Part 8

Figure 2 of the present Plate, represents the plan of the Machine, but turned upside down; so that the feet _G H_ screwed _under_ the lower plate _E F_, are wholly visible. In this figure, also, is shewn at _c d_, the edges (without the bottom) of the horizontal slide which carries the _stand_ for the cutter frame represented in fig. 4. This stand is indicated by the dotted lines of this figure 2, as situated _under_ the arm _D_ of the bar _C D_; but it is better shewn in fig. 5, where _e f_ marks the slide in which the cutter frame (fig. 4) moves up and down, by means of the screw and handle _e f_. In general I avoid dwelling much on these smaller parts, because they exist, probably in a more perfect state, in most other machines. In this fig. 5, _g h_ shews the screw that moves this stand nearer to, or further from the axis _A B_ of the Engine, according to the diameter of the wheels: which is also a common process in Machines of this kind, on which therefore much need not be said. But a somewhat greater importance attaches to the _cutter frame_ represented in the 4th. figure: which is a kind of small _lathe_ whose _spindle_ _n o_, carries the cutter _n_, _outside the frame_, for the purpose of changing the former without displacing the latter. The cutter (of any proper section) is placed in or near that line which is a continuation of the centre of the fixing screw _o p_. It is _in_ that line for wheels whose teeth can be finished with once cutting: but _near_ it for those whose teeth must be cut at twice. In this same figure, _i k_ represent the _ends_ of the standards that form the vertical slide _e f_ of fig. 5; and the separate figure _p q_, shews the _back_ of the cutter frame _l m_, the flat part of which, _p_, presses correctly on these uprights _i k_, and thus fixes this instrument at _any desired height_, and to _any given angle_ with the perpendicular: the _use_ of which arrangement we shall soon have occasion to exemplify.

Turning now to fig. 3 of this Plate, we there see the main shaft _A B_, broken off at _B_: and the letters _a b_ again shew the dividing plate of figs. 1 and 2: under this Plate is seen an _alidade_ or moveable index, shewn by section only at _c_, and in elevation at _d e_; where it clips the plate as far as _n_ and carries a boss _between n and e_, on which the dividing index _e f_, turns; and to which it is strongly fixed by a nut _o_, when the proper number to be cut is determined. Moreover, this boss forms, itself, _the nut_ of a thumb-screw _s_, which, carrying a circular plate at its lower end, clothed with leather or any soft substance, connects strongly, without injuring the plate, the moveable index with any point of it, as determined by the dividing index _e f_. This brings us into the midst of things, as it respects the _use_ of this Engine; for the former index _c d_, is furnished with a small roller, _p_, the motion of which all the foregoing objects must obey, when they have been fastened together by the thumb-screw _s_. We turn then to the figures 1 and 2 of Plate 16, in order to shew those parts in action: after remarking only that the form _p q r_ of this fig. 3, is that of the moveable index shewn before at _c d_; requiring only, to become complete, that the part _q_ should be sufficiently lengthened to make the arc _r q_ a complete semi-circle--for purposes that will shortly be explained.

In the two figures of Plate 16, the Machine is shewn as placed on its bench or table, accompanied by the parts which give it a distinctive character, and in fact embody the System. In addition to the parts already described, we first remark the circular rim _c d_, fixed to the ends of the bar _E F_; and made perfectly concentric with the main shaft _A B_, and the dividing plate _a b_. This rim is shewn in section only, at _v_ fig. 2. Its section resembles an L, and thus forms a basis for certain _plates_ that will soon appear; and receives the screws by which these plates are fastened to it. This being sufficiently clear, we now proceed to describe the table and the connection of its mechanism with the foregoing.

In Plate 16, _K L_ is the table: to which the Engine is screwed through its feet _G H_. _I_, is a square bar of wood, sliding in a mortice through the top of the table; and connected by a joint with the lever _M N_--itself moving round a pin at _O_, and carrying a friction roller, _P_, which pressed by the spiral _Q_, as turned by the handle _R_, raises the bar _I_, and with it the main axis _A B_ of the plate, _and of course the wheel to be cut, centered as usual on this axis above B_. Finally, _p q r_, in both figures, is the moveable index first shewn in fig. 3 of Plate 15; prepared to be _drawn round_ by a weight _W_, hanging to the cord _x_, passing over the pulley _y_, and tied to the _right_ end of the arc _q r_, when _this_ is to move to the left; or to its _left_ end, when the motion is to be toward the right:--these motions depending on the right or left-handed direction of the _teeth_ which it might be wished to cut on the Machine.

Between the two figures 1 and 2 of this Plate, there appears a diagram, the base of which is nothing more than a part of the rim _c d_ supposed straightened, and placed there that its use may be the easier understood. On the rim is seen a right angled triangle _e g f_, against which the roller _p_ will lean by the action of the weight _W_ on the cord _x_, and the arc _q r_ of the moving index _p q r_. So THAT when, by the handle _R_, the spiral _Q_ depresses the lever _M N_, by means of its roller _P_, _then the bar I raises the axis A B of the Engine, and the weight W turns it at the same time_, as much as the small roller _p_ permits by rolling up the side _e f_ of the plate _e g f_. And thus may a _screw-formed tooth_ be cut in any wheel centered above _B_ in the usual manner.

Thus then, in describing this Machine, the manner of using it has been also shewn: for the _cutter_, in this Machine, (to cut spur wheels) is always _fixed_; and _all_ the motion is composed of the _rotatory and longitudinal movements of the principal axis, which carries the wheel along with it_. The cutter I say is fixed, at a proper height just above the wheel, and at an angle to the perpendicular, equal to that it is wished the teeth should form at it’s pitch line. This inclination as before observed is 15 degrees; and the tangent of 15° is in round numbers 268, when the radius is 1000. That is, in our present figure, the basis _e g_ of the plate _e g f_, occupies 268 divisions of a scale, of which the height _g f_ contains 1000. It appears then, that to cut a tooth with 15 degrees inclination, _by this Plate_, the wheel _receiving that tooth_, must be _just as large as the rim itself_; for the surface of the wheel would _turn_ more, with a given elevation, if it were _larger_ than the rim; and would turn _less_, by the same elevation, if it were smaller. In a word the whole theory of this operation, is now clearly seen. The smaller the wheel to be cut, the longer, horizontally, must be the Plate; or in other words, _as the diameter of the wheel is to that of the rim, (c d) so is the length e g of the Plate to the length required_. Now this height _f g_, is _always the same_; all change therefore, in the plates, takes place on the horizontal length: and this length is most easily found by the foregoing RULE OF THREE. If then, instead of the triangle _e f g_, I had used the triangle _e′ f′ g′_ it would have followed at once, that to produce an inclination of 15 degrees, I must have taken a wheel of just _half_ the diameter of the rim; for the plate _e′ f′ g′_ is just _twice_ as long as that _e f g_. To prove this, let us _suppose_ the diameter of a wheel wanted, to equal one half that of the rim _c d_: then the _rule_ will stand thus:

1 is to 2, as 268 is to ...536, the length of the plate according to the theory; which is precisely the length it is drawn to compared with _that_ _e f g_, namely twice as long. Thus the four triangles, drawn to the right and left in this diagram, represent the plates for the wheels of the following diameters respectively:

No. 1, a wheel _equal to the plate rim_ _c d_; 2 do. do. to 1/2 do. 3 do. do. to 1/3 do. 4 do. do. to 1/4 do.

A small anomaly, _of form_, may be mentioned here to prevent mistakes. The shaded triangle _e f g_ in the Plate, _looks_ higher than the rest: but if higher, it is also _longer_ in the same proportion; and the roller _p_ never reaches the bottom: so that the _effect_ of this Plate is the same as though it resembled the others in every respect. In general the effect of the Plates depends on their length _compared with their height_: and indeed they must be made _higher_ than the thickness of the wheel to be cut, that the latter may disengage itself from the (fixed) cutter both above and below.

It is proper to observe, that for every _pair_ of wheels there must be a _pair_ of plates; one leaning to the right and the other to the left, (see the diagram) but, as before said, the degree of obliquity _must_ be different in each pair, except in the case of equal wheels, when the _same_ plate serves for both; only turning it to the right for one wheel, and to the left for the other. Nor does this offer any difficulty, as the plates are made of _common tin plate_: which is easily brought to fit the rim, whichever way it is applied. I shall now add another example of the process for finding the length of the plates: and to that end repeat that the _plate rim_ _c d_, is 22 inches in diameter, or 11 inches radius. Supposing then that we wished to cut a pair of wheels, _one_ of them being 1 inch in diameter and the other 12 inches; _both_ to have teeth inclined 15 degrees to the axes; (as without _that_ they could not work together) to do this we must _effect_ these two proportions:

(1) 1/2 inch (radius of small wheel) is to 11 inches, (radius of plate rim) as 268 parts (of which the height of the plate is 1000) to another number, which is the length of the plate sought: measured on a scale of parts of the same magnitude.

(2) 6 inches, radius of the large wheel; is to 11 inches radius of plate rim; as 268 parts (as before) is to another number, which is the length sought for this second plate.

Both proportions being effected, the first plate is 5896 parts. And the second 491.33 do.

The one of course, to be directed toward the right hand, and the other toward the left, on the plate rim; where note, that if the height (1000 parts) is found so numerous as to create confusion, let 100 parts be assumed; when the _length_ of the plate will become 26.8 or 26 and 8/10 instead of 268, and the operation will be so much the more simple.

It should be added that this process admits of being further simplified: since the product of 11 inches, radius of the plate rim, multiplied by 268 (tangent of 15 degrees, or _length of the plate for a wheel equal in diameter to the plate rim_) since this product, I say, is a _constant number_, namely: 2948--which, divided by the _half diameter_ of any wheel, gives, at once the length of the plate adapted to that operation, in parts of which the height contains 1000; or supposing the height to be 100 only, this constant number becomes (nearly enough for practice) 295. In a word, on a height of plate of 100 _parts_, when wishing to cut a wheel of 4 inches in diameter, I merely divide 295 by 2, and get for _the length of my plate_ 147.5 parts of which the aforesaid height is 100.

It may possibly be suggested that this method of using _plates_ to determine the obliquity of the teeth is a homely method, giving some trouble in the execution, and leaving a certain degree of roughness in that execution. The fact is allowed; but this method has the advantage of a _very general_ application, which many a better looking apparatus would not present.

Besides, for _most_ uses, these teeth require chiefly that the obliquity should be correct, and _not_ that the surface should be licked like those of a gewgaw. In fine, the principle of this Machine once known, its best form will occur to the reflecting mechanician according to the _quality_ of the work he has in view: And in fact, in the hands of a well known _artist_, this form has been already varied so as to produce effects much higher wrought than could be drawn from the Machine above described: which latter however in point of generality, still preserves the advantage.

OF A DOOR-SPRING, _To keep a Door strongly closed, yet suffer it to be opened easily_.

That “necessity is the mother of invention,” is a remark none the less true, for having become a trite proverb; I could mention the time, place, and circumstance which gave birth to this little Invention: but such detail would be superfluous. A certain door was, and is still, most inconvenient, from the stiffness of the spring, and the noise it occasions in a place where silence ought to prevail: which state of things suggested to my mind the Machine represented in fig. 5, of plate 17.

_A B C_ in that Plate, is a horizontal section of the door, door jambs, &c. The door spring now in use, is a barrel-spring, with an arm carrying a small roller which presses in a gutter-formed plate, screwed to the door. My door spring is on a different principle. The roller is fastened in and by a small frame to the door, and the arm is fixed to the axis of the spring, which passes up through the top of the barrel. This spring is _much_ weaker than the former, insomuch as only just to close the door by its elasticity; but when the door is shut, there is a sharp bend in the arm that wedges itself against the roller, and _decuples_ at least the force of the spring, as tending to keep the door closed. When therefore it is desired to open the door, by pressing the door itself, a good push is necessary, but only for an instant: for as soon as the bent part of the arm is forced off the roller, there remains only the small resistance of the spring to be overcome; which latter, when suffered to act in shutting the door, will _not_ shut it with that noise a stronger spring would occasion; and yet, when arrived at its first position, it will keep the door as strongly closed as ever. And should it be wished to avoid the necessity of pushing hard against the door, even at first, there is a sliding button and stem _B_ put through it, which, if pressed from the other side, with the force only of the spring, will raise the latter beyond the roller, and thus open the door with perfect facility: and this same process will take place in pulling the door open by the hook _D_ from the inside: yet still the door when closed will be as firmly so as before; the spring-bar acting in the latter position, as much like an invincible _stay_ as the workman shall have desired--this property depending clearly on the _nearness_ of the bend to a right angle.

This device may appear to some an object too inconsiderable to be justly dignified with the name of an invention. But if I should sometimes fall into such an error as this, I intend to compensate for any thing too trivial by giving in other cases, Inventions of ample size and number. I might even mention the Cutting Engine given in this part, where several Inventions are compressed into one, or rather presented as _one_, of which several examples will occur.

OF A DRAW-BENCH, _For making my twisted Pinions_.

The pinion wire of clock and watch makers is well known. I am not wholly acquainted with the manner in which it is drawn: but I have made my pinion wire, of brass, in lengths of about a foot, by the Machine described below.

A common Draw-bench (not here represented) is worked in the usual manner: but the instrument which forms the pinion (see Plate 17, fig. 1) is of a peculiar construction. It consists of a plate _A B_, containing--1st. a guide tube _a_, (fig. 2) to centre and conduct the blank wire;--2d. a ring _b c_, with _nine_ grooves cut on one of its surfaces, directed to the centre, and in which are _well_ fitted the cutters 1 2 3 4 5 6 7 8 9; and 3d. a ring _d e_, formed into nine spirals exactly like each other, answering to the cutters, and destined to urge them _equally_ toward the common centre whenever this circle _d e_, is turned by the endless screw _C D_, in the direction of the arrow. In fig. 2, _f g_ is merely a top piece to cover at the same time the cutters and the ring _d e_; which latter is thus duly centered. The points of the cutters 1, 2, 3, &c. are formed like the spaces of pinion teeth; and in the other direction, are sloped 15 degrees to the common axis, as taken at their pitch line.

The third figure represents the drawing clams, or pinchers, with a piece of blank wire _d_ in them, tapered off to give easy entrance to the cutters. These clams have a cylindrical part of about a foot long, in which is cut a winding groove _a b_, whose use is to _turn_ the wire in the act of drawing; for which purpose also the _swivel_ _e f_ is provided. The method I employ to _trace_ this groove to the obliquity required, is to measure the circumference of the cylinder, and call that 268; and then, to make its length, in the cylindrical part, equal to 1000 of the same divisions. But this is right, _only_ when the _pinion_ to be drawn is of equal diameter with the clam-cylinder _a b_: so that if it is wished to draw pinions of a smaller diameter, I further say: diameter of clam-cylinder _is to_ diameter of pinion, at the pitch line; As 1000 (present length of clam-cylinder) _is to required length of ditto_. Thus, for example, if the diameter of the pinion were only 1/4 that of the clam-cylinder, the _length_ of the latter would be only 250 of the 1000 divisions, before found: and so in proportion for smaller diameters.

The figure shews this groove receiving a guide screw or stud _a_, which, placed in the fixed headstock _a c_, turns the clams _d_, with the wire, just enough to give the teeth an inclination of 15 degrees, thus adapting them to the wheels of which the proportions have been already given; where note, that the real dimensions of this pinion Machine are _twice_ as large as those of the figures 1 and 2: but the size of every thing is of course _variable_, according to the pinions required to be produced.

OF A GEERING CHAIN, _Formed to work in the Patent Wheels_.

This Chain is shewn in fig. 4 of Plate 17. The links are formed to an angle, in the middle, similar to that of the wheels at their pitch line; of which the obliquity, for the V wheels, is greater than 15 degrees; since the thickness of the wheel, is necessarily divided between the right and left handed slope. Be this slope what it may, the chain and wheels must of course be alike, measured at the pitch line of the wheels; and _then_, as the chain geers with a straight _line_ of pinions, they work together without sensible friction on the teeth, and with nearly the same steadiness of motions as wheels would work together. Moreover, if the drum be of a pretty large diameter, its action will likewise be nearly _equable_. The degree of precision depends, however, on the fineness of the pitch, and the largeness of diameter in the drum; since every chain bending round a cylinder _must_ form a polygon of a _greater or less_ number of sides, dependent on these circumstances. I repeat then, that while the chain works on the pinions in a tangent to them all, there is no necessary friction between them; nor yet on the pins of the chain, but only at the drums which actuate and return the latter:--I shall dismiss the subject, by observing, that I have used the term _drum_, because of the similarity of this chain-motion to that produced by bands, where drums are generally the _movers_. But here, this supposed drum is a wheel of proper diameter, cut into teeth similar to those of the pinions; and placed at the same height on its spindle. I have reason to think that this chain, carefully made, would be an useful addition to the _bobbin and fly frame_, applied both to the bobbins and spindles, instead of the bands now in use; which, though a convenient resource, give a result equally uncertain and imperfect.

OF A SERPENTINE BOAT OR VESSEL, _To lessen the Expence of Traction, &c._

The present description of this Machine, will consist, chiefly, of a translation from my own specification, given at Paris with the application for a _Brevet_, or Patent, obtained in the year 1795, and which is thus introduced.

“It is a well-known fact, that the longer any Boat or Vessel is, in proportion to its width, the less power it requires to convey a given load, from one place to another. But these lengths cannot be extreme, without introducing a degree of _weakness_, that would offer great danger in the use of such vessels. If then a Boat of a given volume, be divided into several long and narrow ones, the head of each adapted with a certain exactness to the stern of its forerunner, they will (with the trifling difference arising from the asperities of their surfaces) _all_ move through the water with the same ease as any single one; and carry, unitedly, the same weight as did the large Boat before it was divided. This idea constitutes the principle of my Serpentine Vessel.”

“This Invention is not to be considered as an imitation of the well-known manœuvre of towing one vessel in the _wake_ of another: for the resistance of the vessels thus towed, remains nearly, though not quite the same as if drawn along separately. But here, by the adaptation of the _prow_ of one Boat to the _poop_ of another, the first alone suffers resistance from the water--which, although it enters between the _joints_, strikes _only_ the first--and from this it follows, that the _resistance_ of these vessels, in passing from one place to another, _bears no necessary proportion to the weight they carry_.”

“Thus then, I obviate the necessity of having _broad_ vessels to carry the heaviest burdens; for I disseminate the load over an indefinite _length_: by which method also, my vessel rides in shallower water, and depends less for its passage, on the state of the rivers or the seasons. Besides, they require a much less number of horses, or exertion of _power_, to transport a given quantity of goods; admitting at the same time, a greater swiftness of motion. And finally, if these vessels travel through different towns on the same voyage, the goods of each town may be lodged in the same _part_, and merely detached in passing, so as to lose _no_ time in unloading them.”

“Fig. 1 of Plate 18, shews the _plan_ of several forms which I give to the articulations or separate parts of these vessels: so as to connect them strongly, yet leave them, as a whole, in some degree flexible. The form _A B_, is, for the first boat, a straight line across to form the _stern_, and for the second an obtuse angle terminated by a semi-sphere or vertical semi-cylinder, which enters a hollow and similar figure in the first Boat--which latter, in this case, forms the _Head_ of the whole Serpentine Vessel.”

“These two parts or joints, of which we have been speaking, are held together by a rope _c d e f_, which, fastened to the second part at _c_, passes over two pulleys _e d_, in the head, to the small capstan _f_, by which, both parts are bound together as tightly as may be judged proper. If it were thought necessary, the spaces _A B_ might be underlined with a piece of leather or metal, _not_ to prevent the water from entering between the Boats, but to prevent its _striking_ those which follow the others through the water--a precaution less urgent in the other kind of joint we are about to describe.”