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Ramsay, a particular person for the crime of which he himself 2160 teeth, in which an endless screw acts. Six revo- Ramsden's
a tyrant to his own slaves, though he might have argued to one degree.
wheel of 10 seconds, six of them will be equal to a mi-
RAMSDEN's Machine for Dividing MATHEMA the clamps by the double-jointed frame, admits a free
any error in the dividing ; and, by a particular contri-
Plate it perfectly steady. On each leg of the stand is placed arbor and the tracer continued, will always make equal cccclix. a conical friction pulley, whereon the dividing wheel angles with the screw.
Plata rests : to prevent the wheel from sliding off the friction Figure 1. represents a perspective view of the en- CCCCLX pulleys, the bell-metal centre under it turns in a socket gine. on the top of the stand.
“ Fig. 2. is a plan, of which fig. 3. represents a sec- Fig. 2. “ The circumference of the wheel is ratched or cut tion on the line na. (by a method which will be described hereafter) into “ The large wheel A is 45 inches in diameter, and
4 L 2
Ramsden's has ten radii, each being supported by edge-bars, as bered at every 6th division with 1, 2, &c. to 10. The Ramdea's
nected by the circular ring B, 24 inches in diameter screw-frame G.
slit in the direction towards the centre of the wheel,
is towards the left hand, that side of the slit is faced " The surface of the wheel A was worked very even with brass, and the pillar is pressed against it by a and flat, and its circumference turned true. The ring steel spring on the opposite side: by this means the C, of fine brass, was fitted very exactly on the circum- pillar is strongly supported laterally, and yet the screw ference of the wheel ; and was fastened thereon with may be easily pressed from or against the circumference screws, which, after being screwed as tight as possible, of the wheel, and the pillar will turn freely on its axis were well rivetted. The face of a large chuck being to take any direction given it by the frame L. turned very true and flat in the lathe, the fattened sur “ At each corner of the piece I are screws n of Fig. 4 face A of the wheel was fastened against it with hold- tempered steel, having polished conical points : two of fasts; and the two surfaces and circumferences of the them turn in conical holes in the screw frame pear o, ring C, a hole through the centre and the plane part and the points of the other two screws turn in holes round (b) it, and the lower edge of the ring B, were in the piece Q; the screws p are of steel, which being turned at the same time.
tightened, prevent the conical pointed screws from un“ D is a piece of hard bell-metal, having the hole, turning when the frame is moved, which receives the steel arbor d, made very straight “ L is a brass frame, which serves to connect the end- Fig. 1, 2, 6. and true. This bell-metal was turned very true on less screw, its frame, &c. with the centre of the wheel: an arbor ; and the face, which rests on the wheel at b, each arm of this frame is terminated by a steel screw, was turned very flat, so that the steel arbor d might that may be passed through any of the holes q in the Fig. 4 stand perpendicular to the plane of the wheel : this piece Q, as the thickness of work to be divided on bell metal was fastened to the wheel by six steel the wheel may require, and are fastened by the fingerscrews l.
Fig. 1.&: " A brass socket Z is fastened on the centre of the “ At the other end of this frame is a flat piece of mahogany stand, and receives the lower part of the tempered steel b, wherein is an angular notch : when Fig. 6. bell-metal piece D, being made to touch the bell the endless screw is pressed against the teeth on the cir. metal in a narrow part near the mouth, to prevent any cumference of the wheel, which may be done by turoobliquity of the wheel from bending the arbor: good ing the finger-screw $, to press against the spring , Fig. 1. $ fitting is by no means necessary here; since any shake this notch embraces and presses against the steel arbor d. Fig. 2. in this socket will produce no bad eflect, as will appear This end of the frame may be raised or depressed by movhereafter when we describe the cutting frame.
ing the prismatic slide u, which may be fixed at any Fig. 1, 2, “ The wheel was then put on its stand, the lower height by the four steel screws v.
Fig. 1, 4, 6. edge of the ring B resting on the circumference of “ The bottom of this slide has a notch k, whose Fig. 1. & three conical friction-pulleys W, to facilitate its mo plane is parallel to the endless screw; and by the point tion round its centre. The axis of one of these pulleys of the arbor d resting in this notch, this end of the Fig. 3. is in a line joining the centre of the wheel and the frame is prevented from tilting. The screw S is premiddle of the endless screw, and the other two placed vented from unturning, by tightening the finger
so as to be at equal distances from each other. Fig. I. “ F is a block of wood strongly fastened to one of the “ The teeth on the circumference of the wheel were
legs of the stand ; the piece g is screwed to the upper cut by the following method :
engine is 2160, or 360 multiplied by 6, I made two Fig. 1. & 4 “ The lower extremity of the conical pillar P termi screws of the same dimensions, of tempered steel, in
nates in a cylindrical steel-pin k, which passes through the manner bereafter described, the interval between and turns in the transverse axis h, and is confined by the threads being such as I knew by calculation a check and screw.
would come within the limits of what might be turned “ To the upper end of the conical pillar is fastened off the circumference of the wheel: one of the scre irs, Fig. 4.
the frame G, in which the endless screw turns: the which was intended for ratching or cutting the terth, pivots of the screw are formed in the manner of two was notched across the threads, so that the screw, when fru-tums of cones joined by a cylinder, as represented pressed against the edge of the wheel and turned round,
at X. These pivots are confined between half poles, cut in the manner of a saw. Then having a segment Fig. 5.
which press only on the conical parts, and do not touch of a circle a little greater than 60 degrees, of about the cylindric parts: the half holes are kept togetber by the same radius with the wheel, and the circumference screws a, which may be tightened at any time, to pre made true, from a very fine centre, I described an arch vent the screw from shaking in the frame.
near the edge, and set off the clord of 60 degrees on Fig. 1, 2,
“ On the screw-arbor is a small wheel of brass K, this arch. This segment was put in the place of the 4, 5. having its outside edge divided into 60 parts, and num wheel, the edge of it was ratched, and the number of 3
Fig. 1, 3
amsden's revolutions and parts of tlie screw contained between coincide with the fixed wire; the screw was then care- Ramsden's dachine. the interval of the 60 degrees were counted. The fully pressed against the circumference of the wheel, by Machine.
radius was corrected in the proportion of 360 revolu- turning the finger-screw S; then, removing the clamp,
section 3 coincided with the fixed wire ; the divi1:5. 3. “ The wheel was now taken off the lathe ; and the sion 10 on the circle being set to its index, the screw
bell-metal piece D was screwed on as before directed, was pressed against the wheel as before, and the screw
was turned nine revolutions, till the intersection 2 “ From a very exact centre a circle was described nearly coincided with the fixed wire, and the screw . 1, 2, 3. on the ring C, about four-tenths of an inch within where was released; and I proceeded in this manner till the
the bottom of the teeth would come. This circle was teeth were marked round the whole circumference of
there was even one tooth or ten miuutes greater than the
accuracy of the divisions, I described another circle on the teeth were equally distributed round the wheel at 7. the ring C, one tenth of an inch within the former, and the distance of nine teeth from each other. Now, as
divided it by continual bisections, as 2160, 1080, 540 the screw in ratching bad continually hold of several
end of the screw is a ratchet-wheel C, having 60 teeth, 7.
“ The arms of the frame L were connected by a thin covered by the hollowed circle d, which carries two Fig. 5. piece of brass of three-fourths of an inch broad, having a clicks that catch upon the opposite sides of the ratchet hole in the middle of four-tenths of an inch in diameter; when the screw is to be moved forwards. The cylinacross this hole a silver wire was fixed exactly in a line der S turns on a strong steel arbor F, which passes to the centre of the wheel; the coincidence of this wire through and is firmly screwed to the piece Y: this with the intersections was examined by a lens seven piece, for greater firmness, is attached to the screwtenths of an inch focus, fixed in a tube which was at frame G by the braces v; a spiral groove or thread tached to one of the arms L (A). Now a bandle or is cut on the outside of the cylinder S, which serves winch being fixed on the end of the screw, the division both for holding the string, and also giving motion to marked on the end of the screw, the division marked 10 the lever J on its centre by means of a steel tooth n, on the circle K was set to its index, and, by means of that works between the threads of the spiral. To the a clamp and adjusting screw for that purpose, the inter- lever is attached a strong steel pin m, on which a section marked i on the circle C was set exactly to brasz socket r turns : this socket passes through a slit
(A) The intersections are marked for the sake of illustration, though properly invisible, because they lie under the brass plate.
Ramsden's in the piece p, and may be tightened in any part of half holes F and T, which were kept together by the Reusden's Machine. the slit by the finger-nut f: this piece serves to regu
Machin, late the number of revolutions of the screw for each “ H represents a screw of untempered steel, having Ramses tread of the treadle R.
a pivot I, which turns in the hole K. At the other Tig. 1.
“T is a brass box containing a spiral string; a strong end of the screw is a hollow centre, which receives the gut is fastened and turned three or four times round the bardened conical point of the steel pin M. When this circumference of this box, the gut then passes several point is sufficiently pressed against the screw, to pretimes round the cylinder S, and from thence down to vent its shaking, the steel pin may be fixed by tightenthe treadle R. Now, when the treadle is pressed down, ing the screws Y. the string pulls the cylinder S round its axis, and the “ N is a cylindric nut, moveable on the screw H; clicks catching bold of the teeth on the ratchet carry which, to prevent any shake, may be tightened by the the screw round with it, till, by the tooth n working in screws 0. This nut is connected with the saddle-piece the spiral groove, the lever J is brought near the wheel P by means of the intermediate universal joint w, d, and the cylinder stopped by the screw-head .z striking through which the arbor of the screw H passes. A front on the top of the lever J; at the same time the spring is view of this piece, with the section across the screw arwound up by the other end of the gut passing round the bor, is represented at X. This joint is connected with box T. Now, when the foot is taken off the treadle, the nut by means of two steel slips S, wbich turn on pins
the spring unbending itself pulls back the cylinder, the between the cheeks T on the nut N. The other ends Fig. 1. clicks leaving the ratchet and screw at rest till the piece of these slips S turn in like manner on pins a. One axis
t strikes on the end of the piece p: the number of revolu- of this joint turns in a hole in the cock b, which is tions of the screw at each tread is limited by the num fixed to the saddle-piece; and the other turns in a bole de ber of revolutions the cylinder is allowed to turn back made for that purpose in the same piece on which the before the stop strikes on the piece p.
cock b is fixed. By this means, when the screw is turn“ When the endless screw was moved round its axis ed round, the saddle-piece will slide uniformly along
with a considerable velocity, it would continue that mo the triangular bar A. Fig. 1.& 4. tion a little after the cylinder S was stopped: to pre “K is a small triangular bar of well-tempered steel,
vent this, the angular lever # was made ; that when the which slides in a groove on the saddle-piece P. The
“ Having measured the circumference of the dividingFig. 1, 2,6. “ D, two clamps, connected by the piece a, slide one wheel, I found it would require a screw about one ibread
on each arm of the frame. L, and may be fixed at plea- in a hundred coarser than the guide-screw H. The sure by the four finger-screws e, which press against steel wheels on the guide-screw arbor H, and that on the springs to avoid spoiling the arms : the piece q is made
ms: the piece q is made steel E, on which the screw was to be cut, were proto turn without shake between two conical pointed screws portioned to each other to produce that effect, by giving f, which are prevented from unturning by tightening the whieel L 198 teeth, and the wheel Q 200. These the finger-nuts N.
wheels communicated with each other by means of the Fig. 6. “ The piece M is made to turn on the piece q by intermediate wheel R, which also served to give the
the conical pointed screws f resting in the hollow cen threads on the two screws the same direction.
s. The saddle-piece P is confined on the bar A by
long account of an equatorial instrument made by Mr of the Dividing Engine was cut.
Ramsden by the direction of Sir George Shuck burgh in
the Philosophical Transactions for 1793, art. x. p. 67. “ Fig. 9. represents this engine of its full dimensions In this instrument the circle of declinations is four feet seen from one side.
in diameter, and may be observed nearly to a second. “ Fig. 8. the upper side of the same as seen from The glass is placed between six pillars, which form the above.
axis of the machine, and turn round by two pivots plaA represents a triangular bar of steel, to which the ced on two blocks of stone. See also BAROMETER. triangular boles in the pieces B and C are accurately RAMSEY, a town of Huntingdonshire, 68 miles fitted, and may be fixed on any part of the bar by the north of London, and 12 north-east of Huntingdon.
It is situated as it were in an island, being everywhere “ E is a piece of steel whereon the screw is intended encompassed with fens, except on the west, where it is to be cut; which, after being hardened and tempered, separated from the terra firma by a causeway fortwo miles
. bas its pivots turned
in the form of two frustumg of cones, The neighbouring meers of Ramsey and Whitlesey, as represented in the drawing of the dividing engine which are formed by the river Nyne, abound with fish, (fig. 5.). These pivots were exactly fitted to the especially eel and large pikes. It was once famous for