[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 Spindle[266], 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.
[266]I 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.
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.