Read Ebook: Pumps and Hydraulics Part 1 (of 2) by Hawkins N Nehemiah

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Just who the first man was, and by what stream he sat gazing on his parched fields, on which the cloudless skies of the Orient shed no rain, and where the early rising sun with eager haste lapped up the dew drops which the more kindly night in pity over his hard lot had shed, and who, looking on his withering grain stalks on the one side and the life-giving waters which flowed by on the other, first caught the inspiring thought that if one could only be brought to the other, how great would be the harvest, we shall never know. Knowing, as we do, that such still is the problem that confronts the toiler on the plains of that far-off Eastern land where man's necessities first prompted man's invention, it does not require a great stretch of the imagination to conceive of such a situation, and to believe that, acting on the impulse of the moment, he called his mate, and tying thongs to the feet of a sheep-skin and standing on either side of the brook, with alternate swingings of the suspended skin they lifted the waters of the stream to the thirsty field, making its blanched furrows to bloom with vegetation, and at the same time introducing to the world the first hydraulic apparatus ever invented, and certainly the first hydraulic ram ever used."

Similar shaped vessels of the Greeks, Romans and other people might be easily produced.

"A vessel containing wine, and provided with an open spout, stands upon a pedestal: it is required by shifting a weight to cause the spout to pour forth a given quantity,--sometimes, for instance, a half cotyle , sometimes a cotyle , and in short, whatever quantity we please. A B , is the vessel into which wine is to be poured: near the bottom is a spout D: the neck is closed by the partition E F, and through E F is inserted a tube, G H, reaching nearly to the bottom of the vessel, but so as to allow of the passage of water. K L M N is the pedestal on which the vessel stands, and O X another tube reaching within a little of the partition and extending into the pedestal in which water is placed so as to cover the orifice O, of the tube. Fix a rod, P R, one-half within, and the other without the pedestal, moving like the beam of a lever about the point S; and from the extremity P of the rod suspend a water-clock, T, having a hole in the bottom. The spout D having been first closed, the vessel should be filled through the tube G H before water is poured into the pedestal, that the air may escape through the tube X O; then pour water into the pedestal, through a hole, until the orifice O is closed, and set the spout D free. It is evident that the wine will not flow, as there is no opening through which air can be introduced: but if we depress the extremity R of the rod, a portion of the water-clock will be raised from the water, and, the vent O being uncovered, the spout D will run until the water suspended in the water-clock has flowed back and closed the vent O. If, when the water-clock is filled again, we depress the extremity R still further, the liquid suspended in the water-clock will take a longer time to flow out, and there will be a longer discharge from D: and if the water-clock be entirely raised above the water, the discharge will last considerably longer. To avoid the necessity of depressing the extremity R of the rod with the hand, take a weight Q, sliding along the outer portion of the rod, R W, and able, if placed at R, to lift the whole water-clock; if at a distance from R, some smaller portion of it. Then, having obtained by trial the quantities which we wish to flow from D, we must make notches in the rod R W and register the quantities; so that, when we wish a given quantity to flow out, we have only to bring the weight to the corresponding notch and leave the discharge to take place."

THE SYPHON.

The general method of use is to fill the tube in the first place with the liquid, and then, stopping the mouth of the longer leg, to insert the shorter leg in the vessel; upon removal of the stop, the liquid will immediately begin to run. The flow depends upon the difference in vertical height of the two columns of the liquids, measured respectively from the bend of the tube, to the level of the water in the vessel and to the open end of the tube. The flow ceases as soon as, by the lowering of the level in the vessel, these columns become of equal height or when this level descends to the end of the shorter leg.

Fig. 54 shows how hot or corrosive liquids may be drawn off from a wide mouthed bottle or jar. The short leg of a syphon is inserted through the cork, and also a small tube, through which the operator blows, and by the pressure of his breath forces the liquid through the syphon.

Fig. 55 represents a syphon sometimes employed by chemists. When used, the short leg is first placed in the fluid to be decanted, the flame of a lamp or candle is then applied to the underside of the bulb; the heat rarefies the air, and consequently drives out the greater part of it through the discharging orifice. The finger is applied to this orifice, and as the bulb becomes cool the atmosphere drives up the liquid into the void and puts the instrument in operation.

Fig. 56 is a syphon charged by pouring a quantity of the fluid to be decanted into the funnel, the bent pipe attached to which terminates near the top of the discharging leg. The fluid in descending through this leg bears down the air within it, on the principle of the trompe, and the atmosphere drives up the liquid in the reservoir through the short leg.

Fig. 57 is a glass syphon for decanting acids, &c. It is charged by sucking, and to guard against the contents entering the mouth, a bulb is blown on the sucking tube. The accumulation of a liquid in this bulb being visible, the operator can always withdraw his lips in time to prevent his tasting it.

Fig. 58 is designed to retain its contents when not in use, so that on plunging the short leg deep into a liquid the instrument will operate. This effect however will not follow if the end of the discharging leg descend below the bend near it, and if its orifice be not contracted nearly to that of a capillary tube.

Fig. 59 is a syphon by which liquids may be drawn at intervals, viz., by raising and lowering the end of the discharging leg according to the surface of the liquid in the cistern.

Figs. 60, 61, 62 are syphons described by Hero of Alexandria who lived 120 B. C.; the descriptions of the figures are the translation of the original.

Let A B C D be a vessel open at the top, and through its bottom pass a tube, either an inclosed pipe as E F G, or a bent syphon G H K. When the vessel A B C D is filled, and the water runs over, a discharge will begin and continue till the vessel is empty, if the interior opening is so near the bottom of the vessel as only to leave a passage for the water.

As before, let there be a vessel, A B , containing water. Through its bottom insert a tube, C D, soldered into the bottom and projecting below. Let the aperture C of the syphon approach to the mouth of the vessel A B, and let another tube, E F, inclose the tube C D, the distance between the tubes being everywhere equal, and the mouth of the outer tube being closed by a plate, E G, a little above the mouth C. If we exhaust, by suction through the mouth D, the air in the tube C D, we shall draw into it the water in the vessel A B, so that it will flow out through the projection of the syphon until the water is exhausted. For the air contained between the liquid and the tube E F, being but little, can pass into the tube C D, and the water can then be drawn after it. And the water will not cease flowing because of the projection of the syphon below:--if, indeed, the tube E F were removed, the discharge would cease on the surface of the water arriving at C, in spite of the projection below; but when E F is entirely immersed no air can enter the syphon in place of that drawn off, since the air which enters the vessel takes the place of the water as it passes out.

Let A B C , be a bent syphon, or tube, of which the leg A B is plunged into a vessel D E containing water. If the surface of the water is in F G, the leg of the syphon, A B, will be filled with water as high as the surface, that is, up to H, the portion H B C remaining full of air. If, then we draw off the air by suction through the aperture C, the liquid also will follow. And if the aperture C be level with the surface of the water, the syphon, though full, will not discharge the water, but will remain full: so that, although it is contrary to nature for water to rise, it has risen so as to fill the tube A B C; and the water will remain in equilibrium, like the beams of a balance, the portion H B being raised on high, and the portion B C suspended. But if the outer mouth of the syphon be lower than the surface F G, as at K, the water flows out, for the liquid in K B, being heavier, overpowers and draws toward it the liquid B H. The discharge, however, continues only until the surface of the water is on a level with the mouth K, when, for the same reason as before, the efflux ceases. But if the outer mouth of the tube be lower than K, as at L, the discharge continues until the surface of the water reaches the mouth A.

WELLS.

This stupendous well is an oblong square, twenty four feet by eighteen, being sufficiently capacious to admit within its mouth a moderate sized house. It is excavated through solid rock to the depth of one hundred and sixty-five feet, where it is enlarged into a capacious chamber, in the bottom of which is formed a basin or reservoir, to receive the water raised from below . On one side of the reservoir another shaft is continued, one hundred and thirty feet lower, where it emerges through the rock into a bed of gravel, in which the water is found, the whole depth being two hundred and ninety-seven feet; the lower shaft is not in the same vertical line with the upper one, nor is it so large, being fifteen feet by nine.

As the water is first raised into the basin, by means of machinery propelled by horses or oxen within the chamber, it may be asked, how are these animals conveyed to that depth in this tremendous pit, and by what means do they ascend? A spiral passage-way is cut through the rock, from the surface of the ground to the chamber, independent of the well, round which it winds with so gentle a descent, that persons sometimes ride up or down upon asses or mules. It is six feet four inches wide, and seven feet two inches high. Between it and the interior of the well, a wall of rock is left, to prevent persons falling into, or even looking down it , except through certain openings or windows, by means of which it is faintly lighted from the interior of the well. The animals descend by this passage to drive the machinery that raises the water from the lower shaft into the reservoir or basin, from which it is again elevated by similar machinery and other oxen on the surface of the ground. In the lower shaft a path is also cut down to the water, but as no partition is left between it and the well, it is extremely perilous for strangers to descend.

The square openings represented on each side of the upper shaft are sections of the spiral passage, and the zig-zag lines indicate its direction. The wheels at the top carry endless ropes, the lower parts of which reach down into the water; to these, earthenware vases are secured by ligatures at equal distances through the whole of their length, so that when the machinery moves these vessels ascend full of water on one side of the wheels, discharge it into troughs as they pass over them and descend in an inverted position on the other side.

Aqueducts, fountains, cisterns and wells, are in numerous instances the only remains of some of the most celebrated cities of the ancient world. Of Heliopolis, Syene and Babylon in Egypt; of Tyre, Sidon, Palmyra, Nineveh, Carthage, Utica, Barca, and many others. "The features of nature," says Dr. Clarke, "continue the same, though works of art may be done away: the 'beautiful gate' of the Jerusalem temple is no more, but Siloah's fountain still flows, and Kedron still murmurs in the valley of Jehoshaphat." According to Chateaubriand, the Pool of Bethesda, a reservoir, one hundred and fifty feet by forty, constructed of large stones cramped with iron, and lined with flints embedded in cement, is the only specimen remaining of the ancient architecture of that city.

NOTE.--Roman wells are found in every country which that people conquered. Their armies had constant recourse to them when other sources of water failed. Pompey and Caesar often preserved their troops from destruction by having provided them. It was Pompey's superior knowledge in thus obtaining water, which enabled him to overthrow Mithridates, by retaining possession of an important post.

NOTE.--The operation of this primitive device may be thus described--Near the well or tank, a piece of wood is fixed, forked at the top; in this fork another piece of wood is fixed to form a swape, which is formed by a peg, and steps cut out at the bottom, that the person who works the machine may easily get up and down. Commonly, the lower part of the swape is the trunk of a tree; to the upper end is fixed a pole, at the end of which hangs a leather bucket. A man gets up the steps to the top of the swape, and supports himself by a bamboo screen erected by the sides of the machine. He plunges the bucket into the water, and draws it up by his weight; while another person stands ready to empty it.

We are now to examine the modes practised by the ancients, in obtaining water from wells. In all cases of moderate depth, the most simple and efficient, was to form an inclined plane or passage, from the surface of the ground to the water; a method by which the principal advantages of an open spring on the surface were retained, and one by which domestic animals could procure water for themselves without the aid or attendance of man.

But when in process of time, these became too deep for exterior passages of this kind to be convenient or practicable, the wells themselves were enlarged, and stairs for descending to the water, constructed within them.

Wells with stairs by which to descend to the water, are still common. The inhabitants of Arkeko in Abyssinia, are supplied with water from six wells, which are twenty feet deep and fifteen in diameter. The water is collected and carried up a broken ascent by men, women and children. Fryer in his Travels in India speaks of "deep wells many fathoms underground, with stately stone stairs." Near the village of Futtehpore, is a large well, ninety feet in circumference, with a broad stone staircase which is about thirty feet deep to descend to the water. The fountain of Siloam is reached by a descent of thirty steps cut in the solid rock, and the inhabitants of Libya, where the wells often contain little water, "draw it out in little buckets, made of the shank bones of camels."

Wells with stairs are not only of very remote origin, but they appear to have been used by all the nations of antiquity. They were common chiefly, among the Greeks and Romans.

As a matter of interest some six or eight representations of the early forms of wells, have been introduced; but little need to be written relating to them--the cuts with the titles speak for themselves and also indicate their manner of use.

A method much used where rivers are available is the wheel and bucket, in which the buckets are mounted on the rim of a large wheel which is of a diameter equal to the height to which the water is to be raised. The processes although extremely crude are well adapted to countries where labor is inexpensive as the running expense of the devices is very small.

WATER-LIFTING INVENTIONS.

Important epochs in the gradual inventions relating to pumps and hydraulics are: The "force pump," due to Ctesibius 200 B. C.; the "double-acting pump," invented by La Hire in 1718; the "hydraulic ram," by Whitehurst in 1772; the "hydraulic press," introduced by Joseph Bramah in 1802.

Most of the machines hitherto noticed, raise water by means of flexible cords or chains, and are generally applicable to wells of great depth. We now enter upon the examination of another variety, which, with one exception , are composed of inflexible materials, and raise water to limited heights only.

One end of the trough as shown in the figure rests upon the bank where a gutter is prepared to carry off the water, and the other end is dipped in the water, by a man standing on a stage, plunging it in with his foot. A long bamboo with a large weight of earth at the farther end of it, is fastened to the end of the jantu near the river, and passing over the gallows, poises up the jantu full of water, and causes it to empty itself into the gutter. This machine raises water three feet, but by placing a series of them one above another, it may be raised to any height, the water being discharged into small reservoirs, sufficiently deep to admit the jantu above, to be plunged low enough to fill it;" water is thus conveyed over rising ground to the distance of a mile and more. In some parts of Bengal, they have different methods of raising water, but the principle is the same.

A little study of the figure will explain its operation.

S, is the shaft; G G, the gutters; A, a trough to take away the water. The arrow indicates the direction in which the wheel turns; each gutter, as it revolves scoops up a portion of water and elevates it, till by the inclination to the axle, it flows towards the latter, and is discharged through one end of it.

Within the enclosure are arranged four scrolls of suitable proportions, dipping the water, at one end, and emptying it out at the center of the wheel as more clearly shown in Figs. 74 and 75.

The Chinese make the noria, in what would seem to have been its primitive form, and with an admirable degree of economy, simplicity, and skill. With the exception of the axle and two posts to support it, the whole is of bamboo, and not a nail used in its construction. Even the vessels, are often joints of the same, being generally about four feet long and two or three inches in diameter. They are attached to the poles by ligatures at such an angle, as to fill nearly when in the water, and to discharge their contents when at, or near the top.

NOTE.--The mode of constructing and moving the noria by the Romans, is thus described by Vitruvius, who lived about the beginning of the Christian Era. "When water is to be raised higher than by the tympanum, a wheel is made round on axis of such a magnitude as the height to which the water is to be raised requires. Around the extremity of the side of the wheel, square buckets cemented with pitch and wax are fixed; so that when the wheel is turned by the walking of men, the filled buckets being raised to the top and turning again toward the bottom, discharge of themselves what they have brought into the reservoir."

GAINING AND LOSING BUCKETS.

In Moxon's machine, the buckets were filled by two separate tubes of unequal bore; the orifices being covered by valves to prevent the escape of water while the buckets were in motion; these valves were opened and closed by means of cords attached to the buckets. The efflux through F in the figure, may easily be stopped as soon as A begins to descend, by the action of either bucket on the end of a lever attached to a valve, or by other obvious contrivances. The water discharged from A, runs to waste through a channel provided for that purpose. These machines are of limited application, since they require a fall for the descent of A, equal to the elevation to which the liquid is raised in B. They may however be modified to suit locations where a less descent only can be obtained. Thus, by connecting the rope of B to the periphery of a large wheel, while that of A is united to a smaller one on the same axis, water may be raised higher than the larger bucket falls, but the quantity raised will of course be proportionally diminished. In the face of these securing advantages it has fallen into disuse; it was much too complex and cumbersome, and of too limited application.

The principle of self-action in all these machines is no modern discovery, for it was described by Hero of Alexandria, who applied it to the opening and closing the doors of a temple, and to other purposes.

THE PULLEY AND WINDLASS.

The wells of Asia, frequently varying from two to three, and even four hundred feet in depth, obviously required more than one person to raise the contents of an ordinary sized vessel; and where numbers of people depended on such wells, not merely to supply their domestic wants, but for the purposes of irrigation, the substitution of animals in place of men to raise water, became a matter almost of necessity, and was certainly adopted at a very early period. In employing an ox for this purpose, the simplest way and one which deviated the least from their accustomed method, was merely to attach the end of the rope to the yoke, after passing it over a pulley fixed sufficiently high above the mouth of the well, and then driving the animal a distance equal to its depth, in a direct line from it, when the bucket charged with the liquid would be raised from the bottom.

The value of a device like this will be appreciated when the great depth of some wells is considered and the consequent additional weight of the chains. In the fortress of Dresden is a well eighteen hundred feet deep; at Augustburgh is a well in which half an hour is required to raise the bucket; and at Nuremburgh another, sixteen hundred feet deep. In all these, the water is raised by chains, and the weight of the one used in the latter is stated to be upwards of a ton.

The general construction of this machine will appear from an examination of those which are employed to raise water from Joseph's well at Cairo, represented on page 45. Above the mouth of each shaft a vertical wheel is placed, over which two endless ropes pass and are suspended from it. These are kept parallel to, and at a short distance from each other, by rungs secured to them at regular intervals, so that when thus united, they form an endless ladder of ropes. The rungs are sometimes of wood, but more frequently of cord like the shrouds of a ship, and the whole is of such a length that the lowest part hangs two or three feet below the surface of the water that is to be raised. Between the rungs, earthenware vases are secured by cords round the neck, and also round a knob formed on the bottom for that purpose.

WHEEL AND AXLE.

SUCCESSIVE INVENTIONS.

With the wide acceptance in practical use of the Duplex steam pump, may be dated the beginning of the modern inventive period of pumping machinery; this introduction of the Duplex pump was only one of five successive advances which it were well for the student to memorize:

The Cornish engines have been alluded to in connection with the Newcomen engine. Probably no large pumping engines in the past have held, and deservedly so, as high repute as have the Cornish engines when used for deep mine pumping. Their construction, with the rude appliances at hand, is not only a marvel but as well a high tribute to the ingenuity of those who designed them and to the skill of the workmen who built them. A rather full illustrated description of this almost unexcelled machine will be found later on in the book.

These engines vary greatly in their design and in the details of their construction. They are of varying sizes, including some of the largest and most expensive in the world. As a general thing they are employed in supplying towns and cities with water, and in some cases freeing shallow mines of water. The application of the power of the steam used in the steam cylinders in this class of engines to drive the plungers or pistons in the pumps, varies greatly, both as to the general design upon which they are built, and in the detail of their construction. In some instances it is through the use of long or short beams or bell cranks, sometimes through gearing, and occasionally through the plunger or piston of the pump direct; but in all cases the limit of the stroke of the steam piston, and of the pump plunger, is governed by a crank on a revolving shaft.

In short, these devices, as employed in both the classes of pumping engines described, were used in order that the best economy in the consumption of steam by means of early cutoff and a high grade of expansion, might be attained.

In the brief description given of these three most prominent classes of pumping engines, no attempt has been made to describe any of the peculiarities of their general construction, beyond what was necessary to describe their action and the principles upon which they operate.

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