Chances are, if you look back into your family history, eventually you will find someone that lived and worked on a farm. Whether you currently live on a farm like I do, or you have to go back three generations, farming has somehow impacted your life. We all are currently living in Iowa and fall is a busy time for farmers. Just driving down the highway you are likely to see a farmer combining. Today I am going to teach you the process of how a combine harvests soybeans. Combines must follow a four step process, they must gather the crop, thresh the crop, clean the grain, and collect the grain.
The first step of how a combine works is by gathering the crop. The bean head is the first contact point between the soybean plant and the combine. The bean head has a cutter bar with knives on the front that move very fast from side to side. These knives cut the bean plant just above the ground just like a mower cuts grass. There is a slow rotating wheel with teeth sticking down above the cutter bar that rakes the plant into the head. Once in the head, the plant finds an auger. The auger is like a turning screw that gathers the plants into the center of the bean head. The plant is then taken inside the combine and is ready for threshing.
Now that the bean plants are all gathered together and are inside the combine, the next step is to thresh the plant. Threshing simply means separating the grain from the crop. The combine accomplishes this with a rotor. The rotor is a big bullet shaped cylinder that spins like a spiral, forcing the material to the back of the machine. While spinning, the rotor rubs the crop against a concave. The concave a metal tubing that surrounds the rotor, and kind of looks like a jail cell door. It has holes in it so as the crop is being rubbed against it, the small materials such as the seed and pods can cross through it. Setting the rotor speed and the distance to the concaves is crucial for proper threshing. According to Dan Anderson from Farm Journal in 2018, if the rotor is too fast then the grain will crack, and if the concaves are too close to the rotor then the grain will get crushed. After finding the proper settings, the seeds and small material cross through the concave, while the stems and bigger material are thrown out the back of the combine. These small materials are called chaff, which is unwanted material such as the bean pods or other light material.
Once the plants have been threshed, the third step is to clean the grain. The seed and small material that passed through the concaves fall onto a sieve. A sieve is like as strainer, as you shake the strainer, material can pass through. There are two sieves in a combine, one right on top of the other. The top sieve is a wider strainer, so more material can pass through. The bottom sieve is a smaller strainer so only the clean grain can pass through. Each sieve can be adjusted in width. According to the Case IH Red Power Team in 2018, if the sieves are set to wide or to narrow, then the grain will not get cleaned properly, or even at all. Underneath and just in front of the two sieves is a fan. This fan blows air through the sieves. This fan is what separates the grain from the chaff, or unwanted material. It is important to have fan speed fast enough to blow away the chaff, but slow enough for the grain to pass through the sieves. The chaff is blown away out the back of the combine. After trial and error, you will find the proper adjustment and the clean grain falls into a pan which is underneath the sieves.
The final step of a combine is to collect the clean grain. At this point in the process, the clean grain is sitting at the bottom of the combine in a pan. There is an auger in the pan that transports the grain to the side of the combine. The grain then enters an elevator. The elevator has the same concept as an elevator in a hospital would. The grain enters at the bottom, travels up, and exits the elevator at the top. There is a big room at the top of the elevator where the grain collects, called a grain tank. The more you combine, the more grain collects in the grain tank, thus completing the process of how a combine works.
In conclusion, combines follow a four step process. They must first gather the crop with the bean head, thresh the crop with a rotor, clean the grain with the sieves, and finally collect the grain in a grain tank. Next time you are driving down the highway, take the time to look out the window at the farmers in the field and the combines they operate. You never know, maybe someday you will get the opportunity to operate a combine.