Thrashing
THRASHING, or THRESHING (from "to thrash," O. Eng. bewow, cf. Ger. dreschen, Du. dorschen, etc.), the process by which the grain or seed of cultivated plants is separated from the husk or pod which contains it.
Historical. It is probable that in the earliest times the little grain that was raised was shelled by hand, but as the quantity increased doubtless the grain was beaten out with a stick or the sheaf beaten upon the ground. An improvement on this, as the quantity further increased, was the practice of the ancient Egyptians and Israelites of spreading out the loosened sheaves on a circular enclosure of hard ground 50 to 100 ft. in diameter, and driving oxen, sheep or other animals round and round over it so as to tread out the grain. This enclosure was placed on an elevated piece of ground so that when the straw was removed the wind blew away the chaff and left the corn. This method, however, damaged part of the grain, and as civilization advanced it was partially superseded by the thrashing sledge the charatz of Egypt and the morag of the Hebrews a heavy frame mounted with three or more rollers, sometimes spiked, which revolved as it was drawn over the spread out corn by two oxen. A common sledge with a ridged or grooved bottom was also used. Similar methods to these were used by the Greeks and are still employed in backward countries. In Italy a tapering roller fastened to an upright shaft in the centre of the thrashing floor and pulled round from the outer end by oxen is still in vogue and would seem to be a descendant of the Roman tribidum or roller sledge.
Doubtless the flail was evolved from the early method of using the stick. It seems to have been the thrashing implement in general use in all Northern European countries, and was the chief means of thrashing grain as late as 1860. It was known to the Japanese from the earliest times, and was probably used in conjunction with the stripper, an implement fashioned very much like a large comb, with the teeth made of hard wood and pointing upwards. The straw after being reaped was brought to this and combed through by hand, the heads being drawn off and afterwards thrashed on the thrashing floor by the flail. At the present day just such an implement, known as a " heckle," is used for combing the bolls or heads off flax or for straightening the fibre in the after treatment.
The flail consisted of two pieces of wood, the handstan or helve and the beater, fastened together loosely at one end by a thong of raw hide or eelskin, which made a very durable join. The handstaff is a light rod of ash about 5 ft. long, slightly increasing in girth at the farther end to allow for the hole for the thong to bind it to the beater. The length of the handstaff enabled the operator to stand in an upright position while working. The beater is a wooden rod about 30 in. long, made of ash, though a more compact wood such as thorn is less likely to split. This also has a hole at one end for the thong to bind it to the handstaff. The shape of the beater was cylindrical, of about ii in. diameter and constructed so that the edge of the grain of the wood received the force of the blow; 30 to 40 blows or strokes per minute was the average speed.
After the grain had been beaten out by the flail or ground out by other means the straw was carefully raked away and the corn and chaff collected to be separated by winnowing when there was a wind blowing. This consisted of tossing the mixture of corn and chaff into the air so that the wind carried away the chaff while the grain fell back on the thrashing floor. The best grain fell nearest while the lightest grain was carried some distance before falling, thus a very rough-and-ready grading of the grain was obtained. It was also performed when there was no wind by fanning while pouring the mixture from a vessel. Later on a fanning or winnowing mill was invented. All ancient barns were constructed with large doors giving on to the thrashing floor and opening in the direction of the prevailing winds so that the wind could blow right through the barn and across the thrashing floor for the purpose of winnowing the corn. The flail is still in use for special purposes such as flower seeds and also where the quantity grown is so small as to render it not worth while to use a thrashing mill.
With regard to the amount of grain thrashed in a day by the flail, a fair average quantity was 8 bushels of wheat, 30 bushels of oats, 16 bushels of barley, 20 bushels of beans, 8 bushels of rye and 20 bushels of buckwheat.
There seem to have been many attempts to devise some form of power-driven machinery for thrashing. In 1732 Michael Menzies, a Scotsman, obtained a patent for a power-driven machine. This was a contrivance arranged to drive a large number of flails operated by water power, but though worked for a time it was not particularly successful. The first practical effort leading in the right direction was made by a Scottish farmer named Leckie about I7J58. He invented what was described as a " rotary machine consisting of a set of cross arms attached to a horizontal shaft and enclosed in a cylindrical case." This machine did not work very well, but it demonstrated the superiority of the rotary motion and pointed out the lines on which thrashing machines should be constructed.
The first really successful thrashing machine the type which is embodied in modern thrashers was invented by another Scotsman named Andrew Meikle in 1786 In this the loosened sheaves were fed, ears first, from a feeding board between two fluted revolving rollers to the beating cylinder. This cylinder or " drum " was armed with four iron-shod beaters or spars of wood parallel to its axle, and these striking the ears of corn as they protruded from the rollers knocked out the grain. The drum revolved at 200 to 250 revolutions per minute and carried the loose grain and straw on to a concave sieve beneath another revolving drum or rake with pegs which rubbed the straw on to the concave and caused the grain and chaff to fall through. Another revolving rake tossed the straw out of the machine. The straw thus passing under one peg drum and over the next was subjected to a thorough rubbing and tossing which separated the grain and chaff from it. These fell on to the floor beneath, ready for winnowing.
A later development of the beater-drum was to fix iron pegs on the framework, and thus was evolved the Scottish " peg-mill," which remained the standard type for nearly a hundred years and is found at nearly every farmstead in Scotland as a fixed machine in the barn to the present day, though in many cases unused since the advent of the portable thrasher. Further, it is the type adopted in America, and all " separators " in use on the great wheat lands of " the West " are simply modifications of the pegmill principle. In Great Britain, however, a reversion has been made to the beating or rubbing principle, where the arms of the " drum " rub the straw against an encircling concave framework and thus shell the grain out, and the portable thrashing machines now taken from farm to farm are all constructed on this principle. It was not till about 1800 that a machine for winnowing was invented to work as part of Meikle's peg-drum thrasher, and this made a complete separator or thrasher which thrashed, cleaned and delivered the grain at one operation. Still, these machines were stationary, being generally built up in homesteads and operated by water power, and the unthrashed corn had to be brought to them. Portable thrashing machines operated by horse power were used to a small extent, but the work was very hard on the horses and took them away when their services were otherwise required on the farm. When steam was developed as a motive power the portable thrashing machine became more general.
When Meikle had brought together the peg-drum" and concave he had solved the difficulty of mechanical thrashing. The development of the machine to the efficiency of the modern thrasher was very gradual, and was in the direction of greater speed to the drum and more beaters on it, and improved arrangements to ensure a clean sample of grain. It is generally supposed that each part was invented and perfected singly, but in reality the early experimenters had tried to make a complete separating machine. In fact they covered the whole ground in theory before any main features were made practical.
The Modern Thrashing Machine. The present-day thrashing machine embodies the main features of Meikle's machine and will thrash up to 16 quarters of oats per hour, depending on the size of the same. There are no fluted rollers at the feed, the sheaves are fed straight to the drum; but as the working of these high-speed drums was attended with considerable risk, the Threshing Machine Act 1878 now provides for some sort of guard or safety feed.
In the most modern thrashing machine the ordinary routine is as follows: The loosened sheaf is fed in at the feed mouth under the drum guard and passes between the drum beaters and the concave; most of the corn falls through the concave on to the corn and chaff receiving board, but some of the corn and chaff remain among the straw; as the " cavings " (the short broken straw and leaf) need to be separated from the straw it is given a thorough tossing up on the shakers, which have an upwards and onwards peristaltic action, and deliver the straw at the end of the machine. The corn, chaff and cavings fall on to a reciprocating board or " upper shoe," which carries them back to the middle FIG. i. The internal construction and arrangement of the " Ruston " double crank finishing Thrashing Machine. (Ruston, Proctor & Co., Lincoln.)
A, Corn feed opening.
B, Thrashing drum. CC, Straw shakers.
D, Collecting board of top shoe.
EE, Caving riddle.
FF, Dressing riddles.
G, Grain spout.
H, Large blower.
I, Shut off lid.
jj. Elevator.
K, Srautter.
L, Creeper.
MM, Riddle.
N, Second blower.
O, Grain passage.
P, Spout.
Q, Rotary screen.
R, Grain passage.
T, Classified grain.
U, Rotary screen brush.
V, Dust spout.
W, Grain delivery to sacks.
X, Dust.
Z, Cavings delivery.
Y, Chaff delivery or chaff collector may be fitted here to deliver chaff upon either side of machine, as desired.
of the machine, where they meet the corn that fell through the concave. The upper shoe passes the cavings, etc., over the end into a " lower shoe," which thoroughly sifts the corn and chaff from the cavings. The cavings are then carried along to the outside of the machine and emerge at an opening beneath the point where the straw passes out. The corn and chaff fall through the lower shoe or caving riddle on to a receiving board FIG. 2. Thrashing Machine at work with stacking elevator behind. (Clayton & Shuttleworth, Lincoln.)
which takes them back to the middle of the machine, where they fall, meeting with a strong blast of wind from the first fan, which blows out the chaff and light matter, the small seeds and light dust being sifted out through finely perforated sieves, while larger debris such as thistle heads and " chobs " (broken heads) are taken off by a coarse sieve. The corn then passes into the shaker shoe, which is fitted with sieves to take off the larger seed, and thence to the elevator, which carries it to the top of the machine in a roughly dressed condition. The elevator delivers the corn into the awner or " hummeller, " which is fitted with helical blades to rub off the awns or beards which may still adhere to the grain. From here the grain falls on to a second series of sieves, where it meets the blast of air from the second fan, which blows and sifts the light and coarse foreign matter from the grain, delivering this debris on the first com and chaff receiving board to undergo separation again along with that just fallen from the concave. The corn falls from the sieve of this second dresser into a rotary screen where separations are made producing the clean sample and the tail corn, which are delivered at separate openings below. There are modifications on the machine described such as single fan-blast instead of double, etc. but the general principles are the same. The concave which surrounds the drum is made adjustable, so that it can be regulated according to the nature of the crop to be thrashed. An ordinary machine will thrash all usual farm crops, but great care has to be taken in adjusting the concave or the seed will be injured. Clover, however, is twice FIG. 3. Thrashing Machine with fan-blast straw-stacker. (Clayton & Shuttleworth, Lincoln.)
passed through a machine of this description, to free the seed from the haulm and afterwards to rub the seed clear from the chaff, but special machines to thrash it all in one operation are made.
The drum is carried on the main shaft and all other pulleys take their motion from it directly or indirectly. Sometimes the main shaft is lengthened to accommodate another pulley and so drive a chaff-cutter behind and chaff up the straw as it leaves the thresher. In some districts an elevator is driven behind to stack the straw. Others use a trusser, which ties the straw into large bundles before delivering it for stacking.
American Machines. In American machines the straw, cavings, etc., are caught in a blast at the rear end of the machine and blown up in a light iron pipe of about 18 in. diameter on to the top of the stack, and the grain is delivered loose at the side through a spout into a box wagon. As the payment for thrashing is per bushel the grain is usually passed through a self-registering weighing apparatus, so that accurate account is kept of the bushels thrashed. In Great Britain payment is per quarter of 8 bushels, and as the machine delivers into 4-bushel FIG. 4. American " Separator " with self-feeder and fan-blast delivery-pipe for straw. (A very Manufacturing Co. , Peoria, Illinois.)
sacks this rough-and-ready measure is accepted. On American machines self-feeders are adopted, in which the sheaves are thrown on to a travelling web which carries them under revolving knives to cut the bands and deliver them loose into the drum, so that while many more bushels of grain are passed per day through an American machine than is done in Great Britain, only about half the men are required at the work.
Thrashing Work. The minimum number of hands required in Great Britain are: An engine-driver, a feeder, a sackman, and ten other men to handle the sheaves, straw, chaff, grain, etc., while half as many more may be needed where the grain has to be carted, as when the thrashing is done in the field in harvest time. An 8-h.p. steam engine is the usual motive power, but the development of the oil engine has provided a very satisfactory substitute. The engine is usually of the "traction" type, so that it can move the thrashing machine or " barn work" (as it is sometimes called) and elevator from place to place. The usual quantities thrashed with a " double blast finishing machine," as described, in the United Kingdom are, with a 5 ft. wide drum, from 60 to 80 bushels per hour of wheat, and one-third to one-half more of oats and barley.
Sometimes the straw is stacked loose, while sometimes it is tied up with twine by a tier exactly like that on a " string binder " and then stacked up. Where all the straw is used at the farm for fodder, etc., the fixed thrashing machine set up in the barn is the most convenient. The sheafed corn has to be carried to it, but, on the other hand, everything is under cover, the work can be done on a wet day, and all the products of thrashing in the shape of grain, straw, cavings, chaff, etc., are kept dry. In the great corn districts, however, the portable thrasher is most convenient; it is set alongside the stack and only the grain and chaff are carried under cover, while the thrashed straw, etc. , is restacked up on the spot as the work goes on. The farmer finds the coal and the men and horses to cart water to the engine and corn to the barn and pays the proprietor of the thrashing outfit, who finds all the other men, about the following rates: wheat, is. iod., oats and barley, is. 6d. per quarter. (P. McC.)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
