Chap. XX Of the Drill-Boxes
The Drill is the Engine that plants our Corn and other Seeds in Rows: It makes the Chanels, sows the Seed into them, and covers them at the same time, with great Exactness and Expedition.
Turnip Seed Box
The principal Parts of the Drill are, the Seed-box, the Hopper, and the Plough, with its Harrow.
Of these the Seed-box is the Chief: It measures (or rather numbers) out the Seed which it receives from the Hopper: It is for this Purpose as an artificial Hand, which performs the Task of delivering out the Seed, more equally than can be done by a natural Hand.
It is described, together with some of its Appurtenances, in Plates 2 and 3.
The Mortise
As the Seed-box is the principal Part of a Drill, so is the Mortise the principal Part of the Seed-box.
The following Descriptions shew how this Mortise differs from a common Mortise.
Fig. 1. Plate 2. shews both the upper and lower Edges of a Turnep-Seed-box, and the Manner how they are posited one over another, a b c d is a rectangled Parallelogram, and shews the upper Edges (or Top) of the Mortise. e f g h, being a Figure of the same Denomination with the former, is the lower Edges (or Bottom) of the Mortise. The Line e h is the Length of the lower Edge of the Hinder-end of the Mortise. a d is the upper Edge of the Hinder-end of the Mortise, and posited just over the lower Edge of the same End. The Space between the Line a b, and the Line e f, shews half the Excess whereby the Bottom of the Mortise exceeds the Top in Breadth; as the Space on the opposite Side, betwixt the Line c d, and the Line g h, shews the other Half of that Excess, both which Halves, taken together, shew the whole Bevel (or Angle of Inclination) described in Fig. 2. That Part of the Line a b, from the Angle at b to the Line f g, which intersects it, shews the Excess whereby the Top of the Mortise exceeds the Bottom in Length.
Fig. 2. Is the Mortise cut down by its Four Corners, and laid open. a b c d is a Trapezium, with Two parallel Sides, and mark’d A, the right Side of the Mortise; its opposite Side e f g h, mark’d B, the left Side of the Mortise; the Areas of both being true Planes261.
Turnip Seed Box d i k h Shew the Fore-end of the Mortise, mark’d C. a l m e shew the Hinder-end of the Mortise, mark’d D. a d h e shew the Bottom of the Mortise already described in Fig. 1. If these opposite Sides and Ends were all raised up, until the Angle at b join the Angle at l, and that at m join f, and that at g join k, and that i join c, the Top of the Mortise would be formed, and the same with the Parallelogram a b c d, in Fig. 1. and then the intire Mortise of the Turnep Seed-box would appear in its true Form, standing upon its Bottom.
This differs from a common Mortise, in that it is impossible to fit it with a Tenon; because it is narrower above, and shorter below, as in Fig. 1.
The Areas, or imaginary Planes, of the Top and Bottom of the Mortise, are parallel to each other, but not equal.
Its Two opposite Sides are equal, but not parallel, by reason of their Inclination to each other upwards, which is the Bevel hereafter to be described.
The Two Ends are neither parallel nor equal, because the Hinder-end D is perpendicular to the Top and Bottom, and the Fore-end oblique, and therefore longer.
When Two opposite Sides, or Surfaces, are inclined to each other upwards, I call that Inclination a Bevel; but when they are inclined downwards, I call it a Bevel revers’d.
The Line a e, being the Bottom, or Base, of the Hinder-end D, by being longer than the Line l m, shews that the Mortise is bevel.
The Two prick’d Lines m n and l o, with the Line l m, and Part of the Line a e, make a rectangled Parallelogram, which shews the exact Depth of the Mortise, and forms on each Side of it a rectangled Triangle, the one m e n, and the other l o a; which Triangles being similar and equal, and their acute Angles at l and m being each of Four Degrees, make the whole Bevel, or Inclination of the Sides of the Mortise, to be of Eight Degrees, their Hypothenuses being the same with the Sides of the Mortise.
This End D, being raised up to its Place, will be at right Angles with the Plane of the Top and of the Bottom of the Mortise; which, being both rectangled Parallelograms, prove that Bevel, or Angle of Inclination, to be the same from one End to the other of the Sides, which Sides are the Hypothenuses of those Two Triangles: But this could not be proved by the Triangles in the opposite End C; because the Bases being the same with the other, and having their Legs longer, the vertical Angles at k and i are more acute. The Legs are longer; because the End C, when in its Place, is not at right Angles with the Top and Bottom of the Mortise, as the End D is.
Wheat Drill Mortise
The next thing to be described in the Mortise, is the Bore, great Hole, or Perforation; which is best shewn in the Side of a Mortise of a Wheat-drill, being larger, as in Fig. 3. wherein c e b d is the great Hole, and is a Section of an hollow Cylinder, that passes through the Mortise, with its Axis parallel to the Edges of the Ends of the Mortise: This Cylinder, being cut by the Side of the Mortise obliquely, and not parallel to its Base, is an Ellipse.
The prick’d curve Line is a Circle parallel to the Base of the Cylinder, and the curve Line b d c e is the Ellipsis; and this Curve is more or less elliptical (or oval) in proportion to the Angle of Inclination, or Bevel, of the Sides of the Mortise.
Of this Ellipse the longest Diameter (or Axis transversus) b c is at right Angles with the upper and lower Edges of the Sides of the Mortise.
Its shortest Diameter (or Axis rectus) d e, is the Diameter of the Cylinder, bisecting the Axis transversus at right Angles in the Centre a; and is in this Figure one Inch and an half.
This Ellipse being concentric with the Circle, the Letter a is the Centre of both.
The Semi-ellipsis c e b is the Part of chief Use; and therefore the Edge must of Necessity be smooth, and without Flaws, as must the Surfaces of the Sides of the Mortise betwixt the Ellipse and the Fore-end.
Seed box tongue Seed box tongue
The Tongue of the Seed-box (Plate 3. Fig. 1.) differs from that in the Sound-board of an Organ (from which I took the Idea of it) in Shape, in Situation, and in the Manner of its being fix’d to the Mortise.
The Tongue, in the Organ, is on its Surface a long Square, or rectangled Parallelogram, a little broader and longer than the Mortise (or Grove) it shuts against; but this Tongue on its upper Surface, which is here turned downwards, being a Plane, is a Trapezium, of the same Shape with the Fore-end of the Mortise just now described, except that the Tongue has a less Bevel.
The Situation of that in the Organ is on the Outside of the Mortise, which it shuts by its Spring behind it, and opens immediately by the Finger of the Organist pressing down the Key to let in the compressed Air to its Pipes; but this Tongue is situate within the Mortise of the Seed-box, and placed almost, in a manner, diagonally; for, had it been placed like the other, the Seed getting betwixt it and the Edges of the Mortise, would not have given Way to its Shutting (as the Air does to the other), but have kept it always open; which would have render’d it useless for sowing of Seeds.
Seed Box Assembly
The Manner of fastening the Organ-tongue to its Mortise is by Parchment and Leather glu’d to its Surface, and also to the Sound-board, at its End which is opposite to that pressed open by the Key, and shut by the Spring; but this our Tongue is held within the Mortise, and moves on an Axis, which passes thro’ its upper and narrower End, which Axis is the Pin A (which must be exactly parallel to the Edge of the End of the Mortise), and also thro’ the Hole f in Fig. 3. in Plate 2. which is seen in its Place at A in Fig. 3. Plate 3. and likewise through both Sides of the Mortise near their upper Edges, and as near the Fore-end of the Mortise as may be, without the Tongue’s rubbing against the said Fore-end.
The Breadth of the Tongue must be conformed to the Breadth and Bevel of the Mortise, and when it is on its Axis, it being raised tight up as far as the short prick’d Line l m in Fig. 3. Plate 2. being One-eighth Part of the great Hole, and being there, you see its upper Edges touch both Sides of the Mortise by their whole Length: Then it is rightly made: and by this touching both Sides of the Mortise tightly and closely, when raised up to that Degree, it appears, that the Two upper Edges of the Sides of the Tongue are inclined to each other in an Angle that is more acute, by about One-third, than is the Angle of Inclination of the Sides of the Mortise.
Hence, when the Tongue is let down to its Place, there will be on each Side of it an empty Space, betwixt it and the Mortise, of the Form of a very acute Triangle, whose vertical Angle is more or less acute, according as the Tongue approaches nearer to, or recedes farther from the Spindle.
This Fig. 1. Plate 3. is the brass Tongue with its Back-side upwards. The Two outer Lines a b and c d are the Edges of the upper Surface (tho’ turned downwards in this Figure), which are inclined to each other, as afore-mentioned; but the Two inner Lines e f and g h are nearer to each other, whereby this under Surface is narrower than the upper: Both must be plain Surfaces, but the upper and its Two Edges very free from Flaws, and smooth, or polished.
The Reason why the under Surface is narrower than the upper, is to preserve the Bevel of the empty Triangle: For though the Bevel of the Sides of the Mortise would be sufficient for this, if both Sides of the Tongue were sure to keep equally distant from the Spindle; yet as the Tongue never is so tight on its Axis, but that sometimes one Corner of it may be nearer to the Spindle than the other, in this Case, that Side which is nearest to the Spindle would reverse that Bevel, so as to make the small empty Space that is betwixt the Mortise and the Tongue, wider above than underneath.
C C are the Two little Knobs that prevent the Spring from slipping to either Side, and are at the Distance from one another of the Breadth of the Spring.
Fig. 2. shews one Side, and the Thickness of the Tongue the other Side, being the same. a b shews the polished Surface (being a true Plane), whereon the Seed runs down to the Spindle. c d the Back-side, which lies turned uppermost in Fig. 1. b e d shews one End of the hollow Cylinder of the Tongue, thro’ which its Axis passes.
The Length of the Tongue must be such, as will reach lower than just to touch the Bottom of the great Hole as a Tangent: for, if it be not longer than that, it might happen, that when the Mortise is empty of Seed, and the Tongue set up close, a Wheel might, in Turning, or otherwise, go a little backwards, and cause a Notch of the Spindle to take hold of the End of the Tongue, and tear it out of the Mortise: Therefore let the Tongue reach a little below the Spindle, as the pricked Line g h, in Fig. 3. of Plate 2. doth.
As for the Posture in which the Tongue ought to stand in the Mortise, it is shewn by the Three pricked Lines in Fig. 3. Plate 2. where the pricked Line g h makes an Angle of Forty-five Degrees, being the nearest that it can stand to the Spindle; the pricked Line i h makes a somewhat greater Angle, and it is a mean (or middle) Distance from the Spindle; and the pricked Line k h is supposed to be its greatest Distance, where the Tongue makes its greatest Angle with the Top and Bottom of the Mortise. If the Tongue stood so obliquely as to make an Angle much less than Forty-Five, the Tongue would rise too much against the Bevel of the Mortise, and the Spring would have the greater Difficulty in returning it to its Place, when driven back by the Force of the Notches.
And beside, when the Tongue stood wide from the Spindle, there might be so much Room betwixt it and the Sides of the Mortise, that some Seeds might fall thro’ there.
The Steel Spring is D, properly placed upon the Back of the Tongue, in Fig. 1. Plate 3.
At first, I made the Spring double, i. e. with Two Legs, in Imitation of that in the Organ, and fastened into its Tongue, much after the same manner as the Spring of the Organ is into its Tongue or Flap, which prevents the compressed Air from passing out of the Sound-board, except whilst the Key is thrust down by the Finger of the Player; but the Drill-spring requiring to be of a vastly greater Strength than that, I made it of Steel, of the Breadth of half an Inch, instead of Brass Wire: This performed very well, and several Drills are yet extant, that have only this Sort of Springs: Yet I found there was great Difficulty to set the Legs at their due Distance from each other; for their Seasoning would alter them from what they were, whilst the Steel was soft: They also took up too much Room in the upper Part of the Mortise. Then, to remedy these Inconveniencies, I made it single, with only one Leg, which by full Experience is found to be much better than the double one; it does not contain a Fourth Part of the Metal, and is most easily made, requiring none of that Trouble and Nicety that the double Spring doth. I shall therefore give a Description of the single Spring only.
B, the End of the Screw, which holds the Spring to the Tongue, thro’ a Hole near the upper End of the Spring; D, the Middle, against which the End of the Setting-screw bears.
Its Length is almost the whole Length of the Tongue; the End E reaching very near to the lower End of the Tongue, and the End B is as near the upper End of the Tongue; as it can be placed without touching the Cylinder of the Tongue.
The Breadth is usually about half an Inch; the Thickness must be in proportion to its other Dimensions, and according to the Degree of Stiffness required.
The longer it is, the thicker it must be, to have the same Stiffness; but the broader it is, the thinner it must be of the same Length; so that it is hard to determine its Thickness. It is made stiffer or stronger by being cut shorter; it is made weaker, or less stiff, by filing or grinding it either thinner or narrower.
The common Thickness is about that of a Shilling262.
The Degrees of Stiffness are measured in this manner; viz. Fix Two Boards together, leaving a Chink betwixt them, in one Place of an Inch long; lay the Spring (when seasoned across this Chink) with its Middle exactly over it; then put a String over the Spring, which may pass with both Ends thro’ the Chink, and tie so much Weight to the Ends of the String under the Boards, that will pull down the Middle of the Spring, till it touch the Chink, and is strait with both its Ends; This will shew the Degree of Stiffness. But note, That the Spring must be crooked, and bear only upon its Ends, with the hollow Side upwards.
If ten or a dozen Pounds Weight pull it down to the Board, it is a good Degree of Stiffness, for a large Box: We are not confined to be very nice or exact in the Degree of Stiffness; for by our Fingers pressing it, we that are practised in it, know well enough, whether a Spring be of a sufficient Degree of Stiffness, without weighing it; but for such who are unacquainted with them, it is best not to trust to Guess, but Weights; and to adjust the Stiffness to that of a Spring, that has been known to perform well.
The Spring must bear against the Back of the Tongue at each End, and lie hollow in the Middle: But the Degree of Hollowness of the Spring is very material; for thereon depends the Distance of the Tongue’s Motion towards the Spindle by Force of the Spring, and back again quite to the Setting-screw, by the Seed that is pressed against it by Force of the Notches, when they are moved by the Wheels; because the more the Spring is curved, the farther will it thrust the Tongue from its Middle, if its Strength be superior to the Force that resists it, as it ought to be when a Notch is passed and before the next: This Motion of the Tongue is called its Play.
In order to measure the Distance (or Quantity) of this Motion, we must consider, that the Tongue, moving on its Axis above, describes with its lower End the Arch of a Circle, the Chord of which Arch is the Measure required.
To measure this by the Angle the Tongue makes at its Centre, would be no Rule for making Boxes; because some Tongues are longer, some shorter, in proportion to the different Diameters of the Spindles they move against; and yet the Play of the shortest must be as much as that of the longest, that is, it must describe as great an Arch at the Place of Pressure (described in Fig. 3. Plate 2.); and therefore the shortest Tongue would make the greatest Angle.
A short and easy Way, then, for a Mechanic to measure, is thus: Screw in the Setting-screw until the Tongue come within a quarter of an Inch of touching the Spindle; then take out the Spindle, and from the Centre of the Hole draw a Line on the Side of the Mortise, perpendicular to the Tongue, and at the Tongue’s Edge make a Mark with the Compasses, or a Pen; then force back the Tongue against the Setting-screw as far as it will go (that is, until the Spring touch the whole Back of the Tongue); produce the said Line to the same Edge of the Tongue, or set the End of the Rule thereon, and draw another Line, by the Rule, from the Mark to the Edge of the Tongue, when farthest back, and there make the second Mark. The Ruler used this Way will shew both the Perpendicular, and the Measure.
But yet a quicker Way is, to set the Tongue, by the Setting-screw up to the Edge of the Hole; and, when it is forced back, measure from the Tongue to the nearest Part of the Hole, which will ever be a perpendicular Line drawn from the Centre of the Hole to the Place of Pressure above-mentioned, and make another Mark there: Now the Distance between these Two Marks is the Measure (near enough) of the Tongue’s Play at the Place of Pressure. Tho’ this Line drawn on the Side of the Mortise be not exactly perpendicular to the Surface of the Tongue, but only to its Edge; yet the Difference is next to nothing, and not to be regarded.
If its Measure be a quarter of an Inch, it is what Experience shews to be of a good Size for all Corn and Peas; a little less is no Harm, but greater is the most fatal Error, into which most of the Pretenders to the making of this Machine have fallen; they give the Tongue half an Inch, sometimes Three quarters of an Inch Play. The Mischief of this Error is yet farther increased, if the Spring be weak, if the Mortise have too great a Bevel, or if the Angle made by the Tongue at the upper Edge of the Mortise be too acute.
When the Tongue has too great Play, the Seed is apt to be turned out too fast, or else too slow, in spite of the Driller. For when the Tongue is set at its due Distance from the Spindle, and is thrust quite back by the Seed pressed against it by the Turning of the Notches; but the Spring being unable to return the Tongue to its former Place at such a Distance, at the time of passing the Intervals which are betwixt the Notches; then the Space between the Spindle and the Tongue being too open, the Seed is sent down too fast.
To prevent that, they set up the Tongue to the Spindle; and then, as often as the Spring happens to overcome the Force of the Seed’s Pressure (as sometimes it will), it is sent out too slowly.
The Inequality of the Running of the Seed makes such Boxes useless, which the Expence of Two-pence (for another Spring, or new Seasoning of that) at most would rectify, if the Maker understood how to mend his own Work. If time did permit, more should be said on this Point, because I find it is the Pons Asini of a Workman. Sometimes it may be prevented, when the Spring is too hollow, and gives too much Play. Screw the Screw, that holds it on the Tongue, down closer, so that the lower Part of the Screw’s Head press against the Spring, and thereby force its Middle nearer to the Tongue, until you find its Play lessened to its just Distance.
The Spring, remaining in this compressed State, has lost the weakest, and retains only the strongest, Part of its elastic Force. Therefore, if you find it then too stiff, make it weaker by Filing or Grinding, or else put another into its Place, which is honestly worth no more than Two-pence.
This Holding-screw has a pretty broad Head, and is screwed in by a Notch, like the Screw-pin of a Gun-lock.
The Hole in the Spring must be somewhat bigger than the Holding-screw, because the Spring must have room to move and play thereon.
If the Middle of the Spring were against the Middle of that Part of the Tongue, that is betwixt its Axis and the Place of Pressure, the Distance of the Spring’s Hollowness would be just half the Distance of the Spring’s Play, to wit, the One-eighth Part of an Inch; but as the Spring does not quite reach up to the Axis, and reaches much below the Place of Pressure, the Hollowness at the Place where the Setting-screw bears against the Middle of the Spring at D, is considerably nearer to the Place of Pressure than to the Axis of the Tongue; this Hollowness of the Spring at the Setting-screw may be something more than the One-eighth Part of an Inch, to give the Spring a Quarter of an Inch Play: but it seldom has so much.
Seed Box Spring
Seed Box Spring Mounted in Place
Seed Box Spring
Fig. 4. in Plate 2. shews the Length and Thickness of the Steel Spring of a Turnep Seed-box: This serves both for a Tongue and Spring: It is made first strait, and then the narrowest End of it is turned round, till it reach to a, and forms the Cylinder A, thro’ which its Axis passes; but is not welded or joined to the other Part of the Spring at a: It is placed in the Box with the Cylinder Part underneath. The Face of this Spring is seen upon its Axis, mark’d K. in Fig. 5. Its Axis is to pass thro’ the Hole E, and screw into the Hole F, in Fig. 2. as is seen more plainly at a in Fig. 9.
Hollow Metal Cylinder
As the Top of every Tongue ought to be even with the upper Edges of the Mortise, the Thickness of the Cylinder of the Brass Tongue causes the Hole in the Sides of the Mortise, into which it is held by its Axis, to be far enough from the Edges of the Mortise, to be bored and screwed without Danger of breaking the said Edges; but the Spring of the Turnep-drill being so very thin, there is some Difficulty in making the Hole so high, and near the Edges: To prevent which Danger, Fig. 7. shews the End of a small hollow Cylinder of Iron or Brass, of the Thickness of the Mortise; which, being put into the Cylinder A, in Fig. 4. raises the Spring higher above the Hole; so that it may be made as low in a Turnep Mortise, as that is which holds the Brass Tongue in the Wheat-drill. But we do not always use this inner Cylinder263; but must then take the more Care in boring the Hole, or else it will burst out at the Edges of the Mortise.
Its Shape must conform to that of the Brass Tongue already described.
The Degree of its Stiffness is known by weighing, as has been directed for the other Spring; and being laid with its Face downwards over a Chink, with a small Piece of Wood of the Thickness of a Barley-corn at Each end, and a String taking hold of its Middle, and descending thro’ the Chink, the Weight of Five Pounds, tied to the End of the String, will just bend the Spring, till it touch the Edges of the Chink; and this is the Stiffness of a Spring that has performed well, for many Years, in drilling of Turnep-seed.
The Setting-Screw
Set Screw
Fig. 6. is the Iron Setting-screw, which passes thro’ the Hole in the Fore-end of the Mortise, Fig. 2. and passes up to the Middle of the Spring by the prick’d Line p q in the same Figure. The Use of this Setting-screw is, to increase or diminish the Proportion of Seed to be turned out by the Notches; and this it does by forcing up the Spring and Tongue (where there is one) nearer to, or farther from the Spindle, whereby the Seed-passage is made wider or narrower, as is shewn by the Three prick’d Lines in Fig. 2. and Fig. 3.
Observe, that the prick’d Line p q, Fig. 2. (being the Mortise of the Turnep-box) stands higher than the same Line doth in Fig. 3. which is the Mortise of the Wheat-box. The Reason of this Difference is, because the Spring in the Wheat-box bears at its lower End against the Tongue below the Seed-passage, and at its upper End below the Axis of the Tongue, whereby the Middle of that Spring is lower than the Spring of the Turnep-box, which, being both Spring and Tongue, bears against its Axis above, and against the Seed-passage below; therefore its Middle is higher. This Setting-screw should be placed perpendicular to the Tongue when at its mean or middle Distance from the Spindle, which may be supposed to be the middlemost of the Three mention’d prick’d Lines. This Setting-screw ought to be smooth and round at its End, which bears against the Spring; for, if it should have sharp Corners or Edges, the Spring might be wounded by them, and in time might break there, being press’d by every Notch that turns against it; and, as I have computed it, a Spring undergoes One hundred thousand of these Pressures in one Day’s Work; and yet, in my whole Practice, I have had only one Spring broken, and that was in drilling a large Sort of Peas with a Wheat-drill, and was occasioned by a jagged End of the Setting-screw, which was not placed perpendicular to the Spring, by which means the rough End of the Screw made Scratches against it a Quarter of an Inch long, and so deep, that the Spring broke off there: Let not this Setting-screw be any longer than just to force the Tongue up to the Spindle; for, if it should be longer, an ignorant Driller might happen, by the Force of the Screw, to break the Tongue, or its Axis; but in the Turnep-drill, which has only a Spring instead of a Tongue, the Setting-screw may be a Thread or Two longer; because the Spring will yield a little to it, after it touches the Spindle, and is sometimes of Use in that respect, when the Notches are too large. This Screw must be of such a Bigness, that it may not be in Danger of bending; for if it should be bent, it could not be screw’d up with any Certainty, because its End, being crooked, would be below its Place at one Half-turn, and above it at the other Half-turn, and so the Spring might be set farther from the Spindle instead of nearer, and nearer instead of farther, by the Crookedness of the Setting-screw. Its Head may be made with a Notch in it, to be screw’d in with a Knife, or else with a Head like a T, to be turn’d with the Fingers, which I think is best, especially for a Wheat-drill; because as the Brine and Lime, which stick on the Wheat, grow drier, it will run faster; and therefore the Setting-screw must be frequently screw’d in to lessen the Seed-passage.
The Seed-passage, or Place of Pressure, is where the Seed passes down betwixt the Spindle and the Tongue; and is in that Part where they are nearest together; for there the Seed is press’d hardest by the Force of the Notches, which carry it down: And this Passage is higher or lower, as the Tongue stands nearer or farther from the Spindle; for as it stands wider, it becomes nearer to perpendicular to the Top of the Mortise, and then the Seed-passage is higher; and when it stands nearest to the Spindle, then the Seed-passage is lowest. This appears in Fig. 3. by the Three prick’d Lines a n, a o, and a p.
The Spindle, with its Notches, is best shewn where it is large, and made of Wood, as that of the Wheat Seed-box; it is a solid Cylinder that passes thro’, and fills the great Hole, or hollow Cylinder, of the Seed-box; it is of various Lengths, according to the Distance its Wheels go asunder; it is always in large Boxes the Axis of Two Wheels, and turns round with them, as the Axis of the One Wheel of a Wheelbarrow does with that: These Wheels, by their Circumferences, measure out the Ground over which they carry the Seed-box, and, by the Notches in their Axis, deliver down the Seed equally, whether they move swift or slow; because an equal Number of Notchfuls of Seed will be deliver’d thro’ the Seed-passage at each Revolution of the Wheels.
The Notches resemble those in the Hinder-Cylinder of a Cyder-mill, which break the Apples by turning against the Notches of the Fore-cylinder, as our Notches turn against the Tongue; and bruise the Apples which come betwixt them, as our Notches might sometimes bruise soft Seeds, if the Tongue stood close to the Notches, without any Spring behind it to give Way to their Pressure, and return the Tongue again to its Place, at every Interval betwixt Notch and Notch.
Notched Spindle
Notched Spindle
The best Way, that I can think of, to shew the making of these Notches, is by a Section of the Spindle at right Angles, in the Middle of the Notches, as in Fig. 4. of Plate 3. which is a Circle whose Circumference is cut off by Six Notches; which shew the different Sort of Notches, that increase or diminish the Proportion of Seed to be carried thro’ the Seed-passage by them: The Length of the Notches we never alter; but make them always parallel to the Axis of the Spindle, and of the Length of the Distance there is between the lower Ends of the opposite Axes transversi of the Ellipses, or great Holes, of the Mortise; for if any Part of the Surface of the Spindle should be betwixt the End of a Notch and the Hole, one or more Seeds coming betwixt that Surface and the Tongue, might hold it open, and prevent its pressing against the Notch, to hold the Seed therein from falling without the Turning of the Wheels.
This Proportion of Seed is alter’d by the Number of Notches, and by their Depth or Breadth, or by both. b c is the Depth of a Notch, which we call its Side; and is that which takes hold of the Seed, and carries it down thro’ the Seed-passage. The Manner of cutting this is seen by its being a Portion of the Radius A c. The Bottom of a Notch is made in different Forms264: As, first, it may be convex, as is shewn by the curve Line b d. We may enlarge the Capacity of this Notch, by taking off the Convexity of its Bottom, as in the Bottom of the Notch shewn by the Line e f; and if we would increase it more, we make it concave, as g h.
Spindle Notch Detail
But of whatever Sort or Dimensions one Notch is made, all the rest should be the same exactly; and consequently, the Interstices (or Intervals) between Notch and Notch, of which the Line f c, being an Arch of the Circle, is the Breadth, must be equal265, and cannot be otherwise, if the Notches are all equal and equidistant, as they appear in the adjoining Fig. 5. which is a Section like the former, and shews Six Intervals, with their Six Notches, of the Size wherewith we drill St. Foin with high Wheels; but when we would drill very thin, it is better to have but Four or Five Notches instead of Six.
Fig. 6. shews a Notch of the Spindle. a b is the upper Edge of the Side of the Notch, being always an acute solid Angle. c d is the Edge of its Bottom, being always an obtuse Angle. e f is the Angle made by the Side and Bottom, and is always shorter than the aforesaid Two Edges, by reason of the Obliquity of the Two Ends; this Angle is never obtuse, except when the Bottom of the Notch is concave. These Three Lines must be parallel to the Axis of the Spindle.
Fig. 7. is one End of the afore-described Notch; the Line a b being joined to the Line f d of Fig. 6. and the Line a c, being joined to the Line b f in Fig. 6. would be the End of that Notch in its proper Posture; and then the Line b c, being an Arch of the cylindrical Spindle, would be the Edge of the upper End of the Notch. a b c, being the Area of this End, is a Plane, and, when in its Place, makes an Angle of Forty-five Degrees with the Axis of the Spindle. The other End is the same with this in all respects, except that, being opposite to it, it is inclined to it in an Angle of Ninety Degrees, at the bottom Angle of the Notch, at the Line e f in Fig. 6.
Spindle Notch
Fig. 8. is a Notch lying with its Ends near it, and is of the same Dimensions with those appearing in the Seed-box, Fig. 3.
The Cover B appears with its upper Surface rightly placed in the Mortise, in Fig. 3. of Plate 3. where its Breadth is shewn to be the same with that of the Mortise; but its Shape, and other Dimensions, are best seen in Fig. 3. of Plate 2. where s t is its Length, and reaches from the Hinder-end of the Mortise, to within the Tenth of an Inch of the upper End of the Axis transversus of the Ellipsis; its greatest Depth is from v to w, and is made so deep, that its Bottom, at w, bearing against the End of the Mortise, may prevent its Point, which is at t, from sinking down to touch the Spindle, which it neither must do, nor be so high above it as to suffer a Seed to pass between the Spindle and it, tho’ the Seed is not apt to pass that Way, because the Notches throw it forwards from the Cover. z is the Hole, thro’ which an Iron Screw-pin passes, and screws into the opposite Sides of the Mortise, to hold it firm in its Place: ’Tis made so thin betwixt x and y both for Lightness, and that the Seed may come the more freely to the Notches, without Danger of Arching at that End. The Use of the Cover is to prevent any Seed from falling down behind the Spindle.
Seed Box Cover
Fig. 10. Plate 2. is the Fore-end of a Wheat Mortise, with its Hole A, thro’ which the Setting-screw is screw’d, and passes up to the Back of the Tongue by the Line q r in Fig. 3.
Rear of Mortise
Fig. 9. in Plate 3. is the hinder End of a Wheat Mortise, which by its prick’d Lines, and the Two right-angled Triangles they make, shews the Bevel of the Mortise, and also its Depth; it also shews the Difference of the Bevel of the Mortise, and that of the Tongue, Fig. 1. which is placed against it: These Figures having been already demonstrated in the Description of the Turnep Mortise, and in these, I need say no more of it, but that I think these last-mention’d Figures sufficient Directions for understanding and making the Mortise of a Wheat-drill.
Fig. 3. of Plate 3. exhibits to View a Wheat Seed-box, with its Appurtenances, standing upon its Bottom; B the Brass Cover; C the Tongue hanging upon its Axis; c the End of the Iron Screw that holds on the Spring, coming thro’ the Tongue, and filed smooth with it; a, a, a, are Three Notches of the Spindle, with their bevel Ends; b, b, are Two Interstices betwixt the Notches.
Hitherto we have been speaking of the Parts contained in the Wheat Seed-box; let us now come to the Parts containing: As, first, d e f g is the upper Surface of the Brass Seed-box, shewing the Top of the Mortise, and what it contains; h h h, and h h h, shew the Ends of the hollow Cylinder, and its Bases coming out on each Side, farther than the Box; for if it did not project farther out than the Sides of the Box, the Surface of it would be so narrow, that it would cut the wooden Spindle by the Friction made between it and the Spindle; but the Surface, being of this Breadth, never wears into the Spindle, but makes it smooth and shining; i i i, and i i i, shew a Portion of the wooden Spindle (of an Inch and an half Diameter) coming out of the hollow Cylinder, on each Side of the Brass Box.
The Spindle is kept from moving end-ways, by Wreaths, in the same manner as the Axis of a Wheelbarrow is; which Wreaths shall be described together with the Hopper. k is the Hole by which the Fore-end of the Seed-box is held up to the Bottom of the Hopper, by a Screw and Nut. l is the Hole where the Hinder-end of the Box is held up, in the same manner as the Fore-end is. m n o p shew where the Two Halves of the Seed-box are joined together.
Outside of Seed Box
Fig. 10. shews the Outside of One Half of the Brass Seed-box. A A A shew the Thickness of the projecting Base of the hollow Cylinder, which is made the thicker, to the end that the Hole may be bored large, and made an Inch and Three Quarters Diameter, when a Spindle that is to go therein is required to be of that Bigness, by reason of its extraordinary Length, as it is in the Fore-hopper of the Wheat-drill. B C shews the Thickness of the Ends of the Seed-box, whereby it is held up to the Bottom of the Hopper; if they are not quite a quarter of an Inch thick, they will be strong enough; especially C, which is the hindermost, and which is never pull’d down by the Turning of the Spindle, but is rather raised up by it.
D is the Head of the Counter-screw, to be turn’d by the Fingers, to press against the Side of the Setting-screw, to keep it from turning of itself, when it is worn loose.
E is the Hole for the Axis of the Tongue. F is the Hole of an Iron Screw-pin, which both holds the Cover to its Place, and also the Two Halves of the Box together. G is the Hole for another Screw-pin, which holds the Two Sides of the Box together. H and I are Holes for Two other Screw-pins, which likewise hold the Two Halves of the Box together, and are placed one above, and the other below, the Setting-screw; for otherwise that Screw, and its Counter-screw, might force open the Joining of the Box, and then the Setting-screw might be loose, and the Bevel of the Box might be altered; but these Screws, being one on each Side of it, prevent this Inconvenience.
Half of Seed Box
Fig. 8. in Plate 2. is one Half of a Brass Turnep Seed-box, lying with its Inside uppermost, which shews the left Side of the Mortise, and half the Fore-end, and half the Hinder-end, of the Mortise, and half of each Screw-pin Hole, by which it is held up to the Bottom of the Hopper. A is half the Hole of the Setting-screw, shewing in the Middle of it the End of the Counter-screw. B is half the Hole, by which the Steel Spring-cover is held in with a Screw. All the other Holes are for the same Purposes, as have been shewn in the Wheat Seed-box.
Fig. 9. is the whole Turnep Seed-box, standing upon its Bottom; Part of its Steel Spring-tongue appears in its Place, as also some of the Notches of the Spindle; but more especially the Cover A, which differs from the Cover of the Wheat Mortise, this being a very thin Spring, whose lower End just reaches to touch (but not to bear upon) the Spindle at the upper End of the transverse Axes of the Ellipses; the Mortise being filed away at the End, in order that the upper End of this Spring, and the Screw which holds it, may not lie above the upper Surface of the Box. This Spring is made very weak, to the end that, if by any Chance a soft Seed should stick in a Notch, and be turned round, this Spring might suffer it to pass by without breaking it. B, C, are the Two Flanks or Sides, made necessarily of this Breadth, for bearing against the Wood of the Bottom of the Hopper, to prevent the Seed from falling out betwixt the Wood and the Brass, and that the Hole in the Hopper may be broader than this narrow Mortise of the Seed-box. The left Flank B, being next the wide Side of the Hopper, lies all open, except on the outside of the pricked Lines, where it is covered by the Wood of the End of the Hopper, when it is screwed on to its Place; but the Flanch C, on the right Side, will be all covered by the End of the Box, that will stand upon it, and will reach to the pricked Line that touches the Edge of the Mortise. D is the End of the Setting-screw, appearing in its Place with a Notch, whereby it is to be turned by a Knife; but I think it better to have an End like a T, to be turned with the Fingers. E is one End of the hollow Cylinder, which projects beyond the Flanch, that there may be more Room for the Crank to turn (without striking against the End of the Hopper, or against the Flanch) on the Outside of the Box or Hopper; and for that, the longer this Cylinder is, the better the Brass Spindle will turn in it.
Spring Cover; Thumb Screws
Fig. 11. is the Spring-cover, with its Hole, whereby it is screwed into its Place, as it is seen marked A, in Fig. 9.
Fig. 12. is the Setting-screw pointing against its Hole, its Head being flat, that it may be turned by the Finger and Thumb.
Fig. 13. is the Counter-screw, to be turned in the same manner.
Fig. 5. shews the Brass Spindle of the Turnep Seed-box, and the Manner of turning it against its Steel Tongue, or Spring; which Manner is different from that of turning the larger Spindles for Boxes of a larger Size, such as the Wheat Seed-box.
This Spindle266, being but half an Inch Diameter, is too small to be turned by the Two Wheels, as the larger Spindles are; not only because it would be in Danger of breaking by the Weight of the Hopper, and by the Twisting (or Wrenching) of the Wheels; but also because it would soon become loose, by wearing the hollow Cylinder thro’ which it passes; and it would be apt to open the Brass Flanches from the Bottom of the Hopper, whereby the Seed might run out, beside several other Inconveniencies; all which are prevented by turning the Spindle in the manner shewn in this Figure; for here the Spindle never presses against the hollow Cylinder, with any greater Force than that of its own Weight, which is so very little, that the Friction made by it is next to nothing.
Wreath or Washer
Slider
A the Spindle, exactly fitting the Bore of the hollow Cylinder; which, when it enters the said Cylinder at its left End, in Fig. 9. will be stopped by the Wreath B B B; which Wreath, being circular, is cast on the Spindle, and is Part of it; the other End of the Spindle will then appear without the right-hand End of the said hollow Cylinder, at E in Fig. 9. and is kept there by the Wreath Fig. 14. which is to be put on upon the End of the Spindle, until it come to the Shoulder at a, which Shoulder is exactly even with the End of the hollow Cylinder; so that this Wreath will touch the End of the said Cylinder by its whole Surface. Then, to fix in this Wreath from coming off, we make use of the Slider, Fig. 15. whose Two Claws A, B, being thrust down by the Two Notches of the Spindle, at b and c, until its other Part C, which is perpendicular to its Claws, comes down to the Flat of the Spindle, and environs one half of the Hole, covering the Part of the Flat which appears of a darker Colour; and then the upper Part of C, in Fig. 15. makes one level Surface with the Flat D of the Spindle; and then the Iron Fork E, being screwed into the Hole F, holds down the Slider fast, so that it cannot rise up; and then the Spindle, being in its Place, will run round without moving endways, being confined by these Wreaths.
The Spindle being thus placed, so that it may turn easily, we place the Seed-box upon its Flanches with its Bottom upwards; and then setting one sharp Point of a Pair of Compasses, or some such Instrument, upon the Spindle, within the Mortise, close to the Edge of the Hole or Ellipse at the End of the transverse Ax, turn round the Spindle, until the said Point makes a Mark round the Spindle, which will be a Circle; by the same means make such another Mark at the opposite Ax; then unscrew the Fork, and take out the Slider, pull off the Wreath, and take out the Spindle, and cut the Notches between the Two said Circles and Marks; the Edges of the Ends of the Notches must be Arches of these Circles. These Notches should differ from those already described in the Wheat-drill, in nothing but the Smalness of their Dimensions; their Depth should be about the Thickness of a Turnep-seed, or something deeper. The Breadth of their Bottoms is uncertain, and must be greater or less according to their greater or less Number; but we commonly have Seven or Eight Notches, and make them about the Breadth in which they appear in this Figure; but whatever their Number be, they must be all equal, and so must all their Interstices.
G is the End of a wooden Spindle, thro’ which passes the Iron Crank H, and is fastened to it by its Screw and Nut, at d; Part of which Crank enters the Wood at e, which prevents its Turning in the Spindle.
This Crank, by its other End, passing thro’ the Two Legs of the Fork E, and equally distant from the Top and Bottom of it, turns the Spindle by the Motion of the Wheel which is fixed on the other End of the wooden Spindle. If this Crank were to turn the Spindle by a single Pin, instead of this Fork, the Seed could never be delivered out equally to the Ground; for as soon as the Pin began to descend, and decline from being perpendicular to the Horizon, it would, by its own Weight falling down, turn the Spindle half round in a Moment, and there remain with its other End downwards perpendicular to the Horizon under the Spindle, until the Crank reached it there, and so no Seed would be turned out by one Semicircle of the Wheel, and a double Proportion would be turned out to the Land that was measured by the other Semicircle; but the hinder Leg of the Fork, bearing against the hinder Part of the Crank, prevents this Inconvenience.
The Line f g is Part of the Surface of a Board, thro’ which the wooden Spindle passes, and by which it is held in its Place; as shall be shewn hereafter.
The Axis of this wooden Spindle ought to fall into a Line with the Axis of this Brass Spindle; but, unless Care be taken to prevent it, the wooden Spindle will so much wear the Hole thro’ which it passes, and be worn by it, as to have Room in the Hole to deviate from this Exactness, and may descend so low, that the Crank may come out of the Ends of the Fork; and for this Reason it is, that the Fork is made so long as it is; but when this wooden Spindle does, by the Contrivances hereafter shewn, keep its Axis in a Line with the Axis of the Brass Spindle, or very nearly so, then the Legs of the Fork need be no longer than half an Inch; and in that Case, the Joint of the Crank, which is perpendicular to the Spindle, must be shorter, or else descend deeper into the Wood, so that its End, which turns the Fork, may be in the Middle betwixt its Bottom and the End of its Legs.
The Use of the other End of the Spindle is this: When we have a mind that it should be turned by the left Wheel instead of the right, we screw in the Fork into the Hole I, and place a short Screw in the room of the Fork, to hold down the Slider.
Note, It is not absolutely necessary, that the hollow Cylinder, which appears on the Sides of the Seed-box, should both, or either of them, project farther than the Flanches; but I think it better that it should do so, at least, on that Side which is next to the Fork.
This Cylinder should be bored as true, and as even, as the Barrel of a Fusil is bored: and the Edges and Surfaces of its Ends must be smooth, and without Jaggs, to the end that the Wreaths may turn glibly against them.
The Figure or Shape of all Sorts of Seeds disposes them, more or less, to form an Arch, when they are pressed from above, and confined on all Sides.
The most effectual Way to prevent this is, to take care, whenever many Seeds are to descend together by their own Gravity thro’ a narrow Passage, that such Passage be never narrower downwards than upwards; but, on the contrary, that it be wider downwards, on some or one of its Sides; in which Case, if the Surfaces of all the Sides of this Passage be smooth, it is impossible, that Seeds should of themselves form an Arch therein.
On this Maxim depends the infallible Performance of a Drill, and from hence are derived the Uses of the Bevel of the Mortise: What I mean by the Word Bevel, in general, has been already defined.
The Bevel of the Mortise of the Seed-box is that Inclination of its Sides, whereby it is wider downwards, and narrower upwards; by which means the Seed is prevented from arching in the Mortise before it descends to the Notches of the Spindle. And this is the First Use of our Bevel; for this Arching might happen in the Mortise, if the Planes of its Sides were parallel to each other; and would be unavoidable, if their Inclination were downwards, as it is upwards; but these Planes opening downwards, the lower the Seed descends, the more Room it has to expand; so that the very Weight, which would otherwise cause it to arch and stop, does by means of this Bevel force it to descend to the Notches, and then it is safe from all manner of Danger of stopping. The Ends of the Mortise are at such a great Distance from each other, and the Cover so very thin, as to lie almost even with the upper Part of the Spindle, that the Seed can never form an Arch that way; or, if it did, the continual Motion of the Tongue would immediately break it down at the Fore-end of the Mortise.
The Second Use of this Bevel is, that it gives room for the Tongue to be in the same manner bevel, tho’ in a less Degree: By this means, the Seed cannot by any Impediment be stopped in its oblique Descent to the Notches, from the Fore-end, and all that other Length of the Mortise, along and upon the Surface of the Tongue.
But if the Mortise had not this Bevel, the Tongue could not have it; for then either the upper Surface of the Tongue must have no Bevel at all, which would destroy the Two empty Triangles which ought to be on its Sides; or else it must have a Bevel the contrary Way (i. e. a Bevel reversed), and be narrower downwards than upwards, which would cause the Seed to arch thereon, and hinder its free Descent to the Notches.
A Third great Use of this Bevel is, that, besides the Bevel of the Tongue aforementioned, it gives place for Two empty Triangles, one on each Side the Tongue, which have each its vertical Angle extremely acute at the Axis of the Tongue, and have their Bases at the Bottom of the Mortise, and of the Tongue: These Triangles are also Bevels, which consist of the Difference, or Complement, of the Bevel of the Tongue, and that of the Mortise, the latter being about One-third greater than the former; i. e. One-third of the whole Bevel of the Mortise is divided between these Two Triangles, to each a Sixth Part; so that if the Angle of Inclination of the Sides of the Mortise were Nine Degrees, then the vertical Angle of each of these empty Triangles would be of One Degree and Thirty Minutes, and Six Degrees, would be left for the Bevel of the Tongue. And these triangular Spaces help to secure the free Motion of the Tongue, and free Descent of the Seed down its Surface; because they permit no Impediment to lodge in them, they being, by means of the Bevel of the Mortise, wider downwards, both obliquely and perpendicularly, so that no Dust, nor whatever else happens to get in betwixt the Tongue and the Side of the Mortise, can rest there; for it will be immediately removed thence by the Motion of the Tongue, and its own Gravity, and either thrown perpendicularly down, or else obliquely to the Notches, and the first Notch that takes it will carry it out at the Seed-passage.
The Fourth Use of the Bevel is, that thereby the Sections of the hollow Cylinder (before described) do form Ellipses instead of Circles; which they must have been, if cut parallel to the Bases of that Cylinder; and the Sections must have been thus parallel, had the Mortise been without any Bevel.
Now the Two Semi-ellipses, which are on the Fore-sides of their longest Axes or Diameters, and next to the Tongue, are opposite to, and do still uniformly depart from each other, even from the upper End of their said longest Axis, until they arrive at the lower End of the same Axis, which is below the Seed-passage, as its upper End is very near the Cover.
This Opening of these opposite Semi-ellipses makes it impossible for any thing, of itself, to get into the remaining Parts of this hollow Cylinder, betwixt them and the solid Cylinder, call’d the Spindle, which turns continually therein, when the Wheels are going: For you will see, that if you make a Mark on the Spindle, close to the Side of the Mortise, at the upper End of the longest Ax of the Ellipse; and then turn the Spindle until this Mark come against the lower End of the same Ax; and there make another Mark on the Spindle, close to the Side of the Mortise; and draw a Line from one Mark to the other, parallel to the Ax of the Spindle, which will be the Measure of that Part of the Bevel of the Diameter of the Hole; every Point in this Line will, by an intire Revolution of the Spindle, generate a Circle, which will cut the Ellipse in Two Places, once on the Foreside of its longest Axis, and once on the Back-side or hinder Half of it; and that all these Points, in this Surface of the Spindle, described by these Circles, will enter the Hole, by the said hinder Semi-ellipse, as the Spindle there turns upwards (as it always does); and they will all again come out on the fore Semi-ellipse, as they descend towards the lower End of the said Ax of the Ellipse.
As these Points thus come out of the Hole, or (if I may use the Expression) as they emerge, they oppose every thing that would enter the Hole, they still moving from the Hole, and push away from it whatever they meet; nay, if any thing were in the Hole, these Points (whereof this Surface consists) would bring it out by this Semi-ellipse, which is always press’d by the Seed when the Drill is at Work; but as these Points immerge by the other Semi-ellipsis which is behind the Spindle, they can carry with them into the Hole nothing but Air, because the Cover never suffers any thing else to come there from above; and the Seed falls out of the Notches by its own Gravity, just before it reaches the lower End of the transverse Ax, being the Place where the opposite Ellipses are farthest asunder; and none of it is ever carried so far back as the hinder Semi-ellipses; and therefore nothing can be carried into the Hole from below.
Thus that Part of the Surface of the Spindle will keep the Hole empty and clear, before ever any Notches are cut; but when the Notches are made on the Spindle, they have yet a much greater Force to drive and expel whatever would enter the Hole, their Shape being such as nothing can enter against their bevel Ends; but what is at their Ends will be thrown presently into the Mortise; insomuch that when a Spindle has been too little for the Hole by a Quarter of an Inch, that is, a sixth Part of the Diameter of the Hole, it will perform very well in drilling large Species of Seeds; and when the Mortise is run empty, nothing at all is found in the Hole, it being thus kept void and clean by the Notches.
Note, That what is here, and elsewhere, said of the Ellipse of the one Side of the Mortise, must be understood the same of its opposite Ellipse, on the opposite Side of the Mortise.
All these Advantages accruing from this Bevel of the Mortise, I believe that, without it, all Attempts of making a Machine to perform the Work, which this does, would have been vain.
There is also within the Mortise unavoidably another Bevel, which is as the Reverse of the former, and notwithstanding is as useful; and this Bevel is, the Inclination which Part of the curvilineal Surface of the Spindle, beginning a little above the fore End of the shortest Diameter of the Ellipses, and descending down to the Seed-passage, has to the lower Part of the Surface of the Tongue opposite against it. These Two Surfaces meeting one another below, when the Tongue is set up close to the Spindle, form a mix’d Angle, which stops up the Seed-passage, except when a Notch comes against it.
When the Tongue is set from the Spindle, to the Distance of several Diameters of one of the Seeds that are to be drill’d, this revers’d Bevel causes the Seed to arch at the Seed-passage, and stop there, till the Notches force it thro’, which would, without this Arching, fall out by its own Gravity, without the Turning of the Wheels.
The Seed arches here the more firmly, the more it is press’d upon by the incumbent Seed from above it; and the former Bevel (which I call the Bevel of the Mortise) permits the incumbent Weight to press the harder on the Seed that is near the Seed-passage; and this might be reckon’d a fifth Use of the former Bevel: For as it prevents the Seed from arching in any other Part of the Mortise, so it does, by the same means, cause it to arch the more strongly at the Seed-passage, which is sometimes (viz. when the Tongue must be set wide) as necessary, as it is for it to escape arching before it comes thither. And the more strongly this Arch presses against the Tongue, the more the Tongue by its Spring presses against it; and this Pressure being reciprocal and equal, the Seed cannot fall out spontaneously; for when the Passage is thus wide, if you throw into the Mortise a few Seeds, suppose Five or Six at a time only, they will all pass through immediately, without any Motion of the Wheels; but if you throw in a large Quantity together, there will only a few of the lowermost fall through, unless the Wheels do turn and throw them down by the force of the Notches.
Indeed we do not care to set the Tongue so very wide from the Spindle, unless it be when we are obliged to plant a very much larger Proportion of Seed than the Notches are design’d for, and when we have no Opportunity of changing the Wheels for such as are lower, nor of changing the Spindle for another that has greater or more Notches in it.
Four-and-twenty Gallons of large Peas are as proper a Proportion to drill on an Acre, as Six Gallons of Wheat are.
There are divers Ways to vary (i. e. increase or diminish) the Proportion of Seed; as, First, by the Setting-screw, with which we can, without any Inconveniency, set the Tongue so far from the Spindle, as to permit one Round of the Notches to turn out Four times the Quantity, as it will do when the Tongue is set close up to the Spindle; and thus we can vary the Proportion by innumerable intermediate Degrees.
Next, if we would increase the Proportion yet farther, we can inlarge the Notches; but we cannot add to their Number, unless there be room to double it, by making a new Notch between every Two; but we cannot diminish the Proportion of Seed by the same Notches, because they cannot be made lesser or fewer.
If we would make any other Alteration in the Proportion of Seed by the Notches, it must be done by making another Set of them; which we may do, because the wooden Spindle may have Three Rows of Notches in it, of which we may use either, by moving the Wreaths and Wheels towards one End or the other of the wooden Spindle; as shall be shewn in the Descriptions of the Hoppers.
But as for the Brass Spindle of the Turnep-drill, we can have but one Set of Notches in it267: And therefore, tho’ we can increase the Proportion of Seed by enlarging the Notches, or perhaps by doubling their Number; yet we cannot lessen the Proportion of Seed by the Notches, unless we have a new Set of them, and that will occasion a Necessity of having another Spindle; but, as to the Setting-screw of the Turnep-drill, it will increase the Proportion of Seed with the same Notches, much more than the Setting-screw of the Wheat-drill will do.
The other Way of varying the Proportion of Seed in the same Boxes, is by the Diameter of the Wheels, when we can alter them; for Wheels, of what Diameter soever they are, must turn round all the Notches at one Revolution; so that Wheels of Twenty Inches Diameter will deliver out a third Part more Seed than Wheels of Thirty Inches Diameter, into the same Length of the Chanels; but we seldom have any Occasion to alter the Wheels, unless it be on account of planting a Species of Seed of a different Magnitude, as the largest Sort of Peas, and small-grain’d Wheat, or St. Foin Seed are.
These are all the Ways we have to alter the Proportion of Seed, we drill with the same Seed-boxes; these Two Sizes, already described, being sufficient for all Sorts of Corn and Seeds which we commonly sow, from Marrow-peas to Turnep-seed; but, for drilling of Beans, the Boxes must be larger, and are commonly made of Wood, the Spindle Two Inches Diameter, or more, and the Boxes Two Inches wide: Where note, That this Increasing of the Width of the Mortise, from an Inch and an half, to Two Inches, increases the Quantity of Seed to almost double; because this Half Inch is all added to the Middle of the Notches, where they are deeper than their Ends; the Bevel of which takes up a considerable Part of the Length of the Notches. For Beans, they also contrive to have their Wheels as low as conveniently they can. These Wooden Drills are now become common in many Places.
The Wooden and Brass Seed-boxes differ not in any of the most essential Parts of them; only the Wooden Box must be thicker, as the Wood is not so strong as Brass; the Spring is made strait instead of crooked; and, being let into the Back of the Wooden Tongue, bears against it at each End; and the Chanel, into which it is placed, being made hollow in the Middle, the Spring has its Play there, and must be stiffer and have a little more Play in the Bean-drill, than in any lesser Seed-box.
I, at first, made all my Seed-boxes of dry Box-tree Wood, which performed very well, and are still used: But, a few Years ago, a Gentleman advised me to make them in Brass; the doing of which has put me to a great deal of Trouble and Expence, for want of understanding the Founder’s Art: Yet this I do not repent, because they are, in some respect, better than those made in Wood; especially to those who do not well understand their Fabric; for, to such, the Swelling and Shrinking of the Wood was inconvenient in small Boxes: And I now am told, that they are cast in London of the best Brass, at the Price of One Shilling per Pound, and so smooth as to require very little filing. And these Brass Boxes being also more lasting than Wood, and not much more expensive, when Workmen know how to make them, I think it not worth while to give any particular Directions for making them in Wood.
As to the Spindles of the Turnep-boxes, I have often made them with a mix’d Metal, of half Pewter, and half Spelter, which perform very well, and are easily made; because this Metal will melt, almost as soon as Lead, in a Fire-shovel, to be cast in a Mould; but Brass will not melt without a Crucible.
The first Idea that I form’d of this Machine, was thus: I imagin’d the Mortise, or Groove, brought from the Sound-board of an Organ, together with the Tongue and Spring, all of them much alter’d; the Mortise having an Hole therein, and put on upon one of the Iron Gudgeons of the Wheelbarrow; which Gudgeon being enlarg’d to an Inch and an half Diameter, having on it the Notches of the Cylinder of a Cyder-mill, on that Part of it which should be within the Mortise, and this Mortise made in the Ear of the Wheelbarrow (thro’ which the Gudgeon usually passes), made broad enough for the Purpose; this I hoped, for any thing I saw to the contrary, might perform this Work of Drilling; and herein I was not deceived.
As for placing a Box over this Mortise to carry a sufficient Quantity of Seed, it was a thing so obvious, that it occasion’d very little Thought; and an Instrument for making the Chanels, not much more; neither for applying Two Wheels, one at each End of the Axis, instead of the single Wheel in the Middle of the Axis of the Wheelbarrow.
At first my Plough made open Chanels, and was very rude, being composed of Four rough Pieces of Planks, of little Value, held together by Three Shoots, or Pieces of Wood, which held them at a Foot Distance one from the other; These Pieces, being cut sharp at Bottom, made the Chanels tolerably well in fine Ground. But I soon contrived a Plough with Four Iron Shares, to make Chanels in any Ground: This drew a Hopper after it, having Four Seed-boxes at its Bottom, carried on a Spindle by Two low Wheels, which had Liberty to rise and sink by the Clods that they pass’d over: The Seed-boxes delivered their Seed immediately into the open Chanels.
This Plough and Hopper were drawn by an Horse, and the Seed, lying open in the Chanels, was covered sometimes by a very light Harrow, and sometimes by an Hurdle stuck with Bushes underneath it.
I soon improv’d this Plough to perform better, and to make Six Chanels at once, and sometimes a great many more.
This Plough and Hopper, with their Improvements and Alterations, are shewn in Plates 4. and 5.
Notes
261Take care that these opposite Sides be sure to be true Planes, especially all that Part of their Areas, that is before the transverse Axes of their Ellipses herein after described; for should they be otherwise, the Bevel of the Mortise would be spoiled, and so would the Ellipses, and the acute Triangles, on the Sides of the Tongue; which how necessary they are to be true, is shewn in the proper Place. Workmen are very apt to fail in this when they file by Hand, and make these Sides of the Mortise convex instead of plane. Therefore this might be done with less Difficulty, and more Exactness, with a File placed in a Frame, whereby it might move upon a true Level without rising or sinking of either End.
262Not quite so thick as a milled Shilling, but rather of an old broad stamped Shilling, which is a little thinner.
263For, instead of this, we may use a Bit of Woolen Cloth of the Breadth of the Mortise, glued on to the Bottom of the Hopper, which, filling the Vacuity above the Steel Tongue, prevents any Seed from running over it, though the Holes are bored as low in the Mortise as if the Cylinder Fig. 7. were to be used.
264The convex Form is best for turning out a great Proportion of Seed; because such a Bottom may be broader than one of any other Form, in a Notch of the same Depth and Capacity; and such a Notch, having its Capacity more in Breadth than Depth, will be less liable to let fall any Seed without the Turning of the Wheels, than a Notch that is deeper and narrower, except it be very narrow, which it cannot be for throwing out a large Proportion of Seed; for a great Number of Notches cannot have altogether the same Capacity as a lesser Number of the same Depth may. The concave Notch, if it were as broad as the convex may be, would make the Interstice, that is before it, liable to be broken out, and so Two Notches would become One; but the Convexity of the other supports the Interstice like an Arch, and for that Reason may be made to reach almost quite to the Notch that is before it, without that Danger.
265But these cannot be equal, unless the Notches are all of equal Breadth, and equidistant from one another; and if they are otherwise, the Seed will not be equally delivered to the Ground.
266I believe, if it were less by a Fourth or Third of its Diameter, it might be better, as being more proportionable to the Smalness of the Turnep-seed. I have had the Mortise much wider; but it cannot well be made much narrower, whilst the Tongue is of this Fashion; for this Steel Tongue, if narrower, would either be too stiff, or else apt to break, nor would there be Room in the Mortise for a sufficient Setting-screw to follow it. But there is another Fashion, wherein a narrower Brass Tongue has a broad Spring behind it; and when it is in this Manner, the Mortise may be a Fourth of the Breadth of this. I have had many of these when I made my Boxes in Wood; but cannot describe them by these Cuts; neither are such narrow Mortises necessary, unless it were for drilling Tobacco seed, Thyme-seed, or some other Sort of an extraordinary Smalness.
267But by putting on a Wreath (that is a little broader than the Mortise) upon the Spindle (made longer for that Purpose) we can, by changing this Wreath from one End of the Spindle to the other, have Two sets of Notches of different Sizes, and of different Numbers in it: Or if we would have Three Sets, we need only make Use of Two such Wreaths, and let the Spindle be long enough to receive them. So we may use which Set we please.
Tho’ several Sets of Notches may be useful to those who drill many Sorts of fine Seeds different in Magnitude in a very great Degree; yet I never found more than one Set of Notches necessary in this Spindle.
Nor have I used any more than one Set of Notches in one Mortise of any Sort; but in a wide Mortise, there may be made a double Set of Notches, consisting of Two Rows, all of equal Bigness, and half of the Length, and double the Number of a single Row, one End of each Notch reaching to the Middle of the Mortise, and pointing against the End of an Interstice, that is between Two or its opposite Notches.
If ever there shall be Occasion for this Sort of Notches, it must be when a great Proportion of Seed is to be drill’d by a small Spindle, and low Wheels: The Smalness of the Spindle may not, by a single Set, admit of a sufficient Number of Notches (of a proper Bigness) in its Circumference; not that a double Set, by its double Number, will throw down a greater Quantity of Seed than a single Set of the same Width and Depth, but a less Quantity; But it may be feared, that a very small Number of Notches might not spread the Seed so much as to cause it to lie even in the Chanels, one Notchful falling all to the Ground, before any of the next Notchful reaches it, which would make Chasms or Gaps in the Row of Corn or Legumes: This, such a double Number of Notches will certainly prevent.
It would seem, that the higher the Wheels, the more need there should be for this double Set of Notches: But it appears to be otherwise; for the greater Distance the Seed has to fall, the more it spreads, and strikes oftener against the Funnel and Trunk; and by that means a Notch from high Wheels will, with the same Quantity of Seed, supply a greater Length of the Chanel (or Furrow) than a Notch will from low Wheels.
In all my Practice I never had any Occasion for such a double Set of Notches, either with high or low Wheels, or even when I drilled into open Chanels, without Funnels or Trunks to my Drill-plough; and yet my Rows of St. Foin, and of Corn, were always free from Gaps, being equally supply’d with Seed from one End to the other.
If ever there is Occasion for more than a single Set, it must be for Beans, for which also I think a large Spindle is better than a double Set of Notches in a small one. The largest Spindle I have known made, is of Two Inches and an half Diameter, and that only for Horse-Beans.
The best Sort of Notches for a double Set are those which have convex Bottoms; because such are less liable to drop their Seeds without the turning of the Wheels, than any other Sort: And a double Set must be in greater Danger of this, as the Tongue is always hindered from pressing so closely against any Notch, being held open by the Seeds on the opposite Interstice; which is contrary to a single Set, where no Seed can lodge at either End of a Notch, to hold open the Tongue, or hinder its pressing against it.
Note, When I made my Boxes of Wood, I had double Boxes, with a Partition between such a double Set of Notches; but never made such in Brass, not knowing whether that Partition, by its Thinness of hard Metal, might not cut the Spindle: Yet I never found any Occasion for a double Row of Notches. I made those double Boxes only for drilling Two Sorts of Seeds at once into the same Chanel.