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Combine Concave Basics

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Combine Concaves

Whether you are using a John Deere or a Case IH combine, your concave plays a vital role in the quality of your harvested crop. The combine concave performs two important functions – threshing and separating. The threshing process frees the seeds from the plants. Then the separation process moves the seeds away from the chaff.

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How Combine Concaves Work

In concaves for combines, friction among the rotating cylinder, the incoming crop, and the concave results in the threshing process. The clearance between the cylinder and the concave is adjustable. Once the crop enters the clearance, it gets squashed by the cylinder against the concave and smaller parts start to sift through the openings. As a result, the grain is separated from the plants.

The clearance distance, the bar and wire patterns of the concave, the speed of the rotor, and the crop types determine how clean the samples turn out in the grain tank. It takes a bit of experience to understand how all these factors influence the process.

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Concave Settings for Crops and Conditions

Striking a balance between the cylinder rotating speed and the concave clearance is like walking a tightrope. The purpose of the clearance between the cylinder and the concave is to regulate the material flow. If there is too much space, then the grains will not separate. If it is too tight, then it results in damaged product. It is a good idea to consult the combine operation manual. Start with the recommended clearance settings. Then adjust according to the field conditions.

Concaves come with different types of bars and wires. The straight bars of the concave run parallel and the curved wires are perpendicular to the rotating axis.

Narrow-wired concaves are great for small grains like wheat and barley. The narrow spacings between the wires allow the small seeds to sift through. The bars are square-edged. Wide-wired ones are for crops like corn or beans. The design is similar to the narrow-wired ones. But there is more spacing between the wires to accommodate larger grains.

Round bar concaves are great for high-volume situations. They have round bars but no wires. The helical design has only diagonal bars. The diagonal pattern makes it harder for unthreshed grain to escape. So it is a great option where you need to ensure cleaner grain. You can also install it in the front concave position to help improve the yield of the other designs.

Besides the concave clearance and design patterns, you can use cover plates to improve the threshing process. The plates are used to strategically cover up certain parts of the installed concaves to let the material stay longer between the threshing cylinder and the concave.

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Why Should I Care?

Understanding the available options will help you get the best performance from your concaves. However, there is no substitute for real-life experience. No two fields are alike. For your particular circumstances, you will have to experiment to find the optimum settings.

With the wrong concave settings, you can end up damaging your threshing cylinder and concaves. So when in doubt, seek out expert advice.

Please feel free to reach out to us if you need any help.

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