Threshing Machine

A threshing machine, also known as a thresher, is a machine used to mechanically separate kernels of grain from chaff and stalks.

The thresher has essentially been replaced by its successor, the combine, which is able to both reap (cut a crop) and thresh.

[edit] History

The introduction of the threshing machine in the 18th century made the process of grain separation considerably less labor-intensive than it had been. The previous process involved the manual removal of kernels from husks, and the cleaning of any leftover material. It was important that as little chaff and weed seeds as possible were present in a yield to get a high price. During this era, all labor was carried out by men and livestock.

[edit] Designs of the 18th Century

One of the first threshing machines was introduced in 1786 by a Scottish millwright named Andrew Meikle.^[1] His machine was actually a combination of a thresher and a winnower. Both the thresher and the winnower were powered by a belt from a common drive pulley. In this machine, shocks of grain came into contact with a series of corrugated rollers. The grain was then conveyed to a fanning mill, which blew off the remaining chaff (in a process known as winnowing).

Following the introduction of the thresher-winnower, an English inventor produced a similar machine, seemingly based on Meikle’s design. Instead of the corrugated rollers, however, his model separated grain from chaff by passing it between a drum and a concave surface, which were both fitted with iron protrusions. This machine would serve as the basis for future English designs.^[2]

Around this period, most threshing machines were still operated by hand crank and required four men for the process; however, some were driven by horse treadmill, or with an implement known as a horse sweep. In the case of a horse treadmill, the horse would walk on a moving, inclined platform, which, in turn, would move a large pulley on the side of the machine, fitted with a leather drive belt. The process of powering a threshing machine with a horse sweep involved horses walking around a device that contained a gear box. This device would supply the threshing machine with power by transferring it through a tumble shaft or rod.

Threshing machines during this time had to be pegged to the ground so they wouldn’t detach from their tumble shafts while operating. This is thought to have led to the nickname “groundhog thresher.” The loud sound the spinning cylinder made—similar to a roar—inspired the nickname “bull thresher."^[3]

[edit] Common Threshers in the 1800s

In the mid-19th century, threshing machines were becoming increasingly well known, often winning prizes at agricultural fairs in Canada; they could also often be seen in manufacturers’ advertisements. It was common for manufacturers to sell their threshers with a corresponding power source.

A threshing machine’s capacity was measured by the width of its cylinder—most groundhog types comprised a cylinder with a diameter of less than 24 inches (60 cm). The thresher’s operator manually fed unbound sheaves into the machine. They were then threshed between a cylinder’s teeth and a concave. Once this process was complete, kernels had to be cleaned manually with a winnowing basket or fanning mill, unlike in Andrew Meikle’s combined thresher-winnower. This type of thresher was capable of processing about 70 bushels of grain each day—this amounted to 10 times the output of a single worker using a flail to thresh grain.^[4]

Other developments surfaced in the early 1860s, including the “Little Giant Thresher,” which was a large-sized groundhog thresher on two wheels produced by Stratford Agricultural Works. The machine itself was available for $100, but the four-horse sweep required for its operation cost an additional $100.^[5]

Around this time, certain machines comprised a slotted conveyor belt or endless apron and integral fanning mill. The straw was fed into the thresher and then carried toward the back via the slotted conveyor, through which the kernels would drop into the fanning mill’s hopper.

[edit] Improving Chaff Removal

Most early threshing machines relied on a conveyor and a fan to remove chaff from kernels. By the mid-1860s, however, a new mechanism was being produced: the “vibrator separator.” The original design was patented by Michigan-based Nichols and Shepard Co.^[6]

Rather than a conveyor, this machine incorporated a series of straw walkers or racks. It had rows of fingers made of metal or wood that would catch and shake threshed stalks as they exited the cylinder—the remaining straw was transported to the rear of the threshing machine. The grains fell to the bottom of the thresher where they were once again fed into the machine by conveyor for a second cleaning. The twice-cleaned kernels then fell through sieves, into an open chute on the side of the machine to be fed into a bushel measure, then into grain sacks. The straw, which had been carried to the back of the machine, then dropped onto the ground to be pitched into a pile or stack by workers.

[edit] More Mechanization: Advantages and Drawbacks

While most of the process of threshing and winnowing was mechanized by the 1860s, the disposal of chaff and straw—a considerably laborious process—was still carried out manually. The following decade, however, certain machines were available with a straw stacker; for example, the MacDonald-MacPherson “Standard.” This straw stacker consisted of a slatted conveyor attached to the rear of the thresher. It carried the straw away and stacked it in a pile. The conveyor could be raised with chains and pulleys as the stack got higher.

By the 1880s horse-drawn machines were used to wire and tie stalks of grain, speeding up the harvesting process. However, it was then necessary for several workers to cut and remove the ties, then pass the bundles to other laborers to be fed into the machine. An additional pair of men was needed to measure and bag the grain once it was separated from the stalks and chaff. In total, six men were needed to operate the thresher.

These examples of mechanization eliminated the need for several workers in certain parts of the threshing process, but actually didn’t serve as much of a labor-saver, as workers were now needed for other tasks.

[edit] Self-feeder

An advancement that did facilitate the process in the late 1880s, however, was the introduction of a twine-tying mechanism that used sisal twine. Workers no longer had to cut and remove wire ties manually, so it was then possible for bundles to be fed into the threshing machine mechanically. There were many brands of self-feeders, such as Sawyer-Massey’s version, but they were all fairly similar.

Self-feeders comprised a conveyor fitted with open slats with short tines that pointed upwards. These tines were attached to the front of the threshing machine, and were level with the bottom of the cylinder. The tines caught the bundles of stalks as they were put on the conveyor to be carried through a row of reciprocating knives that cut the twine bands. The bundles were then opened and directly fed into the cylinder.

By the middle of the 1890s most Canadian- and American-made machines had self-feeders with mechanisms that controlled the speed the bundles were fed into the cylinder. The self-feeder wouldn’t begin to load until the cylinder was spinning at a fast enough rate—this made it almost impossible to jam the cylinder with too much grain.

Though jamming the cylinder was not a concern, separating efficiency was affected when the cylinder was too full. Because of this, manufacturers were forced to increase the size of their machines’ straw walkers and cylinders to accommodate a greater amount of material to be separated. Machines now comprised a 32-inch- (81-cm-) wide cylinder and a 54-inch- (137-cm-) wide straw walker.^[7]

[edit] The Wind Stacker

The 1893 introduction of the wind stacker as a means of managing discarded straw and chaff further mechanized the threshing process. A wind stacker was a large fan attached to the rear of the threshing machine that forcefully blew chopped straw through a large metal tube into a pile. As the capacity of threshers increased and manually bagging grain was no longer possible, the machines had an enclosed bucket elevator that carried the grain from a pan into a wagon beside the thresher. By the end of the decade, most of these bucket elevators included a bushel counter to measure the grain automatically. Most machines could now thresh 1,000 bushels or more, depending on the thresher’s size.^[8]

[edit] Mechanized Process Remains Labor-intensive

The increased mechanization of the threshing process brought about an unintended effect: more laborers were now required. Though fewer men were needed in the direct operation of the threshing machine, number increased in the general labor force involved in the procedure. The more efficient machines with larger capacities resulted in the need for more bundle wagons to supply them with stalks for threshing. As well, two laborers were needed to load the self-feeders, and an operator was needed to supervise the machine’s operation. Other workers had to drive the grain wagon and operate the traction engine.

Due to the cost and size of these machines, their use was limited to threshing contractors and owners of very large farms, known as “bonanza farms.”

[edit] Machines Made of Metal

At the beginning of the 20th century, the first metal threshing machine was introduced—previously, threshers were made of wood. The metal thresher was introduced in 1904 by the J.I. Case Plow Works of Racine, Wisconsin.^[9] The company switched to metal in order to produce machines that could better withstand the strain of operating at full speed. Many companies followed J.I. Case’s lead and began producing metal threshers.

[edit] Mini Machines

Until the 1920s threshing machines had been getting larger in size and capacity. This decade, however, brought the advent of smaller threshers. These machines were suitable to be towed by smaller multipurpose tractors, such as those produced by Fordson. Ferguson Thresher Co. was one of the companies that began to focus on smaller models.

[edit] More Power

As the thresher’s mechanization evolved, so did its requirement for energy. Early on, portable steam engines began to be employed as a continuous power source. By 1900 these engines began to be displaced by traction engines. These traction engines had the benefit of not only offering a stationary power source, but also pulling equipment such as plows.

Soon after the introduction of traction engines as a power source for threshers, larger and more powerful kerosene/gas tractors entered the agricultural scene, creating competition for traction engines. These internal combustion engines were no more costly than their steam counterparts.

[edit] Combining Technologies

Threshers began to be displaced by a new type of machine, the combine, in the mid-1930s. The combine was able to reap (cut) and thresh a crop as part of one process. This machine, either pulled or driven through a ripened crop, drastically decreased the number of laborers needed for the job.

By the beginning of World War II, most companies had ceased production of threshing machines, as most consumers favored the self-propelled combine.^[10]

[edit] How it Works

Though threshing machines are not often used on their own any longer and their features have evolved and varied throughout their history, the following is a general description of how a thresher works.

First, bundles of dried wheat are loaded into the machine. Gears beat the wheat in order to separate the kernels from the wheat stalks.

Once the separation process has taken place, the stalks and kernels are conveyed through the machine—the kernels fall through slots in the conveyor, into a hopper positioned directly below. The stalks travel to the rear of the machine and are discarded out the back.

The kernels in the hopper are then moved via an auger to be sifted again in a secondary sifting area to remove dust and particles. The grain is then taken by another auger and is dumped from a spout into a wagon to be transported.

[edit] References

1. ↑ Threshing Machines: Technological Background. Canada Agriculture Museum. 04-03-09.
2. ↑ Threshing Machines: Technological Background. Canada Agriculture Museum. 04-03-09.
3. ↑ Threshing Machines: Groundhogs and Bull Threshers. Canada Agriculture Museum. 04-03-09.
4. ↑ Threshing Machines: Groundhogs and Bull Threshers. Canada Agriculture Museum. 04-03-09.
5. ↑ Threshing Machines: Groundhogs and Bull Threshers. Canada Agriculture Museum. 04-03-09.
6. ↑ Threshing Machines: Shake It Out. Canada Agriculture Museum. 04-03-09.
7. ↑ Threshing Machines: More Gadgets. Canada Agriculture Museum. 04-03-09.
8. ↑ Threshing Machines: Let the Wind Blow. Canada Agriculture Museum. 04-03-09.
9. ↑ Threshing Machines: Metal Machines. Canada Agriculture Museum. 04-03-09.
10. ↑ Threshing Machines: A New Technology. Canada Agriculture Museum. 04-03-09.

[edit] External Links

• Living History Farm