Chapter 3

The work to be done by a fan consists in putting a weight--that of the air--in motion. The resistances incurred are due to the inertia of the air and various frictional influences; the nature and amount of these last vary with the construction of the fan. As the air enters at the center of the fan and escapes at the circumference, it will be seen that its motion is changed while in the fan through a right angle. It may also be taken for granted that within certain limits the air has no motion in a radial direction when it first comes in contact with a fan blade. It is well understood that, unless power is to be wasted, motion should be gradually imparted to any body to be moved. Consequently, the shape of the blades ought to be such as will impart motion at first slowly and afterward in a rapidly increasing ratio to the air. It is also clear that the change of motion should be effected as gradually as possible. Fig. 1 shows how a fan should not be constructed; Fig. 2 will serve to give an idea of how it should be made.

In Fig. 1 it will be seen that the air, as indicated by the bent arrows, is violently deflected on entering the fan. In Fig. 2 it will be seen that it follows gentle curves, and so is put gradually in motion. The curved form of the blades shown in Fig. 2 does not appear to add much to the efficiency of a fan; but it adds something and keeps down noise. The idea is that the fan blades when of this form push the air radially from the center to the circumference. The fact is, however, that the air flies outward under the influence of centrifugal force, and always tends to move at a tangent to the fan blades, as in Fig. 3, where the circle is the path of the tips of the fan blades, and the arrow is a tangent to that path; and to impart this notion a radial blade, as at C, is perhaps as good as any other, as far as efficiency is concerned. Concerning the shape to be imparted to the blades, looked at back or front, opinions widely differ; but it is certain that if a fan is to be silent the blades must be narrower at the tips than at the center. Various forms are adopted by different makers, the straight side and the curved sides, as shown in Fig. 4, being most commonly used. The proportions as regards length to breadth are also varied continually. In fact, no two makers of fans use the same shapes.

As the work done by a fan consists in imparting motion at a stated velocity to a given weight of air, it is very easy to calculate the power which must be expended to do a certain amount of work. The velocity at which the air leaves the fan cannot be greater than that of the fan tips. In a good fan it may be about two-thirds of that speed. The resistance to be overcome will be found by multiplying the area of the fan blades by the pressure of the air and by the velocity of the center of effort, which must be determined for every fan according to the shape of its blades. The velocity imparted to the air by the fan will be just the same as though the air fell in a mass from a given height. This height can be found by the formula h = v² / 64; that is to say, if the velocity be multiplied by itself and divided by 64 we have the height. Thus, let the velocity be 88 per second, then 88 x 88 = 7,744, and 7,744 / 64 = 121. A stone or other body falling from a height of 121 feet would have a velocity of 88 per second at the earth. The pressure against the fan blades will be equal to that of a column of air of the height due to the velocity, or, in this case, 121 feet. We have seen that in round numbers 13 cubic feet of air weigh one pound, consequently a column of air one square foot in section and 121 feet high, will weigh as many pounds as 13 will go times into 121. Now, 121 / 13 = 9.3, and this will be the resistance in pounds per _square foot_ overcome by the fan. Let the aggregate area of all the blades be 2 square feet, and the velocity of the center of effort 90 feet per second, then the power expended will bve (90 x 60 x 2 x 9.3) / 33,000 = 3.04 horse power. The quantity of air delivered ought to be equal in volume to that of a column with a sectional area equal that of one fan blade moving at 88 feet per second, or a mile a minute. The blade having an area of 1 square foot, the delivery ought to be 5,280 feet per minute, weighing 5,280 / 13 = 406.1 lb. In practice we need hardly say that such an efficiency is never attained.

The number of recorded experiments with fans is very small, and a great deal of ignorance exists as to their true efficiency. Mr. Buckle is one of the very few authorities on the subject. He gives the accompanying table of proportions as the best for pressures of from 3 to 6 ounces per square inch:

| Vanes. | Diameter of inlet Diameter of fans. |------------------------| openings. | Width. | Length. | -------------------------------------------------------------- ft. in. | ft. in. | ft. in. | ft. in. 3 0 | 0 9 | 0 9 | 1 6 3 6 | 0 10½ | 0 10½ | 1 9 4 0 | 1 0 | 1 0 | 2 0 4 6 | 1 1½ | 1 1½ | 2 3 5 0 | 1 3 | 1 3 | 2 6 6 0 | 1 6 | 1 6 | 3 0 | | | --------------------------------------------------------------

For higher pressures the blades should be longer and narrower, and the inlet openings smaller. The case is to be made in the form of an arithmetical spiral widening, the space between the case and the blades radially from the origin to the opening for discharge, and the upper edge of the opening should be level with the lower side of the sweep of the fan blade, somewhat as shown in Fig. 5.

A considerable number of patents has been taken out for improvements in the construction of fans, but they all, or nearly all, relate to modifications in the form of the case and of the blades. So far, however, as is known, it appears that, while these things do exert a marked influence on the noise made by a fan, and modify in some degree the efficiency of the machine, that this last depends very much more on the proportions adopted than on the shapes--so long as easy curves are used and sharp angles avoided. In the case of fans running at low speeds, it matters very little whether the curves are present or not; but at high speeds the case is different.--_The Engineer_.

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MACHINE FOR COMPRESSING COAL REFUSE INTO FUEL.

The problem as to how the refuse of coal shall be utilized has been solved in the manufacture from it of an agglomerated artificial fuel, which is coming more and more into general use on railways and steamboats, in the industries, and even in domestic heating.

The qualities that a good agglomerating machine should present are as follows:

1. Very great simplicity, inasmuch as it is called upon to operate in an atmosphere charged with coal dust, pitch, and steam; and, under such conditions, it is important that it may be easily got at for cleaning, and that the changing of its parts (which wear rapidly) may be effected without, so to speak, interrupting its running.

2. The compression must be powerful, and, that the product may be homogeneous, must operate progressively and not by shocks. It must especially act as much as possible upon the entire surface of the conglomerate, and this is something that most machines fail to do.

3. The removal from the mould must be effected easily, and not depend upon a play of pistons or springs, which soon become foul, and the operation of which is very irregular.

The operations embraced in the manufacture of this kind of fuel are as follows:

The refuse is sifted in order to separate the dust from the grains of coal. The dust is not submitted to a washing. The grains are classed into two sizes, after removing the nut size, which is sold separately. The grains of each size are washed separately. The washed grains are either drained or dried by a hydro-extractor in order to free them from the greater part of the water, the presence of this being an obstacle to their perfect agglomeration. The water, however, should not be entirely extracted because the combustibles being poor conductors of heat, a certain amount of dampness must be preserved to obtain an equal division of heat in the paste when the mixture is warmed.

After being dried the grains are mixed with the coal dust, and broken coal pitch is added in the proportion of eight to ten per cent. of the coal. The mixture is then thrown into a crushing machine, where it is reduced to powder and intimately mixed. It then passes into a pug-mill into which superheated steam is admitted, and by this means is converted into a plastic paste. This paste is then led into an agitator for the double purpose of freeing it from the steam that it contains, and of distributing it in the moulds of the compressing machine.

Bilan's machine, shown in the accompanying cut, is designed for manufacturing spherical conglomerates for domestic purposes. It consists of a cast iron frame supporting four vertical moulding wheels placed at right angles to each other and tangent to the line of the centers. These wheels carry on their periphery cavities that have the form of a quarter of a sphere. They thus form at the point of contact a complete sphere in which the material is inclosed. The paste is thrown by shovel, or emptied by buckets and chain, into the hopper fixed at the upper part of the frame. From here it is taken up by two helices, mounted on a vertical shaft traversing the hopper, and forced toward the point where the four moulding wheels meet. The driving pulley of the machine is keyed upon a horizontal shaft which is provided with two endless screws that actuate two gear-wheels, and these latter set in motion the four moulding wheels by means of beveled pinions. The four moulding wheels being accurately adjusted so that their cavities meet each other at every revolution, carry along the paste furnished them by the hopper, compress it powerfully on the four quarters, and, separating by a further revolution, allow the finished ball to drop out.

The external crown of the wheels carrying the moulds consists of four segments, which may be taken apart at will to be replaced by others when worn.

This machine produces about 40 tons per day of this globular artificial fuel.--_Annales Industrielles_.

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HANK SIZING AND WRINGING MACHINE.

We give a view of a hank sizing machine by Messrs. Heywood & Spencer, of Radcliffe, near Manchester. The machine is also suitable for fancy dyeing. It is well known, says the _Textile Manufacturer_, that when hanks are wrung by hand, not only is the labor very severe, but in dyeing it is scarcely possible to obtain even colors, and, furthermore, the production is limited by the capabilities of the man. The machine we illustrate is intended to perform the heavy part of the work with greater expedition and with more certainty than could be relied upon with hand labor. The illustration represents the machine that we inspected. Its construction seems of the simplest character. It consists of two vats, between which is placed the gearing for driving the hooks. The large wheel in this gear, although it always runs in one direction, contains internal segments, which fall into gear alternately with pinions on the shanks of the hooks. The motion is a simple one, and it appeared to us to be perfectly reliable, and not liable to get out of order. The action is as follows: The attendant lifts the hank out of the vat and places it on the hooks. The hook connected to the gearing then commences to turn; it puts in two, two and a half, three, or more twists into the hank and remains stationary for a few seconds to allow an interval for the sizer to "wipe off" the excess of size, that is, to run his hand along the twisted hank. This done, the hook commences to revolve the reverse way, until the twists are taken out of the hank. It is then removed, either by lifting off by hand or by the apparatus shown, attached to the right hand side. This arrangement consists of a lattice, carrying two arms that, at the proper moment, lift the hank off the hooks on to the lattice proper, by which it is carried away, and dropped upon a barrow to be taken to the drying stove. In sizing, a double operation is customary; the first is called running, and the second, finishing. In the machine shown, running is carried on one side simultaneously with finishing in the other, or, if required, running may be carried on on both sides. If desired, the lifting off motion is attached to both running and finishing sides, and also the roller partly seen on the left hand for running the hanks through the size. The machine we saw was doing about 600 bundles per day at running and at finishing, but the makers claim the production with a double machine to be at the rate of about 36 10 lb. bundles per hour (at finishing), wrung in 1½ lb. wringers (or I½ lb. of yarn at a time), or at running at the rate of 45 bundles in 2 lb. wringers. The distance between the hooks is easily adjusted to the length or size of hanks, and altogether the machine seems one that is worth the attention of the trade.

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IMPROVED COKE BREAKER.

The working parts of the breaker now in use by the South Metropolitan Gas Company consist essentially of a drum provided with cutting edges projecting from it, which break up the coke against a fixed grid. The drum is cast in rings, to facilitate repairs when necessary, and the capacity of the machine can therefore be increased or diminished by varying the number of these rings. The degree of fineness of the coke when broken is determined by the regulated distance of the grid from the drum. Thus there is only one revolving member, no toothed gearing being required. Consequently the machine works with little power; the one at the Old Kent Road, which is of the full size for large works, being actually driven by a one horse power "Otto" gas-engine. Under these conditions, at a recent trial, two tons of coke were broken in half an hour, and the material delivered screened into the three classes of coke, clean breeze (worth as much as the larger coke), and dust, which at these works is used to mix with lime in the purifiers. The special advantage of the machine, besides the low power required to drive it and its simple action, lies in the small quantity of waste. On the occasion of the trial in question, the dust obtained from two tons of coke measured only 3½ bushels, or just over a half hundredweight per ton. The following statement, prepared from the actual working of the first machine constructed, shows the practical results of its use. It should be premised that the machine is assumed to be regularly employed and driven by the full power for which it is designed, when it will easily break 8 tons of coke per hour, or 80 tons per working day:

500 feet of gas consumed by a 2 horse power gas-engine, at cost price of gas delivered s. d. in holder. 0 9 Oil and cotton waste. 0 6 Two men supplying machine with large coke, and shoveling up broken, at 4s. 6d. 9 0 Interest and wear and tear (say). 0 3 ----- Total per day. 10 6 ----- For 80 tons per day, broken at the rate of. 0 1½ Add for loss by dust and waste, 1 cwt., with price of coke at (say) 13s. 4d. per ton. 0 8 ----- Cost of breaking, per ton. 0 9½

As coke, when broken, will usually fetch from 2s. to 2s. 6d. per ton more than large, the result of using these machines is a net gain of from 1s. 3d. to 1s. 9d. per ton of coke. It is not so much the actual gain, however, that operates in favor of providing a supply of broken coke, as the certainty that by so doing a market is obtained that would not otherwise be available.

It will not be overstating the case to say that this coke breaker is by far the simplest, strongest, and most economical appliance of its kind now manufactured. That it does its work well is proved by experience; and the advantages of its construction are immediately apparent upon comparison of its simple drum and single spindle with the flying hammers or rocking jaws, or double drums with toothed gearing which characterize some other patterns of the same class of plant. It should be remarked, as already indicated, lest exception should be taken to the size of the machine chosen here for illustration, that it can be made of any size down to hand power. On the whole, however, as a few tons of broken coke might be required at short notice even in a moderate sized works, it would scarcely be advisable to depend upon too small a machine; since the regular supply of the fuel thus improved may be trusted in a short time to increase the demand.

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IMPROVEMENT IN PRINTING MACHINERY.

This is the design of Alfred Godfrey, of Clapton. According to this improvement, as represented at Figs. 1 and 2, a rack, A, is employed vibrating on the pivot a, and a pinion, a1, so arranged that instead of the pinion moving on a universal joint, or the rack moving in a parallel line from side to side of the pinion at the time the motion of the table is reversed, there is employed, for example, the radial arm, a2, mounted on the shaft, a3, supporting the driving wheel, a4. The opposite or vibrating end of the radial arm, a2, supports in suitable bearings the pinion, a1, and wheel, a5, driving the rack through the medium of the driving wheel, a4, the effect of which is that through the mechanical action of the vibrating arm, a2, and pinion, a1 in conjunction with the vibrating movement of the rack, A, an easy, uniform, and silent motion is transmitted to the rack and table.

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A CHARACTERISTIC MINING "RUSH."--THE PROSPECTIVE MINING CENTER OF SOUTHERN NEW MEXICO.

A correspondent of the _Tribune_ describes at length the mining camps about Lake Valley, New Mexico, hitherto thought likely to be the central camp of that region, and then graphically tells the story of the recent "rush" to the Perche district. Within a month of the first strike of silver ore the country was swarming with prospectors, and a thousand or more prospects had been located.

The Perche district is on the eastern flanks of the Mimbres Mountains, a range which is a part of the Rocky Mountain range, and runs north and south generally parallel with the Rio Grande, from which it lies about forty miles to the westward. The northern half of these mountains is known as the Black Range, and was the center of considerable mining excitement a year and a half ago. It is there that the Ivanhoe is located, of which Colonel Gillette was manager, and in which Robert Ingersoll and Senator Plumb, of Kansas, were interested, much to the disadvantage of the former. A new company has been organized, however, with Colonel Ingersoll as president, and the reopening of work on the Ivanhoe will probably prove a stimulus to the whole Black Range. From this region the Perche district is from forty to sixty miles south. It is about twenty-five miles northwest of Lake Valley, and ten miles west of Hillsboro, a promising little mining town, with some mills and about 300 people. The Perche River has three forks coming down from the mountains and uniting at Hillsboro, and it is in the region between these forks that the recent strikes have been made.

On August 15 "Jack" Shedd, the original discoverer of the Robinson mine in Colorado, was prospecting on the south branch of the north fork of the Perche River, when he made the first great strike in the district. On the summit of a heavily timbered ridge he found some small pieces of native silver, and then a lump of ore containing very pure silver in the form of sulphides, weighing 150 pounds, and afterward proved to be worth on the average $11 a pound. All this was mere float, simply lying on the surface of the ground. Afterward another block was found, weighing 87 pounds, of horn silver, with specimens nearly 75 per cent. silver. The strike was kept a secret for a few days. Said a mining man: "I went up to help bring the big lump down. We took it by a camp of prospectors who were lying about entirely ignorant of any find. When they saw it they instantly saddled their horses, galloped off, and I believe they prospected all night." A like excitement was created when the news of this and one or two similar finds reached Lake Valley. Next morning every waiter was gone from the little hotel, and a dozen men had left the Sierra mines, to try their fortunes at prospecting.

As the news spread men poured into the Perche district from no one knows where, some armed with only a piece of salt pork, a little meal, and a prospecting pick; some mounted on mules, others on foot; old men and men half-crippled were among the number, but all bitten by the monomania which possesses every prospector. Now there are probably 2,000 men in the Perche district, and the number of prospects located must far exceed 1,000. Three miners from there with whom I was talking recently owned forty-seven mines among them, and while one acknowledged that hardly one prospect in a hundred turns out a prize, the other millionaire in embryo remarked that he wouldn't take $50,000 for one of his mines. So it goes, and the victims of the mining fever here seem as deaf to reason as the buyers of mining stock in New York. Fuel was added to the flame by the report that Shedd had sold his location, named the Solitaire, to ex-Governor Tabor and Mr. Wurtzbach on August 25 for $100,000. This was not true. I met Governor Tabor's representative, who came down recently to examine the properties, and learned that the Governor had not up to that date bought the mine. He undoubtedly bonded it, however, and his representative's opinion of the properties seemed highly favorable. The Solitaire showed what appeared to be a contact vein, with walls of porphyry and limestone in a ledge thirty feet wide in places, containing a high assay of horned silver. The vein was composed of quartz, bearing sulphides, with horn silver plainly visible, giving an average assay of from $350 to $500. This was free milling. These were the results shown simply by surface explorations, which were certainly exceedingly promising. Recently it has been stated that a little development shows the vein to be only a blind lead, but the statement lacks confirmation. In any case the effect of so sensational a discovery is the same in creating an intense excitement and attracting swarms of prospectors.