fineness of the product and not the small proportion of bran impurity. The two rolls of a pair have the same peripheral speed, or what is termed a "differential" speed. When run equally speeded, smooth rolls act to granulate, by crushing or squeezing. When hard wheat is passed between smooth rolls equally speeded, and adjusted with proper distance between, the berry is split lengthwise, opening out the crease and setting free crease dirt, and more or less loosening and releasing the germ. With soft wheat there is more of a crushing effect. Smooth rolls are mostly used for all reduction of purified middlings, reducing the large middlings, and when run equally speeded, flatten the germ without the rubbing action, which tends to tear it. When speeded differentially, they effect a combined crushing and rubbing action, and require less pressure to do their work than when equally speeded. This has led to the general use of differential speeds, and thereby power is saved. A differential speed of 1 1/2 to 1 is commonly used on smooth rolls. Prof. Kick states that, theoretically considered, smooth rolls in crushing use about double the force that is required for the shearing action of grooved rolls in the actual work of reduction, or the work of crushing is twice as great as that for shearing. A further advantage of differential speed is the avoidance of "caking" of the material on the rolls. Corrugated rolls are generally used for all reduction other than the sizing and reduction of middlings and treatment of the germ, the number of grooves corresponding to the size of the particles of material operated upon. Many forms of grooves have been employed, though but two have attained extended use. They are the sharp and dull corrugations. The first sharp form of corrugation used had sides of the flute equally inclined, but this form was introduced by Granz and Co., of Buda-Pesth, Hungary, is the type of groove now employed for what are termed cutting rolls, and opposed to the round rib or non-cutting rolls. The action of the sharp groove is essentially that of shearing; relative speed of the grooves, however, being necessary in producing this effect. Rolls equally speeded would act to crush and bruise the grain, while to produce a shearing action a differential speed of 2 to 1 is necessary, that one groove may overtake the engaging grooves on the mate roll. Consequently, these rolls are generally speeded 2 or 3 to 1. The relative position of the acting surfaces of the grooves where the fast rolls, the edge of flute pointing downward, while those of the slow roll, point upward. If the downward pointing roll were made the fast roll, the action would be that of crushing and rubbing. With the sharp flute four dispositions of the acting edges are permissible, thus providing for different qualities and condition of the grain - as, sharp to sharp for tough wheat, and dull to dull for hard wheat; with the other arrangements for intermediate qualities. In December 1881, Mr. William D. Gray, of Milwaukee, Wis., took out letters for a form of corrugation in which the rolls were abrupt on one side and rounded on the other, thus obtaining the cutting and non-cutting effect according to the dispositions of the acting sides of the flutes. With sharp cut rolls the edges left by the corrugating tolls are soon lost, a day or two, it is stated, being sufficient to make them feel smooth. They can be used from one and a half to two years before requiring to be recut. A twist or spiral direction along the rolls is given the grooves to prevent those of one rolls catching in the grooves of its mate. This also tends a more severe shearing action. The direction of the twist may be in the same on each roll of a pair, or disposed in opposite directions. In the former one the grooves cross at line of contact of rolls, while in the latter they are parallel at that time. On May 25, 1880, Mr. John Stevens, of Neenah, Wis., received letters patent for a roll having a dress formed of grooves with rounded divided ridges. For this form of corrugation is claimed less cutting of the bran and breaking of the germ. The number of grooves employed for the several stages of reduction increase as the products become finer. For the five successive break rolls usually employed they may be 10, 12, 14, 16, and 20 grooves per inch of circumference of roll. The bran rolls may have 24, and the middlings reduction rolls 32 grooves per inch. With sharp corrugations there are more grooves than with the round, and practice varies in regard to the numbers given above, some preferring diner grooved rolls. The differential usually employed for breaks is 2 1/2 to 1, while the same, or 3 to 1, is used with scratch rolls - rolls with dress formed of shallow waved grooves, 32 per inch. The diameter of rolls generally used are 9 and 16 inches; the lengths, 12 to 30 inches. Nine inch rolls are usually run at 300 to 400 revolutions per minute, and the 6 inch rolls 600 revolutions, the peripheral speed being 706 to 942 feet feet per minute. First break rolls run at these speed will pass from 90 to 112 pounds of wheat per inch of length of rolls per hour. Where six breaks are employed, an increase of about 1 2/3 to 1 1/2 times the grinding length of first break roll is made, this taking place at the third or forth and following breaks. Variation in practice makes it difficult to state proportions of grinding surface for middlings rolls. A given size of roll grinding middlings will handle about three fourths the weight of material that the first break roll of the same size will pass. The pressure on roll bearings is the controlling factor in the calculation for power required, the actual work of granulation being comparatively insignificant. Pressure up to 3,500 pounds per bearing are used, the work of friction this being for a 2 pair mill 15 horse power. About 1,00 or 1,500 pounds per bearing are perhaps average pressure for 9 inch rolls, having spindles 2 7/8 inches in diameter. Six inch rolls are used with 600 to 1,000 pounds per bearing. Roller - Mills. - The well known Stevens roller mill. The frame is of the "skeleton" construction, composed of the two side frames or legs, which are bolted to a rectangular bed or top. The rolls are mounted in boxes, the two inside boxes being rigidly fastened to the bed, the two outer ones sliding on finished surfaces. A V-shaped gib, bolted to the bed, preserves the linear motion of the sliding box. Relative position of the rolls is attained by the adjustments. At each corner of the bed of the machine are cast lugs sustain the backward thrust of the movable rolls. Into those lugs are fitted threaded sleeves, through which the hand wheel stem is passed. A hexagon head on the outer end of this sleeve provides for turning it, and it is screwed firmly into the lug, so as to act as a stud for the spring nut shown to work upon. The hand wheel stem is treaded at the inner end, and passing through a hexagon nut seated in the sliding box, abuts against the fixed box. Turning the hand wheel moves the sliding box away from or toward the fixed box, and proper grinding tension or pressure is secured by setting up the spring nut. Vertical adjustment of the fixed roll is secured by the parts or adjustment screws. The adjusting screw and dowel in which the box rests raise or lower it, while the binding screws secure the box firmly to the brackets after the necessary adjustment has been made. The dowel aids to preserve the fixed lateral position of the roll bearing. The boxes project beyond the end of the short roll necks and have enlarged recesses to retain the oil and prevent its running down into the frame. The tightened pulley, mounted in the spindle, runs in a frame vertically adjustable by means of a rack and pinion operated by the cross shaft, which latter is held from rotation by pawl and ratchet wheel, and is readily turned when desired from either end of the machine. The pulleys drive the first rolls of each pair, their mates being driven either by belts or gears, arranged to provide the differential of roll speed, the latter varying generally between 3 to 1 and 1 to 1. The spreading device at the front of the machine provides for the simultaneous movement of the ends of the movable roll without disturbing the working adjustment as made by the hand wheel at each end of the roll. Projecting from the bed is a threaded stud, on which turns the curved arm, the hub of this arm being threaded to fit the thread on the stud. In front of this arm is a dog with hub threaded the same as the arm, and having its outer end bent so as to form, a stop for the curved arm to rest against. At the outer end of the stud is a small hand wheel having a left hand thread. Extending from the stud to each hand wheel are levers, one end of each pressing against the hub of the curved arm, the other ends against the inner end of the hand wheel hubs. Near the hand wheel stem and attached to the threaded sleeve through which it passes, is placed a fulcrum, the latter being thus between extremities of the levers - the operation of the whole being such that by rotating the curved arm, say from left to right, it advances along the stud, pushing the inner lever ends toward the frame, and forcing the hand wheels in the opposite direction, and therefore the roll away from its mate. By advancing the dog along the stud and setting up the small hand wheel tight against it, any desired position of the curved arm can be maintained. Rotating the curved arm, the dog remaining fixed, alters the adjustment of the rolls, but they can be restored to their previous adjustment by bring the curved arm back to the dog. Generally about 1/2 inch is the maximum spread of rolls required. The wooden housing is parted horizontal at the roll centers, the top being lifted bodily so that the rolls can be easily removed when necessary. In the top is placed the feed devices. This consists essentially of two gates, extending across the top part of the housing, and swung on axes at their upper edge and connected by levers and links, so that motion of one implies that of the other. The upper gate forms one side of a V-shaped hopper, into which the material falls. The lower edge of the other gate approaches a feed roll located by the extended bearings near the bottom of feed hoppering. Fastened to the shaft on which this gate swings is the arm carrying the counter weight. When no material is in the hopper, this lower gate is swung against the feed roll, but as material enters in the upper gate it accumulates in the hopper formed by the gate and the stationary cant board at center of the housing, until the weight is sufficient to overcome the effect of the counter weight, when this upper gate swings down, allowing the material to pass to the space below it, where it meets the lower swinging gate, and passes between its lower edge and the feed roll to the grinding rolls beneath. The secondary hopper is provided so that material coming into it from the first hopper will have a chance to distribute itself over the entire length of the feed roll. The greater the quality of material pressing against the upper gate, the greater the opening at the feed roll, and consequently the greater the quantity passing to the grinding rolls. The desired quantity of feed can be obtained by adjusting the counter weight on its arm. The lower part of the housing contains the brushes for cleaning the rolls, and the door in front permits access to materials passing from the rolls. The feed rolls are driven by a single belt passing from the neck of one slow roll over each pulley on the feed rolls, and the tightener pulley at the top of the housing. Several makes of roller mills are made with box frame construction, and with rolls mounted in swinging arms. The Gray mill is the pioneer in this form of construction. In this mill the vertical adjustment of the rolls is obtained by an eccentric bush fitting over the stud, on which the swinging arms are suspended. Motion to the rolls is obtained by the use of one belt, a counter shaft and pulleys running in boxes hung to the frame acting to transmit motion from the main belt to the slow rolls, a pulley on one end of the counter being the tightener pulley for the main belt, while the pulley on the other end of the counted serves to carry the slow roll belt. The method for driving both fast and slow rolls in a Stevens double mill which has proved satisfactory. The large pulley on the line shaft beneath the floor drives the fast rolls, the small pulley the slow ones. The means for tightening the belts are readily seen. In some short systems of milling only two or three breaks are made, and in such cases the machines can be used especially where economy of room is necessary. The machine has two pairs of corrugated rolls and two reciprocating sieves. The grain passes through the first or upper sieve. A separation of the product is here made, flour and middlings passing through the sieve and away from the machine: the large unreduced portion passes over the tail of the sieve on the second pair of rolls, and from there on the second sieve, when a second separation is made. The sieves have traveling brushes beneath them, thereby enabling the meshes to be kept clean. The machine is driven by a single belt, and adapted to mills of 75 to 150 bushels capacity, the power required being from 3 1/2 horse power with 9 X 14 inch rolls to 6 horse power with X 30 inch rolls. The type of roller mill used in grinding corn, as made by the Nordyke & Marmon co., of Indianapolis, Ind. Three pairs of rolls are used, disposed so as to break the grain successively. The first pair are adjusted solely by the hand wheels, while the middle and lower pairs are spread or thrown together by a single lever. The fast roll of each pair is driven by one belt from the main shaft. The slow rolls are driven by gears. The machine is built very rigid in order to meet the hard usage found in this class of work. In a mill using rolls 9 X 24 inch the capacity is stated to be 65 to 100 bushels per hour, and the power required 12 to 20 horse power. The upper pulley runs 400, the middle 445, and the lower 500 revolutions per minute. The pulleys are 20, 18, and 16 inches in diameter and 8 1/2 inch face for upper, middle, and lower drives respectively. Scalping - Reels. - The scalping reels handle the break roll products, successively separating the break flour and middlings from the coarser material after each break. The reel frame is made either hexagon or round in form. In the former the tail end is larger than the head; in the latter the shaft is depressed at the tail end to carry the material through. The reel shaft is of iron, and the wooden ribs are attached to iron spiders on the shaft. The wooden head is provided with the usual opening, through which is introduced a feed spout with the customary conveyor spiral to feed the material into the reel. The round reels, in scalping as in flour dressing, are receiving much attention as to detail, and are gaining in popular favor. Scalping reels are clothed with wire cloth, silk cloth, or perforated steel, and are from 18 to 36 inches in diameter and from 4 to 9 feet long. They are now commonly driven by belt or chain direct from the line or counter shaft, and are run about 28 revolutions per minute for a 32 inch reel. The slant is from 1/2 to 3/4 inch per foot. The reel chests are usually made to conform to the style and size of those of the centrifugal and round reels for flour dressing described later. The speed should be about 50 revolutions per minute for 18 inch reels to 28 revolutions for a 32 inch reel. Centrifugal Reels. - In recently erected flour mills the old hexagon bolting reel has been supplanted by the centrifugal and round reels, and especially has the latter been favorably received. The hexagon reel and its chest, the former 32 inches in diameter and from 12 to 16 feet long, the latter exceeding these dimensions, have been found too cumbersome for modern purposes, especially in America, and reels considerably smaller and of far greater capacity are now found taking their places. In the perspective view and the cross section view of the centrifugal reel, as made by the E. P. Allis Co., of Milwaukee, Wis. Referring to the cross section, it will be seen that on the beater shaft are placed the spiders to which are attached the beaters, the latter running lengthwise of the reel and inclined to a radius from the center of shaft, acting thus to throw the material against the bolting cloth, which mounted on a reel frame, surrounds the beaters, etc. The latter are set to the cloth to keep the stock thoroughly in motion, preventing accumulation and thereby giving full action to the reel. They run spirally lengthwise of the reel, thus carrying the material gradually toward the tail end, retaining it long enough on the cloth to do the work properly. The silk reel is mounted on trunnions which surround the beater shaft at the head and tail of the reel, and rotates at a less speed and in the same direction as the beater shaft. A revolving brush, is used to keep the cloth clean. The silk reels are made 21, 27, and 32 inches in diameter and from 4 to 8 feet long. The outside dimensions for a 32 inch reel chest are: 11 feet 7 inches long, 3 feet 6 inches wide, and 5 feet 3 inches high. The conveyors are placed side by side with partition between them to which the cut off tongues are hinged, the latter extending up to the hoppering. Material is directed into either conveyor by placing the tongues against either side of the hopper. With the centrifugal it is necessary to provide some safeguard to prevent foreign substances from entering the reel. This should be a basket of wire cloth or other suitable material which can be readily cleaned. In this class of machines the speed of silk reel should not be so great that the material is held against the cloth by the centrifugal force due to speed. The speed of beater shaft is usually 10 or 12 times that of the silk reel, a usual speed for the latter being 18 to 20 revolutions per minute. It is the aim of makers of centrifugals at the present time to direct the material against the silk at a very acute angle, so that sliding of the material over the surfave of the cloth shall take place, fully recognizing the value of the action as obtained with the now old style hexagon reel. Round Reels. - A latter machine, and one, it is claimed, that overcomes the alleged defects of the centrifugal reel. The class of machine had rapidly gained in favor since its introduction, about four years ago, and is said to have fully demonstrated the superiority of the round reel bolting system. The flour dresser made by Allis Co., which is almost identical with that of the centrifugal already noticed. The reel, mounted on the main shaft, consists of a substantial casting at each end, upon which wooden rings are placed, to which the cloth is attached. Round rods connect the head and tail end castings, and to these are attached rib rings for the cloth carriers, preventing contact of cloth with the rods. Within these rods is placed a light sheet iron drum, fastened firmly to the shaft. The carriers are pitched spirally toward the tail, leading the stock continually in that direction. Sufficient space is left between the outer edge of the carriers and the cloth, also between the inner edge of the carriers and the drum, to enable the stock to bolt properly without heating or rough handling, thus avoiding flouring of the stock. The flouring of the material, as alleged to take place with the centrifugal reel, as also the increased quantity of bolting cloth necessary, are factors against the centrifugal; while the great capacity of bolting cloth necessary, are factors against the centrifugal; while the great capacity and effectiveness of the round reel has led to its extended adoption. The room occupied and power required are greatly decreased as compared with the hexagon reel - the round reel, it is claimed, doing the dame work as the hexagon, with from one half to one third the length of reel. Inventors have striven to produce a reel in which the full circumference could be utilized for sifting, in place of only the lower portion, as is the case with the hexagon reel. The centrifugal and round reels are intended to do this, the latter appearing to have accomplished the action of these two machines manner. The difference in the action of these two machines is readily understood by an inspection of the head and tail cross sections. In erecting new mills a great saving in millwright work is effected by the use of this class of reel. They come from the manufacturer complete and ready to be set in position, one being readily placed on top of another. In mills using the complete system of centrifugal or round reels the saving in room is stated to be about one half, and the saving in first cost of machines nearly one third. The reels are driven by belts, and are usually made from 21 to 32 inch diameter, and the cloth is from 6 to 8 feet long, the approximate power, as given by the makers, being 0-2 horse power and 0-6 respectively. Purifiers. - The George T. Smith purifier, so well and favorably known, is regarded as the standard machine of its class. The main features of this machine have never been departed from, and are: An upward current of air through the covering of a reciprocating sieve, clothed with silk of increasingly coarser mesh from head to tail; an inclosed air space above the sieve, divided by transverse partitions into separate compartments having practically no communication with each other, and each opening into the chamber of an exhaust fan through an adjustable value, arranged to regulate the strength of the air current through each compartment separately; a series of dust setting chambers or testing pockets, corresponding in number to the compartments above mentioned, and a brushing device opening automatically and working against the under side of the sieve clothing. This combination has proved a very efficient one. There are numerous other makers of purifiers, but the Smith purifier may be regarded as a standard machine. The use of dust collectors in connection with these machines has led to economy of space and increase in convenience in providing for the dust laden air coming from the purifier sieve. The Prinz dust collector is favorably known, and has a long since settled the knotty dust room question. A new principle, that of the "cyclone" dust collector, has recently been put into practical operation, the essential features of which are embodied in the machine noted below. This machine, which bids fair to be a formidable rival to the sieve purifier and attached dust collector, was lately devised by Mr. N. W. Holt, of Manchester, Michigan, and made by the Knickerbocker Co., of Jackson, Mich. The stock is fed into the feed spout upon each side of the machine. Two grades of stock may be handled at the same time. From the feed spout it passes to the feed box, which vibrates with the sieve or shaker, causing the stock to flow over the lower overlapping shelves in a thin, even sheet, where it is acted upon by the air current. The purifier middlings then pass out at the spouts, the cut off at and the dust at a spout. The fan placed at the top provides the air circulation required at the several points of the sieve, while gates at the eye of the fan control the air circulation as a whole. The dust laden air is discharged from the fan through the pipe of the machine, where the dust and air separate, the dust eventually settling at the bottom of the cone shaped part and passing away from the machine, the air returning through the sieve, to be again used. The same air is used over and over, and not being renewed from without the machine, excluded the possibility of smoke or dust from the external atmosphere affecting the products. No cloth is used, and the air being confined inside the machine renders it dustless. The power required is very small, a driving pulley 7 inches in diameter and 3 1/4 inch face, running 600 revolutions per minute being all that is required to drive it. The capacity of the machine as now made is equivalent to one medium sieve purifier. Bran - Dusters. - Economy in the production of high grade flours calls for proper cleaning of the bran. The effect of the bran rolls is to flatten the bran, leaving it broad and flaky and loosening the adhering particles, so that by subsequent treatment by the bran duster these particles are regained and further treated. The latter operation is performed in the machine which consists of a rapidly revolving shaft on which are mounted brushes running lengthwise of the shaft and made adjustable toward or from the slowly revolving dusting case which surrounds them. The dusting case, clothed with fine wire cloth, is, in this machine, cone shaped, the material being fed and discharged as indicated. A brush outside the wire cloth keeps it clear, and the conveyor beneath serves to handle the products coming through the cloth. The shaft makes from 400 to 450 revolutions per minute, according to size of machine, the pulleys 14 X 7 inch and 8 X 5 inch respectively. The sizes of machines given handle the offal from mills of 600 to 60 bushels capacity in 24 hours. Books for reference: Gradual Reduction Milling, by L. U. Gibson; Flour Manufacture, by F. Kick, Powles' translation, 1888; Die Osterreichishe Hochmullerei, by Franz Kreuter, 1884.
WATER WHEELS. [Some day]
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