Concave to Cylinder Spacing

The spacing between the concave and cylinder affects:

• Threshing quality.
• The amount of grain separated from straw by the concave.

When threshing is difficult, the cylinder to concave spacing can be reduced to thin the layer of straw between the cylinder and concave so that most of the pods (or heads or ears) contact the cylinder. A smaller gap between the concave and cylinder can also result in more grain being separated from straw. Grain will move more easily over a thin layer of straw over a narrow space than over thick layers in larger spaces. With an adequate separation there will be greater threshing efficiency in front of the concave and most grain will fall through the concave before being unloaded beyond the concave and cylinder area. With a greater spacing between the concave and cylinder, threshing will mostly occur in the rear of the concave and there will be no time for grain to be separated. This grain will then fall through the straw walkers and be reprocessed.

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