Ventilator
By this title I wish to distinguish this Ventilator from all such as act by the mere centrifugal force of the air: and to make this distinction the more palpable, I would add thatthisMachine acts like a pump, that is by means of a space alternately contracted and expanded, into which the air enters, and from which it is expelledby forceas water is from a pump. The means are the following:A B(fig. 4ofPlate 20) is a hollow cylinder, of a diameter proportioned to the effect wanted to be produced.Cis a cylinder closed at both ends, which fills that just mentioned as far as the length goes, exceptinga playof about1⁄8of an inch. This interior cylinder revolves in the former; butnoton its own centre. It revolves on an axisEeccentric to itself, but exactly concentric with the outer cylinderA B. The centre therefore, of the inner cylinderC, describes a circle within the outer one, which is always parallel to its circumference. On the axisof motionof this cylinderC, and outside of thatA B, are fixed two cranksE Ffig. 5, which exactly reach from its centre of motion to its centre of figure: so that whatever circle the latter describesinthe large cylinder, the former describe the same linewithout it. And hence any slide or valveD, driven by these cranks, will always touch,or be equally near, the circumference of that interior cylinderC. The valveDthen, worked by the barsGfrom without, forms a constant separation between the right and left hand parts of thelunularspace left between the fixed and moveable cylinders; and if the latter turns fromCbyBtoD, the right hand spaceC B Gis theplenum, and the left hand spaceC A Dis the vacuum of this Instrument; or in other words the air will flowin, through the passageH, and flowoutthrough the passageI: and by a contrary motion ofC, it would do the contrary—but I prefer the first process because any pressure within the valveDis not liable, then, to press the valve upon the drumC, and produce contact and friction; which in the second case it might do. Suffice it to add, that the quantity of air displaced at each revolution ofCround its centre of motion, is the difference between the area of the drumCand that of the cylinderA B: and that its quantity at each part of the revolution is proportionate to the curvilinear triangleG B, multiplied by the length of either cylinder.
In the prospectus, this Machine was said to be good as “a gas meter,” which I still think it is. For such a purpose however,friction and eccentricity of weightshould be obviated, by placing the axisE,in a perpendicular position: when I doubt not it would measure flowing gas better than many of the machines that have been proposed for that purpose.
Improved Persian water wheel
Thismodeof raising water in its simplicity, is I think called the Persian wheel. The buckets hang upon centres, dip in theunderwater, fill themselves there, and by meeting an obstacle above which turns the buckets aside, they empty themselves into the upperback, from which the water is conveyed to the general reservoir prepared for it. This present Machine is such an extension of the above principle as to make it applicable to considerable degrees of elevation, and to many situations where a single wheel would be of no service. Having observed that in everytrain of wheels, the circumferences of any two wheels, have motionstowardseach other, as well asfromeach other; I perceived that, in a vertical train, this circumstance might be laid hold of to compose a machine for raising water. Be therefore, (Plate 21,fig. 1)A B C Dfour of a set of wheels thus intended: on the left of the lowest wheel the buckets moveupward, as indicated by the arrow; while those atBmove downward, coming thus to meet the former. The bucketsAare full, and thoseBare empty; and as the latter, by the motions of theequaltoothed wheels on which they are hung will infallibly meet the former, and even plunge into them atI KandL, it is only to put aclackof leather or a valve, inthe bottom ofallthe buckets, and we have a machine that will raise water to the top-most wheel, be it ever so high, and there the water will be poured out into the vesselM, as in the common Persian wheel above alluded to. On this principle the first change of buckets will take place atI; where the lower bucket belonging to the wheelB Gwill take the water from the upper bucket of the wheelA H; when the bucketIwill go down, nearly empty, byHand fill itself again in the under water; But the bucket of the wheelB Ghaving nowgotthe water, will rise byGtoK, where another bucket belonging to the wheelC Fwill come empty, and plunging itself intothat, take its water and go upward by way ofCtoL, where a similar change will take place and the water fromLwill rise byEtoM, into which vessel it will be poured by thecantingof the bucket as seen in thefigure. Thus it appears that any number of toothed wheels geering together, surrounded with bucketsvalvedat bottom, and receiving power from any one of their number, will raise simply and effectually a quantity of waternot smallin proportion to the power employed, and by means that promise great durability to the Machine.
Eccentric bar press
This press (seePlate 21,fig. 2) is indefinitely powerful. It was invented for the use of my late beloved brother, then contractor with government for cleansing the sea bedding. It is composed of a centre pieceA, strongly fixed to a post in the ground, the barsA BA Cbeing suspended above it, so as to remain horizontally moveable, while describing1⁄4of a revolution round the general centreA. The blankets (or other goods) are put into the spaces, (on a net nailedunderthe bars) while in the positionA B; and the whole is then thrown with force towardsB C; the lengthA Cbeing so calculated as to cease pressing at the desired moment: for such is thepowerof this Machine, even without this projectile force, that were the stress not moderated, nothing could remain whole under its operation. It is clear however, that, when this operationbeginsats, the relative motion of the jawssandBis assignable, and even visible, as shewn by the dotted circles; but as the whole approaches towardB Cthat relative motion becomes insensible, the circles parallel, and consequently the power infinite: which is all I shall say on the theory of this Machine.
Pigment mill
This Machine is delineated infig. 3ofPlate 21. It has several properties which I think important in the process of grinding colours, either in a wet state or a dry. It consists of a frameA B, which has a hollow centre, through which the axis of the bevel wheelC Dis brought in such manner as to geer with the bevel pinionP, in whatever position the frameA Bmay be placed. The axis of the pinionPcarries a vesselof whichE F Gis a section, and in which rolls a well turned and heavy ballH,uponthe colour to be ground: which it crushes in the line of direction of its centre, and to a greater or lesserwidthaccording to the diameter of the ball, as compared with the section of the grooveE G, in which it rolls. Now as the motion of the vesselE G F, is oblique to the perpendicular, the contact between it and the ball doesnottake place in any great circle of the latter: but is constantly varying by a twist in its motion dependent upon the angle of the vessel’s inclination to the horizon. From hence arises theimpossibilityof any colour remaining on the ball unground: and in order likewise, that none may remain uncrushed in any part of the vesselE F G, the frameA Bgives it constantly new positions,oneof which is represented by the dotted linesI K:where it is seen that the ball bears on a different line of the vessel’s bottom than it did before. This also adds still greater change of action to the ball itself, and occasions (taking both these properties together) an unbounded variety of effect, which necessarily brings every particle of colour under the ball by the mere continuance of motion: and thus grinds it all without any care on the part of the attendants. It may be added, that this vibrating motion of the frameA B, is easily made to result from an eccentric stud and proper connecting rods behind the frame; all which is too easy to require further description.
Dynamometer
InPlate 21fig. 4, there is a representation of this Instrument. It is composed of a frameA B, containing a strong shaftC D, on which are placed the three following objects. First, a fixed pulleyE, working by a strap, the Machine whose resistance is to be measured. 2ndly, a loose pulleyF, receiving the power from themoverwhatever it be. And 3rdly, a barrelG, which is the acting pulley, when the strap is put on it fromFin the common method. But this barrelGacts by means of a barrel-spring within it, which is hooked by one end to the boss of the shaft, and the other to the rim of the barrel, as is usual for barrel-springs in general. Now the power produces the desired motion by coiling this spring to the necessary degree: and to make that degreevisible, there is fixed to this barrelGa spirals, which as the spring bends, drivesoutwardthe studt, and with it thefingerv, which, pointing to the graduated scale, shews at once the number of pounds with which the spring acts on the shaftC Dto turn it. By these means the stress on the straps and on the Machine turned is known; of which also the velocity is easily determined by counting the number of revolutions performed by either of the pulleysE F G, which are alike in diameter.
In ending the first part of this work, I gave my readers room to expectthis part“within three months,” and am happy now to fulfil that engagement. Although these pages contain fewer errors than the former—an apology is due for those that have crept in: to which I add the promise that every thing shall be done to lessen them further in the future parts, and wholly to correct them before the work closes.
A few words seem wanting to complete the description of the Cutting Engine above given. They relate principally to the cutter-frame and cutters. Although, with a view to celerity, I have shewn the cutteroutof the frame (fig. 4) yet a common frame, carrying the arbor on points, may be used with propriety; and would often be an eligible substitute for the frame above described. In cutting bevel wheels however, either on this Machine or thatto be described, there is a form of the cutter frame which leaves less freedom of choice, as the cutter itselfmusthave a peculiar form and position. To return to the cutter for spur wheels, their form (or section) depends on the degree offinishwhich the wheels require. Forroughwork they may be cylindrical on the face, the sides beingunder cut, so as to leave them thickest at the circumference—whence a certain coarseness of cut ensues, but withoutany injuryto the spiral form. But, generally speaking, the cutters are best, when made a little tapering towards the edge, and toothed on both sides as well as on the circumference. The teeth should be tolerably fine, but not very so, unless greatsmoothnessof surface were required: and we have seen above that, in this System, great smoothness is very seldom necessary,provided the obliquities be correct. I may add, that those cutters used on common engines, whose great rapidity compensates for the small number of their teeth, would not answer here, on account of the twisting motion in the wheel. But nothing prevents using cutters, so formed on the sides, as to round off the teeth in the act of cutting—only the cutter must be so thin as that its thickness, added to the aforesaid twist, may not make thespacestoo wide. A little observation will render these things familiar to an attentive observer: nor shall this work conclude before all that I have gathered from long observation on this subject, be fully known to my readers.
J. W.
5, Bedford-street, Chorlton Row,20th. November, 1822.
PART THIRD.A NEW CENTURY OFInventions.
A NEW CENTURY OF
Inventions.
It has been observed and regretted by a well-known writer, that “a periodical work resembles a public carriage—whichmustdepart at the usual hour, whether full or empty;”—and having undertaken to deliverthiswork at stated periods, I have found myself in a situation not unsimilar: the consequence of which has been a too cursory view of some of the subjects. I feel however, thatthisis not a sufficient apology for any essential defect: nor would it be more so to say that, although verging to old age, I am still a young author. Yet I may claim the privilege of supplying, in the latter parts of the work, what is most deficient in the former; and thus of proving that I do not intentionally neglect any thing that might make it practically useful.
With these views I commence this thirdpart: intending first to continue the description of the Cutting Engine given atpage 121,and here applied to Bevil Wheels; and then to re-consider, shortly, one or two other objects, that were too rapidly passed over in their proper places.
Extended version of gear cutter
Plate 22, repeats atfig. 1, thefirst figureofPlate 15; by way of shewing the additions required to extend this method of cutting teeth, to Bevil Wheels. These additions arefirst, a diskn n, concentrically fixed to the main axisA Bof the engine. And,second, an inclined planeo, ofvariableobliquity,connected by a joint with theforkedsliding barp q, by which the planeois put in contact with the disk, at whatever distance the cutter-stande fmay be from the common centre,which distancedepends, of course, on the diameter of the wheel to be cut; and to secure which is the office of the fixing screwr, in the figure.
It is now evident that for the diskn n, and the shaftA Bto rise, the slidep qand the cutter-stande fmust recede: andthismore or less according to the degree of obliquity of the inclined planeo, that is according to the slope of thebottomof the teeth in the wheelw: see the dotted linew p.
A circumstance presents itself, that should be here explained: when the bevil of the wheelw, or the cone of which the wheel is a part, is very obtuse, the cutter-stande f, can not be driven back by the action of the diskn non the planeo, without too great a stress being applied from below, to the axisA B. (See the apparatusI M O N,Plate 16,fig. 2.) In this case therefore, the handleRis not used: but a weight is suspended to the endNof the leverM N, sufficient to give the whole SystemA B, a tendencyto rise; and the operator now acts on the screwg, so as to draw back the planeo; by which motion the diskm nwith it’s axisA Bissufferedto move upward, and the wheel is cut, as desired. But on the other hand when the wheels are portions ofacutecones,they are cut by means of the aforesaid handle; by which the planeoand the cutter-stand areforcedbackward as before intimated.
We proceed now to describe the perpendicular part of the cutter stande f; which is made double, as shewn ati kinfig. 4ofPlate 15; and is also perforated at various heights to receive the bolt which forms the centre of motion of the armm u, the latter having a cylindrical bossu, fitted into theforkof the stande f, and so graduated as to determine the angle of it’s obliquity to the horizon, or it’s parallelism to the dotted linew p, which indicates the slope of the bottom of the teeth on the wheel. Finally, the cutter-framexis fastened to this arm at right angles to it, and thus forms a right angle (or nearly so) with the surface of the wheel: and is, moreover, directed to the centre, produced, of the shaftA B. This latter fact is strictly true, only when the teeth required are of so common a kind asnotto require greater exactness: for in theory the sides of the cutter (supposed cylindrical) must alternately direct to that centre—namely,thatside which is actually cutting: so that a provision must be made to shift the cutter spindle sideways, a distance equal to it’s diameter; this being no more than what is necessary in every system of wheel cutting.
We may also consider here, the form of the cutter itself,v,fig. 1. It is slightly conical, (more or less so according to it’s use) and of no greater diameter than the smallest width ofthespacesbetween the teeth of the wheel. A common disk-like cutter would not produce perfect, nor even tolerable teeth on a bevil wheel. The reason of this will appear by considering that a spiral line, either on a cone or it’s base,turnsmore the further it is from the centre, and less the nearer it comes to it. So that aflatcutter placed atanyangle, is parallel to the curve atoneplace only; whence the propriety of using a cutter of the kind represented in this figure. It is however true, that the first opening of the spaces may be made with a common cutter; but it should be very thin comparatively with the spaces required: and it’s cut would serve only as asketchof such space, serving principally to permit the metal to escape while finishing the teeth with the cutter just described.
I proceed now to the examination ofthe plates, and the manner of adapting their length to the process of cuttingspiral teeth on bevil wheels. But before entering on this subject, I would explain a kind of inadvertency into which I fell at the close of my former description of this Engine (seepage 129). In my zeal to be candid in stating the properties of my Machines, I have suffered it toappearthat I thought this an “imperfect” one:—an expression which, although modified among the errata, may still cause it to be looked upon as radically defective; than which nothing could be further from the idea I wished to convey. I intended merely to express the want ofabsoluteconnection between the two movements of the shaft—the rotatory and longitudinal motions. I meant that the processby this Machine was not theoreticallycertain, because dependent on the action of a weight (Plate 16,fig. 1 and 2) and anunforced obedienceto the direction of the plates. But this small remove from rigourous principle is in my opinionmuchoverballanced by the facility of cuttinggood wheels of all diameters, by the sole change of a morsel of tin, which leaves untouched every other part of the Engine.
Entering then on this branch of the subject, I first observe that if we chuse for the teeth an inclination of 15 degrees (in imitation of the cylindrical wheels) it can only be for one point of such wheels—as observed above. This point therefore I have placed atrin the middle of the face. And supposing now that at this point the wheelOwere 4 inches in diameter and the wheelStwo inches, these plates would be found as before by these analogies:
(1)wr, or 2 inches : 11 inches (rad. of plate rim) ∷ 26.8 :294.8⁄2= 147.4 plate required.
(2)vr, or 1 inch : 11 inches (rad. of plate rim) ∷ 26.8 :294.8⁄1= 294.8 2d. plate required.
But it is plain that the conical face,b C, (common to both wheels) isbroaderthan the supposed cylindrical onesb eandb d: and therefore that the above plates must be made longer (to furnish the said obliquity) in the following proportions, namely: for the wheelOin the ratio ofb etob C; and for the wheelsin that ofb dtob C: that is, these plates should belengthened as the tabular cosines of the anglesB A CandD A Cto radius (forb e:b C∷A B:A C; andb d:b C∷A D:A C.) Thus then,
(1) Cos. 63°27′ : radius ∷ 147.4 (present plate) : required platex, =147.4 r⁄Cos. 63°27′; and
(2) Cos. 26°33′ : radius ∷ 294.8 (present plate) : required platey, =294.8 r⁄Cos. 26°33′.
Now, by the tables, cosine 26°33′ = 894, and cosine 63°27′ (it’s complement) = 447, when radius is 1000: whence dividing the two equations byr, and substituting these values of cosines 63°27′ and 26°33′ we shall find the two quantitiesxandy,equal. Whence it appears that for everypairof bevil wheels, whose shafts lie at right angles,the same plate serves for both wheels: only turning it once to the right, and once to the left hand on the plate rim.
And if now wemeasureon a scale ofequalparts, the lineA rand call it 100, we shall find the linew r(near enough for practice) to be 90, and the linev rto be 45, and these numbers respectively, put for rad. for cos. 26°33′, and for cos. 63°27′, will make the first equationx= 147.4 ×100⁄45andy= 294.8 ×100⁄90orx= 327.55 andy= 327.55, &c. confirming the above deduction that thesame plateserves for both wheels; and giving, withal, the length of the plate required.
In performing this operation by actual measurement of the lines, I have had in view to trace a path for those of my readerswho may not have the tables, or may be unaccustomed to use them. The process, generally, is to take the diameter of any bevil wheelOfig. 4, in the middle of it’s face; andsupposingit a spur wheel, to find it’s plate by the method above given: and then to multiply the length of that plate by the lineA rand divide the product by the lineA w, both measured on the same scale of equal parts.
It may be well to observe, likewise, that the same method of finding the plates, applies to bevil wheels of every description or angle: but that it does not give equal plates for everypair, except in the above case of wheels placed at right angles to each other.
I would just remark that by thefigurenearB, is shewn asectionof the Machine on which I centre the wheels to be cut on this Engine. It is an inverted cups t, into which thearboris screwed in atrueposition; and this cup is fixed on the top of the shaftA B, by thethreepressure screws nears t, which enter a triangular neck made round the shaft, against theupperslope of which, the screws press so as to draw the cup downward in the act of centering it. This I say is my present method; but it is in a measure accidental, the shaft not having been perforated to receive arbors of the usual kind. Mine, however, have their utility in the ease with which they are varied in size, and changed on the Machine: but on theircomparativeusefulness I give no opinion. The other is the most solid method.
Analysis of steel yard
In the description of my differential Steel-yard, (seepage 163) I stated that the loadPwas wholly collected in the pointo; and that dividing the lineA Cby the lineA o, the power of the Machine was known. But I should have shewn that this line (A o) isequal to one half the difference between the armsA DandA E. To do this, here, (seePlate 23,fig. 4) I take the Machine in the state of infinite power, before mentioned; and observe, that in moving the point of suspension fromotowardsA, I at oncelengthenthe armA E, andshortenthe armA D: by which process, (supposing each arm to have been calleda) that which I lengthen by any quantitydbecomesa+d, and that which I shorten by the same quantity becomesa-d, and the difference of these quantities, is 2d: so that the lineA ois in reality one half the difference between the two armsA DandA Eas was required to be shewn.
But we may go a step further: The two arms of the equibrachial leverx ymay likewise be madeunequal: and the lines abe subdivided in any ratio: which division will augment still more the power of this Machine. If for example, we hang the load on the pointv, halfway betweenaands, that power will be doubled; for the linec v(representing the space movedthrough by the load in this case) is only one half ofthatw s, oro q, and might be still less at pleasure. Thus the whole power of the Machine isnowfound by dividing the length of the long arm, beyondD, by the linea v, instead of the former lineA o, or dividing themotionof it’s extremity upward, by the linec v, the motion downward, of the loadP.
Analysis of excentric bar press
It has been further suggested, that the description of my excentric Bar Press was not sufficiently explicit. I have therefore added thefigure 2ofPlate 22, to assist in elucidating that description. I had, perhaps made an undue use of the principle of virtual velocities by saying, too concisely, (page 174) that “as the whole approaches towardB C, the relative motion (of the cheekssandB) becomes insensible, the circles parallel, and consequently, the power infinite.” It is howevervulgarlysaid thatpowercannot be gained without losingtime—which implies that if timeislost, power will be gained: and the principle of virtual velocities says the same thing, though in more appropriate terms—that if a small movement be given to a system of bodies actually counterpoising each other, the quantity of motion with which one body ascends, and the other descends perpendicularly, will be equal: so that, as remarked inpage 50, by “whatever means a slow motion is obtained, dependent on that of a moving force, the power is great in the same proportion.” Now, in the eccentric Bar Press, (seefig. 2) this is so in an eminent degree: for when the bars are in the positionA B, the distance of the cheeks is equal toB s; and they must move, circularly, as far asA f, to bring them closer to each other by the quantitys a: dividing therefore, the distanceB gby the lines a, we find (near enough for practice) the power of the Machine within the limitsA g B. It is nearly as 10 to 1. In like manner this power atA e g, is equal to the arce gdivided by the linef b; and atA l nto the arcl ndivided by the lined k, namely by the difference of the linesk landm n. From the above it appears that thenearingmotion of the cheeks of the press, becomes slower and slower as the barsAandCcome nearer to the pointC: insomuch that the difference between the linesm nando pis nearly imperceptible, andthatbetween the lineso pandC qentirely so. But according to the above process, the distancep Cshould be divided by thisimperceptible line, to find the power of the press at the pointC; which therefore isimmense. Another proof of this may be drawn from the supposition (seefig. 3) that the small levera dis turned round the centreoby a baro Cfixed to it, and of equal length with the lineA Cfig. 2.Fig. 3shews that the lines or barsC d, anda Care moved endwise by thecircularaction of the pointsaandd; and therefore (by statics) their motion is the same as though caused by the perpendicularsb oando clet down from the centreo, on each of them. Hence the power of this Machine is found by dividing the distanceo Cby the sum of the linesb oando c; which sum (when these linesvanishby the union of the bars over the centre) becomes infinitely small: the quotient of which division therefore is infinitely great—as was to be shewn.
Analysis of excentric press
The usual method of making Punches for engraving Copper Cylinders, (otherwise than by themillingsystem) is tocutthe desired pattern ona die, and then to transfer that pattern by blows or pressure to the punch, from which it is again transferred to the cylinder. My Machine in this operation, unites motion to the needful pressure; and thus renders the result more easy and complete. This effect I could the better ensure, because the surfaces ofmypunches are essentially convex, or rather cylindrical; as will appear when my engraving Machine comes to be described. Their convexity however, can be diminished at pleasure—whence this Machine is capable of offering useful assistance to a maker of flat punches.
Punch machine
InPlate 23,A Bfig. 1 and 2, is the body of the Machine, with the vibrating barC Dlaid upon it; reposing especially on the correct and level parts of the body ata b; this bar contains thediec, with which it vibrates between the cheeksB R, as impelled by the screwsE F, it’s centre of motion being the pinP, duly supported by the strong shoulderA. In a line with the barC D, is placed a secondvibratorG, containing the steeld, that is to become a punch, already roundedinto the cylindrical shape it must have when finished. This vibrator has it’s centre of motion atefig. 1, and it need not be added that the curvature of the punch depends on it’s distancee dfrom that centre: for the centre of the long barC Dissodistant as to have little influence on it’s formation. Further, the cap or bridgeH I, which furnishes a centre for the smaller vibratorG, can be brought forward to any useful position by the nutsK L: that cap sliding horizontally between the cheeksM Nas directed by the smallarmsm n. This motion, then, taken from the nutsK L, serves to impress theworkof the die on the steel prepared for the punch; and this being done to afirstdegree, both the handlesO Q, are laid hold of: and by turning the screws the same way one of them goes forward and the other recedes, until the punch and die have been in contact over half their surface. At this moment both screws are turned backward, and the motions of the two vibrators reversed: by the repetition of which alternate motions accompanied by the needful pressure, the whole pattern is transferred from thedieto the punch—when the latter is taken out of the Machine, andfiled upin the usual method.
It should be observed, that the smaller vibratorGcan be displaced with ease when the nutsK Lare withdrawn: and this should be frequently done to examine the progress of the impression. Nor is there any difficulty in re-entering the figures. In a word, the perfection of this process depends more onmuchmotion than on violent pressure: whence this facility of re-entering is a desirable property. This Machine is usually laid on a bench or tressel, with a long mortice in it, into which the featherxof this Machine enters so as to be firmly fixed.
I was the rather induced to attend a second time to the differential Steel-yard, because I had it in contemplation to apply that principle to the present purpose; since, to make flat punches, is to some engravers a more desirable thing than to make cylindrical ones. I am not fully persuaded that it is even possible to transfer a large pattern, from a flat die to a flat punch, byanypressure acting simultaneously on the whole surface. In those cases, if there is muchwork, the whole surfacegoesdown; and the parts that form the pattern do notrise. But, all that can be done in this case, is, I believe, feasible by the Machine now to be described.
Punch machine
Plate 23, gives infig. 3 and 4, a representation of this Machine;A BandC D, are twoslides, having wedge-formed ends aboveAand belowD, well made, well steeled, and well tempered. One of these slides contains thedieand the other the steel prepared for the punch (seeB C). These wedge-ended slides areembracedby two leversE F,G H, which are themselves connected by two stirrupsI KandL M, better shewn atfig. 3. These latter are supposed infig. 4to be broken atL M, to leave the leversE FandG Hmorevisible. They are formed, at the turning below, into wedge-like edgesa b; well hardened, that clip thenicksc dof the lower lever: and at the top of the Machine their armse f, pass through the capsm n, above which they arenuttedlike a common bolt, and made to press strongly on the main leverE F. The stirrup placed to the right hand, presses in particular, by it’s capn, on the moveablestepo, exactly in the notchq: this step having a backward and forward motion communicated by the regulating screwp. Before beginning to use this Machine, I make all it’s armsA E,A g,D e,D d, equal, when it’s power (seepage 162) is infinite; and to put it in a working state, I turn the screwpbackward, say one half round: which motion (if the screw has 20 threads to the inch) makes a difference in the two armsA randA qof1⁄40of an inch, and the virtual centre of the Machine is therefore1⁄80of an inch from the former pointA, that is from theedgeof the slideAin thisfig. 3. Supposing now, the whole working leverE Fto be 3 feet, and the workman’s force to be 100lbs. in each arm, then by displacing the lever to any proper distance fromFtowardsf, he will produce a pressure between the die and the punch of 200lbs. multiplied by 1440, the number of times that1⁄80of an inch is contained in 18 inches.—That is, a pressure of two hundred and eighty-eight thousand pounds!
I have been seduced, by the anticipated brilliancy of this result, from the regular course of description,—and the platew x,y z, which forms the base or frame of this whole Machine has not yet been spoken of. But that plate is supposed screwed down to a horizontal bench, at or near the height of a man’s breast; the slides or cases are fastened to it, and the man is supposed toworkthe Machine nearly as he would a die-stock in tapping a screw. This however is not indispensable; the Machine might be placed vertically, and these motions given by any proper mover; or a weight may be suspended to the armF, so as to add continuity to pressure. It is however important, that the position should comport with the frequent extraction of the punch in order to examine the progress of the work, or cut away any redundant metal. I have before given it as my opinion thatmuchcould not be expected from mere pressure: butthisis a pressure of a peculiar kind, consisting of immense powers withveryshort motions. In this respect it isjustwhat was wanted, as it can be renewed and repeated frequently, without loss of time. And the more to facilitate this delicate operation, the hollow slides or casesB C, are made slightly pyramidical, to be furnished withset-screwson the four sides, by which to change the place of bearing; and thus to meet the case of a flat punch with the advantage of impressing it byportions, so as to have only tofinishit by brute pressure.
The foregoing application of the principle of the differential Steel-yard, is, I think, important, and founded on unobjectionable principles; for although by changing alone the placeof the stepo, we disturb alittlethe parallelism of the stirrupsI K, andL M; we do it not enough to produce, any material change in the theoretical result. With respect then to the lesser properties of this Machine, I leave them with confidence in the hands of those whom they most concern—who doubtless, will treat them with greater practical utility than I could myself hope to do.