Finally, my readers will please to advert to what has been already said on the forms of these teeth, and their uses: and recollect especially what was observed on the epicycloid, as applied to them. It will easily be perceived, that to put that form on one of these teeth would be an almost hopeless attempt!—and, happily, it is not necessary. We can, however, by using the cutter r with various slopes, and going several times through each space, cut facets on the teeth, quite near enough to the theoretical form to make them work well together; and, as before observed, nothing is wanting to make the teeth perfect, but to run them together with the wheels placed in due position.
OF
A CENTRIFUGAL DASH-WHEEL,
For Bleachers, Dyers, &c.
To form a true estimate of the value of any new machine, it is necessary to examine the nature and operation of those that have been used before for similar purposes. And this is the more needful here, because the present Dash-wheel is essentially good, both in it’s properties and effects. The only room left for improvement, seemed to respect the quantity of work done by it: and this is, the chief point of comparison we shall establish in what follows:—
The [third figure], in [Plate 33], is a sketch of the common Wash or Dash-wheel. The pieces of calico (or other goods) are put into it through the round holes, dotted in the figure; and, by the revolution of the wheel from right to left, are carried up from a to b, or nearly so; from whence they drop by their weight to about the point c, where they meet the angle formed by the circumference of the wheel and one of the four arms or partitions, by which it is divided. If the wheel go too fast, the line of falling becomes more like the curve b d, and the goods strike the circumference too high, and in an oblique direction;—whence the blow is reduced, and the washing becomes imperfect. If, on the other hand, the wheel move too slowly, the pieces slide down the ascending partition (a) before it comes to the vertex, and thus only fall from the axis to the lowest point of the wheel;—whence, also, an inefficient stroke. Thus, do these wheels require a moderate velocity: and they are reckoned to do their work best when making from 22 to 24 turns, and giving, of course, four times that number of strokes per minute.
The produce of these wheels is thus circumscribed by a natural cause that cannot be altered—namely, by the law of falling bodies; and my Invention has in view to elude the shackles which confine this process, and to produce a much greater effect in the same space,—the same time,—and with the same expence of workmanship.