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MECHANICS.

ON THE THRASHING MACHINE.

machines

In a country like this, where agriculture has Utility of arrived at such a high state of perfection, the for abridg utility of thrashing machines cannot easily be ing labour. called in quesion. The universal prevalence of these engines is a strong proof that they are advantageous to the farmer; and, however much some men may inveigh against the adoption of every kind of machinery that has for its object the abridgement of manual labour, yet we are convinced, that no evil consequences can possibly accrue from their introduction; and that such insinuations have a tendency to inflame the minds of the vulgar, and retard the progress of science. As a proof of this, we might mention the fate of the celebrated Arkwright, the inventor of the fly-shuttle, whom the fury of an English rabble banished from his native country.

The thrashing machine was invented in Scot- History of land, in 1758, after five years labour, by Mr. the thrashing maMichael Stirling, a farmer in Perthshire. The chine. honour of this invention has been claimed by Mr. Andrew Meikle, an ingenious mill-wright in East Lothian, who obtained a patent for one Vol. II.

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of these machines, about the year 1785; and in this country his claims have been generally admitted. Mr. Meikle, however, was merely an improver of the thrashing machine, and I am assured by a gentleman of the most unquestionable authority, who, from his local situation, had access to the best information, that Mr. Meikle had seen Mr. Stirling's thrashing machine before he erected any of his own, and that he merely altered and improved it. About 26 years prior to the date of Mr. Stirling's invention, a thrashing machine was constructed in Edinburgh, by Mr. Michael Menzies, which operated by the elevation and depression of a number of flails, by means of the motion of a crank; and, in 1767, the model of a thrashing mill, invented by Mr. Evers of Yorkshire, was laid before the Society of arts in London, who rewarded the inventor with a premium of 60 pounds. This machine, which was driven by wind, consisted of a number of stampers, that beat out the grain when laid upon a moveable thrashing floor, and was actually used on a large scale in Yorkshire, where it received the approbation of several intelligent gentlemen of the county. All these machines, however, and others of a similar kind, with which the public are perpetually harassed, are completely defective in principle, and are greatly inferior to the worst of those now in use, which operate by the revolution of a thrashing scutch furnished with beaters, the exclusive invention of our countryman Mr. Stirling.

Bailey's Drawings of Machines laid before the Society of Arts, vol. i, pp. 54-59.

On Thrashing Machines driven by Water.

water.

In Fig. 1, Plate VII, AB is an undershot water Plate VII, wheel, which drives the machinery. On its axis Fig. 1. is fixed the spur-wheel CD, furnished with 150 machines Thrashing teeth, which impel the pinion b, containing 25 driven by teeth. On the axis H of the pinion is placed another wheel E, carrying 72 teeth, which take into the 15 leaves of the pinion c. The axle xx of the thrashing scutch, represented more distinctly in Fig. 2, by yxy, is fastened upon the same axis with the pinion c, and is therefore carried round with the same velocity. The thrashing scutch, a section of which may be seen in Fig. 3, is generally furnished with Fig. 3. four, and sometimes with a greater number of beaters, yy, whose surfaces, o, o, are covered with iron rounded off at the edges, in order to prevent them from cutting the straw. these beaters strike upwards, the scutch must be contained in a hollow cylinder of wood mn, so that the tops y, y, 0, 0, of the beaters may be above it; in which case, the scutch is called the thrashing drum. But when the beaters strike downwards, there is no occasion for covering it with boards.

When

The gudgeon of the axis H carries a wheel i of 22 teeth, which acts upon the wheel h with 18 teeth; on the axis he is fixed another wheel e with 17 teeth, that drives the crown wheel d, furnished with three rows of teeth, 13, 17, and 21, which, by means of the spindle R, gives motion to one of the feeding rollers, not visible. in Fig. 1, but represented distinctly by RR in Fig. 2. On the axis of the upper feeding roller RR is placed a small pinion, which drives the

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Fig. 2.

under feeding roller by acting upon another pinion, with the same number of teeth, fixed upon its spindle. The two feeding rollers, which are generally 3 inches in diameter, are fluted, or cut into small leaves like pinions, so that the leaves of the one may take into the leaves of the other; and their gudgeons move in mortises of such a nature, that the upper roller may rise in its frame, and the under one remove from the beaters, when too much corn is admitted between them. In order that the velocity of the rollers may be increased and diminished at pleasure, according to the nature of the corn to be thrashed, the wheel e is made to shift on its axis so as to act upon any of the three rows of teeth in the crown wheel d, which enable us to communicate three different degrees of velocity to the rollers.

As the machinery which drives the strawshaker interferes, in Fig. 1, with that which gives motion to the fluted rollers, it will be seen in Fig. 2, which is a plan of the machine where the corresponding parts are marked by similar letters. The wheels b, E, c, in Fig. 1, are not represented in this figure, but H is the extremity of the axle on which E and b are fixed. The small wheel i of 22 teeth, fixed upon the extremity of the gudgeon i H gives motion to m, a wheel of 17 teeth, which, by the intervention of the spindle m n and wheel n of 24 teeth, drives o, a wheel carrying 34 teeth. On the same

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* The dimensions of the thrashing machines here de scribed are chiefly taken from Gray's Experienced Millwright, a book of great utility in a manufacturing country. It consists chiefly of plans, sections, and elevations, of different machines, which the author himself has either erected, or whose construction he has immediately superintended. We are afraid, however, that Mr. Gray has

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axis with o is fixed the straw-shaker KK, on whose cross arms are fastened the rakes zr, furnished with a number of iron, or wooden, teeth, which carry off the straw, while the grain falls down into the fanners. The axis of these fanners p q, Fig. 1, is put in motion by the belt pp passing over the two rollers p, p. A section of the straw-shaker is shewn in Fig. 4, where K is its axle, z, z, its arms, and r, r, &c. the teeth fastened at the extremity of these

arms.

its different

parts.

That the reader may have a distinct idea of Velocity of the thrashing machine, we have calculated the following table, which exhibits the number of teeth in the wheels, and the velocity of its different parts. It is scarcely necessary to premise, that when one wheel drives another, the number of turns, or parts of a turn, performed by the wheel which is driven, is represented by a fraction, whose numerator is the number of teeth in the wheel that gives the motion, and whose denominator is the number of teeth in the wheel which receives it. Thus, a wheel with 25 teeth, driven by another with 150, will perform or six revolutions for one revolution of the impelling wheel; and a wheel with 16 teeth, driven by a pinion with 8 teeth, will make or of a turn for one revolution of the pinion. When two or more wheels are upon the same axis, they all perform the same number of revolutions, however different be their magnitude

150

259

8

not rendered these machines sufficiently intelligible to the uninstructed mechanic, from the great brevity of his descriptions; and, we hope, if his work reaches a second edition, as we trust it will, that he will take advantage of this friendly hint.

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