49 It is a powerful regulator. weight of the fly, the irregularity of the motion may be rendered as fmall as we pleafe. It is much better to enlarge the diameter. This preferves the friction more moderate, and the pivot wears lefs. For thefe reafons, a fly is in general a confiderable improvement in machinery, by equalifing many exertions that are naturally very irregular. Thus, a man working at a common windlass, exerts a very irregular preffure on the winch. In one of his pofitions in each turn he can ex. ert a force of near 70 pounds without fatigue, but in another he cannot exert above 25; nor muft he be loaded with much above this in general. But if a large fly be connected properly with the windlafs, he will act with equal ease and speed against 30 pounds. This regulating power of the fly is without bounds, and may be used to render uniform a motion produced by the most defultory and irregular power. It is thus that the moft regular motion is given to mills that are driven by a fingle ftroke fteam engine, where for two or even three feconds there is no force preffing round the mill. The communication is made through a maffive fly of very great diameter, whirling with great rapidity. As foon as the impulfe ceafes, the fly, continuing its motion, urges round the whole machinery with almost unabated speed. At this inftant all the teeth, and all the joints, between the fly and the firft mover, are heard to catch in the oppofite direction. If any permanent change fhould happen in the impelling power, or in the refiftance, the fly makes no obftacle to its producing its full effect on the machine; and it will be obferved to accelerate or retard uniform ly, till a new general fpeed is acquired exactly correfponding with this new power and refiftance. Many machines include in their conftruction movements which are equivalent with this intentional regulator. A flour mill, for example, cannot be better regulated than by its milftone; but in the Albion mills, a heavy fly was added with great propriety; for if the mills had been regulated by their militones only, then at every change of ftroke in the fteam engine, the whole train of communications between the beam, which is the first mover, and the regulating milftone, which is the very laft mover, would take in the oppofite direction. Although each drop in the teeth and joints be but a trifle, the whole, added together, would make a confiderable jolt. This is avoided by a regulator immediately adjoining to the beam. This continually preffes the work ing machinery in one direction. So judiciously were the movements of that noble machine contrived, and fo nicely were they executed, that not the leaft noife was heard, nor the flighteft tremor felt in the building. Mr Valoué's beautiful pile engine employed at Weft minster Bridge is another remarkable inftance of the Sec PILE-regulating power of a fly. When the ram is drop, Engine, En-ped, and its follower difengaged immediately after it, the horfes would inftantly tumble down, because the load, against which they had been ftraining hard, is at once taken off; but the gin is connected with a very large fly, which checks any remarkable acceleration, allowing the horses to lean on it during the defcent of the load; after which their draught recommences immediately. The fpindles, cards, and bobbins, of a cotton mill, are also a fort of flies. Indeed all bulky ma. chies of the rotative kind tend to preferve their motion with fome degree of fteadinefs, and their great mo mentum of inertia is as ufeful in this refpect as it is prejudicial to the acceleration or any reciprocation when wanted. There is another kind of regulating fly, confifting of A bad con wings whirled briskly round till the refifiance of the air ftruction of prevents any great acceleration. This is a very badly. one for a working machine, for it produces its effect by really wafting a part of the moving power. Frequently it employs a very great and unknown part of it, and robs the proprietor of much work. It fhould never be introduced into any machine employed in manufactures. 42 Some rare cafes occur where a very different regula. A conical tor is required; where a certain determined velocity is pendulum found neceffary. In this cafe the machine is furnifbed, is the mofe at its extreme mover, with a conical pendulum, confist- perfect re gulator. ing of two heavy balls hanging by rods, which move in very nice and fteady joints at the top of a vertical axis. It is well known, that when this axis turns round, with an angular velocity fuited to the length of thofe pendulums, the time of a revolution is determined. Thus, if the length of each pendulum be 39 inches, the axis will make a revolution in two feconds very nearly. If we attempt to force it more fwiftly round, the balls will recede a little from the axis, but it employs as long time for a revolution as before; and we cannot make it turn fwifter, unless the impelling power be increased beyond all probability; in which cafe the pendulum will fly out from the centre till the rods are horizontal, after which every increase of power will accelerate the machine very fenfibly. Watt and Boulton have applied this contrivance with great ingenuity to their fteam engines, when they are employed for driving machinery for manufactures which have a very changeable refiftance, and where a certain speed cannot be much departed from without great inconvenience. They have connected this recefs of the balls from the axis (which gives immediate indication of an increase of power or a diminution of refiftance) with the cock which admits the team to the working cylinder. The balls flying out, caufe the cock to close a little, and diminish the fupply of fteam. The impelling power diminishes the next moment. and the balls again approach the axis, and the rotation goes on as before, although there may have occurred a very great excefs or deficiency of power. The fame contrivance may be employed to raise or lower the feeding fluice of a water mill employed to drive machinery. 43 A fly is fometimes employed for a very different pur- A fly fome. pose from that of a regulator of motion-it is employ- times coled as a colle&er of power. Suppofe all refiitance remo-le&spower. ved from the working point of a machine furnished with a very large or heavy fly immediately connected with the working point. When a fmall force is applied to the impelled point of this machine, motion will begin in the machine, and the fly begin to turn. Continue to prefs uniformly, and the machine will accelerate. This may be continued till the fly has acquired a very rapid motion. If at this moment a refifting body be applied to the working point, it will be acted on with very great force; for the fly has now accumulated in its circumference a very great momentum. If a body were expofed immediately to the action of this circumference, it would be violently. ftruck. will it be fo, if the body be expofed to the action of the working 44 working point, which perhaps makes one turn while the fly makes a hundred. It will exert a hundred times more force there (very nearly) than at its own circum ference. All the motion which has been accumulated on the fly during the whole progrefs of its acceleration is exerted in an inftant at the working point, multiplied by the momentum depending on the proportion of the parts of the machine. It is thus that the coining prefs performs its office; nay, it is thus that the blacksmith forges a bar of iron. Swinging the great fledge hammer round his head, and urging it with force the whole way. this accumulated motion is at once extinguished by impact on the iron. It is thus we drive a nail; and it is thus that by accumulating a very moderate force exerted during four or five turns of a fly, the whole of it is exerted on a punch fet on a thick plate of iron, fuch as is employed for the boilers of fteam engines. The plate is pierced as if it were a bit of cheese. This accumulating power of a fly has occafioned many who think themselves engineers to imagine, that a fly really adds power or mechanical force to an engine; and, not understanding on what its efficacy depends, they often place the fly in a fituation where it only added a useless burden to the machine. It should always be made to move with rapidity. If intended for a mere regulator, it should be near the first mover. If it is intended to accumulate force in the working point, it fhould not be far separated from it. In a certain fenfe, a fly may be faid to add power to a machine, because by accumulating into the exertion of one moment the exertions of many, we can fometimes overcome an obftacle that we never could have balanced by the fame machine unaided by the fly. It is this accumulation of force which gives fuch an appearance of power to fome of our first movers. When a man is unfortunately catched by the teeth of a paltry country mill, he is crushed almoft to mummy. The power of the ftream is conceived to be prodigious; and yet we are certain, upon examination, that it amounts to the preffure of no more than fifty or fixty pounds. But it has been acting for fome time; and there is a milftone of a ton weight whirling twice round in a fecond. This is the force that crushed the unfortunate man; and it required it all to do it, for the mill ftopped: We faw a mill in the neighbourhood of Elbingroda in Hanover, where there was a contrivance which difengaged the milftone when any thing got entangled in the teeth of the wheels. It was tried in our fight with a head of cabbage. It crushed it indeed, but not violently, and would by no means have broken a man's arm. Simplicity It is hardly neceffary to recommend fimplicity in the of conftruc- construction of machines. This feems now fufficiently tion recom- understood. Multiplicity of motions and communicamended. tions increases frictions; increases the unavoidable lofles by bending and yielding in every part; expofes to all the imperfections of workmanship; and has a great chance of being indiftinctly conceived, and therefore conftructed without fcience. We think the following conftruction of a captan or crab a very good example of the advantages of fimplicity. It is the invention of an untaught but very ingenious country tradefman. Fig. 3. EAB is the barrel of the capftan, ftanding vertically in a proper frame, as ufual, and urged round by bars 45 Example of a very fimple and powerful fuch as EF. The upper part A of the barrel is 17 inches in diameter, and the lower B is 16. C is a ftrong pulley 16 inches in diameter, having a hook D, which takes hold of a hawfer attached to the load. The rope ACB is wound round the barrel A, paffes capitan. over the pulley C, and is then wound round the barrel B in the oppofite direction. No farther defcription is neceffary, we think, to fhew that, by heaving by the bar F, fo as to wind more of the rope upon A, and unwind it from B, the pulley C must be brought near. er to the capftan by about three inches for each turn of the capftan; and that this fimple capitan is equivalent to an ordinary capftan of the fame length of bar EF, and diameter of barrel B, combined with a 16 fold tackle of pulleys; or, in short, that it is 16 times more powerful than the common capftan; free from the great lofs by friction and bending of ropes, which would abforb a third of the power of a 16 fold tackle ; and that whereas all other engines become weaker as they multiply the power to a greater degree (unless they are proportionally more bulky), this engine becomes really ftrenger in itself. Suppofe we wanted to have it twice as powerful as at prefent; nothing is neceffary but to cover the part B of the barrel with laths a quarter of an inch thick. In fhort, the nearer the two barrels are to equality, the more powerful does it be come. We give it to the public as an excellent cap. ftan, and as fuggefting thoughts which an intelligent engineer may employ with great effect. By this contrivance, and ufing an iron wire inftead of a catgut, we converted a common eight day clock into one which goes for two months. WE intended to conclude this article with fome obfervations on the chief claffes of powers which are employed to drive machinery; fuch as water, wind, atmospheric preffure, gunpowder, and the force of men and other animals, giving fome notion of their abfolute magnitudes, and the effect which may be expected from difcovered as to their variation by a variation of velothem. We fhould then have mentioned what has been city. And we intended to conclude with an account of what knowledge has been acquired concerning fric tion, and the lofs of power in machinery arifing from this caufe, and from the ftiffness of ropes, and fome other caufes: But we have not yet been able to bring thefe matters into a connected form, which would fugget the methods and means of farther information thereon. We must endeavour to find another oppor tunity of communicating to the public what we may yet learn on thofe fubjects. We have now established the principles on which machines mut be conftructed, in order that they may produce the greateft effect; but it would be improper to difmifs the fubject without ftating to our readers Mr Bramah's new method of producing and applying a more confiderable degree of power to all kinds of machinery requiring motion and force, than by any means at prefent practifed for that purpofe. This method, for which on the 31ft of March 1796 he obtained a patent, confifts in the application of water or other denfe fluids to various engines, fo as, in fome inftances, 02 to to cause them to a& with immenfe force; in others, to communicate the motion and powers of one part of a machine to fome other part of the fame machine; and, laftly, to communicate the motion and force of one machine to another, where their local fituations preclude the application of all other methods of connection. The firft and moft material part of this invention will be clearly understood by an infpection of fig. 4. where "A is a cylinder of iron, or other materials, fufficiently ftrong, and bored perfectly fmooth and cylindrical; into which is fitted the pifton B, which muft be made perfectly water-tight, by leather or other materials, as ufed in pump making. The bottom of the cylinder must also be made fufficiently strong with the other part of the furface, to be capable of refifting the greatest force or ftrain that may at any time be required. In the bottom of the cylinder is inferted the end of the tube C; the aperture of which communicates with the infide of the cylinder, under the pifton B, where it is shut with the small valve D, the fame as the fuction-pipe of a common pump. The other end of the tube C communicates with the fmall forcing pump or injector E, by means of which water or other dense fluids can be forced or injected into the cylinder A, under the piston B. Now, fuppofe the diameter of the cylinder A to be 12 inches, and the diameter of the pifton of the finall pump or injector E only one quarter of an inch, the proportion between the two furfaces or ends of the faid piftons will be as 1 to 2304; and fuppofing the intermediate space between them to be filled with water or other denfe fluid capable of fufficient refiftance, the force of one pifton will act on the other juft in the above proportion, viz. as 1 is to 2304. Suppose the small pifton in the injector to be forced down when in the act of pumping or injecting water into the cylinder A, with the power of 20 cwt. which could eafily be done by the lever H; the pifton B would then be moved up with a force equal to 20 cwt. multiplied by 2304. Thus is conftructed a hydro-mechanical engine, whereby a weight amounting to 2304 tons can be raised by a fimple lever, through equal space, in much lefs time than could be done by any apparatus conftructed on the known principles of mechanics; and it may be proper to obferve, that the effect of all other mechanical combinations is counteracted by an accumulated complication of parts, which renders them incapable of being usefully extended beyond a certain degree; but in machines acted upon or contructed on this principle, every difficulty of this kind is obviated, and their power fubject to no finite reftraint. To prove this, it will be only neceffary to remark, that the force of any machine acting upon this principle can be increafed ad infinitum, either by extending the proportion between the diameter of the injector and the cylinder A, or by applying greater power to the lever H. Fig. 5. reprefents the fection of an engine, by which very wonderful effects may be produced inftantaneously by means of compreffed air. AA is a cylinder, with the pifton B fitting air tight, in the fame manner as defcribed in fig. 4. C is a globular veffel made of cop per, iron, or other ftrong materials, capable of refifting immenfe force, fimilar to thofe of air guns. Dis a ftrong tube of small bore, in which is the ftop-cock E. One of the ends of this tube communicates with the cylinder under the piston B, and the other with the globe C. Now, fuppofe the cylinder A to be the fame diameter as that in fig. 4. and the tube D equal to one quarter of an inch diameter, which is the fame as the injector fig. 4. then, suppose that air is injected into the globe C (by the common method), till it preffes against the cock E with a force equal to 20 cwt. which can easily be done; the confequence will be, that when the cock E is opened, the piffon B will be moved in the cylinder AA with a power or force equal to 2304 tons; and it is obvious, as in the cafe fig. 4. that any other unlimited degree of force may be acquired by machines or engines thus conftructed. "Fig. 6. is a fection, merely to fhew how the power and motion of one machine may, by means of fluids, be transferred or communicated to another, let their diftance and local fituation be what they may. A and B. are two fmall cylinders, smooth and cylindrical; in the infide of each of which is a pifton, made water and air tight, as in figs 4. and 5. CC is a tube conveyed under ground, or otherwife, from the bottom of one cylinder to the other, to form a communication between them, notwithstanding their distance be ever so great; this tube being filled with water or other fluid, until it touch the bottom of each pifton; then, by depreffing the pifton A, the pifton B will be raised. The fame effect will be produced vice verfa: thus bells may be rung, wheels turned, or other machinery put invifibly in motion, by a power being applied to either. "Fig. 7. is a fection, fhewing another inftance of communicating the action and force of one machine to another; and how water may be raised out of wells of any depth, and at any diftance from the place where the operating power is applied. A is a cylinder of any required dimenfions, in which is the working pifton B, as in the foregoing examples: into the bottom of this cylinder is inferted the tube C, which may be of lefs bore than the cylinder A. This tube is continued, in any required direction, down to the pump cylinder D, fuppofed to be fixed in the deep well EE, and forms a junction therewith above the pifton ; which pifton has a rod G, working through the ftuffing-box, as is ufual in a common pump. To this rod G is connected, over a pulley or otherwife, a weight H, fufficient to overbalance the weight of the water in the tube C, and to raise the pifton F when the pifton B is lifted: thus, fuppofe the pifton B is drawn up by its rod, there will be a vacuum made in the pump cylinder 1), below the pifton F; this vacuum will be filled with water through the fuction pipe, by the preffure of the atmosphere, as in all pumps fixed in air. The return of the piston B, by being preffed downwards in the cylinder A, will make a ftroke of the pifton in the pump cylinder D, which may be repeated in the ufual way by the motion of the piston B, and the action of the water in the tube C. The rod G of the piton F, and the weight H, are not neceffary in wells of a depth where the atmofphere will overbalance the water in the fuction of the pump cylinder D, and that in the tube C. The fmall tube and cock in the cistern I, are for the purpose of charging the tube C." That thefe contrivances are ingenious, and may occafionally prove ufeful, we are not inclined to controvert; but we muft confefs, that the advantages of them appear |