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plungers, C and D, work air-tight for a pumping operations, for which they are portion of their length, driving cranks usually applied, the water pumped can set at 95° on the shaft above. The be made to circulate in the casing, and method of packing is most ingenious, so act as a cooler; but, in common with consisting of two reversed leather col- nearly all hot-air engines, they are heavy lars, which seem to wear satisfactorily, in proportion to their power. Hot-air although in direct communication with engines, then, have decided advantages, the heating chamber. A is the cooling and in the country their employment or compression cylinder, in which, by the might, and probably will be, profitably device of an annulus of air between the extended. plunger and casing E, round which water Compressed air has been applied to circulates, a rapid cooling can be transmit power for a variety of objects ; effected; and in the same way an annu- but the purpose for which, on a small lus of air in the other, or working cylin- scale, it seems specially adapted, is to suder B, enables a rapid transfer of heat persede manual and animal labor in rock to take place when this is necessary. boring and mining operations. For mine The action is as follows: When the air in and tunnels there are many advantages C is compressed by hand at starting to attending its use; for not only is the air about $ its original volume, the rising of which is compressed by external machinthe piston B, which is of equal area, ena- ery of great importance for ventilation, bles it to be transferred without change of but the fall in temperature by expansion, volume to that cylinder with which there which accompanies the necessary loss of is a communication. Here the heating, heat occasioned by its use, is valuable, which is facilitated by the shape of the as tending to reduce the temperature in bottom of the plunger, takes place, and close and heated workings. The princithe consequent expansion causes the pal objects to which it is put are for uncontinuance of the upstroke of D. Upon derground haulage, pumping, and rock the return stroke of D, the air is trans- boring or coal-cutting operations. The ferred to the compression cylinder, but first of these has been considered by is made on the way to give up heat to Mr. W. Daniel, in a paper before the Inthe thin plates in the regenerator H, of stitution of Mechanical Engineers,* and which a partial view is shown, and this is rather applied to motors of a size not heat is restored when the repetition of here dealt with; the second may use the first operation takes place; the rest any of the ordinary steam pumps; but of the heat which must be abstracted is it is the last which is particularly an extaken away by the water in the casing, ample of the successful application of and the engine now continues to work, machinery to replace individual physical the difference between the positive work effort. A vast amount of attention and in the working cylinder, and the nega- ingenuity have been bestowed upon rocktive work in the compression cylinder boring and coal-cutting apparatus, of being the effective work. The 4-HP. which drilling shot holes in the former engine has been found to consume 4 is the most important and toilsome part pounds of coke per hour; the 1-HP. a of the labor required, and one to which little more than twice that amount. One the application of motive power has been was tested at the Royal Agricultural most beneficial. Only one form of rock Show at Birmingham, and the work done borer will be described, but one which, by pumping showed a consumption of at the Bristol docks, has proved efficient 13 pounds of coal per hour per HP., or and durable. Figs. 12 and 13 are two a little more than that used by the views of the drill of R. Schram; the pulsometer pump, or } of that in the action simply imitates that of hand borTangye pump, in the experiments al- ing, viz., a succession of blows, accomready referred to. The cost of coal for panied by a turning motion. The maa week's work of six days, working ten chine consists of a strong cylinder suphours a day, is advertised not to exceed ported by three legs, in which works a 28. 6d. for a 4.HP. engine. These en- solid piston rod, driven by a double pisgines are thus economical; they are reli. ton, the end of the rod carrying the able and simple in action, and require no
* Vide Institution of Mechanical Engineers. Proskilled attendant; they are safe, and, in ceedings, 1874, p. 204.
drill. The blows are given as rapidly as but when the drill and piston rod make 400 or 500 per minute, by means of the the in-stroke, the spiral rod running into valve ff, which acts in a somewhat simi- the former, and being itself held firmly, lar way to that of the special pump; turns it through the necessary angle; in when the opening 0, shown by dotted the out-stroke no turning takes place. lines, in the cylinder is open to the press- The feeding is effected by the handure of the air, the opposite end of the screw T. valve will be also under pressure, and will It is well known that compressed air remain in one position ; but directly it is necessarily involves considerable loss, opened to the exhaust, by the edge of the from the fact that most of the heat depiston passing it, the end of the valve will veloped by compression cannot at presalso be opened to the exhaust, the press- ent be retained, so as to act when the conure removed, and the valve thrown over, verse expansion takes place in the motor. and the action on the piston reversed. This subject has been fully treated, both
theoretically and experimentally, by many engineers, especially in France. . From Mr. Robinson's paper, * already re
ferred to, the total loss appears to be Fig. 12.
never in practice less than 50 per cent. of the energy used in compression, and sometimes as much as 75 per cent. Again, the result of some experiments by Mr. W. Daniel shows a loss f from 54.2 per cent., with 19 pounds per square inch air pressure, to 74.2 with 40 pounds air pressure.
But the work lost is more than compensated for by the attendant advantages, and where, as in the Mont Cenis tunnel, a natural head of water can be employed, it must be superior to all other agents; though for purposes above ground, notwithstanding several attempts to introduce it, and except in the . Westinghouse brake, the loss with compressed air is sufficient to prevent its general adoption, and even rock-boring drills
are then worked by steam. ED
WATER. A natural head of water was, perhaps, the first power applied to take the place of manual labor, and though used all
over the world on a large scale, and in Similarly for the opening o', communi- Switzerland and some other countries for cating with the other end of the valve. small powers—where mountain streams The second action, or turning, is effected are employed even for such domestic by means of a small piston p, shown in purposes as churning and rocking crasection, Fig. 13, which acts at right an- dles—yet in this country the extension gles to the stroke of the drill, but is not of small water motors has been confined quite in the same center line, and there- almost entirely to towns having artificial fore every stroke it takes will turn the sources of supply. Nevertheless, as has ratchet wheel w, which is in that line, been forcibly brought forward on several and, consequently, the position of a occasions of late, the natural power at spiral rod s fitting into the end of the
* Vide Minutes of Proceedings Inst. C. E., vol. xlix., piston rod.
This happens when the drill p. 17 is down, and the spiral rod free from it ; ceedings, 1874, p. 210.
+ Vide Institution of Mechanical Engineers. Pro
present running to waste might, by sources will in towns, no doubt, continue means of more efficient transmitting to be principally used. Still in the country agencies, be taken advantage of. There small water wheels, or turbines, are often are several instances in which this is be- conveniently applied, and many of the ing done, as at Tortona, in Italy, where, former have been erected by Mr. W. since 1876, the force of the torrent Anderson, M. Inst. C. E. (of the firm of Scrivia has been made to supersede Messrs. Easton and Anderson), of 0.018, steam by applying telodynamic transmis- 0.04, 0.26, &c., HP., chiefly for pumping sion, and a daily saving of 60 per cent purposes. * in cost thereby effected.* Again, on the The two sources of water power in a estates of M. Menier, the power derived town are: from the river Marne is used, by means (1) The reservoirs for supplying waof electric transmission, for ploughing ter for domestic purposes. and other agricultural purposes, and it (2) The accumulators specially erected is proposed to extend it to a distance of for obtaining a head of water. 3 miles from the source.
Also, in Ameri Up to the year 1849 the supply in ca the use of the almost boundless sup- towns was drawn from reservoirs, and it ply of natural head of water is being was one of the original ideas, set forth rapidly extended for similar labor-saving in a letter by Sir W. Armstrong, F.R.S., objects; but it is a significant fact with V.-P. Inst. C.E., to the Mechanics' Magregard to this country, that although azine," and referred to by him in a paper Sir W. Armstrong, who, if not the first, before the Institution, that “the water has certainly been the chief, engineer in already supplied to towns for domestic introducing the present hydraulic sys- purposes could in many cases be advantem, was led to the subject by noticing tageously employed for working cranes, the waste above referred to. His first printing presses, and in short, all kinds idea, like that of many others, was to of machines where manual labor was prevent that waste, and he has estab. usually employed.” This is an artificial lished a magnificent system, not, how- source, since steam engines are generally ever, based upon the use of the natural employed to raise the water into the ressource of power, but upon a source ervoirs. The expense, however, is a seriwhose essential principle is the produc- ous consideration, for it must be rememtion of an artificial head of water-in bered that the water is supplied for a most cases by the use of steam. The different purpose, and the head is only fact is, that the supply of power refer- made sufficiently great to distribute the red to must be turned into work at its water to the summit of the various source, or stored up under a, so to speak, buildings, and in London, for instance, higher pressure ; since, when it is the it is not even so great as that. Besides power of the water, and not the water being small, the pressure is found to itself that is required, the proportional vary considerably, and not only by diurloss by transmission would otherwise nal changes, due to reasonable causesrender its use impracticable. Now the it being, for example, 45 pounds per obvious advantages to small industries square inch at Westminster in the mornfrom localization seems to account for ing, and rising to somewhat over 60 the undoubted tendency in this country pounds in the afternoon, and in Bristol to cary on small manufactories in towns, from 40 pounds to 70 pounds—but also to which the power must be conveyed: to sudden and erratic changes, most trytherefore, their connection with the nat- ing to the water motor employed. The ural source is an important problem, the consumer is, nevertheless, charged for solution of which necessitates (1) an the quantity used, independently of the abundant supply, and (2) an efficient pressure ; and as inquiry seems to indimeans of transmission. England cannot cate that this is often highest in the be said to be rich in the former, and the towns where the average pressure is lowlatter is far from being in a satisfactory est, the system must be far from satisor settled state; so that, until the want factory. These causes no doubt led to of fuel is more keenly felt, artificial
* Vide Transactions Inst. C. E. of Ireland, vol. ix., p. * Vide Minutes of Proceedings Inst. C. E., vol. 1., p. + Vide Minutes of Proceedings Inst. C.E., vol. 1., p.
the second method, viz., the use of the olutions per minute. The inward-flow accumulator for supplying water under turbine of Professor James Thomson is considerable pressure, which brought made to very small sizes ; but in a letter out the advantages of water as an agent, to the author the inventor says: “I do and showed its superiority under great not recommend any kind of turbines for pressures, from its incompressible na- ordinary use with very small water supture, which both renders it capable of plies and high-water pressures.” The transmitting great power and at the reaction wheel can be made to work same time obviates all danger from ex- economically up to moderately high plosion ; and the size of the motor can pressures, because the radius of its disbe so reduced as to render the amount charge orifices can be increased, and so of water used but trifling. The press the law connecting the head with the ure under which the water is used has linear velocity of the jet (which is veeverything to do with the kind of motor locity=8vh) can be nearly satisfied. In employed; and before comparing the a paper read by Mr. W. C. Kernot, M.
cost of the two foregoing modes of sup- A., C. E.,* at Melbourne, a small motor ply, the types of apparatus must be dis- of this kind, shown in Fig. 14, is advocussed.
cated, in which, by means of a counterNo doubt the motors giving the high- weight a, one arm is dispensed with, and est efficiency, under proper conditions, the hydraulic radius doubled, all sharp are turbines and reaction wheels, but bends are avoided, and, as
& result of these conditions are such as to exclude experiment, with a consumption of 2.8 them for water under much pressure, gallons of water per minute (at 1s. per and even with water from the mains the 1,000 gallons), pressure by gauge 75 use of the former is practically out of pounds per square inch, speed of 1,300 the question, for the linear velocity of revolutions per minute; 0.055 HP. were the rim of the wheel should bear some obtained to drive a small lathe, the effiratio to the velocity due to that pressure, ciency being 40 per cent. An ingenious and as the size of the wheel diminishes, form of governor was used, in which the its number of revolutions must, for a increased speed by the centrifugal force constant head of water, increase ; so of a weight, closed the orifice of escape that to obtain any reasonable efficiency, and acted most effectually to check the the velocity for a very small wheel would have to be as much as 4,000 or 5,000 rev- toria, Oct. 9, 1879.
* Notes on Small Motors. Royal Society of Vic
racing and variation in speed, reducing the length. One side conveys the water unwater used from 2.8 gallons per minute der pressure to the cylinders by ports, in full work, to 0.75 gallon when all the which, when the cylinders are in an inmachinery was disconnected. There are clined position, communicate with cornumberless cases in which such a motor responding ports in their. basis ; in a as the foregoing might be advantageously employed in towns, and where its use would compare favorably in efficiency
Fig. 16. with some of the engines at present chiefly employed and known as "waterpressure engines."
The form of water-pressure engine which is almost universally adopted for obtaining rotary motion is the oscillating type. A sectional view is shown in Fig. 15 of Haags' engine, which is ex
similar manner the other side conveys away the water when the cylinder is inclined in the opposite direction. Experiments were made with a dynamometer upon two of these, through the kindness of Mr. Camp, of Bristol, the inventor of hair brushing machinery, and which was used for that purpose, the other being erected at The Institution of Civil Engi
neers, Great George Street, for driving tensively used on the continent, and is largely supplied by Schmid, of Zurich,
Fig. 17. where small water motors are used to the number of one hundred and thirteen, as alluded to by Mr. E. Matheson, M. Inst. C. E.* The action of the engine is extremely simple. The oscillation of the cylinder about its center alternately opens the opposite ends of the cylinder to the supply and exhaust of water. There seems to be a large amount of clearance by the long ports which would entail waste, but otherwise the engine is cheap and efficient. It is being introduced into this country by Messrs. Bailey and Co., of Manchester. Another form is Rambottom's patent, of which a general view is shown in Fig. 16. This, from its small first cost and simplicity of action, is at present the most extensively used in this country. Three cylinders oscillate about their lower extremities, and work upon a hollow cast-iron pipe, which is divided into two parts by a verti. the ventilating and warming apparatus. cal diametral partition running its whole The annexed table gives a tabulated re
sult of the experiments, from which the * Vide Minutes of Proceedings Inst. C. E., vol. xlix. P.!35.
curves (Fig. 17) bave been constructed.
Engine at Inst.
Revolutions per minute
Supply Pipe 1 diam.
15. 12.5 10. 7.5 5. 2.5